Article

Heterogeneous catalytic degradation of cyanide using copper-impregnated pumice and hydrogen peroxide

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Abstract

The main objective of this research was to investigate the oxidative destruction of free cyanide with hydrogen peroxide and copper-impregnated pumice as a heterogeneous catalyst. Original or copper-impregnated pumices added alone were not effective adsorbents of negatively charged cyanide ions due to incompatible surface interactions. Peroxide and original pumices added together were also ineffective in removing cyanide. However, for all of the three natural pumices tested with various particle size fractions, the use of copper-impregnated pumices and peroxide together significantly enhanced both the initial rate and extent of cyanide removal. Although copper-impregnated specific surface area was the major factor affecting the rate and extent of cyanide destruction for a particular pumice source with similar surface chemistries, the type of surface chemistry (i.e., specific functional groups) within different pumice sources also appears to be a very important factor. Lower rates and extents of cyanide removals were observed at pH 11 compared to pH 8 probably because of the negative impacts of alkaline conditions in terms of scavenging peroxide and forming more negatively charged pumice surfaces. Both the initial rate and ultimate extent of cyanide removals were generally higher at a temperature of 20 degrees C compared with those found at 10 degrees C. The use of copper-impregnated pumice as a light, cheap, readily available, natural, and porous heterogeneous catalyst either in completely mixed/suspended or fixed-bed reactor configurations may be an effective treatment technology for cyanide removal from solution. This new approach may minimize downstream metal removal problems experienced in conventional cyanide oxidation technologies.

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... Adsorption process has become the most studied one to remove metals, organic matter, dyes, etc. [2,5,8,[31][32][33][34][35][36][37][38][39][40][41]. Recent investigations focused on integrating pumice stone to advanced oxidation processes (AOPs) such as ozonation and photocatalysis after supporting its surface by coating or doping metals with the purpose of increasing its catalytic capacity [4,9,14,[42][43][44][45][46]. ...
... In the literature, different kinds of modification methods have been used on adsorbent such as base solutions (sodium hydroxide, calcium hydroxide, and sodium carbonate), minerals and organic acid solutions (hydrochloric acid and nitric acid), and oxidizing agent (hydrogen peroxide). The natural pumice was mainly pretreated with 1-M HCl (or pH was set 1 with HCl) for 24 h for purification due to the containing residual inorganic salts and acid-soluble contents [5,8,9,14,25,28,43,83]. Kitis [5,8,83]. ...
... Those papers on AOPs applications compose of a 11% portion of all scientific papers published so far. Most of AOPs related papers focused on catalytic ozonation [45,50,51,104], catalytic oxidation [9,14,43], and photocatalytic oxidation process [42,44,105,106]. Table 3 overviews some of those investigations. ...
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Pumice is a valuable scouring, scrubbing, and polishing material both in powdered form and as a pumice stone. It has been traditionally used in construction industry and biomedicine. It has been evaluated in recent years in the field of water, wastewater, and air treatment. The present study aimed to review the scientific literature of pumice stone with the particular focus on its use for the treatment of water and wastewater. It was observed that most of the publications from 1995 to 2015 dealt with construction materials and treatment use. A number of 143 papers published focused on the removal of cadmium, dyes, color, and many other pollutants by adsorption and catalytic oxidation, while 49% of the papers on water and wastewater treatment was dedicated on adsorption processes. Besides, pumice has been used as a filter medium and integrated to biological treatment. More recent publications have been focusing on integrating pumice with advanced oxidation processes (AOPs) after enrichment with other materials. The use of pumice in AOPs, in particular, integrated with nanotechnology has been attracting more scientists to remove micropollutants.
... Pumice rocks are porous and amorphous materials which consist mainly of SiO 2 and Al 2 O 3 . Traditionally, pumice has been used in the construction industry [12][13][14]. In recent years, pumice has also been used in the field of water and wastewater treatment, both in natural and modified forms, to remove fluoride [15], azo dyes [16], phenol and 4-chlorophenol [17], heavy metals [18], SO 2 [19], and natural organic matter [20]. ...
