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Effect of Span-80 and Ultrasonication on Biodesulphurization of Lignite by Rhodococcus erythropolis: Lab to Semi-pilot scale tests
Abstract
Turkey is a country with vast lignite reserves, which can serve as a potential source of energy to meet the rising energy demands. However, the sulphur present in coal delimits its application in several sectors. Recently, various techniques have emerged for sulphur removal from coal. In the present study, the efficacy of Rhodococcus erythropolis DSM 44308 towards biodesulphurization of a Turkish lignite (TL) sample has been studied. Additionally, the effects of ultrasonication and surfactant, Span 80 (S80), on biodesulphurization of the lignite sample have been studied and compared. Optimum parameters obtained through shake-flask experiments have been considered for further scale up in laboratory (1L) and semi-pilot (10L) bioreactors. To the best of our knowledge, the biodesulphurization approach indicated in the present study using R. erythropolis is being reported for the first time. The study revealed that a maximum desulphurization of 44.6% was achieved in shake-flask experiment using S80 concentration of 2% v/v. In the scale up bioreactor studies, 49.2% and 51.2% sulphur removal was achieved in 1L and 10L bioreactors respectively. The ultrasonication technique (upto 1 hour treatment) was observed to have a marginal effect, leading to only 6% enhancement in biodesulphurization when compared with the control. Mineralogical analysis of original and treated samples provided better insights into the structural and phase changes following microbial treatment in presence and absence of Span-80.
... Table 3 provides a detailed account of the major differences between the pyrometallurgy, conventional hydrometallurgy, and biometallurgical processes. Although biotechnology has made remarkable advances in various fields, including medicine, pharmaceuticals, agriculture, and biofuels, its application to coal [71][72][73] and coal-derived products has been relatively less explored. CFA waste, in particular, presents significant challenges owing to its heterogeneous chemical and physical nature, which makes it difficult to propose a robust workflow. ...
Coal fly ash (CFA) is a highly versatile raw material that has the potential to yield multiple value-added products, including cenospheres, zeolites, carbon nanotubes, and fertiliser substrates. Despite its versatility, a majority of these components are often overlooked, and CFA is primarily used for construction. Conventional processing methods of CFA are known to pose significant environmental challenges, including the leaching of hazardous materials, emission of toxic gases, and the high energy consumption needed to extract the value-added components. Herein, we explore the potential of biometallurgical approaches as an eco-friendly alternative to conventional processing methods for the comprehensive utilisation of CFA. Our focus is on the application of different microorganisms to CFA, the domestication of microorganisms, preprocessing of CFA to facilitate effective biometallurgical processes, the use of bioreactors, and synthesis of nano silica particles. We also propose a novel method for extracting the value-added components from CFA using a preprocessing technique (i.e., washing cycle), combined with multiple interactions with biometallurgical processes. Adopting this approach, we not only enhance environmental stewardship but also improve the circular economic aspects of multi-component utilisation, while providing valuable insights for the development of sustainable techniques for utilising CFA.
... Surfactants are known to modulate the solubility of hydrophobic compounds and improve their transport through bacterial membranes by reducing surface and interfacial tensions thus favoring the desulfurization rate. However, limited data is available regarding the role of surfactants particularly in BDS processes (Mishra et al., 2018). Another way of enhancing the stability, longevity, and efficient removal of the cells along with their successive recycling for the enhanced desulfurizing capabilities can be achieved by immobilizing technique (Mohebali & Ball, 2008). ...
Excessive emission of sulfur dioxides from the combustion of coal and other fossil fuels for thermal and industrial purposes has been associated with serious environmental hazards. Biodesulfisation (BDS) can be an effective approach for reducing the impact of toxic gases to its inbuilt operational feasibility under ambient environmental
conditions. In the present research, two strategies for BDS of a standard organosulfur compound such as dibenzothiophene (DBT) were investigated under laboratory conditions. In the first treatment, the role of different surfactants such as Tween-20, Tween-80, SDS, and EDTA on the desulfurization of DBT was investigated by the
application of bacterial consortium IQMJ-5. In the second treatment, Iron oxidenanoparticles were synthesized and immobilized on the surface of bacteria cells. Shake flask experiments were conducted with immobilized cells, surfactant amended immobilized cells, and control or noncoated cells. Among different surfactant treatments,
Tween-80 was found to be the most effective surfactant, showing maximum desulfurization activity at a concentration of 5 g/L. The transmission electron microscopy and X-ray diffraction analysis indicated that produced nanoparticles were spherical in shape with a size of about 46 nm and had a stoichiometric ratio of 55.85% and
44.15% between O and Fe, respectively. The nanoparticle treatment enhanced the DBT desulfurization process up to 11.37% as compared to the control, specifically when immobilized cells were used. Therefore, it was concluded that nanoparticles treatments with immobilization of the bacterial cells enhanced the desulfurization
rate of DBT under ambient reaction conditions and provide a sustainable alternative for commercial coal BDS
... Mishra and co-workers used the minimum amount of Span 80 (surfactant) in a bioreactor during the desulphurization process of Turkish coal using a micro-organism (Rhodococcus erythropolis) and they achieved an excellent result by removing approximately 51.2% sulphur. 77 Surfactants reduce the interfacial tension and the surface tension, which provide assistance to microbial attack and increase the probability of the biodegradation of coal (Turkish Lignite). 78 This bio-degradation takes place in both the aqueous phase and micellar phase in the presence of Span 80. Here, we present an experimental data set, which gives a clear idea about the effect of Span 80 on the desulphurization process using Leptospirillum ferriphilum (Table 8). ...
The rapidly increasing modern industrial world demands a huge uninterrupted energy supply, where high-quality coal (HQC) is one of the major sources of the required energy. In this regard, a gigantic amount of solid waste including ash and toxic chemicals, such as heavy metals, nitrate and sulphur, gases including NOx and SOx are emitted during the direct incineration process of low-rank coal. About 10 Gt of CO 2 and about one-fifth of total greenhouse gases in the world are emitted each year due to coal combustion in power plants, making it the single largest cause of climate change. The UN proposed that OECD countries stop producing electricity from coal by 2030 and the rest of the world by 2040. Herein, we discuss the development of modern technologies that can convert low-quality coal (LQC) into high-quality coal (HQC) to minimize the impact of fossil fuel burn, climate change, premature death of animals and all other related environmental hazards. Amongst the many established technologies, flotation pre-treatment is the most common and effective method used worldwide due to its lower energy input than other methods. In this review, we attempt to present an up-to-date understanding of the applications and utilities of surfactants in coal floating. We also demonstrate the possible modernization of this surfactant chemistry and its prospects.
... Some earlier studies have also indicated the use of Acidithiobacillus ferrooxidans towards oxidation of sulphide ores and concentrates for release of the associated gold (Komnitsas and Pooley 1990;Natarajan 1998). In addition, bioleaching has also been used to remove impurities such as sulphur from coal; this process is more specifically called as bio-desulphurization (Mishra et al. 2018a(Mishra et al. , 2018b(Mishra et al. , 2017Ye et al. 2018), removing iron from kaolin and quartz (Barnett, Palumbo-Roe and Gregory 2018;Giese et al. 2019;Jun et al. 2020) and dissolution of rare-earth elements from both primary and secondary resources (Fathollahzadeh et al. 2019;Panda et al. 2021a). The following sub-sections presents more detailed insights into the fundamentals and applications of this process. ...
