Article

Biohydrometallurgy and Biomineral Processing Technology:A Review on its Past, Present and Future

October 2012

Authors:

Dr Haragobinda Srichandan

Dong J Kim

Korea Institute of Geoscience and Mineral Resources

Ata Akcil

SDU/Beijing University of Chemical Technology/Satbayev University/Nazarbayev University

The Microbial hydrometallurgy and microbial mineral processing of metal sulphides is currently a well established technology. Over past years there has been a huge amount of developments with regards to the understanding of its both engineering perspective as well as fundamental approach with regards to the microorganisms. The huge diversity of the microorganisms, which has come into picture over the years of research and development have made the engineers to go beyond several limitations of working temperature to salt tolerance of the microorganisms in harsh conditions to deliver better technologies for the future operative plants. Today scientists have been able to deliver the various mechanisms involved in bioleaching but still there are facets to be really understood and more importantly on the front how lab scale research can be turned out into full scale operation by scaling up the research and optimizing the engineering aspects of the research. Most of the bioleaching operation has shown their productivity in commercial application of refractory gold concentrates using mesophilic microorganisms followed by the cyanide leaching to recover optimum amount of gold with an environment friendly method compared to the conventional method of roasting. Research in the area of chalcopyrite bioleaching is still continuing o solve the mysteries of jarosite precipitation and formation of passivation layer, which inhibits the copper recovery in a heap leaching of chalcopyrite by biological methods. Use of extreme thermophiles in chalcopyrite bioleaching is making a revolutionary movement to solve the mystery behind the scaling up the process, which could be possible to be solved in future. Bioleaching with other sulphide minerals together with Acid Mine Drainage (AMD) mitigation, which is a serious concern today, is taking is taking shape today in order to cater the needs of the mankind. However the biohydrometallurgy research seems to contribute to a greater extent in framing environmental friendly process with regards to hydrometallurgical operations in future and establish a developed technology to benefit human beings needs by its upcoming research and development. Keywords: Biomining, refractory gold, copper, chalcopyrite, bioleaching, nickel sulphide, biooxidation, acid mine drainage

Energy Efficient System For Galena Concentrate Processing

Article

Full-text available

Jan 2019

A new system of processing galena concentrates has been developed using non-blast method of lead reduction from its sulphides, by metallic iron. Excavated slag was used as flux agents to generate stackable sulfur-containing products, instead of sulfuric acid. Based on this relatively modern technical concept of extreme energy saving, the new system of concentrate processing has been developed. The system includes; an iron reduction and zinc sublimation system from excavated slag by soot-hydrogenic mixture, products of pyrolysis of natural gases, lead ousting in crude metal from its sulphides by metallic iron in the autogenous conditions of rotary mixer, regenerative utilization of thermic wastes of system and neutralization of SO2 gases by reagents obtained aboard (ZnO, Fe). The new system will reduce the effective specific equivalent fuel consumption by a factor of 3.77 and it will also expand the utilization factor of material waste products by a factor of 2.5-3 in comparison with the traditional methods of concentrate processing.

Recent progress in biohydrometallurgy and microbial characterisation

Article

Jun 2018
HYDROMETALLURGY

Since the discovery of microbiological metal dissolution, numerous biohydrometallurgical approaches have been developed to use microbially assisted aqueous extractive metallurgy for the recovery of metals from ores, concentrates, and recycled or residual materials. Biohydrometallurgy has helped to alleviate the challenges related to continually declining ore grades by transforming uneconomic ore resources to reserves. Engineering techniques used for biohydrometallurgy span from above ground reactor, vat, pond, heap and dump leaching to underground in situ leaching. Traditionally biohydrometallurgy has been applied to the bioleaching of base metals and uranium from sulfides and the biooxidation of sulfidic refractory gold ores and concentrates before cyanidation. More recently the interest in using bioleaching for oxide ore and waste processing, as well as extracting other commodities such as rare earth elements has been growing. Bioprospecting, adaptation, engineering and storing of microorganisms has increased the availability of suitable biocatalysts for biohydrometallurgical applications. Moreover, the advancement of microbial characterisation methods has increased the understanding of microbial communities and their capabilities in the processes. This paper reviews recent progress in biohydrometallurgy and microbial characterisation.

Metallurgical sludges, bio/leaching and heavy metals recovery (Zn, Cu)

Thesis

Full-text available

Dec 2015

Manivannan Sethurajan

This research was carried out in order to develop a technology to demonstrate the metallurgical residues as a potential secondary source for heavy metals (Cu and Zn). Three different (based on their age of generation and deposition) zinc leach residues (ZLR1, ZLR2 & ZLR3) and zinc purification residue (ZPR) were collected from a Zn-metallurgical industry located in Brazil. The characterization of ZLRs and ZPR were examined for their mineralogical, physico-chemical, bulk chemical features. Fractionation of heavy metals and liquid-solid partitioning with respect to pH were also determined. Geo-chemical modelling was done to understand the mechanisms affecting the mineral solubilities of these residues. Following the above, the residues were subjected to (bio) leachability tests to optimize the maximal extraction of heavy metals. Later, the recovery of Zn (ZLRs) and Cu (ZPR) from the polymetallic acidic leachates were investigated. Finally, hydrometallurgical flow charts for the selective recovery of Cu and Zn were proposed. The results reveal that the ZLRs contain significant concentration of Zn (2.5% to 5%), Pb (1.7% to 2.3%) and metals such as Mn, Cu, and Al in detectable fractions. The ZPRs contain high concentration of Cu (47%), Zn (28%), Cd (9%) and Pb (5%). Fractionation with acetic and nitric acid suggest that both the leach and purification residues are hazardous wastes, releasing higher concentration of Pb and Cd into the environment, than the permissible concentration suggested by U.S. EPA. Leaching of metals from the residues is highly pH dependent. Heavy metals leaching (Zn & Cu) is high at low pH and the release of metals was decreased with increase in pH. Sulfated and carbonated mineral phases were predicted to be the solubility controlling minerals. The leaching of Zn from ZLRs was highly influenced by temperature and acid concentration. The results of the optimization of leaching parameters state that more than 92%, 85% and 70% of zinc can be extracted from ZLR1, ZLR2 and ZLR3 by H2SO4 (1.5 M) leaching (at 80 °C for 6 hours with a pulp density 2%, while the agitation speed was maintained 250 rpm). The sulfuric acid leaching of ZLRs follows the shrinking core diffusion model. The activation energy required to leach zinc from the ZLR1, ZLR2 and ZLR were estimated to be 2.24 Kcal/mol, 6.63 Kcal/mol and 11.7 Kcal/mol respectively, by Arrhenius equation. Order of the reaction with respect to the sulfuric acid concentration was also determined as 0.2, 0.56, and 0.87 for ZLR1, ZLR2 and ZLR3, respectively. Selective precipitation of Zn (as sphalerite) from the leachates was achieved by the combination of hydroxide and sulfide precipitation. Biohydrometallurgy is also as effective as the chemical hydrometallurgy for the selective Zn recovery from the ZLRs. Cu leaching from ZPR was highly influenced by solid to liquid phase ratio and agitation speed, suggesting that the mass transfer depends on the diffusion. More than, more than 50%, 70% and 60% of the total Cd, Cu and Zn can be leached from ZPR by 1M H2SO4 with 2% pulp density continuously shaken at 450 rpm at 80 °C. Covellite was selectively recovered from the acid multi-metallic (Cd, Cu & Zn) leachates were investigated by optimizing the initial pH and Cu to sulfide ratio. In conclusion, these hazardous metallurgical residues can be seen as potential alternative resource for Zn and Cu. Not only the capital costs and environmental issues associated with the storage/disposal of these ZLRs & ZPR but also the gradual depletion of high grade sulfidic ores (for Zn and Cu) can be addressed. The study also leaves a perspective of investigating the leached ZLR & ZPR, for the selective leaching and recovery of Pb

Ulasan kaedah kitar semula sisa bateri

Article

Full-text available

Aug 2016

The generation of waste batteries is increasing due to the wide application and short life span of batteries. The heavy metals used inside a battery are highly toxic and can cause harm to humans and to the environment. However, if waste batteries are recovered properly through a recycling process, precious metals inside the batteries can be extracted. In general, there are three methods for recycling waste batteries, namely pyrometallurgy, hydrometallurgy and bio-hydrometallurgy. This article reviews and discusses the efficiency and effectiveness of these methods in recycling waste batteries. Based on the review, each recycling method has its specific characteristics. The hydrometallurgy method tends to be used for recycling Li-ion batteries while the pyrometallurgy method tends to eliminate plumbum in automotive waste batteries. In general, the hydrometallurgical method is commonly used for recycling batteries due to its shorter process and lower cost.

Biochemical Engineering Parameters for Hydrometallurgical Processes: Steps towards a Deeper Understanding

Article

Full-text available

Apr 2014
jmin

Increasing interest in biomining process and the demand for better performance of the process has led to a new insight toward the mining technologies. From an engineering point of view, the complex network of biochemical reactions encompassed in biomining would best be performed in reactors which allow a good control of the significant variables, resulting in a better performance. The subprocesses are in equilibrium when the rate of particular metal ion; for example, iron turnover between the mineral and the bacteria, is balanced. The primary focus is directed towards improved bioprocess kinetics of the first two subprocesses of chemical reaction of the metal ion with the mineral and later bacterial oxidation. These subprocesses are linked by the redox potential and controlled by maintenance of an adequate solids suspension, dilution rate, and uniform mixing which are optimised in bioreactors during mining operations. Rate equations based on redox potential such as ferric/ferrous-iron ratio have been used to describe the kinetics of these subprocesses. This paper reviews the basis of process design for biomining process with emphasis on engineering parameters. It is concluded that the better understanding of these engineering parameters will make biomining processes more robust and further help in establishing it as a promising and economically feasible option over other hydrometallurgical processes worldwide.

A Review of Approaches and Techniques Used in Aquatic Contaminated Sediments: Metal Removal and Stabilization by Chemical and Biotechnological Processes

Article

Jan 2015
J CLEAN PROD

The contamination of aquatic sediments with metals is a widespread environmental problem. Coastal aquatic ecosystems with low hydrodynamics need to be periodically dredged in order to maintain the navigation depth and facilitate sailing; consequently large volumes of contaminated sediments need to be managed. Conventional remediation strategies include in-place sediment remediation strategies (e.g. in situ-capping) and relocation actions; in particular, landfill disposal and dumping at sea are still widely applied. Both this options are becoming unsustainable, due to problems associated with contaminant transport pathways, the uncertainties about long-term stability under various environmental conditions, the limited space capacity, costs and environmental compatibility. Alternative approaches have received increased attention; treatment and reuse of contaminated sediments is politically encouraged, but its application is still very limited. Because of the potential human health and environmental impacts of contaminated sediment, different chemical treatments are conventionally applied for contaminated sediments before reuse in other environmental settings. Environmentally friendly techniques developed for soils and other environmental matrices have been investigated for applications with sediments. Biotechnological approaches are gaining increasing prominence in this field and they are often considered as a promising strategy for the eventual treatment of contaminated sediments. In this paper an overview of the main treatment strategies potentially available for sediment contaminated with metals is given, together with a brief overview of the issue associated with the problem of the sediment management.

Processing of Refractory Gold-Bearing Sulfide Concentrates: A Review

Article

Jul 2023

This review presents an updated data on various technologies for the processing of refractory gold-bearing sulfide concentrates. It primarily focuses on the hydrometallurgical treatment for sulfide mineral oxidation and gold extraction, including the use of bacteria, pressure oxidation, ultrafine grinding, and the Albion ProcessTM. The main operating plants that use hydrometallurgical technologies and their key characteristics are listed, along with schematics of primary processing routes. Besides, advantages and disadvantages of each technology are discussed, along with their cost comparisons.

Analysis and Characteristics of Thermal Springs in Kazakhstan

Chapter

Oct 2021

Hot springs are extensively distributed across the world, and the territory of Kazakhstan covered with folded and mountainous areas is no exception. They harbor plenty of microorganisms that can be the source of complex bioactive compounds. Although several microbiological studies on geothermal hot springs from different areas of the planet are available, there is limited information regarding the microbial diversity of similar ecosystems from Kazakhstan. This chapter provides information about thermal springs located in the territory of Kazakhstan as well as microbial diversity analyses of Zharkent hot spring. In Kazakhstan, thermal waters are widespread, which is due to the presence of large artesian basins with the immersion of water-bearing rocks to great depths, as well as the development of folded areas experiencing the impact of the latest tectogenesis. A survey of the available literature has revealed a considerable amount of information on the location of the springs, flow rates, temperature, chemical composition of the water and how the thermal spring has been used. All of these data have been tabulated by geographic areas of Kazakhstan and this tabular information for each geographic zone includes a summarized description of the geology and a map showing the situation of the thermal springs.