... In recent years, pumice has also been used in the field of water and wastewater treatment, both in natural and modified forms, to remove fluoride [15], azo dyes [16], phenol and 4-chlorophenol [17], heavy metals [18], SO 2 [19], and natural organic matter [20]. In order to improve the adsorption capacity of naturally occurring pumice, various organic and inorganic chemicals such as hydroxy-aluminum [21], hydroxy-iron salts and magnesium chloride [12], and hydrogen peroxide [14] have been used. ...
Article
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In this study, the potential of natural pumice (NP) and iron-coated pumice stone (Fe-CP) as novel low-cost adsorbents to remove ethidium bromide (EtBr) from aqueous solutions was investigated. The operational parameters affecting removal efficiency and adsorption capacity such as adsorbent dose, initial EtBr concentration, pH, and contact time were studied in order to maximize EtBr removal. The maximum amount of adsorbed EtBr (qm) using NP and Fe-CP was 40.25 and 45.08 mg g‒1, respectively. It was found that EtBr adsorption followed the Freundlich isotherm model and fitted the pseudo-second-order kinetics equation for both adsorbents. In addition, the experimental system could be easily modeled by artificial neural network calculations.
... Modification of natural absorbents with different agents as an adsorbent for organic and inorganic compounds has been studied by researchers [8,15,16]. If structural adsorption was reformed the potential adsorptive capacity would increase, for this purpose modified zeolite and pumice was used for a different class of compounds such as zero-valent iron, iron chloride, acid ammonium sulfate, hexadecyltrimethylammonium, and copper sulphate [17]. In this regard, the present study aimed to investigate the effect of modified pumice and zeolite with copper as low prices and available adsorbent in PCP removal from aqueous solution. ...
... Then, the dried mixture were rinsed with DDW several times. Finally, the pumice and zeolite samples were dried at 100 °C for 24 h, until all moisture was removed and constant weight was achieved [17,19]. ...
... where, R is the gas constant, T is the Kelvin temperature. Therefore, the diagram of Lnq e against e 2 is a line of slope which can yield to the value of K, which is related to the adsorption energy, E, by Eq. (8) in the following relationship [32]: ...
... The adsorption kinetics are used for the determination of the rate controlling mechanism of adsorption processes such as adsorption on surface, chemical reaction or diffusion mechanisms. In a pseudo-first-order kinetic model [33], it is assumed that the rate of change in the solute concentration over time is logarithmically proportional to changes in the saturation concentration and the amount of adsorbent over time [32]. ...
... It is a light, highly porous stone, which is formed during volcanic activities. The low cost, availability, low density, and high surface-to-volume ratio of pumice make it a good candidate for the elimination of hazardous compounds (10). ...
... In this study, considering the components in the pumice structure, the dominant component was quartz (SiO 2 ), which constitutes around 64% of its structure. Existence of such oxides in an aqueous environment leads to the formation of surface functional groups, which are very effective in the removal of contaminants from water (10,19). Also, in studies by Ozturk Akbal et al. and Kitis et al. ...
... Among these methods, using adsorbents were always of attention (Karagozoglu et al., 2007).Since these kinds of pollutants are present in trace amounts in water resources, the adsorption process could be applied as a rational physicochemical method to remove those.In this regard various adsorbents have been of use, such as granular and powdered activated carbon, silicon dioxide, and activated alumina. Pumice is a light material with a highly porous structure which was formed during volcanic activities.Being inexpensive, available,having low specific weight and large surface area have caused its use as adsorbent (Kitis et al., 2005).Various studies have been conducted on the removal of organic compounds by pumice impregatedwith different metals such as iron, aluminum, manganese and copper.In these works, pumice impregnated with different metals have shown relatively high removal efficiency for some organic compounds.Asgard et al., (2012) studied on pumice modified with copper under three different pH; 6 retention times, 8 adsorbed concentrations and 4 adsorbent concentrations, which their results indicated that the removal efficiency of phenol was increased up to 93% by increasing modified pumice dose, retention time and initial concentration of phenol while having an inverse relationship with increasing pH. Asgari et al., (2012) andGucziet al., (1999)showed that the behavior of catalyst in removingphenylacetylenethrough the pumice modified by copper-palladium and converting it into different isomers is affected by different temperatures (Guczi et al., 1999). ...