Mineral biotechnological applications e.g. bioleaching and bio-beneficiation, for waste treatment and resource recovery have invited due attention owing to their economic and eco-friendly benefits in comparison to the conventional methods. Although research has progressed well, there are several aspects that are still not well understood and require more attention in view of full scale industrial application of these processes. For example, microbe-mineral/galvanic interactions, passivation phenomenon, synergistic effects among the microbes, identification of novel and robust microbial strains etc., require more studies to explore the fundamental aspects. In addition, mode of treatment for a wide variety of ores and/or concentrates, advances in engineering applications and scaling-up of bio-processes to industrial level along with the assessment of techno-economic feasibility, life-cycle and environmental impact can provide numerous opportunities for the researchers to further explore the applied aspects. This paper presents comprehensive details, including the latest research, on the fundamentals and applications of bioleaching, bioflotation and bioflocculation for the readers. The key microorganisms and their mode of action, factors affecting each bio-processes and aspects related to their scale-up and industrial applications are reviewed, analyzed and compared. It is believed that the recent advances, emerging dimensions and future directions of research presented in this paper will serve as a guide for the researchers to further explore this exciting field of research.
... The study was further scaled-up and tested in both laboratory (IL) and semi-pilot scale (20L) bioreactors using the same microbe [26]. In yet another study using the same lignite sample, Mishra et al. [27] also studied the biodesulphurization ability of Rhodococcus erythropolis DSM 44308 strain. It was observed that about 49.2% sulphur could be removed in a bioreactor system (1L scale) and 51.2% sulphur from a 10L bioreactor system. ...
Of late, sustainable energy development has received considerable importance throughout the world due to the growing concerns regarding climate change and environment protection. This in turn, has led to the search for alternatives, which are ecofriendly and cost-effective. Turkey possesses vast resources of lignite and renewable energies, which if utilized properly can reduce the current energy deficit and imports from other countries. Though renewables have received more attention in the past few years; yet, the vast lignite reserves of Turkey cannot be averted while considering the major indigenous energy resources of the country. The present review briefly discusses the existing energy situation in Turkey with particular focus on the indispensable role of coal as a valuable energy resource in meeting the country’s growing energy demand. Biodesulphurization as a green treatment technique for sulphur removal from coal is discussed along with some of the recent advances made with respect to the Turkish lignite. A brief description relating to the impact of COVID-19 on the energy sector is also discussed. Furthermore, future outlooks towards sustainable development are presented.
... Cardona and Márquez (2009) biodesulfurized Colombian coals with Acidithiobacillus ferrooxidans-like and Acidithiobacillus thiooxidans-like bacterium and observed 85-95% pyritic sulfur reduction and 31-51% of total sulfur reduction during 30 days treatment. Mishra et al. (2018) desulfurized lignite using R. erythropolis and observed a maximum desulfurization of 44.6% in shaking flask method. In the bioreactor study, they observed 49.2% and 51.2% sulfur removal. ...
Present investigation entails the results of desulfurization of high sulfur Giral (Rajasthan-India) lignite with the help of Burkholderia sp. GR 8–02. Total sulfur varies from 3.73% to 7.91%, where inorganic sulfur is 2.17–3.82%, pyritic and Sulfate sulfur is 0.90–2.42% and 0.47–2.84%, respectively. Chemical analysis, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM/EDS) were used in order to understand desulfurization. Bacterial treatment caused a significant reduction in total sulfur content ranging from 23.59% to 37.55%. Organic sulfur removal ranges from 11.06% to 20.54% while pyritic and Sulfate sulfur removal vary from 10.40–43.39% and 50.89–96.97%, respectively. In addition to desulfurization of lignite, the reduction in the ash yield and the volatile matter was also observed whereas there was a relative increase in the fixed carbon and elemental carbon content. Further, an increase in the gross calorific value from 3189 kcal/kg to 3482 kcal/kg was noticed.
... To overcome the handicaps caused by the above explained obstacles, researchers have begun to direct cleaning of low rank lignites by physical and chemical methods, biodesulphurization and combinations of these to reduce high ash and sulphur contents. Among these methods, biodesulphurization arises as a promising technique that is a process of sulphur removal by microbiological operations, which this environmentally friendly method is performed under the ambient temperature and pressure (Aytar et al., 2011;He et al., 2012;Koca et al., 2017a,b;Mishra et al., 2018). Both bacteria and T fungi were utilized to remove sulphur and ash in lignites (Acharya et al., 2005;Aytar et al., 2013Aytar et al., , 2014Liu et al., 2017;Ye et al., 2018). ...
Biological desulphurization is a good option because of simple equipment, easy operation, and low cost advantages. In this study, biodesulphurization of low rank lignites having high ash and sulphur content was investigated through a drum reactor using Alternaria sp. fungus which provided high removal of sulphur at erlen scale in our previous study. Designing of experiments, analysing of experimental results, creating the mathematical models and optimization of conditions were performed using Central Composite Design Method. Experimental work resulted in about 20% sulphur removal, about 21% ash removal and about 42% reduction in sulphur emission values. Analyses showed that both pyritic (17% removal) and organic sulphur (about 19% removal) were reduced. Besides, after biotreatment, FTIR, SEM-EDS, TGA-DTA analysis as well as volatile matter and major oxide analysis were carried out. Furthermore, data for increasing sulphur removal in drum type bioreactor and moving to larger scale by enhancing solid ratio were provided.
... Hence reduction of sulfur are necessary to make such coal suitable for utilization. In past research on desulfurization of high sulfur coal has been reported by many researchers [2][3][4][5][6][7][8][9]. Particularly considering the coal available in Assam and nearby other states in north eastern part of India, some research work has been carried by chemical treatment using NaOH and KOH, H 2 O 2, DMF, K 4 Fe(CN) 6 etc. [1,[6][7][8][10][11][12], by ultrasonic treatment [6][7][8]13,14], by flotation [15]. ...
Biosolubilization of coal to produce non-fuel products (humic acid) has offered an alternative method for coal clean utilization. Previous studies have proved pretreating low-rank coal with surfactant can improve fugal biosolubilization. However, limited reports referred high-rank coal. In the present work, a fungus HN-1 isolated from Yanzhou coal mine soil in Shandong province, northeast China was used to biodegrade Shandong bituminous coal, and the possible degrading mechanism was analyzed. The results showed that the homology of HN-1 was 97% with the white-rot fungus Hypocrea lixii, so it was assigned as Hypocrea lixii HN-1. The fungal strain HN-1 had the ability to solubilize the bituminous coal to produce black droplets within 10 days. Furthermore, it appeared that pretreatment by the surfactant sodium dodecyl sulfate could promote coal biosolubilization. The weight losses after biosolubilization of raw coal (YM) and surfactant-treated coal (A coal) were 11.33% and 14.02%, while the humic acid of YM and A coal increased by 1.42% and 2.99%, respectively. The FT-IR showed that the raw coal almost remained unchanged after biosolubilization. However, some small molecule functional groups including disulfides, amino groups, hydroxyl groups and oxygen-containing were introduced into the coal after pretreatment with surfactant.
The present work investigated an effective method to remove organic sulfur in coal utilizing different microorganisms (Nocardia mangyaensis and Pseudomonas putida). The most obvious finding to emerge from the sulfur forms analysis is that the organic sulfur removal of these two bacterial strains on Yunnan bumuga high sulfur coal were 61.58% and 54.19%, respectively. This result may be confirmed by the FTIR analyses that there were obvious decreases of intensity after biotreatment in the C‐S bond. Besides, the results of X‐ray diffraction (XRD) and X‐ray photoelectron spectroscopy (XPS) showed that major mineralogical phases in the forms of kaolinite and pyrite exist in raw coal. And more than 80% of thiophene and sulfoxide in the raw coal were removed by Nocardia mangyaensis and Pseudomonas putida. In addition, the results of the thermogravimetric analysis indicated that the combustion performance of biotreated coal samples was better than that of raw coal, and the most probable models to describe the combustion kinetics for biotreated coal and raw coal at different stages were obtained by the Arrhenius method and Coats‐Redfern method. This article is protected by copyright. All rights reserved.