Thermoacidophiles for Bioleaching of Copper

Chapter

Oct 2021

Biohydrometallurgy is a modern, steadily developing alternative metal production technology based on the use of microorganisms and their metabolic products, such as ferric iron, sulfuric acid, etc. for the extraction of metals from ores. Microbiological processing of ores and concentrates has economic, technical and, most importantly, environmental advantages over traditional technologies. Heap leaching is successfully used for recovery of copper from a secondary mineral—chalcocite (Cu2S). However, the main world reserves of copper are found in the form of chalcopyrite (CuFeS2). Chalcopyrite is the most refractory mineral and undergoes chemical or biological oxidation at a very low rate. One of the most common ways to enhance copper extraction from chalcopyrite is the use of thermophiles. Besides, the intensity of biooxidation of sulfide minerals depends on the pH, redox potential, Fe²⁺/Fe³⁺ ratio, metals ion concentration and the microorganisms used. It was revealed that the mixed cultures and consortia of moderate thermophilic microorganisms were more efficient and stable in the oxidation of chalcopyrite than pure cultures. From this point of view, developing and optimizing microbial associations for use in commercial copper leaching systems remain an important challenge. In this paper bioleaching of chalcopyrite by pure and mixed cultures of moderate thermophilic bacteria S. thermosulfidooxidans and thermotolerant sulfur or iron oxidizing bacteria L. ferriphilum CC, as well as the influence of physicochemical factors on this process have been investigated.

Heavy Metal Resistance in Prokaryotes: Mechanism and Application

Chapter

Oct 2021

Metal-rich natural and artificial habitats are extreme environments for the development and evolution of unique microbial communities, which have adapted to the toxic levels of the metals. Diverse bacterial groups have developed abilities to deal with the toxic metals by bioaccumulation of the metal ions inside the cell actively or passively, extracellular precipitation, efflux of heavy metals outside to the microbial cell surface, biotransformation of toxic metals to less toxic forms, and metal adsorption on the cell wall. Metalophilic microbes are found in all bacterial and archaeal groups studied, but mostly appear among aerobic and facultative anaerobic chemoheterotrophic and chemolithoautotrophic microorganisms of the Bacillus, Pseudomonas, Staphylococcus, Actinobacteria, Cuprividus, Acidobacterium, Acidithiobacillus, Thiobacillus, Ferroplasma, and Sulfolobus genera. The phenomenon of microbial heavy metal resistance has fundamental importance and is particularly relevant in microbial ecology, especially in connection with the roles of microbes in biogeochemical cycling of heavy metals and in the bioremediation of metal-contaminated environments. The heavy metal resistance mechanisms and different applications of metal resistant/metalophilic bacteria and archaea have been expounded deeply in this chapter.

Biohydrometallurgy as an environmentally friendly approach in metals recovery from electrical waste: A review

Article

Full-text available

Jan 2020
WASTE MANAGE RES

Nowadays, large amount of municipal solid waste is because of electrical scraps (i.e. waste electrical and electronic equipment) that contain large quantities of electrical conductive metals like copper and gold. Recovery of these metals decreases the environmental effects of waste electrical and electronic equipment (also called E-waste) disposal, and as a result, the extracted metals can be used for future industrial purposes. Several studies reported in this review, demonstrated that the biohydrometallurgical processes were successful in efficient extraction of metals from electrical and electronic wastes. The main advantages of biohydrometallurgy are lower operation cost, less energy input, skilled labour, and also less environmental effect in comparison with pyro-metallurgical and hydrometallurgical processes. This study concentrated on fundamentals and technical aspects of biohydrometallurgy. Some points of drawbacks and research directions to develop the process in the future are highlighted in brief.

Technologies for processing of Barite: A conceptual review for use in Nigeria

Article

Full-text available

Jan 2024

Technologies for processing of barite: A Conceptual review for use in Nigeria Articles in Press Document Type: Review Article

Article

Jul 2024

The authors reviewed the global technologies for baryte processing, and highlighted its potential application in meeting global standards with emphasis on Nigeria. Baryte (BaSO4) an exceptional industrial mineral has various applications based mostly on its physical properties. Over 80% of the world's baryte is applied as a weighting agent in drilling fluids. Nigeria has an estimated reserve of over 20 million metric tons .of baryte ore scattered in different parts of the country, yet loses over ₦5billion annually in foreign exchange to the importation of baryte by the oil and gas companies (IOC) operating in the country. Presently, the total national demand for barytes in Nigeria is estimated at 10,000,000 ton per annum. The IOC's import baryte, on the grounds that the locally produced baryte has lower quality compared to the imported baryte. The Nigerian Content Development and Monitoring Board (NCDMB) has currently approved the implementation of a set of measures geared towards enforcing a ban on the use of imported baryte and drilling fluids in the Nigerian Oil and Gas Industry in line with the provisions and aspirations of this Guideline and the NOGICD Act of 2010. Such measures are design to bring about an optimal production and huge patronage of locally produced baryte in oil and gas operations within Nigeria.

Biorecovery of Critical and Precious Metals

Chapter

Dec 2023

Disposal of electronic waste (e-waste) has increased many folds post-Covid 2019 (TBRC 2022). E-waste can be an alternate ore to leach out precious metals as compared to conventional techniques, but only a few regions like Europe (42% recycling rate) and Asia (12% recycling rate) are accountable for effective recycling at the global scale; others majorly follow unsafe strategies to recycle e-waste (Cui and Zhang 2008), releasing hazardous contents into the environment and leading to many complications (Loganathan and Masunaga 2015). This chapter gives insights on various methods used for leaching metals from e-waste, their limitations, and biorecovery using microorganisms, as an alternative strategy to extract valuable metals such as gold, copper, palladium, silver, iron, and platinum. Mechanisms of microbial leaching with examples of bacteria used are also discussed. Interventions of biotechnological approaches, like developing new strains with high microbial leaching efficiency, are also suggested for sustainable development.

Chemical and Microbial Leaching of Valuable Metals from PCBs and Tantalum Capacitors of Spent Mobile Phones

Article

Full-text available

Aug 2022
Int J Environ Res Publ Health

We compared chemical and microbial leaching for multi-metal extraction from printed circuit boards (PCBs) and tantalum capacitor scrap. A mixed consortium of acidophiles and heterotrophic fungal strains were used in the experiments and compared to chemical leaching using specific acids (sulfuric, citric and oxalic acids). Under optimum conditions, 100% extraction efficiency of Cu, and nearly 85% of Zn, Fe, Al and Ni were achieved from PCB and tantalum capacitor scrap samples using sulfuric acid. The mixed consortium of acidophiles successfully mobilized, Ni and Cu (99% and 96%, respectively) while Fe, Zn, Al and Mn reached an extraction yield of 89, 77, 70 and 43%, respectively, from the PCB samples. For the tantalum capacitor samples, acidophiles mobilized 92% Cu, 88% Ni, 78% Fe, 77% Al, 70% Zn and 57% Mn. Metal mobilization from PCBs and tantalum capacitor scrap by A. niger filtrate showed efficient solubilization of Cu, Fe, Al, Mn, Ni, Pb and Zn at an efficiency of 52, 29, 75, 5, 61, 21 and 35% from PCB samples and 61, 25, 69, 23, 68, 15 and 45% from tantalum capacitor samples, respectively. Microbial leaching proved viable as a method to extract base metals but was less specific for tantalum and precious metals in electronic waste. The implications of these results for further processing of waste electronic and electrical equipment (WEEE) are considered in potential hybrid treatment strategies.

Acidophilic chemolithotrophic microorganisms: prospects for use in biohydrometallurgy and microbial fuel cells

Article

Full-text available

Apr 2021

Acidophilic chemolithotrophic microorganisms are used in biohydrometallurgy for the extraction of metals from sulphide ores. Some types of microorganisms belonging to this group are capable of generating electricity under certain conditions. This circumstance determined a recent upsurge of research interest in their use in biofuel cells. Under a constant supply of the substrate to the bioelectrochemical system, acidophilic chemolithotrophic microorganisms are capable of producing electricity for a prolonged period of time. The use of extremophiles in microbial fuel cells is of particular interest, since these microorganisms can serve as bioelectrocatalysts at extreme pH, salinity and temperature, while the vast majority of microorganisms are unable to survive under these conditions. Therefore, selection of optimal conditions and approaches to controlling the work of acidophilic chemolithotrophic microorganisms in such fuel cells is of particular importance. On this basis, a technology for the simulteneous bioleaching of metals from poor ores and the generation of electricity can be developed. Biofuel cells operating at low pH values using acidophilic chemolithotrophic microorganisms are yet to be investigated. The number of studies on acidophilic electroactive microorganisms is very limited. In this regard, the purpose of this review was to consider the prospects for the use of acidophilic chemolithotrophic microorganisms as bioagents in microbial fuel cells. The reviewed publications demonstrate that chemolithotrophic microorganisms can act as both anodic (metal-reducing, sulphur-oxidizing microorganisms) and cathodic (metal-oxidizing prokaryotes, sulfate reducers) highly efficient bioagents capable of using mining wastes as substrates.

RNA transcript response by an Acidithiobacillus spp. mixed culture reveals adaptations to growth on arsenopyrite

Article

Full-text available

Feb 2021
EXTREMOPHILES

Biooxidation of gold-bearing refractory mineral ores such as arsenopyrite (FeAsS) in stirred tanks produces solutions containing highly toxic arsenic concentrations. In this study, ferrous iron and inorganic sulfur-oxidizing Acidithiobacillus strain IBUN Ppt12 most similar to Acidithiobacillus ferrianus and inorganic sulfur compound oxidizing Acidithiobacillus sp. IBUNS3 were grown in co-culture during biooxidation of refractory FeAsS. Total RNA was extracted and sequenced from the planktonic cells to reveal genes with different transcript counts involved in the response to FeAsS containing medium. The co-culture’s response to arsenic release during biooxidation included the ars operon genes that were independently regulated according to the arsenopyrite concentration. Additionally, increased mRNA transcript counts were identified for transmembrane ion transport proteins, stress response mechanisms, accumulation of inorganic polyphosphates, urea catabolic processes, and tryptophan biosynthesis. Acidithiobacillus spp. RNA transcripts also included those encoding the Rus and PetI proteins involved in ferrous iron oxidation and gene clusters annotated as encoding inorganic sulfur compound metabolism enzymes. Finally, mRNA counts of genes related to DNA methylation, management of oxidative stress, chemotaxis, and motility during biooxidation were decreased compared to cells growing without mineral. The results provide insights into the adaptation of Acidithiobacillus spp. to growth during biooxidation of arsenic-bearing sulfides.

Chemical Leaching of Inactive Gold Mine Tailings as a Secondary Source of Cobalt and Nickel—A Preliminary Case Study

Chapter

Feb 2021

Tailings from inactive gold mines, that are not yet successfully restored (generation of As- and Co-contaminated neutral mine drainage), represent a promising secondary source of strategic metals including Co and Ni. Three different mine tailings (sites A, B and C) from CobaltCobalt Mining Camp were collected and characterized. Preliminary chemical leachingLeaching tests were conducted with inorganic acids (HCl, H2SO4 and HNO3) to solubilize Co and Ni at different concentrations (0.01–0.5 N). The influence of the number of the leachingLeaching steps on the recovery of Co and Ni was also evaluated. Promising concentrations of Co (0.7%) and Ni (0.3%) were reported in tailings from site A, while lower concentrations were measured in tailings from sites B and C (0.02–0.1%), requiring pre-concentration steps (not tested in this preliminary study) before leachingLeaching to reduce operating costs. More than 85% of both Co and Ni were solubilized from tailings from site A after only 30 min using H2SO4 (0.25 N) at room temperature. Lower efficiencies (36–62%) were observed for tailings from sites B and C, which can be partially explained by the higher amounts of acid-consuming minerals present in the gangue. Additional experiments are required to better understand the mechanisms involved in Co and Ni solubilization and to optimize operating conditions in terms of Co and Ni recovery.

Phosphoric acid purification sludge: Potential in heavy metals and rare earth elements

Article

Jan 2018
WASTE MANAGE

The present study was carried out to show the potential in heavy metals (HM) and the rare earth elements (REE) which presents the residues of phosphoric-acid(PA) purification. Three different cadmiferous solid residues (according to the nature of the purification process of the PA: BG, BC and BS) were collected from an industrial site located in the south of Tunisia. The mineralogical study showed the predominance of anhydrite, accompanied by quartz, malladrite; calcium sulfate hemihydrate and fluorapophyllite. The microanalysis showed (i) the association of cadmium and zinc, (ii) as well as the presence of associated REEs. The chemical analysis showed that (i) the calcium sulfate concentrations are majority in samples BS, BG and BC (44, 34 and 44%, respectively), (ii) significant concentrations of phosphoric acid (28, 18 and 21% P2O5, respectively), (iii) the HM: Cd, Zn, Cr, Ni, V, Cu, Pb, Co, Mo, Mn and U have proportion in the order of 0.1%. The concentrations of Cd, Zn and Cr are respectively in the order of: 230, 149 and 189 mg/kg for BS, 346, 243 and 153 mg/kg for BG and 183, 129 and 440 mg/kg for BC and (iv) the REEs: La, Ce, Nd, Eu, Y et Yb present considerable mass percentages able to reach 0.2%. A series of extraction tests was led on the cadmiferous sludges to evaluate the rates of HM (Cd, Zn) and REE dissolution, using two solvents (deionized water (DW) and aqueous sodium based alkaline metal solution). The results showed that the dissolution rates of Cd and Zn are respectively in the order of (12–29% and 41–45% for DW; 67–86% and 83–93% for Na2SO4 solution). The extractability of HM and REE is strongly influenced by pH, solvent nature and mineral load in the cadmiferous sludges. The water-soluble metals represent a significant mobile fraction, making the toxic elements more sensitive to mobilization processes, such as leaching and erosion. Whereas, the metals extractable by the Na2SO4 solution represent a very important exchangeable and “co-crystallization” fraction, which reflects the bioavailability of these metals.