... The results of the pumice structure analysis showed that about 74% of pumice constitutes of Quartz (SiO 2 ). The presence of these metal oxides in aqueous solutions causes the formation of surface functional groups which have an effective role in removing pollutants from water resources (Kitis et al., 2005;Ghanizadeh et al., 2009). Eghbal et al. and Kitis et al. reported that the main ingredient of pumice was SiO 2 , whichconforms to our result (Kitis et al., 2007;Ozturket al., 2000).StudyingtheSEM imagesof copper-impregnated pumice with an accuracy of 10 and 100µm revealed that this structure appears to be highly capable of mechanical adsorption and in other words we could say that such structure has a significant surface to volume ratio. ...
... It is a light, highly porous stone, which is formed during volcanic activities. The low cost, availability, low density, and high surface-to-volume ratio of pumice make it a good candidate for the elimination of hazardous compounds (10). ...
... In this study, considering the components in the pumice structure, the dominant component was quartz (SiO 2 ), which constitutes around 64% of its structure. Existence of such oxides in an aqueous environment leads to the formation of surface functional groups, which are very effective in the removal of contaminants from water (10,19). Also, in studies by Ozturk Akbal et al. and Kitis et al. ...
Article
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Tetrachloroethylene (TCE) is a chlorinated aliphatic hydrocarbon, used in many industries. Effective and efficient treatment of industrial wastewater, containing TCE, is one of the environmental requirements. The purpose of this study was to determine the role of alkaline environments in TCE removal rate from aqueous solutions, using copper-doped pumice. This experimental study was performed, using granulated pumice stones with a mesh 4 (8.4 mm) in alkaline conditions; the samples were coated with copper. Copper-doped pumice was prepared as a bed at doses of 1, 2, and 3 g/L; the study was performed at pH ranges of 3, 7, and 11. Based on the results, copper-doped pumice showed good efficacy in TCE removal; in addition, its performance increased in alkaline conditions. Therefore, use of this stone for the treatment of wastewater, containing TCE, is effective due to its availability and low cost. Besides, it can be considered a good option, given its high efficiency in the absorption process.
... However, it suffers from the long reaction time. The inclusion of heterogenous catalyst has been shown to promote the reaction between cyanide and hydrogen peroxide [5]. The oxidation of dilute aqeous cyanide solution using hydrogen peroxide at room temperature was enhanced by the presence of Ru/MgO catalyst [6]. ...
... The oxidation of dilute aqeous cyanide solution using hydrogen peroxide at room temperature was enhanced by the presence of Ru/MgO catalyst [6]. Kitis et al., [5] carried out the oxidative destruction of free cyanide with hydrogen peroxide and copper-impregnated pumice as a heterogeneous catalyst. The peroxide oxidizes free and weakly complexed metal cyanides (i.e. ...
Article
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Owing to the common phenomenon of cyanide toxicity, this study focused on oxidative catalytic detoxification of aqueous cyanide in the presence of copper-crown chitosan nanofiber. To overcome the difficulty in electrospinning chitosan, chitosan-salicylaldehyde was initially synthesized via Schiff base condensation, electrospun, and post neutralised into chitosan nanofiber. The copper-crown nanofiber was prepared using the impregnation method. The nanofiber material was characterized using FT-IR, SEM, TGA and DSC. The observed pseudo first-order rate constant for the catalytic H2O2 oxidation of aqeous cyanide with copper-crown nanofiber as catalyst was found to be 16 times greater than the oxidation with only copper catalyst. In addition, the reaction was found to be dependent on the size of the copper-crown nanofiber, pH, temperature, and H2O2/CN-. The reusability of the copper-crown nanofiber catalyst makes the process economically and potentially viable for commercial application.