Screening and studying the lignite solubilization/degradation capacities of indigenous microorganisms are key to exploring the in-situ biotransformation of lignite. Here, a fungus was isolated from in-situ lignite samples and identified as Fusarium sp. NF01. This isolate was then cultured on four different carbon sources to evaluate its lignite transformation capacity. When cultured on a solid agar medium containing sodium gluconate or sodium glutamate, Fusarium sp. NF01 completely liquefied 0.5 g of lignite within six days, and when cultured in a liquid medium containing sodium gluconate, the weight of lignite decreased by 28.4% within seven days. Elemental analysis showed that the lignite biodegradation rate was inversely proportional to the C/O ratio of the residual lignite samples. Additionally, a 5.9% biodesulfurization rate was achieved when Fusarium sp. NF01 was cultured in the presence of sodium gluconate. Finally, Fourier-transform infrared analysis of the residual lignite samples revealed relatively weak signal intensities of the signature peaks representing the following: aromatic ring side chains; ether, ester, and alcohol bonds; aromatic ring carbon-carbon double bonds; and aliphatic methyl and methylene. The results showed that Fusarium sp. NF01 can degrade lignite in a carbon-dependent manner and could be thus used for the bioconversion of subsurface coalbeds.
Coal is one of the most commonly utilized fossil fuel for energy production across the globe leading to higher amount of emission of sulfur-di-oxide (SO2) in the atmosphere. Combustion of coal containing higher contents of sulfur is a major factor responsible for acid rain and associated environmental degradation. The currently used physico-chemical approaches for removal of sulfur from coal are expensive, toxic in nature and inappropriate for different types of coal. The application of microbial resources for removal of sulfur from coal is an ecofriendly technique and could be successfully employed at industrial scale after laboratory scale process optimization. The process of sulfur removal by microbes is carried out by enzymes and is considerably influenced by different factors including pH, temperature, nutrient composition, shaking or standing condition, coal types and most importantly type of microorganisms used. Different bacteria and fungi isolated from coal contaminated site as well as non-contaminated site exhibiting sulfur removal potential can be used as next generation tool for development of clean coal technology. Furthermore, through the application of modern genetic manipulation techniques, enhanced expression of genes responsible for desulfurization can be performed in order to accelerate the process of sulfur removal from coal. The present chapter is prepared with an aim to discuss the diverse microbial population participating in desulfurization, their efficiency, mechanism of sulfur elimination, role of important environmental factors along with possible applications and challenges in industrial scale sulfur removal.
Mineralogically distinct coal samples respond differentially to microbial attack. In the present study, a mixed meso-acidophilic bacterial consortium predominantly comprising of Acidithiobacillus ferrooxidans strain was investigated for its biodesulphurization abilities for three distinct sulphur bearing samples (Goa CPC, Rajasthan Lignite, Assam Coal) of Indian origin in iron (9K+) and iron-free (9K-) media. A media devoid of Fe (II) iron was seen to be more effective for sulphur removal with maximum desulphurization of 45.19% for Assam coal followed by 36.8% for Rajasthan Lignite and 23.38% for CPC respectively. The proximate analysis, FTIR patterns and XRD analysis of the samples provided better insights into understanding the mineralogical and compositional changes in the coal matrix. Owing to the higher efficiency, Assam coal was additionally subjected to further optimization studies and characterization of the treated coal through TGA. The study indicated that the gross calorific values for all the samples increased following microbial treatment in 9K- media thereby providing a scope for further scale-up studies.
This study mainly combines single factor experiment with orthogonal experiment to systematically investigate the effects of particle size, inoculum amount, pH value of the medium, ultrasonication time and species of surfactant on biodesulfurization of the high sulfur coal from Shanxi by using Thiobacillus ferrooxidans, Escherichia coli and Pseudomonas putida. The results revealed that the dominant strain was Pseudomonas putida which attained 58.23% of total sulfur removal during 10 days at the particle size of -125 + 75 μm, pH of 6.0, inoculum amount of 25 mL, ultrasonication time of 60 mins and Tween 80 concentration of 0.1%. Analysis of raw coal and biotreated coal by FTIR spectroscopy and X-ray diffraction indicated a modification of the coal structure after biodesulfurization. The curves of thermogravimetry (TG) for raw coal and biotreated coal also showed that the temperature of the coal pyrolysis significantly reduced, which meant that the thermal stability of the coal after biodesulfurization was lowered than raw coal. And the energy value of coal was not affected in the biodesulfurization process. After treatment with Pseudomonas putida, its calorific value only increased from 6308 cal/g to 6326 cal/g. Liquid products after biodesulfurization were extracted with a series of organic solvents, and each extract was characterized by gas chromatography-mass spectrometry (GC/MS), indicating the presence of sulfur-containing organic compounds in the liquid phase product. Ultimately, following these characterization results, the desulfurization mechanisms of all three bacteria were derived.
The worldwide increasing demand for environmentally-friendly transportation fuels and the strict regulations by the environmental protection agencies have put a great pressure on crude oil refining and upgrading industry. The main current technology for the desulfurization of crude oil and its fractions is hydrodesulfurization. However, this process is plagued with several drawbacks. The growing pressure on petroleum refining industries to reduce sulfur contents in fuels has made hydrodesulfurization process even more unappealing. Hence, more effective alternatives have been (and are still) sought by petroleum refining industries. Enzymatic desulfurization process has recently emerged as a promising alternative that has the potential to be cost-effective, efficient and environmental-friendly. In enzymatic desulfurization process, enzymes (whether intracellular or extracellular) attack organosulfur components in the crude oil or its fractions and remove sulfur through a series of enzymatic reactions. The process is an energy-saving process, devoid of emission of harmful gases into the atmosphere, and utilizes completely biodegradable catalysts. This article reviews the recent progress in desulfurization of crude oil and its fractions using extracellular and intracellular enzymes. Challenges encountered during enzymatic desulfurization are highlighted, and some potential solutions to tackle the challenges are proposed. Future outlooks into the development of more efficient enzymatic desulfurization processes have been pinpointed.
Coal continues to be a significant source of energy in the world. It is very important to utilize this energy source as much as possible, to operate unutilized loss reserves due to its characteristics. In this context, the necessity to continue studying on clean coal technologies was emphasized in terms of sustainability in energy production and its use, safety and environmental issues. Since approximately 50% of total coal deposits of the world are low rank, it is required to clean them by implementing different and efficient technologies to improve the utilization of low rank coals. This review summarized importance of clean coal technology, biological treatments until now, recent advances and future trends in coal biobeneficiation technologies as energy conserving and environmentally friendly processes. Finally, in the lights of the data obtained from all studies, the basic steps for the possible use of biocleaning methods in industrial scale are also summarized in this review.