A Comparative Assessment on the Effect of Different Supplemental Iron Sources on the Bio-dissolution of Zn, Pb, Cd, and As from a High-grade Zn–Pb Ore

Article

Apr 2019
MINER METALL PROC

The present study investigates the influence of ferrous iron (as FeSO4) and ferric iron (as Fe2 (SO4)3), and pyrite (FeS2) on the ability of bacterial leaching of a high-grade sulfide Zn–Pb ore. In this regard, shake flask experiments were carried out at 5% (w/v) pulp density of the ore sample (having 40.7% Zn and 12.4% Pb initial metal content) using a consortium of mesophilic iron and sulfur-oxidizing acidophiles. A concentration of 0.04 mol/L of ferric iron in the leaching media was found to be optimum for zinc extraction without affecting growth of the microorganisms. Under this concentration, the dissolution of Zn, Pb, Cd, and As was found to be 57%, 0.2%, 0.03%, and 9.9% in 25 days. Using ferrous iron in the media, 0.16 mol/L of Fe²⁺ was found to be the optimum concentration for efficient bacterial growth and metal dissolution (54.6% Zn, 0.08% Pb, 0.03% Cd, and 10.2% As) from the sample in 25 days. On the other hand, using pyrite as the source of energy for bacterial growth, an initial 12-day lag period was observed when compared to the effect of ferrous iron in the media. Under the optimum concentration (test with 0.24 mol/L iron in the form of pyrite), the dissolution of Zn, Pb, Cd, and As was found to be 39.8%, 0.1%, 0.03%, and 10% in 25 days. The surface chemistry analysis indicated formation of a sulfur layer over the particle surface that hindered reagent diffusion and affected metal recovery through bioleaching.

UV-Irradiated Strain of Acidithiobacillus ferrooxidans Improved Copper Bioleaching in Chalcopyrite

Article

Full-text available

May 2018

Bioleaching is a process that uses microorganisms to perform dissolution of sulfide minerals. Actually, most copper is found as chalcopyrite ore, which is the most abundant form of copper sulfide, but it is recalcitrant to dissolution. The biggest challenge for biohydrometalurgy is the microorganisms involved in it. This study aims to obtain mutants of Acidithiobacillus ferrooxidans by using a methodology that uses classical genetic tools [ultraviolet radiation (UV)], and evaluates its efficiency by using mathematical tools (mathematical modeling and desirability). The mutant strains were evaluated considering their kinetics of initial velocity of ferrous ions oxidation. The selective pressure of UV caused different profiles in the consumption kinetics of strains' energy sources. The cells with higher consumption kinetics than the wild strain were submitted to shake flask experiments in the presence of chalcopyrite and evaluated by mathematical models. The cell culture irradiated for 1 minute outperformed the wild strain in copper solubilization according to the desirability parameters. The mathematical tools allowed confirming that the UV protocol improved the bioleaching capability of Acidithiobacillus ferrooxidans.

Copper recycle from sulfide tailings using combined leaching of ammonia solution and alkaline bacteria

Article

Apr 2018
J CLEAN PROD

Simulating the main stages of chalcopyrite leaching and bioleaching in ferrous ions solution: An electrochemical impedance study with a modified carbon paste electrode

Article

Jun 2016
MINER ENG

In this work, we present an electrochemical study using a carbon paste electrode modified with chalcopyrite (CuFeS2) in solution A of T&K medium with different ferrous ion concentrations, in the absence and presence of the bacterium Acidithiobacillus ferrooxidans. The aim was to evaluate the influence of ferrous ions and bacteria on the electrochemical behavior of chalcopyrite. Electrochemical impedance spectroscopy (EIS) was used to investigate the processes occurring at the electrode/solution interface in the different systems, considering the charge transfer reactions involving chalcopyrite and ferrous ions, the presence of a multicomponent layer, and diffusion. The main changes in the chalcopyrite response occurred before 67 h or 43 h of immersion, in the absence or presence of ferrous ions, respectively, indicating that the surface oxide layer present on chalcopyrite was dissolved faster in the presence of ferrous ions. The addition of bacteria decreased the charge transfer reaction resistance, especially when ferrous ions were present. In the presence of Fe2+, sulfur and jarosite were detected in the solid residues after leaching, while only jarosite was detected in the bioleaching experiment. The results suggested that ferrous ions accelerated the dissolution of chalcopyrite, and that overlayers including biofilms did not halt chalcopyrite dissolution, indicating that there was no passivation.

Simulating the main stages of chalcopyrite leaching and bioleaching in ferrous ions solution: an electrochemical impedance study with a modified carbon paste electrode

Article

Mar 2016
MINER ENG

Denise Bevilaqua

In this work, we present an electrochemical study using a carbon paste electrode modified with chalcopy-rite (CuFeS 2) in solution A of T&K medium with different ferrous ion concentrations, in the absence and presence of the bacterium Acidithiobacillus ferrooxidans. The aim was to evaluate the influence of ferrous ions and bacteria on the electrochemical behavior of chalcopyrite. Electrochemical impedance spectroscopy (EIS) was used to investigate the processes occurring at the electrode/solution interface in the different systems, considering the charge transfer reactions involving chalcopyrite and ferrous ions, the presence of a multicomponent layer, and diffusion. The main changes in the chalcopyrite response occurred before 67 h or 43 h of immersion, in the absence or presence of ferrous ions, respectively, indicating that the surface oxide layer present on chalcopyrite was dissolved faster in the presence of ferrous ions. The addition of bacteria decreased the charge transfer reaction resistance, especially when ferrous ions were present. In the presence of Fe 2+ , sulfur and jarosite were detected in the solid residues after leaching, while only jarosite was detected in the bioleaching experiment. The results suggested that ferrous ions accelerated the dissolution of chalcopyrite, and that overlayers including biofilms did not halt chalcopyrite dissolution, indicating that there was no passivation.

Biohydrometallurgy in Turkish gold mining: First shake flask and bioreactor studies

Article

Jun 2013
MINER ENG

The first laboratory tests on biooxidation and cyanidation of gold ores in Turkey were carried out using samples of the Copler Gold Mine. Over a 3 year R&D test period, mixed bacterial/archaeal cultures improved biooxidation of the Copler ore. The highest sulphide oxidation of 87.35% over 432 h was achieved in shake flasks in the presence of the mixed culture (MODM: Sulfolobus acidophilus and Sulfolobus thermosulfidooxidans). Bioreactor tests resulted in greater dissolution rates for iron and arsenic than did shake-flask tests, which led to a greater extent of sulphide oxidation within a shorter period of time. The maximum sulphide oxidation in the bioreactor tests was 97.79% after 240 h when the EXTM (Acidianus brierleyi and Sulfolobus metallicus) mixed culture was used. After the biooxidation experiments with solids contents of 10% and 20% (w/v), the gold recovery from the oxidised ore was lower than that achieved in the presence of 5% solids (w/v) because the extent of sulphide oxidation was reduced as the pulp density increased. A strong correlation between the sulphide oxidation and gold recovery was also established. The highest gold recovery of 94.48% was achieved during cyanidation from the biooxidised ore produced from the experiment conducted using the EXTM mixed culture.

From E-Waste to High-Value Materials: Sustainable Synthesis of Metal, Metal Oxide, and MOF Nanoparticles from Waste Printed Circuit Boards

Article

Full-text available

Dec 2023

The exponential growth of electronic waste (e-waste) has raised significant environmental concerns, with projections indicating a surge to 74.7 million metric tons of e-waste generated by 2030. Waste printed circuit boards (WPCBs), constituting approximately 10% of all e-waste, are particularly intriguing due to their high content of valuable metals and rare earth elements. However, the presence of hazardous elements necessitates sustainable recycling strategies. This review explores innovative approaches to sustainable metal nanoparticle synthesis from WPCBs. Efficient metal recovery from WPCBs begins with disassembly and the utilization of advanced equipment for optimal separation. Various pretreatment techniques, including selective leaching and magnetic separation, enhance metal recovery efficiency. Green recovery systems such as biohydrometallurgy offer eco-friendly alternatives, with high selectivity. Converting metal ions into nanoparticles involves concentration and transformation methods like chemical precipitation, electrowinning, and dialysis. These methods are vital for transforming recovered metal ions into valuable nanoparticles, promoting sustainable resource utilization and eco-friendly e-waste recycling. Sustainable green synthesis methods utilizing natural sources, including microorganisms and plants, are discussed, with a focus on their applications in producing well-defined nanoparticles. Nanoparticles derived from WPCBs find valuable applications in drug delivery, microelectronics, antimicrobial materials, environmental remediation, diagnostics, catalysis, agriculture, etc. They contribute to eco-friendly wastewater treatment, photocatalysis, protective coatings, and biomedicine. The important implications of this review lie in its identification of sustainable metal nanoparticle synthesis from WPCBs as a pivotal solution to e-waste environmental concerns, paving the way for eco-friendly recycling practices and the supply of valuable materials for diverse industrial applications.

New insights into oxidative-reductive leaching of chalcopyrite concentrate using a central composite factorial design

Article

Apr 2022
MINER ENG

A response surface capable of describing the extraction of copper with high statistical confidence (R² = 0.9973) was obtained using a central composite factorial design (CCD). The parameters used were the initial concentration of Fe²⁺ ions ([Fe²⁺]i) and pulp density (ρpulp). The results evidenced that chalcopyrite leaching was strongly influenced by the solution potential, which was a function of the [Fe²⁺]i:ρpulp ratio. The optimal parameters obtained for maximizing the copper extraction percentage were those that satisfied a [Fe²⁺]i:ρpulp ratio of ≈ 80 (mmol L⁻¹/%), in the range from 200 to 398 mmol L⁻¹ of Fe²⁺. The [Fe²⁺]i:ρpulp ratio of ≈ 80 allowed an optimal range of solution potential for most of the experiment duration, which provided a copper extraction of 91 ± 3% in 28 days, under moderate conditions. The leaching residues were analyzed by inductively coupled plasma optical emission spectrometry (ICP-OES), X-ray diffractometry (XRD), and scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDS). The mathematical model, together with the calculated Nernst potentials of the main oxidation–reduction reactions of chalcopyrite, indicated that the copper extraction was governed by experimental conditions that favored chalcopyrite reduction coupled with the chalcocite oxidation reaction. Hypotheses to explain the reasons for certain experimental conditions that could increase or decrease chalcopyrite dissolution were formulated and are extensively discussed. These findings contribute to the development of new routes for the processing of chalcopyrite mineral.

Leaching Behavior of Heavy Metals from an Ore Containing High Concentration as Utilizing Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans

Article

Apr 2021

Bio-oxidation of Gold from Refractory Sulfide Ores: A Journey Ahead

Article

Sep 2021

Biomining through bioleaching and bio-oxidation aims at recovering desired metals at the required specifications with lower environmental impact and costs from ores and waste streams. Research and developments related to the process technology and efficient implementation of this approach are advanced worldwide. Small particles of gold, a metal of higher interest, are mostly found in a matrix of sulfide-based minerals and not affordably recovered with conventional approaches encompassing cyanidation, pyrometallurgy, extreme heating (roasting), oxidation of ore samples at high pressure. Recently, advances in bio-oxidation have been made in addressing scientific and technical challenges that arise during the pilot and demonstration scales in the operations units in bioreactors and heaps. Through including high-throughput bacterial growth data and better process knowledge of the extraction and recovery approaches, bio-oxidation becomes more economically feasible and efficient. More advancements are necessary to evaluate the wide range of mineralogical structure of ores being processed, microbiological, and physicochemical that can significantly influence the bio-oxidation reaction within the different types of reactors (heap and continuously stirred tank reactors), the microbial interactions between metal and microbes, geographical localizations of the mining sector, economic as well as data interpretation by using advanced artificial intelligence methods toward obtaining optimized operation and efficiency. This review covers important advances and developments and associated industrial and academic research and challenges from the past few years for gold bio-oxidation.