... Among the methods used in removing cyanide from wastewater include photocatalysis [38], biotreatment [39], copper-catalysed hydrogen peroxide oxidation [40], ozonation [33], electrolytic decomposition, alkaline chlorination [22], reverse osmosis, thermal hydrolysis and adsorption [41]. Most of these methods have limited applications due to the high cost, production of toxic residues and incomplete degradation of all cyanide complexes [42,43]. ...
Chapter
Cyanide has been widely used in several industrial applications such as electroplating photography, metal processing, agriculture, food and the production of organic chemicals, plastics, paints and insecticides. The strong affinity of cyanide for metals such as gold and silver makes it suitable for selective leaching of these metals from ores. Cyanide is highly toxic; hence, there is a need to regulate and limit the amount of cyanide that may be discharged into the environment. Technologies focusing on the use of physical, chemical and biological methods have been developed to reduce the concentration of cyanide and cyanide compounds in wastewaters to permissible limits. This chapter reviews the current and emerging technologies for treatment of cyanide from wastewaters generated in gold mining processes.
... Adsorption process is one of the most simple, effective and cost benefit alternative methods to phenol removal from aqueous environments (32)(33)(34)(35). Active carbon, silica and active aluminum are used as the absorbent (36) but problems like high costs and the possibilities of activation and reclamation of the absorbent which are important from economic point of view, provoke investigators to search for new absorbents (37). At the present time, biomass draws increasing interest all over the world because it is a renewal material which is available widely with low costs and no damage to the environment (38). ...
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Background and purpose: Phenol is one of prevalent contaminants found in many industrial wastewaters. The combination with special features, such as high toxicity, carcinogenic properties, vitality gathering ability, low biodegradation potentiality and others, based on the U.S Environmental Protection Agency, classified as a priority pollutant. The purpose of this study was to determine the efficiency of Moringa Peregrina tree shell ash for the removal of phenol from aqueous solutions. Materials and Methods: This study is experimental and pilot scale. To determine the efficiency of Moringa Peregrina tree shell ash for the removal of phenol from aqueous solutions; the examination was carried out in a batch system. To achieve the aim of this study, the effect of each of the parameters affecting the adsorption process, such as initial pH of solution, contact time, adsorbent dose and initial concentration of phenol in solution were studied. Results: The results showed that the highest percentage of phenol removal by the ash occurred at pH 6, initial concentration100 mg.L -1 and adsorbent dose 0.4 g/l in which the 79.96% phenol was removed. For the analysis of the absorption constant, the Freundlich and Langmuir isotherm were used. The results showed that the experimental data fit the Langmuir (R 2 =0.9833) much better than the Freundlich model (R 2 =0.9373).
... Similar results can be found in the literature. Kitis et al. (Kitis et al., 2005) show the effect solution pH has on the oxidation of cyanide with H 2 O 2 and copper-impregnates pumice as catalyst, they observed that the lower cyanide removal rate was at pH 11 compared to the rate at pH 8. ...