Coal is one of the most abundant nonrenewable fossil fuels, in Pakistan. However, in general, the quality of coal is too low to offset the practical, economic, and regulatory barriers to its utilization. High sulfur content comes up as one of the bottlenecks in productive usage of indigenous coal. Biotechnology can emerge as a panacea for upgrading the huge reserves of high sulfur coal. In current study, the sulfur removal potential of Rhodococcus spp. (Eu-32) was investigated using coal from Dukki, Baluchistan, Pakistan. Biodesulfurization process was optimized for various parameters and maximum decrease of 40% and 60% in total and organic sulfur contents, respectively were achieved in 15 days. The Langmuir and Brunauer–Emmett–Teller (BET) surface areas of the biotreated coal were increased by 20 and 16 times, respectively. Scanning electron microscope showed higher tendency of attachment of bacterial cells to the coal particles. Our results revealed that Eu-32 could remove significant amounts of organic sulfur from coal and could be used in the pre-combustion operations with appropriate arrangements.
In the present study pistachio shells obtained from Aegina island, Greece, were subjected to slow pyrolysis for the production of biochar. Pyrolysis was carried out over a temperature range of 250-650 °C for 1 h using a heating rate of 10 °C min−1 and the quality of the produced biochar was assessed by evaluating its main properties, namely pyrolysis yield, pH, volatile matter, char, fixed carbon, ash and C, H, S, N content. Thermogravimetric analysis, X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy were used for the identification of the morphology and structure of the produced biochar. Finally, the potential of biochar to remove heavy metals, namely Pb and Cu, from synthetic solutions was investigated. A kinetic study indicated that sorption can be very well described by the pseudo-second order kinetic model, while simulation of the sorption isotherms provided better fit for the Freundlich model. The experimental data show that Pb is adsorbed more efficiently compared to Cu in all biochars, while the highest % adsorption for both heavy metals, almost 100 %, is shown for 10 g L−1 biochar produced after pyrolysis at 550 °C when the initial Pb and Cu concentration in solution was 15 mg L−1.
The moderate thermophilic mix culture bacteria were used to depyritize the Illinois coal of varying particle sizes (–100 μm, 100–200 μm, +200 μm). Mineral libration analysis showed the presence of pyrite along with other minerals in coal. Microbial depyritization of coal was carried out in stirred tank batch reactors in presence of an iron-free 9K medium. The results indicate that microbial depyritization of coal using moderate thermophiles is an effi cient process. Moreover, particle size of coal is an important parameter which affects the effi ciency of microbial depyritization process. At the end of the experiment, a maximum of 75% pyrite and 66% of pyritic sulphur were removed from the median particle size. The XRD analysis showed the absence of pyrite mineral in the treated coal sample. A good mass balance was also obtained with net loss of mass ranging from 5–9% showing the feasibility of the process for large scale applications.
During beneficiation of coal at the coal mining area of Tula, Russia, huge volumes of coal wastes with considerable residual pyrite content are produced. These wastes that are usually disposed of without specific care in the environment are active sources of coal mine drainage generation which severely contaminates soils, surface- and groundwater and endangers the ecosystems of the area.
In the present paper a complete environmental characterization research is carried out in order to determine the characteristics of the wastes, establish their acid generation potential, the leachability and bio-availability of several hazardous constituents and predict the environmental impacts at the disposal sites. Based on this data as well as on process parameters and disposal practices, an evaluation of desulphurization technologies is carried out.
Experimental studies reveal that these wastes are considered as permanent sources of coal mine drainage generation and therefore cause extensive contamination at the disposal sites. In addition, due to several technological constraints of the desulphurization technologies and the characteristics of the wastes, the potential of in situ desulphurization is considered low. Desulphurization technologies present a higher potential only if applied in the framework of an integrated waste management scheme.
In this study, the use of a bituminous coal for the production of activated carbons with chemical activation was investigated. The effects of process variables such as chemical reagents, activation temperature, impregnation ratio and carbonization temperature were investigated to optimize these parameters. The resultant activated carbons were characterized in terms of iodine number, BET surface area, and total and micropore volumes. Acidic surface groups were established by Fourier Transmittance Infrared Spectroscopy (FTIR) technique.
The Seyitomer basin, which is one of the most productive coal basins of western Anatolia-Turkey, contains two seams, lower and upper, in the Lower-Middle Miocene lacustrine Seyitomer Formation. The lower seam in this basin is only extensively exploited by open-cast methods and produced lignites are mainly consumed in coal-fired power plants. A total of thirty-six lignite samples, of which thirty-one are from the lower seam and five from the upper seam, were collected from the two locations (DK and S30), and have been subjected to chemical and petrographic analyses. The chemical analyses of the coal ash samples with XRF show that the lignite samples on a whole-coal basis are enriched for Cr and especially Ni, and Bi, Co, Cu, Mo, Sc and V, and also exceed the range values of the most world coals. The most abundant maceral group of all the samples is huminite, in which textinite, ulminite and especially densinite are rich. Liptinite group macerals in all the samples, which are considerably higher than the inertinite group macerals, include mainly sporinite and liptodetrinite. The mean values of maximum reflectance (av. 0.29%) in oil of ulminite from the lignite samples in the Seyitomer Basin show a lignite stage (soft brown coal) in rank. In addition, vertical variations of some results in the two lignite seams have been also considered in this study.
More than 10 tons of coal samples from Luxing Coal Mining Company, Guizhou Province have been collected from various points and sieved into different sizes from the as mined products according to its market demand and utilization. The series samples with different sizes have been characterized using X-Ray diffraction (XRD), Laser Raman (LR), Infrared spectroscope(IR), 13 C solid state magic angle spinning nuclear magnetic resonance (13 C MAS NMR), and scanning electron microscope. It is seen that the bigger lump coal has higher pyrite content and quartz, the big lump coal normally has higher inorganic sulphur content, while the coal powder has higher organic sulphur content. In addition, the coal powders with smaller size have higher dolomite content. The kaolinite and quartz are present in the coal with various particles size. The carbon in the Luxing Coal is present in good crystalline structure, in which 95% of the coal is graphitic structural in the coal with smaller size.
High sulphur coal sample from Ledo colliery of Makum coalfield, Assam, India was studied using FT-IR and XRD methods. FT-IR
study shows the presence of aliphatic -CH, -CH2 and -CH3 groups, aliphatic C-O-C stretching associated with -OH and -NH stretching vibrations and HCC rocking (single and condensed
rings). XRD pattern of the coal shows that it is amorphous in nature. Function of Radial Distribution Analysis (FRDA) indicates
that coal is lignite in type and there is no evidence of graphite-like structure. The first maximum in the G(r) plot of FRDA at r = 0.14 nm relates to the aliphatic C-C bond (Type C-CH=CH-C), the second maximum at r = 0.25 nm relates to the distance between carbon atoms of aliphatic chains that are located across one carbon atom. The curve
intensity profiles obtained from FRDA show quite regular molecular packets for this coal. The coal was found to be lignite
in nature.
Short-term water solubility characteristics of bottom ashes and fly ashes from two important Turkish lignites were investigated in association with the concentrations of some heavy metals. For this, the alkaline ashes were interacted with acidic rain water and dilute acidic solutions for leaching times changing from 10 min to 2 days to assess the mobilization potential during ash–water interactions. The concentrations of leachable trace elements such as chromium, lead, cadmium, zinc, and nickel were determined in leachate using Atomic Absorption (AA) Spectrometry. Iron concentrations were also investigated since it plays a critical role on trace element enrichment mechanism. The mineralogical and structural identification of the parent ash samples were carried out by X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) techniques. The extent of the mobility of the ashes was identified regarding the physical and chemical properties of the ashes. Concentrations of the trace elements in leachates were compared to the several guideline values regulating the maximum contaminant levels in drinking water and irrigation water as well as the regulatory threshold concentrations in leachate.