Isolation of Arsenic Resistant and Arsenopyrite Oxidizing Acidithiobacillus Species from pH Neutral Colombian Mine Effluents

Article

May 2020

Inactive mines provide a great source of bacterial diversity for studying acidophilic communities and their biotechnological applications, but prospecting of these anthropogenic environments in Colombia has been limited. Conventional microbiological methods were used to isolate acidophilic bacterial strains from effluents emanating from the Colombian gold mine ‘El Zancudo’ (Titiribí, Antioquia). Despite the drainage waters having circumneutral pH, all of the isolated strains were phylogenetically related to the extreme acidophile Acidithiobacillus genus. However, based upon 16S rRNA gene sequences the mesophilic sulfur-oxidizing indigenous strains could not be assigned to a species. Pure cultures were selected by screening in medium with soluble inorganic arsenic (III) and their mineral-oxidative activity was evaluated at 30 °C in Erlenmeyer flasks with arsenopyrite ore under rotary shaking conditions. The indigenous strains were able to catalyze arsenopyrite oxidation in a mixed culture with a pulp density of 10%, maintaining their growth in the presence of >80 mM leached arsenic. This research provides information regarding the isolation of arsenic resistant bacterial communities from neutral effluents from El Zancudo mine and the possibility of the isolated strains to be useful in the biooxidation pretreatment of refractory gold-bearing arsenopyrite ores and concentrates.

Mesophilic bioleaching performance of copper, cobalt and nickel with emphasis on complex orebodies of the Democratic Republic of Congo: a review of dynamic interactions between solids loading, microbiota activity and growth

Article

Nov 2019

The copper, cobalt and nickel ores are still currently mined in the world. Its complex mineralogy creates extraction challenges by means of conventional metallurgical methods. Meanwhile, dealing with mesophilic strains in leaching process requires a compromise between solid loading and microbiota activity and growth. That is why, the influence of solid loading with fine or coarse particulates, the cell disturbance during the metal–microbes interactions depending upon the influence of gangue nature as well as metallic ions concentration on bacterial tolerance and the chemical and biological pathways involved in bioleaching mechanism of complex ores are summarised in detail in this paper. The current trends in mechanism research and diverse discovered set of microbiota and bacterial population coupled with bacterial adaptation methods contribute to optimise and improve the metals leaching performance and knowledge. In addition, the different existing complex mineralogical structures elaborate a main indirect mechanism with two different transitory mechanisms, before metal is converted into metal sulphate as wealthily explained in this comprehensive review. More data for cost analysis concomitant with extraction efficiency of metals using mesophilic bioleaching process are needed. However, it does not mean that other options are excluded in order to set a bio-hydrometallurgical chain. In fact, to consider also the concentration and purification of the pregnant leaching solution via phase separation and solvent extraction will be helpful. This obeys to the idea of option trees, where possible options are then systematically gaged with respect to critical criteria.

Biotechnology for Environmentally Benign Gold Production

Chapter

Oct 2019

K. A. Natarajan

Biotechnology relevant to gold exploration, mining, recovery, and waste disposal is illustrated with respect to microbiological aspects of gold mineralization, Biooxidation of refractory sulfide ores and concentrates, cyanide-free gold dissolution, and biodegradation of cyanide containing effluents. Current industrial status of technological innovations in the bioreactor processing and heap bioleaching of refractory sulfide ores and concentrates are discussed. Biodetoxification and degradation of cyanides in waste tailings and waters are critically analyzed with examples from industrial practice. Prospects for direct biodissolution of gold are brought out. Recovery of gold from spent leach cyanide solutions and electronics wastes is examined. Bright future prospects for Biotechnology in gold exploration, mining, extraction, and waste disposal are emphasized.

Leaching and Recovery of Metals

Chapter

Oct 2017

Sludges, dusts, residues and other wastes originating from ferrous and non-ferrous metallic industries pose a serious environmental threat, if not disposed properly. Disposal of these wastes is expensive and remediation is a necessary step to be implemented to control the adverse environmental effects if disposal is done improperly. Since the past couple of decades, the world’s high-grade metal reserves have been depleted considerably, but the demand for metals in day-to-day life in this electronic era is growing rapidly. The depletion of high-grade ores urges the mineral industry to look for alternative resources for metal extraction. Sludges, dusts, and other wastes generated by the metallurgical industries are interesting options as they still contain significant amounts of valuable base and heavy metals, sometimes even precious metals like gold and silver and also rare earth elements, depending on the nature of the mining site and composition of the primary ores used. This chapter overviews various hydrometallurgical and bio-hydrometallurgical leaching processes for the extraction of metals from these wastes. Different strategies of metal recovery such as solvent-extraction, electrowinning, bio/chemical sorption and bio/chemical precipitation from the wastes generated by various ferrous and non-ferrous metallic industries are overviewed.

A review of sulfide minerals microbially assisted leaching in stirred tank reactors

Article

Full-text available

Apr 2017
INT BIODETER BIODEGR

-------Abstract------------------ Compared to conventional extractive techniques, bacterial assisted leaching, also called “biomining” is an eco-friendly technology that provides improved metal/solid separations. These separations are enhanced by the synergistic activities of astonishingly diverse groups of microorganisms, which lead to an extraction process with low energy consumption, low capital investment and low impact on the environment. Recently, biomining has received great attention in a variety of niche areas, especially in the mineral industries and solid industrial waste materials (e.g. galvanic sludge, sewage sludge, fly ash, electronic waste, spent petrochemical catalysts, medical waste, spent batteries, waste slag) where the metals values are low, or where the presence of certain elements would lead to smelter damage, or where environmental considerations favor biological treatments options. It allows the recovery of metal from low-grade sulfide ores and concentrates that cannot be processed economically by conventional techniques, as well as the production of concentrated metal salt solutions, which could be recycled. Bacterial assisted leaching processes are based on the ability of certain microorganisms to solubilize/or expose the metals contained in the ores and concentrates by direct oxidation, or through indirect chemical oxidation instigated by the corrosive metabolic by-products generated by an electrochemical option, or a combination of both of these. The valuable metals in solution can be recovered using conventional hydrometallurgical techniques. If the material of interest constitutes part of or is in the pre-treated residue then it can be further processed for metal recovery. The majority of microorganisms involved in bacterial assisted leaching processes are chemolithotrophs. Carbon dioxide (CO2) and oxygen (O2) are essential nutrients that are used by microorganisms for their growth, maintenance, metabolite production, and survival. This literature review aims to provide a fundamental understanding of the various mechanisms involved in microbial leaching of sulfide minerals and provide a brief look at the various factors affecting this process. Special attention is focused on the mass transfer rates in the gas phase and how they exert a pivotal role in microbially assisted leaching of sulfide minerals. Also reviewed are the major parameters that can affect gas phase mass transfer, with particular emphasis on how it is related to the efficiency of bacterial assisted leaching. ----------Keywords-------- Biomining; Bioleaching; Biooxidation; Sulfide minerals; Microorganisms; Gas transfer ---------------------------------- ----> This review has been written and prepared jointly by Dr. Akrama Mahmoud and Professor Andrew Hoadley (Monash University, Australia). We would like to thank all authors of the papers given in the reference list for obtaining a great deal of useful information on biomining processes, and thus in helping to prepare this paper. The principal author (Dr. Akrama Mahmoud) would like to thank Jean Michel Sorbet and Olivier Gelade for their kind technical assistance and help. Finally, Dr. Akrama Mahmoud dedicate this paper to his parents for their love and sacrifices.† For more information, Please go to: A review of sulfide minerals microbially assisted leaching in stirred tank reactors. International Biodeterioration & Biodegradation Volume 119, April 2017, Pages 118-146. http://www.sciencedirect.com/science/article/pii/S0964830516304097. https://doi.org/10.1016/j.ibiod.2016.09.015

Study of Acidithiobacillus ferrooxidans and enzymatic bio-Fenton Process Mediated Corrosion of Copper-Nickel Alloy

Article

Mar 2016

This study presents the corrosion behavior of the copper-nickel (Cu-Ni) alloy in the presence of Acidithiobacillus ferrooxidans (At. ferrooxidans) and glucose oxidase enzyme. Results show that in both the cases ferric ions played important role in weight loss and thereby to carry out the corrosion of Cu-Ni alloy. A corrosion rate of 0.6 (±0.008), 2.11 (±0.05) and 3.69 (±0.26) mm/year was obtained in 72 h using 9K medium with ferrous sulfate, At. ferrooxidans culture supernatant and At. ferroxidans cells respectively. A corrosion rate of 0.7 (±0.006) and 0.08 (±0.002) mm/year was obtained in 72 h using glucose oxidase enzyme and hydrogen peroxide (H2O2) solution respectively. Scanning electron microscopy (SEM) and optical profilometer (OP) were used to document surface appearance and arithmetic average surface roughness (Ra) respectively. The change in surface appearance was clearly visible in SEM micrographs and it showed that variable extent of corrosion was caused by 9K medium with ferrous sulfate, glucose oxidase and At. ferrooxidans cells. A Ra of 174.78 nm was observed for the control work-piece. The change in Ra was observed with the treatment of the Cu-Ni alloy using various systems. The Ra for 9K medium with ferrous sulfate, glucose oxidase and At. ferrooxidans cells was 374.54, 607.32 and 799.48 nm respectively after 24 h. These results suggest that At. ferrooxidans cells were responsible for more corrosion of Cu-Ni alloy than other systems used.

Enhanced Column Bioleaching of Copper Sulfides by Forced Aeration

Article

Nov 2015

To assess the effects of forced aeration on leaching dynamics of sulfides, five sets of column bioleaching of copper sulfides using Acidithiobacillus ferrooxidans were conducted when the aeration rates ranged from 0 to 150 L/h. The experimental results show that forced aeration can ameliorate the porosity and flow rates throughout the heap, and improve the bacterial concentration and oxidative ability. Forced aeration at the column bottom can enhance the interactions of air, flow and particles, and then facilitate the heap porosity and connectivity. The oxidant Fe ³⁺ concentrations are proportional to the aeration rates, and lead to an accelerating dissolution rate of sulfides. In addition, the bacterial concentration, oxidative ability and Fe ³⁺ concentration are susceptible to aeration rates, and the forced aeration remarkably enhances the bioleaching when aeration rates are higher than 60 L/h compare to those with none or slight aeration.

Environmental aspects of metals removal from waters and gold recovery

Article

Sep 2015
AICHE J

Mining and metals processing are not invisible activities and are heavy industries, which require energy, water, chemicals, and land area. Recently more emphasis is given to environmental and societal aspects in mining and processing. Development of good practices with improved resource efficiency, new recovery methods and sustainability thinking are increasingly required. This work shows pH titration method for acid mine drainage (AMD) water incorporated with aqueous thermodynamic model for selective metals precipitation from complex solution. Also two examples on gold recovery methods from aqueous streams are shown: biosorption using fungal matter and solvent extraction using a task-specific ionic liquid. By understanding chemical thermodynamics and natural phenomena, there is a better chance of developing solutions for environmental problems and new industrial processes. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2739–2748, 2015

Fungal jarosite biomineralization in Río Tinto

Article

Oct 2014
RES MICROBIOL

Río Tinto is an extreme environment located at the core of the Iberian Pyrite Belt (IPB). It is an unusual ecosystem due to its size, constant acidic pH, high concentration of heavy metals and a high level of microbial diversity, mainly eukaryotic. Recently it was described the biomineralization of jarosite by Purpureocillium lilacinum, an acidic filamentous fungi isolated from the banks of the Tinto basin. In this study we further investigate the specificity of jarosite biomineralization by this fungi and its importance in the generation of jarosite in the Río Tinto basin. Our results clearly show that the ratio of the redox pairs and the Fe3+ concentration is important to achieve a specific biomineralization of jarosite. The amount of nucleation sites also seems to be critical, although the presence of nucleation sites by itself is not sufficient to precipitate jarosite. There is a good correlation between the sampling sites along the river in which hydronium-jarosite has been identified and the presence of P. lilacinum.

Bio-Oxidation and Biocyanidation of Refractory Mineral Ores for Gold Extraction: A Review

Article

Full-text available

Oct 2014

Bioleaching has emerged as a green technology with promising applications in mining industries in the context of recovery of precious metals from mineral ores. The authors synthesize the current knowledge available in the bioleaching of gold (Au) from ores by bringing together historical developments and recent endeavors. In addition, the role of the microbial community in the bio-oxidation of refractory ores for removal of base metal impurities and in the recovery of Au based on biocyanidation is reviewed. They also address the future research directions in the bioleaching of Au in order to make further advances toward practical industrial applications.

Bench-scale batch bioleaching of spent petroleum catalyst using mesophilic iron and sulfur oxidizing acidophiles

Article

May 2013

Microbial leaching of a petroleum spent catalyst was carried out using mixed mesophilic iron and sulfur oxidizing acidophiles. Bench-scale batch stirred tank reactors with a working volume of 1 L were used in this study at 35 °C. The pulp density considered for the study was 10% (w/v), while the particle size of the spent catalyst was varied by 45–106, 106–212 and >212 μm. The leaching percentage of Ni from the spent catalyst was found to be highest (97–98%) with varying particle size. However, the leaching yield for rest of the metals like Al, Fe, V and Mo was 70–74%, 66–85%, 33–43% and 22–45%, respectively. Influence of particle size was predominant on the recovery of all metals except Ni. Assessment of the generation of the bioleach residue after bioleaching showed a weight loss of 54–62% due to the dissolution of the metal values from the spent catalyst. The mineralogical study conducted by X-ray diffraction and scanning electron microscopy supports the dissolution of metals from the spent catalyst. Jarosite mineral phase was the dominant mineral phase in the bioleach residue due to the dissolution of the oxidic and sulfidic mineral phases present in the feed spent catalyst.