Article
The main purpose of this research has been to evaluate and optimize the application of hydrodynamic cavitation (HC), combined with hydrogen peroxide, as a promising process for the effective degradation of cyanide in aqueous effluents. The experimental work was carried out using cavitation equipment with a venturi device connected to a tubular circuit which allowed a closed-cycle flow to run for 120 min, in which the effect of control parameters as inlet pressure, H2O2:CN─ ratio, pH, and temperature have been evaluated for the treatment of solutions with initial cyanide concentration in range 100 to 550 mg L─1. The results showed that in optimal conditions cyanide degradation using only HC reached 70% and, using solely H2O2 as oxidizing agent it reached 63%. Efficiency of the combined treatment process was evaluated on the basis of their synergetic effect as it turned out to be more effective showing a 99.9 % cyanide degradation in less than 120 min. The optimum set of conditions that produced the highest degradation rate and efficiency was: inlet pressure 4 bar; pH 9.5; and H2O2:CN─ ratio = 1.5:1. The process was also evaluated on the basis of cavitational yield and in terms of energy and chemical treatment costs. The results have demonstrated that the combined treatment technology of HC + H2O2 can be effectively used as a fast and highly efficient treatment of wastewater containing cyanide.
... Pumice and tuff are highly porous volcanic stones that are rich in silicon and aluminum [24,25]. Their chemical resistance and high mechanical strength make them efficient substrates for different catalysts and absorbents [26,27]. ...
Conference Paper
Olive oil production process creates a large volume of organic waste rich in phenols and other substances hazardous for human health and the environment. The olive-mill wastewater (OMW) is usually disposed of into unprotected and uncontrolled evaporation ponds nearby the main olive oil production facility. OMW disposal often leads to soil and groundwater degradation and is a direct threat to the flora and fauna of the area. A holistic strategic approach for the management of OMW is required. One promising method for organic load removal is the use of biochar. Lately, rice husk and corncob biochar have shown high sorption capacity towards phenolic compounds (Mohan et al., 2014). Essential to the success of any organic load removal approach is the accurate monitoring of the process. The spectral induced polarization (SIP) method is a prime candidate for a monitoring tool in OWM remediation processes using biochar. Previous work has established the sensitivity of induced polarization on OMW (Ntarlagiannis et al., 2016); as part of this work we established the dependence of electrical parameters on OMW concentration in porous media. Furthermore, the links between SIP and a variety of biochar materials have been established (Haegel et al., 2013). With this work we present early results on the use of spectral induced polarization (SIP) method as a monitoring aid in a controlled laboratory experiment with biochar used as a tool for countering land degradation (Barrow, 2012).
... 26 Pumice is a volcanic stone that includes numerous voids in its structure, and since it is fallen into the category of the lightweight materials, it can be well dispersed/submerged in the reaction mixture. 27 The volcanic pumice (VP) consists of internal particles, totally separated from outside, and external particles linked to the surface resembling a sponge. 28 Generally, porous compounds such as metal-organic frameworks, pumice particles, carbon nanotubes, and graphene oxide are promising materials in the catalytic applications due to their broad surface area, which increases the catalytic performance and efficiency. ...
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Herein, silver nanoparticles (Ag NPs), as an effective catalyst for the reduction process of nitrobenzene derivatives to non-hazardous and useful aniline derivatives, are conveniently synthesized on an inherently magnetic substrate. For this purpose, an efficient combination of volcanic pumice (VP), which is an extremely porous igneous rock, and a chitosan (CTS) polymeric network is prepared and suitably used for the stabilization of the Ag NPs. High magnetic properties of the fabricated Ag@VP/CTS composite, which have been confirmed via vibrating-sample magnetometer (VSM) analysis, are the first and foremost advantage of the introduced catalytic system since it gives us the opportunity to easily separate the particles and perform purification processes. Briefly, higher yields were obtained in the reduction reactions of nitrobenzenes (NBs) under very mild conditions in a short reaction time. Also, along with the natural biocompatible ingredients (VP and CTS) in the structure, excellent recyclability has been observed for the fabricated Ag@VP/CTS catalytic system, which convinces us to do scaling-up and suggests the presented system can be used for industrial applications.
... The biosorption kinetics are used for the determination of the rate controlling mechanism of biosorption processes such as; biosorption on surface and chemical reaction or diffusion mechanisms. The pseudo-first order kinetic model assumes that the rate of change in the solute concentration over time is logarithmic proportional to changes in the saturation concentration and the amount of absorbent over time [23,24]. The pseudo-first order model equation is given as follows [25]: ...