The U.S. Geological Survey (USGS) and the Turkish General Directorate of Mineral Research and Exploration (Maden Tetkik ve Arama Genel Müdürlügü, MTA) are working together to provide a better understanding of the chemical properties of Turkish coals from major Turkish lignite producing areas.The coals in Turkey are generally low rank (lignite or subbituminous) formed in several different depositional environments at different geologic times and have differing chemical properties. Eocene coals are limited to northern Turkey; Oligocene coals, found in the Thrace Basins of northwestern Turkey, are intercalated with marine sediments; Miocene coals are generally located in Western Turkey. The coal deposits, which have limnic characteristics, have relatively abundant reserves. Pliocene–Pleistocene coals are found in the eastern part of Turkey. Most of these coals have low calorific values, high moisture, and high ash contents.Analysis of 143 coal channel samples (most are lignite and subbituminous in rank, but a few are bituminous and one is anthracitic in rank) has been completed for up to 54 elements and other coal properties using a variety of analytical techniques, including inductively coupled plasma emission and mass spectrometry, instrumental neutron activation analysis, and various single element techniques and ASTM standard procedures. Many of these coals have elemental concentrations similar to U.S. lignites found in the Gulf Coast and Fort Union regions. However, maximum or mean concentrations of B, Cr, Cs, Ni, As, Br, Sb, Cs, and U in Turkey are higher than the corresponding maximum or mean values found in either the Fort Union or Gulf Coast regions.
The aim of this work was to evaluate the effect of several non-ionic surfactants (Tween-80, Triton X-100 and Tergitol NP-10) on the ability of different bacteria (Enterobacter sp., Pseudomonas sp. and Stenotrophomonas sp.) to degrade polycyclic aromatic hydrocarbons (PAHs). Bacterial cultures were performed at 25 °C in an orbital shaker under dark conditions in BHB medium containing 1% of surfactant and 500 mg l−1 of each PAH. Experiments performed with Tween-80 showed the highest cell density values and maximum specific growth rate because this surfactant was used as a carbon source by all bacteria. High degree of PAHs degradation (>90%) was reached in 15 days in all experiments. Toxicity increased at early times using Tween-80 but decreased to low levels in a short time after the firsts 24 h. On the other hand, Triton X-100 and Tergitol NP-10 were not biodegraded and toxicity kept constant along time. However, PAHs-degradation rate was higher, especially by the action of Enterobacter sp. with Tween-80 or Triton X-100. Control experiments performed without surfactant showed a significant decrease in biomass growth rate with a subsequent loss of biodegradation activity likely due to a reduced solubility and bioavailability of PAHs in absence of surfactant.
In biocatalytic conversions, substrates and products may display inhibitory or toxic effects on the biocatalyst. Rhodococcus erythropolis 1awq could further remove sulfur from hydrodesulfurized diesel oil, and the biodesulfurization was enhanced by the surfactant
Tween 80. Tween 80 was shown to decrease the product concentration associated with the cells, reducing product inhibition.
Biodesulfurization is a microbial biocatalytic process that removes sulfur from hydrocarbons. Because this bioprocess can be influenced by substrate bioavailability, we studied the effect of natural and synthetic surfactants on biodesulfurization using metabolically active and immobilized bacterial cells. Surfactants are surface-active molecules that improve the solubility of solids or water insoluble substrates. Metabolically active cells of the desulfurizing strain Rodococcus rhodochrous IGTS8 were immobilized on Silica (Si), Alumina (Al) and Sepiolite (Sep) by adsorption. The desulfurization activity was determined in the presence of biological and synthetic surfactants. The results indicate that adding surfactants to the catalytic system formed by non-immobilized or immobilized cells increases desulfurizations of DBT and gas oil. A major effect was observed when a microbial biosurfactant was used to improve the interaction between insoluble sulfured substrates and the respective immobilized biocatalytic systems. The bioavailability of the sulfured substrates improved because of micelle formation. The use of a biocatalytic system conformed by immobilized cells; biological surfactants and sulphured substrates can be an improvement methodology for BDS makes more feasible a potential application on industry.
Coal has been serving as a profuse source of energy since centuries and several attempts are being made to reduce sulphur emission levels from coal. Recently, pretreatment techniques such as ultrasonication and utilization of surfactants as additives have surfaced aiming at improving the biodesulphurization of coal. In the present study, biodesulphurization of Turkish lignite was studied for the first time using Leptospirillum ferriphilum. Attempts have been made to study the biodesulphurization aspects of the lignite sample where the effect of Fe²⁺ iron, surfactant Span 80 and ultrasonication were studied under shake flask conditions. The study indicated Fe²⁺ to be an essential component in the growth media for improving biodesulphurization performance (with 56.2% total sulphur removal). Span 80 (0.05% v/v) marginally enhanced the biodesulphurization of the lignite sample (nearly 61% of total sulphur removal). The carbon content in the lignite sample increased following biodesulphurization. Ultrasonication of the lignite sample, on the other hand, did not yield significant sulphur removal when compared to the effect of Span 80. About 57.6% of total sulphur could be removed from the sample when ultrasonicated for 60 min. Mineralogical characterization along with thermal analysis of the samples pre and post biodesulphurization provided more information on different phases present in coal and the effect of microbial treatment on them.
The floatability of lignite is usually known to be very poor. Generally, surfactants are applied to improve its hydrophobicity in the flotation process. This research focuses on the adsorption performance of a nonionic surfactant, sorbitan monooleate, on the lignite particles with different densities, including −1.45 g/cm³, −1.80+1.45 g/cm³, and +1.80 g/cm³. From Fourier transform infrared spectroscopy results, it was obvious that organic oxygen functional groups determined the surface properties of lower density lignite, whereas inorganic Si-O determined the surface properties of higher density sample. Qualitative similarities are found in the curves of the surface electrokinetic potentials versus pH values. Points of zero charge of the samples were measured to be at pH values of 2.3, 3.0, and 3.0, respectively. Hence, organic oxygen functional groups are similar to Si-O on the coal surface in adsorbing OH– and H⁺ in electrolyte solution. The X-ray photoelectron spectroscopy results show that the lower density lignite particle has stronger adsorptions of sorbitan monooleate. In other words, organic oxygen functional groups have the priority over inorganic Si-O in adsorbing sorbitan monooleate. In addition, polar groups of the surfactant have different adsorbing abilities with organic oxygen functional groups. Interestingly, the oxygen content of +1.8 g/cm³ lignite nearly does not change after the pretreatment by sorbitan monooleate solutions. Therefore, the sorbitan monooleate molecule almost cannot adsorb on the mineral surface.
In this study, low-rank lignite coal sample collected from Jining coalfield of Shandong province in China was subjected to desulphurization by using a new bacteria and Acidithiobacillus ferrooxidans isolated from the native coal mine site. The molecular identification of the 16S rRNA gene showed that the new native bacteria was Pseudomonas sp., denoted as NP22, and it is reported for the first time for the capability to remove about 46% of total sulphur from the lignite coal. In the present study, the effects of various parameters such as medium pH, incubation time, pulp density, particle size, incubation temperature on desulphurization from lignite coal with the Pseudomonas sp. NP22 and Acidithiobacillus ferrooxidans were investigated. Analytical characterization indicated that total sulphur content of lignite coal was reduced to 2.76% and 3.23% by using two microorganisms. Also, the calorific value of lignite coal was not affected adversely after two microorganisms' desulphurization but rather its calorific value increased from 6219 cal/g to 6406 cal/g and 6315 cal/g, however, the ash content of the lignite coal was eliminated.