Effect of biooxidation conditions on cyanide consumption and gold recovery from a refractory gold concentrate

Article

Sep 2010
HYDROMETALLURGY

This study investigates the biooxidation of a refractory gold concentrate using a mixed culture of acidophilic mesophiles, moderate thermophiles and extreme thermophiles and their effect on the subsequent cyanidation and gold recovery. The experiments with high % solids using mixed mesophiles showed better oxidation potential compared to moderate thermophiles and extreme thermophiles. However, the extreme thermophiles performed better than mesophiles and moderate thermophiles during the biooxidation with

Bio-dissolution of zinc sulfide concentrate in 160 1 4-stage continuous bioreactor

Article

Oct 2003
MINER ENG

This paper reports the bioleaching of zinc sulfide concentrates by mesophilic chemolithotrophic bacteria. The leaching studies were carried out in 160 l 4-stage bioreactor in optimized conditions based on 40 l batch scale studies. Extraction of zinc up to 83.4% could be obtained in continuous operation.

Cueva de Villa Luz, Tabasco, Mexico: Reconnaissance study of an active sulfur spring cave and ecosystem

Article

Full-text available

Jan 1999

Cueva de Villa Luz (a.k.a. Cueva de las Sardinas) in Tabasco, Mexico, is a stream cave with over a dozen H2S-rich springs rising from the floor. Oxidation of the H2S in the stream results in a abundant, suspended elemental sulfur in the stream, which is white and nearly opaque. Hydrogen sulfide concentrations in the cave atmosphere fluctuate rapidly and often exceed U.S. government tolerance levels. Pulses of elevated carbon monoxide and depleted oxygen levels also occassionally enter the cave. Active speleogenesis occurs in this cave, which is forming in a small block of Lower Cretaceous limestone adjacent to a fault. Atmospheric hydrogen sulfide combines with oxygen and water to form sulfuric acid, probably through both biotic and abiotic reactions. The sulfuric acid dissolves the limestone bedrock and forms gypsum, which is readily removed by active stream flow. In addition, carbon dioxide from the reaction as well as the spring water and cave atmosphere combines with water. The resultant carbonic acid also dissolves the limestone bedrock. A robust and diverse ecosystem thrives within the cave. Abundant, chemoautotrophic microbial colonies are ubiquitous and apparently act as the primary producers to the cave's ecosystem. Microbial veils resembling soda straw stalactites, draperies, and 'u-loops' suspended from the ceiling and walls of the cave produce drops of sulfuric acid with pH values of <0.5-3.0 ±0.1. Copious macroscopic invertebrates, particularly midges and spiders, eat the microbes or the organisms that graze on the microbes. A remarkably dense population of fish, Poecilia mexicana, fill most of the stream. The fish mostly eat bacteria and midges. Participants in an ancient, indigenous Zoque ceremony annually harvest the fish in the spring to provide food during the dry season.

Minerals biotechnology: Trends, opportunities and challenges

Article

Full-text available

Jan 2008

Bio-oxidation is a well-established technology for the pre-oxidation of refractory gold-bearing concentrates in agitated reactors, as well as for the heap leaching of crushed secondary copper sulphide ores. Smelting seems set to remain the economically-preferred route, in the short- to medium term, for the processing of clean, high grade copper concentrates. However, bioleaching offers one hydrometallurgical alternative for base metal recovery in cases where, for example (a) only a very low grade flotation concentrate can be produced at an acceptable recovery, (b) penalty elements in the concentrate eliminate the smelting option, (c) geographical location or road, rail and/or harbour logistics prevent the economic transport of the concentrate to a smelter, or (d) authorities require local value-addition. The flexibility and economics of direct agitated bioleaching could be greatly enhanced if control could be exercised over the extent to which the intermediate elemental sulfur, formed during base metal sulphide oxidation, is oxidized to sulfate. Furthermore, since bioleaching produces large quantities of gypsum residues from neutralization with lime and limestone, maximising the density of the gypsum residues deserves specific attention during the process design of an agitated bioleach process. Indirect bioleaching can provide a relatively low-energy processing option with virtually perfect and self-regulating acid and iron balances for concentrates of secondary copper sulphides, or of chalcopyrite concentrate that leaches under low redox potential at moderate temperature. That is provided a suitable configuration is chosen for the bacterial ferrous iron oxidation step so that it can tolerate iron precipitation. Whether copper heap bioleaching is possible on ore in which chalcopyrite and pyrite are the major minerals depends on the reactivity of the pyrite to reach sufficiently high temperatures for acceptable leach kinetics as well as the feasibility of simultaneously finding an economic combination of crush size for liberation, acid consumption at temperature, heap height, and permeability to irrigation liquor and air. Temperatures of the order of 80°C and above are more readily achievable in heaps with lift heights greater than the normal 4 to 8 m, and pyrrhotite provides a more favorable heat source than pyrite. More refined laboratory scale test procedures and data interpretation is needed for predicting the acid consumption during commercial scale heap leaching. This requirement is more critical where high temperature heap bioleaching needs to be considered due to the greater acid-gangue reaction at higher temperature. Operator-advisory software is now available for the administration of a large number of cells under various stages of heap leaching that require counter-current leaching and manipulation of the irrigation and aeration rates to maximize heat accumulation within the operating range of the drippers/sprinklers while also controlling the copper tenor in the liquor feed to solvent extraction. As more challenging ore-types are being explored, classification or dense medium separation steps may more frequently be incorporated into heap bioleaching circuits for either the separate treatment of different classification products or the treatment of only a concentrated portion of the ore mined. Some of the uranium ores currently being explored will almost certainly be exploited by heap leaching. The employment of microbial oxidation activity in uranium ore heaps is suggested as a means of maintaining a high redox potential for the leaching of reduced uranium minerals in such heaps.

The GeoBiotics GEOCOAT® technology - Progress and challenges

Article

Full-text available

Jan 2007

Minerals biooxidation is now accepted as a viable technology for the pretreatment of refractory sulfidic gold ores and concentrates, and for the leaching of base metals from their ores and concentrates. Tank bioleaching or biooxidation is successful in achieving high metal recoveries, but both capital and operating costs are relatively high. Heap biooxidation has lower costs, but to date has suffered from low metal extraction rates and low ultimate metal recoveries. These disadvantages may outweigh the lower capital and operating costs of heap processes. GeoBiotics has developed and patented the GEOCOAT® biooxidation and bioleaching technology, which combines the high recoveries of tank processes with the low costs of heap-based processes. The process has been commercialized for the pretreatment of a refractory sulfidic gold concentrate. GeoBiotics is also developing the GEOLEACH™ technology for bioleaching and biooxidation of gold and base metal ores in heaps (Fig. 5.1).

Thermophilic Bioheap Leaching of Chalcopyrite Concentrates

Article

Full-text available

Jan 2002

The extraction of copper from chalcopyrite has for centuries been limited to pyrometallurgical methods. Smelting of chalcopyrite is an efficient process but costly both in terms of capital investment, operating costs and environmental compliance. Biological extraction appeared as an appealing alternative. Unfortunately, traditional mesophilic biological extraction methods have met with little success. The chalcopyrite quickly becomes passivated and unacceptable copper extractions are achieved. It was not until the adoption of thermophilic systems that the biological leaching of chalcopyrite became a reality. Several questions remain as to the applicability of the thermophilic system for chalcopyrite; can the system operate auto-thermally; can high extraction rates be achieved; is the process sensitive to mineralogy or grade; and can the precious metals be recovered? GeoBiotics, LLC has embarked on an extensive program to develop the GEOCOAT ® bioleaching system to chalcopyrite ores. This program encompasses mathematical heap modeling, laboratory amenability and column tests, and large scale field trials. The GEOCOAT ® process involves the coating of concentrates onto a suitable substrate, usually barren rock, then stacking the coated material in a conventional heap fashion. The heap is irrigated with acidic solutions containing iron and nutrients while low pressure ambient air is applied at the heap base. To-date, copper extractions in excess of 97% have been achieved in approximately 140 days. Excellent gold extractions have been achieved from the biooxidation residue by cyanidation. Modeling indicates that obtaining thermophilic temperatures within the GEOCOAT ® heap is not a problem. Development is continuing, focusing on the heap design parameters and additional copper concentrates including enargite. Plans are now underway for the first large scale field test in the fall of 2002.

Origin and distribution of mineral species in limestone caves

Article

Full-text available

Jan 1971

Paul L. Broughton

Beginnings of rational bioleaching and highlights in the development of biohydrometallurgy: A brief history

Article

Full-text available

Jan 2004

Henry Ehrlich

The origin of a rational (scientific) approach to extraction of metal values from ores with the aid of microorganisms (bioleaching) is traced. The removal by microbiological means of ore constituents that interfere with metal extraction (biobeneficiation), an outgrowth from bioleaching, is also traced. © 2004 SDU. All rights reserved.

Acidic Cave-Wall Biofilms Located in the Frasassi Gorge, Italy

Article

Full-text available

Apr 2000

Acidic biofilms present on cave walls in the sulfidic region of the Frasassi Gorge, Italy, were investigated to determine their microbial composition and their potential role in cave formation and ecosystem functioning. All biofilm samples examined had pH values Thiobacillus and Sulfobacillus. An acid-producing strain of Thiobacillus sp. also was obtained in pure culture. Stable isotope ratio analysis of carbon and nitrogen showed that the wall biofilms are isotopically light, suggesting that in situ chemoautotrophic activity plays an important role in this subsurface ecosystem.

Risk assessment of heavy metal toxicity through contaminated vegetables from waste water irrigated area of Varanasi, India

Article

Full-text available

Dec 2010

In certain areas of Varanasi city, waste water from Dinapur sewage treatment plant is used for irrigating vegetable plots. We quantified the concentrations of heavy metals, viz. Cd, Cr, Cu, Ni, Pb and Zn in soil, vegetables and the waste water used for irrigation. The waste water used for irrigation had the highest concentration of Zn followed by Pb, Cr, Ni, Cu and Cd. Continuous application of waste water for more than 20 years has led to accumulation of heavy metals in the soil. Consequently, concentrations of Cd, Pb and Ni have crossed the safe limits for human consumption in all the vegetables. Percent contribution of fruit vegetables to daily human intake for Cu, Ni, Pb and Cr was higher than that of leafy vegetables, while the reverse was true for Cd and Zn. Target hazard quotient showed health risk to the local population associated with Cd, Pb and Ni contamination of vegetables. Therefore, to reduce the health risk and the extent of heavy metal contamination, steps must be taken for efficient treatment of sewage. Regular monitoring of heavy metals in the vegetables grown in waste water irrigated areas is also necessary.

Archaean metabolic evolution of microbial mats

Article

Full-text available

Dec 1999

Microbial mats of coexisting bacteria and archaea date back to the early Archaean: many of the major steps in early evolutio probably took place within them. The earliest mats may have formed as biofilms of cooperative chemolithotrophs in hyperthermophil settings, with microbial exploitation of diversifying niches. Anoxygenic photosynthesis using bacteriochlorophyll could hav allowed mats, including green gliding bacteria, to colonize anaerobic shallow–water mesothermophile habitats. Exploitatio of the Calvin–Benson cycle by purple bacteria allowed diversification of microbial mats, with some organisms in more aerobi habitats, while green sulphur bacteria specialized in anaerobic niches. Cyanobacterial evolution led to more complex mat and plankton, allowing widespread colonization of the globe and the creation of further aerobic habitat. Microbial mat structur may reflect this evolutionary development in broad terms, with anaerobic lower levels occupied by archaeal and bacterial respirers fermenters and green bacteria, while the higher levels contain aerobic purple bacteria and are dominated by cyanobacteria. A possible origin of eukaryotes is from a fusion of symbiotic partners living across a redox boundary in a mat. The geologica record of Archaean mats may be present as isotopic fingerprints: with the presence of cyanobacteria, mats may have had a nearl modern structure as early as 3.5 Ga ago (1 Ga=109 years).

Mining history in Anatolia - Part 3

Article

Full-text available

May 2006

Ata Akcil

Recovery of gold from secondary sources—A review

Article

Full-text available

Mar 2012
HYDROMETALLURGY

Sabir Syed

This paper presents an overview of the various methodologies used in the recovery of gold from secondary sources. Gold recovery is interesting due to its vast industrial applications, high market prices and extensively used precious metal, the sanctuary value attributed to gold during international political and economical crises, and the limited resource of this metal may explain the recent increasing gold share value. The state of art in recovery of gold from spent sources by pyrometallurgy; hydrometallurgy; bio-hydrometallurgy techniques is highlighted in this paper. This article also provides an overview of past achievements and present scenario of recovery studies carried out on the use of some promising methods which could serve as an economical means for recovering gold. The present review also highlights the used varieties of leaching, cementing, reducing agents, peeling, coagulants, adsorbents, agglomeration solvents, ion exchange resins and bio-sorbents in real situations and hopes to provide insights into recovery of gold from spent sources. Evaluation of lucrative and environmentally friendly technologies to recover gold from primary and secondary spent sources was made in this study.