Article
The removal of tartrazine from aqueous solutions using masau stone (MS) as a novel low-cost biosorbent was investigated. The impact of several influential parameters such as; initial pH, contact time, initial concentration and temperature on the biosorption process of tartrazine was studied and optimized. The mechanisms of tartrazine removal by the MS biosorbent and their kinetics and isotherm studies are also presented. It was observed that the efficiency of the removal of tartrazine depends on the pH of the solution and the maximum efficiency (approx. 87% at Co = 100) was found at pH 2. Kinetic studies were well suited and found to be in good agreement with the pseudo-second order model. The biosorption equilibrium data was adequately described by the Langmuir isotherm model at 20 °C and 30 °C. High temperatures seem to promote multilayer biosorption as the tartrazine experimental data best fits both Freundlich and Redlich-Peterson isotherms (R² = 0.996 for both). The maximum biosorption capacities of tartrazine were between; 0.096 mmol/g (51.3 mg/g) at 20 °C and 0.126 mmol/g (65.1 mg/g) at 60 °C. The thermodynamic parameters obtained indicated a positive and low value of ∆ H°, suggesting an endothermic and physical nature process with biosorption mechanisms related to H-bonds, van der Waals and electrostatic interactions. The results clearly indicated that masau stone would be a suitable biosorbent for the anionic dye, tartrazine, from contaminated wastewater under specific conditions.
... Many studies have analyzed the use of homogeneous or heterogeneous catalysts for the removal of cyanide by treatment with hydrogen peroxide. For instance, catalyzed treatment has been investigated in the presence of Ru/MgO (Pak and Chang 1997), cadmium (Lee et al. 2004), activated carbon (Yeddou et al. 2010), copper (Sarla et al. 2004;Kitis et al. 2005a;Yazici et al. 2006;Chen et al. 2014), copper-impregnated pumice (Kitis et al. 2005b), and copper-impregnated activated carbon (Yeddou et al. 2011). The rate and extent of cyanide decomposition by hydrogen peroxide are dependent upon different factors including the pH, temperature, initial cyanide concentration, hydrogen peroxide concentration, absence or presence of catalyst, and type and concentration of catalyst (Lee et al. 2004;Kitis et al. 2005a;Yazici et al. 2006;Yeddou et al. 2010). ...
Article
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This research work evaluates the use of hydrogen peroxide for the removal of cyanide from coking wastewater deriving from the washing of gases in coal combustion furnace. The effect of the presence or absence of suspended solids and organic micropollutants on the efficiency of the treatment is analyzed. Various dosages of hydrogen peroxide (6.5–200 mg/L) were added to both aqueous solution (at pH 10.5) and industrial wastewater (at pH 10.3) samples. The influence of suspended solids in coking wastewater was analyzed by applying a coagulation–flocculation–decantation process before the hydrogen peroxide treatment. The preliminary cyanide removal treatment in aqueous solution showed that the maximum cyanide removal did not exceed 14 % using a mass ratio of hydrogen peroxide to cyanide of 11.6. The maximum cyanide removal obtained in coking wastewater was 47 % with a mass ratio of hydrogen peroxide to cyanide of 12.2 provided that a coagulation–flocculation–decantation pretreatment was applied to remove the suspended solids composed mainly of coal, calcium carbonate, and magnesium carbonate. On the other hand, the cyanide removal treatment in coking wastewater with hydrogen peroxide showed promising results in the removing of different organic micropollutants formed mainly by polycyclic aromatic hydrocarbons and quinolines.
... The majority of inner micropores, are not connected in pumice. Pumice has irregular cavities and 60 to 75 percentage of silica [4][5][6]. ...
... Pumice and tuff are highly porous volcanic stones that are rich in silicon and aluminum [24,25]. Their chemical resistance and high mechanical strength make them efficient substrates for different catalysts and absorbents [26,27]. ...