Microorganisms in a biofilter play important roles in the gas contaminants treatment process. In this study, thermophilic desulfurization bacteria were inoculated in a thermophilic biofilter for SO2 treatment after acclimation and enrichment. Molecular biology techniques were applied to detect temporal variation of microbial population during acclimation and biofilter start-up period. The acclimation temperatures were 50, 55, and 60 °C. Desulfurization bacteria dominated the enrichments. During acclimation, desulfurization bacteria and thermophilic bacteria increased from 36.84% to 78.95%–52.94% and 88.24%, respectively. In addition, the microbial diversity indices of these enrichments decreased with time. Substrate species and acclimation temperature influenced the microbial structure of the enrichments. The thermophilic biofilter inoculated with enrichments could achieve a rapid start-up, and over 80% of removal efficiency could be obtained within two weeks. The maximum elimination capacity was 38.71 g m−3 h−1 at 152 mg m−3 inlet concentration. The total sulfur bacteria proportion increased obviously during the start-up period. Moreover, desulfurization bacteria that originally existed in inocula, e.g., Pseudomonas putida, Bacillus thioparans, Microbacterium sp., and Thermoanaerobacteriaceae, were abundant in the thermophilic biofilter for SO2 removal.
Atmospheric pressure-temperature programmed reduction coupled with on-line mass spectrometry (AP-TPR/MS) is used for the first time on microbiologically treated coal samples as a technique to monitor the degree of desulfurization of the various sulfur functionalities. The experimental procedure enables the identification of both organic and inorganic sulfur species present in the coal matrix. A better insight in the degradation of the coal matrix and the accompanying processes during the AP-TPR experiment is obtained by a quantitative differentiation of the sulfur. The determination of the sulfur balance for the reductive pyrolysis gives an overview of the side reactions and their relative contribution in the total process. The volatile sulfur species are unambiguously identified using AP-TPR off-line coupled with gas chromatography/mass spectrometry (GC/MS). In this way, fundamental mechanisms and reactions that occur during the reductive pyrolysis could be quantified, explaining the differences in AP-TPR recoveries. Therefore, this study gives a clearer view on the possibilities and limitations of AP-TPR as a technique to monitor sulfur functionalities in coal.
For an efficient operation in biodesulfurization of petroleum and related fuels, the aqueous solubility of insoluble or very slightly soluble sulfur compounds contained in the petroleum products has to be increased. In this study, polyoxyethylene nonionic surfactants were used in order to enhance the aqueous solubility of insoluble or very slightly soluble sulfur compounds contained in the bunker-C oil and the solubilized sulfur contents in the aqueous surfactant solutions were measured by X-ray sulfur spectrophotometer. The most hydrophobic surfactant used during this study showed the maximum solubilization capacity for sulfur compounds contained in the bunker-C oil and the solubilization of sulfur compounds was found to increase with temperature and to be abruptly increased at above 5 wt % surfactant concentrations. It was found that Tergitol series surfactants showed higher solubilizing capacity than Neodol series surfactants presumably due to the disruption of the regular packing in the hydrocarbon region of the surfactant micellar aggregates and that the addition of a cosurfactant and/or an electrolyte increased the solubilization of sulfur compounds in the bunker-C oil. It was also shown that partitioning phenomena were shown to be significant with a hydrophobic surfactant especially at high temperature and pH of the Tergitol surfactant solution did not affect the solubilization of sulfur compounds. The growth of M6 sulfur-reducing bacteria was not greatly affected by the addition of both nonionic surfactant and cosurfactant. Desulfurization experiments with M6 sulfur-reducing bacteria showed that the biodesulfurization rate of bunker-C oil was enhanced with addition of nonionic surfactant and these data suggested the potential applicability of surfactant to the actual biodesulfurization system.
Studies on the desulfurization of three or more ringed-compounds, which are considered to inhibit biodesulfurization of crude oil, are rare. In this paper, desulfurization of a three-ringed compound benzo[b]naphtho[2,1-d]thiophene (BNT) by an isolated strain Gordonia sp. IITR100 is described. The bacterium mediates desulfurization of BNT and utilizes the released sulfur for its growth. The reaction is accompanied with the formation of metabolites BNT-sulfone and BNT-sulfinate, in addition to the reported BNT-hydroxide. Recombinant E. coli cells, harboring DszC or DszA, were also able to mediate the metabolism of BNT to BNT-sulfone, or of BNT-sulfone to BNT-sulfinate, respectively. Desulfurization of BNT, both by IITR100 and E. coli-DszC cells was strongly inhibited in the presence of dibenzothiophene. The results are discussed in the context of the biodesulfurization of petroleum fractions where several organosulfur compounds are present together.
Microwave heating has been used in desulfurization of coal. Removal of organic sulfur and organic sulfur forms alterations of Xishan (XS) coal and Yunnan (YN) coal was investigated under microwave and ultrasonic irradiation. The results showed the optimum conditions for desulfurization were 50 min and 560 W for microwave and ultrasound for both coals. The desulfurization rate was maximum 23.53% for XS coal and 76.58% for YN coal. The effect of combining microwave and ultrasonic irradiation on desulfurization was stronger than simple microwave irradiation. The content of sulphone sulfur in coal was increased from the XPS after microwave and ultrasonic co-enhanced oxidative desulfurization.
The effects of inoculum percentage, initial pH, growth temperature, shaking rate, substrate type and initial substrate concentration on the growth kinetics of Rhodococcus rhodochrous, a sulfur-removing bacterium, were investigated. The optimum value for each parameter that favoured the maximum specific growth rate was calculated from models established through linear of non-linear regression of the relevant data. Around these optima, biodesulfurization experiments were performed with sterile lignite. An increase in sulfate, pyritic and organic sulfur reduction with increasing reaction time were observed. The highest decreases in the total (30.2%) and organic sulfur (27.1%) contents were obtained with Mengen lignite at 75 h of biodesulfurization.
Organic sulfur components of the petroleum are too resistant to be removed by the conventional
desulfurization processes. This study aimed to investigate the removal of dibenzothiophene (DBT) as an
organic sulfur compound, from the oily phase by a bioprocess employing the immobilized cells.Rho-dococcus erythropolisR1 cells were encapsulated in calcium alginate beads by considering factors such as
the alginate concentration, size of the beads, the concentration of surfactants andƔ-Al2O3nano particles
for optimizing biodesulfurization (BDS) via Taguchi approach. The impact of two cofactor precursors
(nicotinamide and riboflavin) on the long term BDS efficiency was also examined. The results indicated
that the optimum factor levels for the bigger is better criterion could be achieved at 20% (w/w) ofƔ-Al2O3
nano particles, alginate beads size equal to 1.5 mm, 1% (w/v) of the alginate and 0.5% (v/v) of span 80. The
related statistical analysis showed that the concentration ofƔ-Al2O3nano particles was the most sig-nificant factor in the BDS process. Moreover, the addition of nicotinamide and riboflavin significantly
decreased the biocatalytic inactivation of the immobilized cells system after successive operational steps
enhancing the BDS efficiency by more than 30% after four steps. It can be concluded that a combination
of the nanoƔ-Al2O3particles with alginate immobilized cells could be very effective in biodesulfurization
process.
Acid leaching is an alternative to the conventional stabilization
of ash by carbonatization or polymer induced
coagulation/flocculation [1-3]. It has also been suggested that ash can
replace limestone in biohydrometallurgical processing [4, 5].