The Sociedad Minera Pudahuel bacterial thin-layer leaching process at Lo Aguirre

Article

Full-text available

Jul 1993
FEMS MICROBIOL REV

The thin-layer leaching process originally conceived and developed for leaching oxide ores has been successfully adapted to bacterial leaching of mixed and secondary sulphide ores. The process is currently being applied at the Socicdad Minera Pudahuel Lo Aguirre Plant. About 3000 ton of ore per day are being processed to produce 14000 ton of high-grade copper cathodes per year, in a closed circuit integrated with SX-EW. Changes in the soluble copper grade of the ore from about 1.8C4 to (I.6% have occurred during the last years, which have been compensated by an equivalent increase in the insoluble copper grade. In addition, ore from satellite ore bodies has resulted in acid consumption variations ranging from 611 to 120 kg H2SO4 per ton of ore. The main sulphide mineralogical species are chatcocite and bornite, with small amounts of chalcopyrite and covellite. An intensive research program in columns and large-scale heaps has been carried out to define the operating conditions which assure adequate bacterial growth and bacterial activity towards the sulphides. Agglomerated ores with 1.7 2.5% Cur and (I.3-0.6%: Cus, with the insoluble copper mainly present as chalcocite bornite, were leached at a flow rate of 0.2 1 min1 mu2 with a SX-Raffinate solution containing (in g-1) 5–10 H2SO4, 2–4 FeT, 1–3 Fe+3, 0.5 Cu, as well as impurities resulting from a closed circuit operation. Copper recoveries of 75 85% CuT were obtained after 180–250 days of total leaching time, depending on the copper grade, the mineralogical composition, and the acid consumption of the ore. Important bacterial activity was detected. About 10 3−105 bacteria ml−1 were measured in effluent solutions. Iron oxidation rates of 7–100μg Fe2+ h−1 g−1, measured from respirometric tests on agglomerated ore, suggest that an adsorbed biomass of about 107-108 bacteria g−1 must also be present. Further applications of the bacterial thin-layer leaching process to Cerro Colorado and Qucbrada Blanca ores in North Chile are being studied.

Biologically Induced Mineralization by Bacteria

Article

Full-text available

Jan 2003

Bacteria are small, prokaryotic, microorganisms that are ubiquitous in surface and subsurface terrestrial and aquatic habitats. Prokaryotes comprise two Domains (Superkingdoms) in the biological taxonomic hierarchy, the Bacteria and the Archaea. They exhibit remarkable diversity both genetically and metabolically even within the same microenvironment and they are thought to play a major role in the deposition and weathering of minerals in the earth’s crust. The synthesis of minerals by prokaryotes can be grouped into two canonical modes: 1) biologically induced mineralization (BIM) and 2) biologically controlled mineralization (BCM) (Lowenstam 1981; Lowenstam and Weiner 1989). In this chapter, we focus on biologically induced mineralization. Minerals that form by biologically induced mineralization processes generally nucleate and grow extracellularly as a result of metabolic activity of the organism and subsequent chemical reactions involving metabolic byproducts. In many cases , the organisms secrete one or more metabolic products that react with ions or compounds in the environment resulting in the subsequent deposition of mineral particles. Thus, BIM is a presumably unintended and uncontrolled consequence of metabolic activities. The minerals that form are often characterized by poor crystallinity , broad particle-size distributions, and lack of specific crystal morphologies. In addition , the lack of control over mineral formation often results in poor mineral specificity and/or the inclusion of impurities in the mineral lattice. BIM is, in essence, equivalent to inorganic mineralization under the same environmental conditions and the minerals are therefore likely to have crystallochemical features that are generally indistinguishable from minerals produced by inorganic chemical reactions. In some cases, the metabolic products diffuse away and minerals form from solution. However , bacterial surfaces such as cell walls or polymeric materials (exopolymers) exuded by bacteria, including slimes, sheaths, or biofilms, and even dormant spores, can act as important sites for the adsorption of ions …

A Two-Dimensional CFD Model for Heap Bioleaching of Chalcocite

Article

Full-text available

Jun 2005

A 3-phase computational ∞uid dynamics (CFD) model for heap bioleaching of chalcocite is investigated to identify and understand the efiect of oxygen ∞ow during air sparging. The study uses an existing one-dimensional model of liquid ∞ow, bacterial transport (including attachment/detachment of bacteria to ore particles), and the depletion of a copper-sulphide, coupled with a two-dimensional (2D) model of gas ∞ow in the heap. The CFD model includes the efiects of oxygen and ferrous ion consumption, coupled with leaching of copper-sulphide via a shrinking core model. The model is used to investigate the 2D efiects of air ∞ow in heap bioleaching with regard to oxygen limitation.

A Stable Isotope Study of Organic Cycling and the Ecology of an Anchialine Cave Ecosystem

Article

Full-text available

Aug 1997

Stable carbon and nitrogen isotope data, complemented with other geochemical parameters, were used to identify the sources of organic matter that support the food web of an anchialine cave ecosystem in the northeastern Yucatan Peninsula, Mexico. Anchialine caves, common along tropical karstic and volcanic coastlines, are completely or partially inundated by highly stratified layers of fresh and marine waters. Stable isotope data from the cave fauna, the particulate organic matter (POM) from the cenote pool and from the cave, the forest soil and the cave sediments indicated that at least 3 sources of nutritive organics could support the anchialine food web. These sources were: (1) soil from the overlying forest; (2) freshwater algae from adjoining open water pools; and (3) chemoautotrophic nitrifying bacteria living in the cave. Production of nitrate and a decrease in O-2 along the halocline provided geochemical evidence of nitrification. Stable nitrogen isotope data defined 2 to 2.5 trophic levels in the food web. Furthermore, it was found that troglobitic (cave-limited) species residing in the water column are capable of preferentially feeding on specific organic reservoirs. This study presents the first extensive description of the ecological and biogeochemical relationships of the anchialine cave ecosystem.

Fatty acid characteristics in two symbiotic gastropods from a deep hydrothermal vent of the West Pacific

Article

Full-text available

Oct 1996

Two deep-sea gastropods, Ifremeria nautilei and Alviniconcha hessleri, collected on a hydrothermal site of the North Fiji Basin (Southwestern Pacific) were analysed for polar and neutral lipids using gas-liquid chromatography/mass spectrometry. A high level of monounsaturated fatty acids (MUFAs) and a low level of omega 3 series polyunsaturated fatty acids (PUFAs) indicated that nutrition of both gastropods was related to a food web based mainly on bacterial supply. From differences in MUFA distribution between the 2 gastropods, it appeared that most of the energy requirements of A. hessleri were supplied by sulfur-oxidizing endobacteria whereas I. nautilei probably had a mixotrophic diet based on endogenous as well as exogenous bacteria. Given the relatively high level of linoleic acid, which represented from 2 to 8% of the phospholipid fatty acids, hydrothermal gastropods did not appear to be depleted in omega 6 PUFAs. It was hypothesized that they obtain linoleic acid from a pathway different to that in heterotrophic marine molluscs. In contrast to omega 6 PUFAs, both hydrothermal gastropods appeared to be depleted in omega 3 PUFAs, indicating the limited importance of photosynthesis-based food supplies. Some non-methylene-interrupted dienes, particularly 20:2 omega 9,15 which represented from 9 to 18% of the phospholipid fatty acids, may be synthesized by deep-sea symbiotic molluscs in order to restore the depleted omega 3 PUFAs considered as essential for animals. Gills of both gastropods had high levels of neutral lipids, mainly MUFAs that may have originated from degradation of endobacterial phospholipids.

Hydrothermal petroleum of Lake Chapala, Citala Rift, western Mexico: Bitumen compositions from source sediments and application of hydrous pyrolysis

Article

Apr 2006
APPL GEOCHEM

Hydrothermal simulation experiments were performed with contemporary sediments from Lake Chapala to assess the source of the lake tars. The precursor-product relationships of the organic compounds were determined for the source sediments and their hydrous pyrolysis products. The pyrolysis products contained major unresolved complex mixtures of branched and cyclic hydrocarbons, low amounts of n-alkanes, dinosterane, gammacerane, and immature and mature hopane biomarkers derived from lacustrine biomass sources. The results support the proposal that the tar manifestations in the lake are not biodegraded petroleum, but were hydrothermally generated from lacustrine organic matter at temperatures not exceeding about 250 °C over brief geological times.

Some challenges in the design and operation of smart and safe metallurgical plants

Article

Jan 2008

J. Canterford

Despite the increasing sophistication of process design and improvement tools and a substantial catalogue of operating plant characteristics, the mineral resource industry still manages to be plagued by operating plants that fail because they are neither smart nor safe. While the actual number of plants that fall into this category is not that substantial, the adverse end effects are generally widely publicised and they do little to reflect the complexity and broad expanse of knowledge that is required to achieve the ultimate objective of the development of our mineral resources in an economically and environmentally sustainable manner. The general public and the finance industry are generally totally uniformed about projects that ramp-up to name plate capacity on time and on budget. There are many reasons why these "wayward" metallurgical plants come into being, ranging from scientific-engineering incompetence, project owner/developer avarice, insufficient attention to future market/product requirements, impossible conditions imposed by our generally ignorant government/political authorities, through to obvious bad luck, but more likely a combination of all such factors. This presentation attempts to provide an overview of what should be regarded as some very basic ground rules, ranging from a proper understanding of the resource itself (location, geology, mineralogy) through to completion and detailed analysis of risk mitigation strategies before it is too late. Along the way potential problems of over-design as well as under-design will be canvassed, as will be the less than adequate generation of an expanded pool of "top gun" metallurgists/process engineers. The presentation will be illustrated by a number of disasters as well as examples of what can be achieved.

Scaling fresh heights in heap-leach technology

Article

Apr 2008

P. Moore

A process by which ore that has usually been crushed and often agglomerated to be stacked on a prepared containment system is known as heap leaching. They use cyanide as the leachant with feeds that are characterized as oxide gold ores in the case of gold. Sulfuric acid is the only commercialized technology for copper heap leaching, but there has also been some experimentation with other lixiviants like ammonia. Copper oxide ore leaching is just about dissolution process but sometimes need a mix of dissolution and bioleaching, where the bioleaching makes the copper available to acid leaching. In the case of nickel laterite ores, heap leaching them is more complicated than copper or gold ores.

An Improved Method for the Vacuum Impregnation of Stone

Article

Feb 1976

K. Hempel

An efficient and simple method for the vacuum impregnation of stone is described, based on the formation of an airtight jacket around the object allowing a vacuum to be applied to the surface and acting as a wick for the consolidating material. /// Une méthode simple et efficace pour l'imprégnation sous vide de la pierre est décrite, basée sur la formation d'une enveloppe étanche à l'air autour de l'objet permettant d'appliquer le vide à la surface et agissant comme une mèche pour le matériel de consolidation. /// Ein wirksames und einfaches Verfahren zur Vakuumimpregnierung von Stein wird beschrieben, das auf der Bildung eines luftdichten Mantels um den Gegenstand basiert, welcher die Aufbringung eines Vakuums auf die Oberfläche erlaubt und als Docht für das Konsolidierungs-material wirkt.

Stromatolites: A key to understanding the early evolution of life

Article

Jan 1992

Stromatolites are sedimentary structures produced by the sediment-trapping, binding and/or precipitation activity of microbial communities, in particular by photosynthetic cyanobacteria. They occur today in a wide range of aquatic habitats, both marine and non-marine, from shallow subtidal to supratidal and in lakes, streams and thermal springs. Although uncommon today, stromatolites were widespread in the past, and are the most conspicuous fossils in Precambrian rocks. It has been suggested that microbes played a major role in the development of the banded-iron formations that are widespread in Precambrian rocks, and that they played a crucial role in the formation of atmospheric oxygen. -from Authors

Microbial Calcification of Gypsum-Rock and Sulfated Marble

Article

Aug 1988

A broth containing the sulfate reducing bacterium Desulfovibrio desulfuricans was used to treat samples of reagent calcium sulfate, gypsum-rock specimens, fragments from a marble monument with a black weathering crust rich in gypsum, and a marble monument with similar crust. Calcite was found to have formed on all treated surfaces suggesting that this microbe has the potential to clean crusted marble monuments whilst also regenerating calcite, the parent mineral of the marble. /// Un bouillon de culture contenant une bactérie réductrice des sulfates, le Desulfovibrio desulfuricans, a été utilisé pour traiter des échantillons de sulfate de calcium, des spécimens de pierre en gypse, des morceaux provenant d'un monument de marbre recouverts d'une croûte noire de vieillissement riche en gypse, et un monument de marbre avec une croûte semblable. Il s'est formé de la calcite sur toutes les surfaces traitées, suggérant que cette bactérie peut nettoyer les monuments de marbre recouverts d'une croûte, tout en régénérant le calcite qui est le principal constituant du marbre. /// Calciumsulfate, gipshaltige Gesteine sowie gipsreiche schwarze Verwitterungskrusten von zwei Denkmälern aus Marmor wurden mit einer Desulfovibrio desulfuricans Kultur in Nährbouillon behandelt. Die Bakterien reduzieren Sulfate. Die Untersuchungen ergaben, daß sich auf allen behandelten Oberflächen Calcit (Calciumcarbonat) gebildet hatte. Dies scheint die Möglichkeit zu eröffnen, mit Hilfe dieser Bakterien Objekte aus Marmor zu reinigen. Der gebildete Calcit ist wiederum der Hauptbestandteil von Marmor.