Article
ZrO2-pumice and ZrO2-tuff nanocomposites were synthesized via a modified sol–gel method and used as efficient catalysts for sonocatalytic degradation of rifampin (RIF). Subsequently, the physico-chemical properties of the prepared catalysts were examined using XRF, SEM, EDX, FT-IR and BET analyses and compared to pure pumice and tuff samples. The efficacy of catalysts in degradation of RIF was assessed under various experimental conditions. Both ZrO2-pumice and ZrO2-tuff (1.5 g L-1) exhibited favorable catalytic activity for sonocatalytic degradation of RIF at its initial concentrations of 20 mg L-1 and natural pH under ultrasonic irradiation of power 300 W, wherein 95.3% and 83.1% of RIF was removed through US/ZrO2-pumice and US/ZrO2-tuff processes, respectively. Furthermore, the influence of the addition of a number of scavengers, enhancers and gases on the degradation of RIF were studied. The great degradation capacities of the catalysts under ultrasound irradiation could be described on their synergetic ability to produce reactive species and subsequently radical reactions. Intermediate byproducts formed in the solution from degradation of RIF also identified and decomposition pathway was well interpreted using GC-MS, COD and IC analyses.
... A pseudo-first-order kinetic model suggests that the rate of change in the solute concentration with time and the changes in the concentration of the adsorbate and the amount of adsorbent over time are logarithmically proportional. 64 On the other hand, a pseudo-second-order kinetic model proposes that the number of active sites occupied on the adsorbent is directly proportional to the adsorption capacity. The pseudofirst-order 49 (eq 3) and pseudo-second-order 38 (eq 4) model equations are given as follows: ...
Article
This study investigates and compares arsenic, As(V), removal from aqueous media using the water-stable zinc metal–organic frameworks (Zn-MOF-74) prepared via room-temperature precipitation (RT-Zn-MOF-74) and a solvothermal procedure (HT-Zn-MOF-74). The Zn-MOF-74 crystals possess average particle sizes of 66 nm and 144 μm for RT-Zn-MOF-74 and HT-Zn-MOF-74, respectively. Moreover, nanosized RT-Zn-MOF-74 exhibited a superior performance to HT-Zn-MOF-74. While the Brunauer–Emmett–Teller surface area of RT-Zn-MOF-74 was smaller than that of HT-Zn-MOF-74, higher adsorption uptake took place on the room-temperature-synthesized ones because of their small particle size and better dispersion. Adsorption isotherm studies showed that the Langmuir isotherm was effective for the adsorption of As(V) onto RT-Zn-MOF-74 and HT-Zn-MOF-74 with maximum adsorption uptake (qmax) values of 99.0 and 48.7 mg g–1, respectively. These values exceed most reported maximum adsorption capacities at neutral pH. The thermodynamics of adsorption revealed a spontaneous endothermic process that is due to the substitution of adsorbed water molecules by arsenate in the pores of the MOF crystal. This was further investigated using plane-wave density functional theory calculations. This study constitutes direct evidence for the importance of tuning the size of the MOF crystals to enhance their properties.
... The mixture was left inert for 72 h and then was dried for 14 h at 110 °C. Finally, the mixture was washed with distilled water several times and dried for 14 h at 110 °C; it was put in a closed bottle for later use (Kitis et al. 2005). In each experiment, a 10 g sample was used. ...