Dissolved metals can be recovered from the effluent in the downstream
stages of a bioleaching process. Metals extracted at
delocalized units, i.e., in separate acid leaching processes,
precipitated and shipped to the main biohydrometallurgical plant as
hydroxides or sulfides. The above scenario is threefold beneficial: (i)
it saves limestone in the hydrometallurgical processing of sulfidic
minerals, (ii) it recycles metals and (iii) it creates an inert solid ash
residue. All three come with economic as well as environmental
gains. The acid consumption in ash/water slurries (pH 1.0, initial S/L
ratio 1:10) starts at a modest 5 L 1 M H2SO4 per kg dry peat fly-ash
and reaches 15 L /kg for bottom-ash from the combustion of wood
chips and 18-24 L/kg for ash from lignites [4, 5]. Mn and Mg are
regularly leached to near unity, but the yields of other dominant
elements - K, Na, Al and Fe - vary, probably due to the presence of
stable oxides.
The current work shows the time dependencies of acid
consumption and elemental compositions in the aqueous phase for
four ashes and the kinetics of acid consumption of an additional 10
coal-ashes and whole coals. Time dependent studies can link acid
consumption to the dissolution of major ash components and
correlate trace element extraction to the destabilization of certain
major phases [6]. This is the topic of a subsequent paper [7]. The
current work forms a platform to
Energy is an essential factor to achieve sustainable development. So, countries striving to this end are seeking to reassess their energy systems with a view towards planning energy programmes and strategies in line with sustainable development goals and objectives. As would be expected, the rapid expansion of energy production and consumption has brought with it a wide range of environmental issues at the local, regional and global levels. States have played a leading role in protecting the environment by reducing emissions of greenhouse gases. Turkey is an energy importing country with more than half of the energy requirement being supplied by imports, and air pollution is becoming a great environmental concern in the country. On the other hand, Turkey's geographical location has several advantages for extensive use of most of the renewable energy sources. In this regard, renewable energy resources appear the most efficient and effective solutions for clean and sustainable energy development in Turkey. This paper provides an overview of global energy use and renewables for clean and sustainable energy policies in Turkey.
Control of air pollution originating from sulfur oxide emissions has gotten increasing attention in Turkey during the past decade. Consequent upon serious episodes of air pollution in the capital city, Ankara, and in several other Anotolian cities, it is now clear that the prime cause of pollution is the burning of high-sulfur Turkish lignites for space heating. Furthermore, the Transboundary Air Pollution Control International Act stipulates that sulfur oxide emissions from power plants must be lowered drastically as we approach the end of the century. One method of controlling sulfur oxide emission is by desulfurization of coals prior to combustion. Among the methods available, bacterial desulfurization prior to coal combustion seems promising for the future in many respects. The common method of testing microbial desulfurization is by using shake flask cultures. Several factors are reported to affect the rate and extent of bacterial desulfurization.
Modes of distribution of sulphur have been determined in eleven lignite samples from major reserves in Turkey. Total sulphur contents have been found to vary 0.91%–10.32% on dry basis. The lignites contain relatively high amounts of organic sulphur. Distributions of sulphur have been determined in chars from the pyrolysis of lignites at 440 °C. Reductions in combustible sulphur contents have been found to vary 15.7%–72.0%. No correlation has been found between the extent of desulphurization by pyrolysis and the relative amounts of forms of sulphur in the parent lignites.
The extractive desulfurization of four high sulfur coals from China were promoted with ultrasonic and microwave in tetrachloroethylene organic solvents. It was shown that the joint promotion with ultrasonic and microwave had an active effect on extractive desulfurization. The rate of desulfurization increased with the increase of time in ultrasonic field as well as with the power of ultrasonic, but declined with the increase of the particle size of coal. The rate of desulfurization was not identical for different coal, which was perhaps related to the existed forms of organic sulfur in coal.
Experiments have been carried out to determine the effects of biodesulfurization time on the removal of sulfur constituents of six Turkish lignites by Sulfolobus solfataricus. The changes in sulfur content of Tuncbilek, Karliova, Beypazari, Can, Elbistan, and Mengen lignites are shown as functions of time. A decrease in all sulfur forms with increasing time was observed for each coal. The highest total and organic sulfur reductions were observed with Beypazari lignite as 57.1 and 47.8%, respectively. The influence of analyses of the original samples on total and organic sulfur reductions has been investigated through multiple linear regression analysis. The resulting determination coefficients are compared to obtain the beat fitting parameter set. For the six lignites the experimental values of total and organic sulfur reductions appeared to agree with the values calculated for the models.
The effects of surfactants on dibenzothiophene (DBT) degradation by Corynebacterium sp. ZD-1 were investigated in hydrocarbon aqueous biphasic (O/W) systems in shake flask. Among Brij-35, Tween-80, Triton-100X
and β-cyclodextrin, Tween-80 was a suitable surfactant to improve the desulfurization rate of dibenzothiophene. The amount
of 2-hydroxybiphenyl (2-HBP) formed with Tween-80 present was about 50% more than that formed without surfactant. The results
demonstrated that Tween-80 could improve the mass transfer of DBT between organic and aqueous phases, and could be used in
dibenzothiophene biodesulfurization systems.
Bioremediation processes based on biofilms are usually very effective. The presence of (bio)surfactants in such processes can increase bioavailability of hydrophobic pollutants in aqueous phase. However, surfactants can affect the biofilm as well as individual microbial cells in different ways. Biosurfactants produced by a microbial population can be involved in the final structure of biofilm. An external application of synthetic surfactants or 'foreign' biosurfactants often results in partial or complete destruction of the biofilm and their high concentrations also have a toxic effect on microbial cells. Finding a suitable surfactant and its concentration, which would minimize the negative effects mentioned above, would allow to construct effective bioremediation processes using the benefits of both the biofilm and the surfactant. In this context, G(+) bacterium Rhodococcus erythropolis, which has a wide potential for biodegradation of aromatic compounds, was studied. High surface hydrophobicity of its cells, given mainly by the presence of mycolic acids in the cell envelopes, allows formation of stable biofilms. Three synthetic surfactants (Spolapon AOS 146, Novanik 0633A, Tween 80) and rhamnolipid isolated from Pseudomonas aeruginosa were used. Changes in initial adhesion and biofilm formation caused by the surfactants were monitored in a flow cell equipped with hydrophilic/hydrophobic carriers and analyzed by image analysis.
Artificial neural networks procedures were used to predict the organic and inorganic sulfur reduction from coal using mixed culture consisted ferrooxidans species extracted from coal washery tailings, for pyritic sulfur, and Rhodococcus species, extracted from oily soils, for the organic sulfur removal. The particle size, pulp density, initial pH, shaking rate, leaching time and temperature, in pyritic sulfur removal prediction, and pulp density, shaking rate, leaching time and temperature, in organic sulfur removal prediction, were used as inputs to the network. Feed-forward artificial neural networks with 4-8-4-1 and 3-5-6-1 arrangements, were capable to estimate organic and inorganic sulfur removal, respectively. The outputs of the models were percentage of organic and inorganic sulfur reduction. It was achieved quite satisfactory correlations of R2 = 1.00 and 0.98 in training and testing stages for pyritic sulfur removal prediction and R2 = 1.00 and 0.97 in training and testing stages, respectively, for organic sulfur removal prediction. The proposed neural network models accurately estimate the effects of operational variables in organic and inorganic desulphurization plants and can be used in order to optimize the process parameters without having to conduct the new experiments in laboratory.