A Preliminary Note on the Use of Enzymes in Conservation: The Removal of Aged Acrylic Resin Coatings with Lipase

Article

Jan 1999

Lipases, hydrolytic enzymes that act on glycerol-ester bonds, are often used in conservation for their ability to degrade aged oil films, as a non-toxic and often less aggressive alternative to highly polar organic solvents and/or alkaline mixtures. One such enzyme has been used to remove layers of an aged acrylic resin (Paraloid B72) in two instances, a fifteenth-century tempera painting on panel and a nineteenth-century oil painting on canvas. A plausible mechanism for the action of the enzyme is discussed.

Microorganisms in Leaching Sulfide Minerals

Article

Dec 1954

Practical Building Conservation

Article

Nov 1991

The Use of Microorganisms To Increase the Recovery of Oil From Cores

Conference Paper

Sep 1985

A method for oil recovery enhancement by stimulating the growth of indigenous microbial populations in sandstones by nutrient injection was investigated. Incremental oil recovery from the cores ranged from 10–38% of the original oil in place. Volumetric and microscopic sweep efficiency was improved by the microbial selective plugging process. Biogenic gas production accompanied the oil produced from the cores. The combination of stratification correction, gas production, and pressure increase assisted in recovery of previously trapped oil.

Diagenetic Evolution of Mudstones: Black Shales to Laminated Limestones, an Example from the Lower Jurassic of SW Britain

Article

Jan 2004

Nasser Arzani

The degree of carbonate cementation in argillaceous sediments represents one of the significant diagenetic evolutions in ancient mudstones. The alternation of the black shale and laminated limestone of the Lower Jurassic of SW Britain is an example, which typify extent of diagenetic modification of marine clay and organic-rich sediments. The Lower Jurassic mudstones of the SW Britain include black shales, marls and alternate with limestone beds and nodules. Laminated limestones are also present and are only enclosed between the black shales. Detailed petrography combined with geochemical analysis of the black shales and enclosed laminated limestoned have been carried out and compared to the typical isolated nodules in order to interpret the diagenetic history of mudstones. Displacive growth of the microspar crystals was an important process that occurred during the diagenetic evolution of these mudstones. The black shales show carbon (+0.9 to +1.9‰ (PDB)) and oxygen (−2.2 to −4.1‰ (PDB)) isotopic values, which is compared to their enclosed laminated limestones, that show more negative carbon (−0.2 to −1.2 ‰ (PDB)) and oxygen (−5.4 to −6.8‰ (PDB)) values. The stratigraphic position, petrography and isotopic relationship of the black shales and enclosed laminated limestones indicate a degree of diagenetic evolution and carbonate cementation of mustones during progressive burial.

Hot-Water Deposition of Pyritic Stromatolite and Its Relation to Biomineralization

Article

Sep 2000
ACTA GEOL SIN-ENGL

Abstract Pyritic stromatolite, a rich pyrite ore, is scattered as reef masses in sedex deposits of the Proterozoic Yanshan rift trough. The pyritic stromatolite consists of a core and alternating concentric rims of light colloidal pyrite and dark organic materials. The concentric rims are cemented together by trichomes highly similar to the trichomic microorganisms inhabiting substantively around the black chimneys on the current sea beds while the core is composed chiefly of groups of thermophilous sulphur bacteria. Biomarkers for the molecules of pyritic stromatolite include pristane, phytane, regular isoprenoids paraffin, methyl-heptadecyl, and so on. This study reveals the existence of methane-yielding bacteria in the pyritic stromatolite and reflects the evolution of thermophilous thallophyta. Long pulsation of mineralizing thermal solutions venting up along contemporaneous faults in rift troughs contributed greatly not just to the reproduction of thermophilous organisms living around the vents, but to their adsorption of Fe2+ from the solutions in a reducing environment. Pyritic stromatolite constantly took shape through metabolism and reduction of these organisms. Owing to the uneven development of the organic communities close to the vents or the hydrothermal plumes, pyritic stromatolite occurred eventually as scattered reef masses. This mineralizing mechanism may be summarized as the following procedure: flowing of hydrothermal fluids associated with submarine exhalatio→adsorption and metabolism of thermophilous micro-organisms→reduction of organic materials→formation of deposits of pyritic stromatolite.

Biomediated Precipitation of Calcium Carbonate Metastable Phases in Hypogean Environments: A Short Review

Article

Sep 2003

Natural precipitates of metastable polymorphs of CaCO 3 , such as vaterite, are rarely found in nature however, they have been widely synthesized in laboratory under particular conditions (ie, supersaturated solutions, relative high temperatures, etc.). By SEM and XRD we recognize vaterite spherulites from culturable microbial colonies isolated from hypogean environments. Spherical bodies (~10 w in diameter), probably composed of vaterite, occur in submilimetric microbial mats and biofilms on volcanic substrates (Saint Callixtus Catacombs, Rome, Italy) and karstic caves (Altamira, Candamo, and Tito Bustillo caves, Spain, and Grotta dei Cervi, Italy) where cyanobacteria and actinomycetes are the major microbial components. These particles form beneath dense biofilms, where particular physicochemical conditions are developed by the microbial activity. Natural biofilms seems to generate microenvironments favoring the formation and preservation of metastable CaCO 3 polymorphs. This also shows a major role of microbes in processes of low-temperature alteration of different hypogean rock-substrates.

Geomicrobiology of carbonate-silicate microbialites from Hawaian basaltic sea caves

Article

Sep 2000
CHEM GEOL

Modern microbial mats and microbialites are described from basaltic sea caves on the island of Kauai, HI. The mats grow on the ceilings and walls in the photic zone of several open caves where fresh water seeps out of the rock. Scanning (SEM) and transmission electron microscopy (TEM) showed that the active mats are dominated by filamentous and nonfilamentous cyanobacteria in the surface layers and heterotrophic bacteria in deeper layers. Energy dispersive X-ray analysis revealed that copious amounts of extracellular polymeric substances (EPS) are rich in Mg, Si, O, and Ca, likely concentrated from solution. Petrographic microscopy and electron microprobe analysis of the mineralized microbialites showed textures reminiscent of stromatolitic laminations, consisting mainly of alternating calcium carbonate (calcite and aragonite) and magnesium-rich silicate (kerolite). Thin coatings rich in magnesite, hydromagnesite and monohydrocalcite surround the microbialites on the rock surfaces and are likely inorganic in origin. Within the mats, minerals tend to form and concentrate within, or around, dense matrices of EPS. Microenvironments with geochemical conditions favorable for mineral crystallization likely develop in the mats as a result of the mucilaginous extracellular material and the development of bacterial microcolonies. In addition, copious amounts of extracellular polymers bind ions from solution and provide nucleation sites for mineral crystallization and growth. This combination of biological and inorganic processes can explain the occurrence of the secondary minerals in these caves, as well as the stromatolitic textures of the microbialites.

Potential risks of gene amplification by PCR as determined by 16S rDNA analysis of a mixed-culture of strict barophilic bacteria

Article

Dec 1991

The 16S rDNA genes of an apparently pure culture of a psychrophilic and strict barophilic bacterium (WHB 46) were studied by PCR-mediated amplification and cloning into phage M13 mp18. Sequence analysis of five individual clones revealed the presence of two different 16S rDNA types. The homology value of 90% indicates that culture WHB 46 is actually composed of two closely related species (WHB 46-1 and 46-2). Both strains are members of the γ-subdivision of proteobacteria. Analysis of a sixth clone (WHB 46-1/2) leads to the conclusion that it represents a 16S rDNA hybrid molecule assembled during the PCR reaction. This hypothesis was confirmed by secondary structure analysis of the chimeric rDNA. The appearance of such hybrid molecules point to a potential risk in studies on the diversity of bacterial populations by analysis of rDNA pattern via PCR-mediated amplification because they suggest the existence of organisms that do not actually exist in the sample investigated.

Studies on multi-metal ion tolerance of Thiobacillus ferrooxidans

Article

Jul 1997
MINER ENG

The influence of different concentrations of base metal ions, such as Cu2+, Zn2+ and Fe3+, when present either alone or in different possible binary and ternary combinations in a 9K medium, on the ferrous ion oxidation ability of Thiobacillus ferrooxidans was studied. Levels and degree of toxicity of these ions have been quantified in terms of toxicity index (TI). Copper and zinc tolerant strains of the bacteria were developed through serial subculturing and their activity tested in the presence of the above metal ions in comparison with the behavior of wild unadapted cells under similar conditions. Copper tolerant strains (25 g/L Cu2+) were found to be more efficient in the bioleaching of both copper and zinc concentrates than wild unadapted strains, while zinc tolerant strains (40 g/L Zn2+) exhibited better leaching efficiency only in the bioleaching of sphalerite concentrates. The significance and relevance of multi-metal ion tolerance in Thiobacillus ferrooxidans has been highlighted with respect to bioleaching of sulphide mineral concentrates.

Phylogeny of the Vibrionaceae, and Recommendation for Two New Genera, Listonella and Shewanella

Article

Sep 1985
SYST APPL MICROBIOL

Ribonucleotide sequences were determined for 5S rRNAs purified from 31 type cultures and freshly isolated strains representing species of the eubacterial family Vibrionaceae. These were compared with published 5S rRNA sequences for 11 other species of rRNA superfamily I (Vibrionaceae, Enterobacteriaceae) for the purpose of constructing a phylogenetic taxonomy of the Vibrionaceae. Sequence data were compiled and analyzed, using single, average, and complete linkage clustering methods, resulting in the generation of evolutionary trees. Results of this study indicate a good correlation between the taxonomy of the Vibrionaceae established using conventional and molecular genetic data and evolutionary relationships deduced from 5S rRNA sequences. However, several species, including V. anguillarum, V. pelagius, V. damsela, V. fischeri, V. logei, V. psychroerythrus, V. marinus, and Plesiomonas shigelloides require reconsideration of their taxonomic status, based on the new information obtained in this study. Furthermore, the genus Aeromonas appears to be sufficiently distantly related to the Vibrionaceae to warrant exclusion from the family Vibrionaceae. We propose a restructuring of the family Vibrionaceae along phylogenetic lines, and establishment of two new genera Listonella and Shewanella, and a new family Aeromonadaceae.

The bioleaching of nickel-copper sulfides

Article

Mar 2008
HYDROMETALLURGY

Helen Watling

Demand for nickel, largely driven by the Chinese stainless steel market, currently exceeds production, causing an unprecedented rise in the price of nickel and renewed interest in bioleaching technology for the processing of low grade nickel sulfide ores and concentrates. Although nickel inhibits bacterial physiological functions such as iron- and sulfur-oxidation, some bacteria adapt readily to high concentrations. In pilot‐scale continuous reactors, mixed microbial populations grew actively over many months in the presence of up to 400 mM nickel (23 g/L). The results of bench-scale test work have been sufficiently encouraging to prompt pilot- and demonstration-scale trials in heaps and agitated tanks in Australia, China, Finland and South Africa in recent years. The first commercial implementation of nickel sulfide heap leaching is likely to be the operation at Talvivaara, Finland.

Abundance, distribution and ??13C analysis of microbial phospholipid-derived fatty acids in a black shale weathering profile

Article

Jun 2003
ORG GEOCHEM

Phospholipid ester-linked fatty acids [PFLA] were isolated from a weathering profile developed on Ohio Shale. PLFA distributions were used to describe the microbial communities living in this weathering profile. PLFA are interpreted as mixed aerobic (eukaryote+prokaryote) and anaerobic communities, with a very distinct PLFA distribution at 40–50 cm depth in the core. This depth in the weathering profile corresponds to the onset of shale OM loss and the accumulation of Fe3+ and soil OM. Stable carbon isotopic analysis of PFLA reveals complex patterns of isotopic enrichment and depletion for individual PFLA relative to bulk soil and shale OM. PLFA δ13C values suggest at least some assimilation of shale OM by anaerobic microorganisms. This phospholipids study reveals that weathering profiles developed on black shales are environments of degradation of ancient OM and both accumulation and degradation of more modern soil OM, highlighting the complexity of near-surface microbial processes in sedimentary rocks.

Dissolution of jarosite [KFe3(SO4)2(OH)6] at pH 2 and 8: Insights from batch experiments and computational modelling

Article

Feb 2006
GEOCHIM COSMOCHIM AC

Jarosite [KFe3(SO4)2(OH)6] is a mineral that is common in acidic, sulphate-rich environments, such as acid sulphate soils derived from pyrite-bearing sediments, weathering zones of sulphide ore deposits and acid mine or acid rock drainage (ARD/AMD) sites. The structure of jarosite is based on linear tetrahedral–octahedral–tetrahedral (T–O–T) sheets, made up from slightly distorted FeO6 octahedra and SO4 tetrahedra. Batch dissolution experiments carried out on synthetic jarosite at pH 2, to mimic environments affected by ARD/AMD, and at pH 8, to simulate ARD/AMD environments recently remediated with slaked lime (Ca(OH)2), suggest first order dissolution kinetics. Both dissolution reactions are incongruent, as revealed by non-ideal dissolution of the parent solids and, in the case of the pH 8 dissolution, because a secondary goethite precipitate forms on the surface of the dissolving jarosite grains. The pH 2 dissolution yields only aqueous K, Fe, and SO4. Aqueous, residual solid, and computational modelling of the jarosite structure and surfaces using the GULP and MARVIN codes, respectively, show for the first time that there is selective dissolution of the A- and T-sites, which contain K and SO4, respectively, relative to Fe, which is located deep within the T–O–T jarosite structure. These results have implications for the chemistry of ARD/AMD waters, and for understanding reaction pathways of ARD/AMD mineral dissolution.

Effect of ultrasound on acidified brine leaching of double-kiln treated EAF dust

Article

Oct 1992
MINER ENG

The U.S. steel industry produces approximately 500,000 tons/year of electric arc furnace (EAF) dust, which is classified as a hazardous waste. Increasing disposal costs of these dusts have encouraged studies to investigate treatment processes to render the material non-hazardous, and to possibly recover metal values. This research project was designed to examine the hydrometallurgical recovery of zinc from EAF dusts that have been treated by a double-kiln fuming process. The test work consisted essentially of acidified brine leaching of the pelletized calcine to determine the influence of traditional conditions, such as acid concentration, temperature and agitation, plus the application of ultrasound, on the zinc dissolution efficiency and selectivity.Preliminary leaching tests using acidified calcium chloride indicated that selective leaching of zinc over iron could be attained if ultrasound was employed. The effect of air and nitrogen on the leaching process was investigated and it was established that selective leaching with ultrasound was not dependent upon external agitation or on the availability of oxygen. Without ultrasound, zinc dissolution was enhanced by the presence of oxygen, while iron dissolution was greatly retarded by the absence of oxygen. The role of surface area was examined by pellet grinding and it was demonstrated that selectivity was strongly time dependent and that zinc recovery and iron rejection were enhanced at finer particle sizes.The results of the test work permitted possible mechanisms to be established for the acidified brine leaching process, and it is apparent from the results that ultrasound leaching can significantly improve the selective leaching of zinc from double-kiln treated EAF calcine.

Fungicides for use on textiles employed during the restoration of works of art

Article

Dec 1987

In this paper the possible use of fungicides as a preventive measure during the restoration of works of art is considered.The efficacy of 8 fungicides, already widely experimented with in other sectors, was tested after 28 days, on three types of textiles, commonly used in restoration operations.The interaction between the fungicides and the textiles was evaluated through changes in the degree of reflectance, measured before and after artificial ageing, in the presence and absence of ultraviolet radiation.Finally conclusions are drawn on the possible use during restoration of these fungicides, also taking into consideration their known toxicity factors.

Evaluation of process variables in bench-scale bio-oxidation of the Olympias concentrate

Article

Jul 1993

A statistically designed set of eight bio-oxidation tests on the Olympias concentrate was conducted in bench-scale equipment to evaluate the effects of important variables on pyrite/arsenopyrite oxidation and gold extraction. The variables studied were total retention time, feed solid concentration and particle size. High degrees of arsenopyrite oxidation were observed in all tests, as the arsenopyrite oxidation was very fast and therefore not dependent on the variables within the studied range. Statistical analysis of the experimental data reveals that the pyrite oxidation and gold extraction are dependent mainly on the retention time and to a lesser extent on the particle size. The feed solid concentration had a small influence only on the gold extraction. Regressed equations of the experimental data can be used to predict proper operating conditions.

Leduc LG, Ferroni GD.. The chemolithotrophic bacterium Thiobacillus ferrooxidans. FEMS Microbiol 14: 103-119

Article

Jun 1994
FEMS MICROBIOL REV

The iron-oxidizing bacterium ThiobaciUus ferrooxidans is the most important microorganism in mineral leaching. It plays the dominant role in bioextractive processes because of its ability to oxidize both iron and reduced sulfur compounds. T. ferrooxidans is also an important microorganism in acid rock/mine drainage, a serious environmental problem. In this article, the current status of this bacterium is described with particular emphasis on the biomining industry.

A HYPOTHESIS FOR BIOGENIC CAVE FORMATION: A STUDY CONDUCTED IN THE BAHAMAS

Article

ABSTRACT

Variations in Heavy Metal Concentrations Following the Dredging of an Oil Well Access Canal in the Niger Delta

Article

Jul 2008

3 Abstract: In a study to assess the impact of dredging on heavy metal contamination, surface water was monitored for over one year, from December 1997 to December 1998. Samples were collected twice before dredging, in December 1997 and in June 1998, corresponding to dry and raining seasons respectively. Samples were also collected immediately after dredging in July 1998 and were monitored in August, September and December 1998. Samples were collected analysed from five stations within the study area, station 1-5. Station 1 was in the dredged canal, which was originally a side branch of the Warri River tributary. In the Warri River tributary, Station 2 was 500m upstream and Station 3 was 1000m upstream of the mouth of the dredged canal, whilst Stations 4 and 5 were respectively 500m and 1000m downstream of it. Stations 3 and 5 represented the reference situation to which possible dredging effects could be compared. Prior to dredging, the concentration of heavy metals in the surface water samples of Warri River occurred in traces; lead (0.01-0.28 mg l̄ ), 1 zinc (0.04-1.02 mg l̄), copper (0.00-0.17 mg l̄), iron (0.22-0.88 mg l̄), chromium (0.00-0.03 mg l̄) and cadmium 1 1 1 1

Anaerobic Production of Magnetite by a Dissimilatory Iron-Reducing Microorganism

Article

Nov 1987
NATURE

The potential contribution of microbial metabolism to the magnetization of sediments has only recently been recognized. In the presence of oxygen, magnetotactic bacteria can form intracellular chains of magnetite while using oxygen or nitrate as the terminal electron acceptor for metabolism1. The production of ultrafine-grained magnetite by magnetotactic bacteria in surficial aerobic sediments may contribute significantly to the natural remanent magnetism of sediments2-4. However, recent studies on iron reduction in anaerobic sediments suggested that bacteria can also generate magnetite in the absence of oxygen5. We report here on a sediment organism, designated GS-15, which produces copious quantities of ultrafine-grained magnetite under anaerobic conditions. GS-15 is not magnetotactic, but reduces amorphic ferric oxide to extracellular magnetite during the reduction of ferric iron as the terminal electron acceptor for organic matter oxidation. This novel metabolism may be the mechanism for the formation of ultrafine-grained magnetite in anaerobic sediments, and couldaccount for the accumulation of magnetite in ancient iron formations and hydrocarbon deposits.

The Origin of Nitrates in Cavern Earths

Article

Feb 1900

William H. Hess

Overview of the geologic history of cave development in the Guadalupe Mountains, New Mexico

Article

Jan 2000

CAROL A. HILL

The sequence of events relating to the geologic history of cave development in the Guadalupe Mountains, New Mexico, traces from the Permian to the present. In the Late Permian, the reef, forereef, and backreef units of the Capitan Reef Complex were deposited, and the arrangement, differential dolomitization, jointing, and folding of these stratigraphic units have influenced cave development since that time. Four episodes of karsification occurred in the Guadalupe Mountains: Stage 1 fissure caves (Late Permian) developed primarily along zones of weakness at the reef/backreef contact; Stage 2 sponge work caves (Mesozoic) developed as small interconnected dissolution cavities during limestone mesogenesis; Stage 3 thermal caves (Miocene?)formed by dissolution of hydrothermal water: Stage 4 sulfuric acid caves (Miocene-Pleistocene) formed by H2S-sulfuric acid dissolution derived hypogenically from hydrocarbons. This last episode is reponsible for the large caves in the Guadalupe Mountains containing gypsum blocks/rinds, native sulfur, endellite, alunite, and other deposits related to a sulfuric acid spelcogenetic mechanism.

Weathering of phlogopite in simulated bioleaching solutions

Article

Jan 2011
INT J MINER PROCESS

The purpose of this study was to examine structural alterations of finely ground phlogopite, a trioctahedral mica, when exposed to acid, iron- and sulfate-rich solutions typical of bioleaching systems. Phlogopite suspensions were supplemented with ferrous sulfate and incubated with iron- and sulfur-oxidizing bacteria (Acidithiobacillus ferrooxidans) at 22°C. As bacteria oxidized ferrous iron, ferric iron thus formed partially precipitated as K-jarosite. K-jarosite precipitation was contingent on the preceding ferrous iron oxidation by bacteria and the release of interlayer-K from phlogopite. This chemically and microbially induced weathering involved alteration of phlogopite to a mixed layer structure that included expansible vermiculite. The extent of phlogopite weathering and structure expansion varied with duration of the contact, concentration of ferrous iron and phlogopite, and the presence of monovalent cations (NH4+, K+, or Na+) in the culture solution. NH4+ and K+ ions (100mM) added to culture suspensions precipitated as jarosite and thereby effectively prevented the loss of interlayer-K and structural alteration of phlogopite. Additional Na+ (100mM) was insufficient to precipitate ferric iron as natrojarosite and therefore the precipitation was coupled with interlayer-K released from phlogopite. When ferrous iron was replaced with elemental sulfur as the substrate for A. ferrooxidans, the weathering of phlogopite was based on chemical dissolution without structural interstratification. The results demonstrate that iron oxidation and the concentration and composition of monovalent ions can have an effect on mineral weathering in leaching systems that involve contact of phlogopite and other mica minerals with acid leach solutions.

Microbial contributions to cave formation: New insights into sulfuric acid speleogenesis

Article

May 2004
GEOLOGY

The sulfuric acid speleogenesis (SAS) model was introduced in the early 1970s from observations of Lower Kane Cave, Wyoming, and was proposed as a cave-enlargement process due to primarily H2S autoxidation to sulfuric acid and subaerial replacement of carbonate by gypsum. Here we present a reexamination of the SAS type locality in which we make use of uniquely applied geochemical and microbiological methods. Little H2S escapes to the cave atmosphere, or is lost by abiotic autoxidation, and instead the primary H2S loss mechanism is by subaqueous sulfur-oxidizing bacterial communities that consume H2S. Filamentous ''Epsilonproteobacteria'' and Gammaproteobacteria, characterized by fluorescence in situ hybridization, colonize carbonate surfaces and generate sulfuric acid as a metabolic byproduct. The bacteria focus carbonate dissolution by locally depressing pH, compared to bulk cave waters near equilibrium or slightly supersaturated with calcite. These findings show that SAS occurs in subaqueous environments and potentially at much greater phreatic depths in carbonate aquifers, thereby offering new insights into the mi- crobial roles in subsurface karstification.

Cultivation of Spirulina in sewage for poultry feed

Article

Oct 1983

Summary A method for cultivatingSpirulina platensis in domestic raw sewage, coupled with pisciculture and water reclamation in an integrated recycling system, has been standardized. The alga is grown in an indigenously designed open-air pilot production unit consisting of 4 concrete basins with a total surface area of 450 m2. The harvesting and processing methods are based on simple filtration and sun drying. Extensive bench and field experiments have made it possible to produce pure blooms of AfricanSpirulina in sewage, using sodium bicarbonate and nitrate, and employing a fertilizing schedule which replenishes nitrogen withdrawn from the medium by the alga. Although urea and several ammoniacal nitrogen sources have been tried, the best source of protein-inducing nitrogen for mass cultivation ofSpirulina appears to be nitric nitrogen.

Observations on coastal erosion in Bermuda and measurements of boring rate of sponge Cliona Lampa

Article

Apr 1966

A. CONRAD NEUMANN

Measured profiles of the submerged portion of the steep cliffs that ring Harrington Sound, Bermuda, show that they are undercut as much as 4 to 5 m by a notch whose flat roof coincides closely with the level of extreme low tides. Nips, intertidal indentations with sloping roofs, are not present. Because of the largely subtidal position of the notch, the morphology of the undercut region, and the restricted wave energy, wave cutting is ruled out and bioerosion is proposed as the mechanism of undercutting. Bioerosion is suggested as a term for the removal of consolidated mineral or lithic substrate by the direct action of organisms. Observations of the emerged and submerged carbonate coastline of Bermuda reveal that organisms of many types alter the exposed rock surface from the upper reaches of the spray zone to depths well below sea level by processes that vary with degree of exposure, tidal range, rock type, organic community, and probably other ecological variables. A series of experiments with common rock‐destroying organisms has been initiated. Experiments in the laboratory and under natural conditions show that Cliona lampa, a boring sponge, is capable of removing as much as 6 to 7 kg of material from 1 m ² of carbonate substrate in 100 days. This corresponds to an erosion rate of calcarenite of more than 1 cm/year. If previous estimates are correct (that 90% of the boring by C. lampa is mechanical and not chemical), then 5 to 6 kg of fine‐grained carbonate detritus can be supplied from 1 m ² of sponge‐infected substrate in 100 days.

Biohydrometallurgy – This Microbiologist´s Perspective

Biohydrometallurgy and Biomineral Processing Technology:A Review on its Past, Present and Future

Abstract

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