The raw coal from the Çayirhan mine, Beypazari basin, Turkey contains an average of 28.5% mineral matter, consisting up to 80% zeolites. The coal seam is split by a 1-m-thick tuffaceous siltstone into the upper, first (Tv) and lower, second (Tb) seams, which contain essentially different zeolites. The first seam contains Ca-rich zeolites (clinoptilolite/heulandite) whilst the second seam contains Na-rich zeolites (analcime). Experimental work has shown that a Na-rich activation solution will produce Na-rich zeolites when the original volcanic glass is Na-rich, but will produce Ca-rich zeolites when the volcanic material is Ca-rich. It is thought that a Na-rich activation solution, derived from contemporaneous volcanics in the Beypazari basin, reacted with volcanic tuffs of different chemical composition to produce the vertical variability in the mineral matter of the two seams. Trace element analyses of the raw coal showed that they are enriched in As, B, Cr, Ni and Zr when compared to world-wide averages of coal. They are also enriched in the major elements Na and K. These elements are probably also derived from a volcanic source. Barium and Sr show a clear affinity for analcime, whilst Li, Cr, Ni, Cu, Zn, Co and Ga show a clear affinity for clinoptilolite/heulandite. Trace elements showing a positive correlation with the organic matter are Mn, B, Be, Ge, Y, Zr, Nb, Hf, W and U. Manganese, U, Th, Sc, Ge and HREE (heavy rare earth elements) show correlations with phosphate. Trace elements showing correlation with both Fe and S contents are Co, Mo, Ta, Pb and IREE (intermediate rare earth elements). Arsenic and V seem to have mixed affinities with sulphides and zeolites, and organic matter and zeolites, respectively. Although a proportion of the As, B and S are retained in the ash during coal combustion, due to the sorption mechanism of CaO derived from the clinoptilolite/heulandite decomposition, significant emissions of these elements may arise from the Çayirhan thermal power station due to the anomalously high concentrations of these elements in the Beypazari coal. The high total alkali metal content of these coals exceeds the recommended maximum for steam coal, but it is believed that sodium occurring in a mineralogical form such as analcime is not as likely to contribute to boiler fouling as organically-associated sodium.
Arthrobacter sp. P1-1 was isolated from a polycyclic aromatic hydrocarbon (PAH)-contaminated site in Hilo, HI, USA. This strain can degrade approximately 82% of dibenzothiophene (DBT) (40 mg l−1) and 57% of carbazole (CBZ) (40 mg l−1) in 14 days incubation. Dibenzothiophene-5,5′-dioxide was formed from sulfur oxidation of DBT. Dibenzothiophene diols that were transformed from 1,2- and 3,4-dioxygenations of DBT underwent ortho- and meta-ring cleavages to produce benzo[b]thiophene-2,3-dicarboxylic acid and hydroxyl-benzo[b]thiophene carboxylic acid, respectively. These products were converged into benzo[b]thiophene-2,3-diol, which was further transformed to 2,2′-dithiosalicylic acid via 2-mercaptobenzoic acid. These results indicate that strain P1-1 has diverse lateral dioxygenase systems and subsequent metabolic enzyme systems. The five detected CBZ metabolites by strain P1-1 were 4-(3-hydroxy-1H-indol-2-yl)-2-oxobut-3-enoic acid, 2-(2-carboxy-vinyl)-1H-indole-3-carboxylic acid, pyrido[1,2-a]indole-6,10-dione, indole-2,3-dicarboxylic acid, and 2-aminobenzoic acid. The results suggest that CBZ degradation underwent 3,4-dioxygenation followed by ortho- and meta-ring cleavage.
The distribution of trace elements in the lower Eocene coal seam mined in the Yeniceltek, Kucukkohne and Ayridam coal mines from the Sorgun Basin was investigated in relation to ash content and maceral composition. The coal seam is mainly composed of huminite. In the present study, 35 samples from five seam sections were collected on the basis of megascopic characteristics. Results were determined using an energy dispersive polarised X-ray fluorescence (EDP-XRF) spectrometer on a whole-coal dry basis. Most of the major and trace elements studied are enriched in high-ash samples, while Ba, Br, Mn and W show relative enrichments in low-ash samples. Most of elements studied, such as Ga, Ce, La, Th, Nb, Rb, Zr, V, Cu, U, Pb, Sb, Cs, Sn, Cr, Se, Y and Zn, are primarily associated with mineral matter (clay minerals). Arsenic and a part of Zn, Se and Sb are probably concentrated in pyrites in the samples. Element concentrations show statistically significant negative correlations with many macerals and positive relationships with only attrinite that is mainly mixed with mineral matter (clay minerals and small quartz grains) in the samples. Nine trace elements (As, Cr, Mn, Ni, Pb, Sb, Se, Th and U), considered as potentially Hazardous Air Pollutants, are present in low to moderate concentrations. The mean values of trace element concentrations display relative enrichments in Se (2.8 ppm), Th (21 ppm) and W (26 ppm) in the investigated samples in comparison with other coals in the world.
Coal mining and processing activities in Russia result in the generation of huge quantities of wastes containing elevated concentrations of residual S (Sdt=2.1–9%), C (Cdo > 12%), heavy metals and other hazardous elements. These wastes which are usually piled or dumped without specific care close to mining sites and processing plants are subjected to adverse climatic conditions and in most cases cause severe impacts to various receptors. The worst impacts, in Russian mining and disposal areas, are due to the oxidation of the residual sulfide phases and the generation of coal mine drainage, with pH often ranging between 2.5 and 4. These acidic leachates contaminate severely soils, surface- and groundwater; therefore the risk for humans and ecosystems in these sites is considered as extremely high.The present paper examines the feasibility of thermal treatment of high sulfur coal wastes, in particular those containing elevated content of carbon, kaolin and iron, in order to reduce environmental risk at the disposal sites and produce saleable by-products. Carbon reduces substantially fuel consumption while kaolin and iron assist the formation of secondary products. Parameters studied include temperature and air excess ratios, up to 1400 °C and 1.4 respectively. Coal wastes were subjected to thermal treatment (a) as such, in order to study the removal of sulfur and the production of saleable products (sulfuric acid, various construction materials, products with high magnetic susceptibility, aluminum sulfate) and (b) after mixing with calcium carbonate in order to study the fixation of sulfur in multi-mineral phases possessing binding properties. Prior to implementation of laboratory experiments in order to assess the potential of thermal treatment, thermodynamic calculations were performed to determine optimum operating parameters and possible phase transformations.
Biodesulphurization experiments were carried out with Tunçbilek lignite, characterized by high sulfur content (2.59%) by using Trametes versicolor ATCC 200801 and Phanerochaete chrysosporium ME 446. At fungal biomass studies, the effects of various parameters on fungal desulphurization of coals such as pH, temperature, pulp density, incubation time, and sterilization were investigated for both microorganisms. The maximum desulphurization (40%) was observed after 6 days of incubation at 35 °C for T. versicolor. The optimum pH was measured at 6, and the agitation rate was fixed at 125 rpm. The pulp density was found as 5% (w/v) for the high extent of desulphurization. Also, calorific value did not change during this experiment. However, the ash and metal contents of coal were eliminated.
Sulfur emission from coal combustion presents many environmental problems. It is believed that the best method to limit the amount of sulfur oxides emitted into the atmosphere is to reduce the amount of sulfur in coal before combustion. The techniques used include physical, chemical and biological processes. Biological processes based on degradation of sulfur compounds by microorganisms offer many advantages over the conventional physical and chemical processes. The processes are performed under mild conditions with no harmful reaction products and the value of coal is not affected. In this article the progress achieved to date in coal biodesulfurization processes is reviewed. The barriers for biodesulfurization processes to scale up to commercial applications are highlighted. In addition, the future needs of research for the development of efficient biodesulfurization processes are included.