Article
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The combined application of ozone and various sorbent/zeolites has been extensively investigated as an effective advanced oxidation processes to eliminate poorly biodegradable organic pollutants and/or toxic compounds. In this work, copper oxide/clinoptilolite zeolite was synthesized and its performance in a catalytic ozonation process (COP) was investigated for the removal of formaldehyde from an air stream. BET measurements showed that the specific surface area of the raw zeolite sample was 15.78 m²/g, which increased to 81.67 m²/g in zeolite–CuO. SEM images confirmed good fixation and distribution of CuO on the different points of the zeolite. The formaldehyde decomposition time in the COP using unmodified zeolite occurred at 80, 30, and 10 min at 10, 50, and 80 ppm initial concentrations of formaldehyde, respectively. Using copper-coated zeolite, it occurred at 13, 3.3 and 1.3 h, respectively. It appears as if this increase in yield with copper-coated zeolite can be due to the catalytic properties of copper oxide which give the absorbent its oxidizing property. Overall, it can be concluded that clinoptilolite zeolite is effective for the removal of formaldehyde by COP from the air stream. If natural zeolite is modified with copper oxide, it can provide an effective method for the removal of this pollutant from the air stream. The combination of clinoptilolite with copper oxide catalyst in the COP can be used in future studies to remove more VOC with considerable efficiency. Graphical abstract Open image in new window
... The oxidation of cyanide with hydrogen peroxide is a widely used chemical method because it does not produce dangerous by-products or harmful environmental pollutants (Chergui et al. 2015). Some studies showed that higher performances in the removal of cyanide can be reached by the combined action of hydrogen peroxide and other materials such as activated carbon (plain and metal-impregnated) (Deveci et al. 2006, Yeddou et al. 2010, Yeddou et al. 2011, activated alumina (Chergui et al. 2015) and copper-impregnated pumice (Kitis et al. 2005). The combined effect of hydrogen peroxide and ozone on the oxidation of cyanide was also tested and remarkable results were reported by Monteagudo et al (2004). ...
Article
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Cyanidation is widely used by several gold mining companies worldwide. Since its wastewaters contain cyanide, appropriate treatments must be applied to remove this pollutant. Combinations of ozone (O3), hydrogen peroxide (H2O2) and activated carbon (AC) can be used for this purpose. In this work, synthetic cyanide solutions ([CN¯]o = 15.37 mM) were treated using O3 and the combinations O3/H2O2, O3/AC and O3/H2O2/AC under alkaline conditions. O3 was produced from dry oxygen at a rate of 2.51 g O3/h([O3] gas-phase = 6.9x10–2 g/L). The concentration of cyanide (CN¯) and O3 consumption were measured and the performance of the treatments evaluated. The highest cyanide removal was reached at pH 11.0 for all cases and with 10 mg H2O2/mg O3 upon adding H2O2. In contrast, the addition of AC did not improve the cyanide removal in comparison with O3 alone. The best cyanide removal was achieved with the combination O3/H2O2 followed by the combination O3/H2O2/AC. Moreover, cyanidation effluents were treated using the combination O3/H2O2. In this case, almost a total removal of free cyanide was achieved after 3 min of treatment.
... Equation 6 expresses the pseudo-second-order Lagergren equation, where k 2 is the second-order rate constant in g/mg × min. The pseudo-first-order kinetic model provides a general idea about the rate of change in arsenate concentration with the passage of time and stated that the change in the concentration of the adsorbate and the amount of adsorbent over time is logarithmically proportional [27], while a pseudo-second-order kinetic model suggests that the number of active sites occupied on the adsorbent is directly proportional to the adsorption capacity. The pseudo-first-order [28] [Eq. ...
Article
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In this work, the MgAl–NO3 layered double hydroxide (LDH) developed by the single-step in situ growth method is used as a robust sorbent to remove arsenic from aqueous solution. The MgAl-LDH exhibiting two different distinct morphologies (platelet structure and cauliflower-shaped structure) was developed on the AA6082 substrate with the variation in synthesis parameters, where AA6082 specimen acts as both the reactant and support. The structural characterizations were investigated through scanning electron microscopy, X-ray diffraction analysis, and energy dispersion spectroscopy, while the adsorption of arsenic on MgAl-LDH was studied through Langmuir and Freundlich models. The Langmuir isotherms have shown a maximum adsorption capacity of around 213 and 239 mg/g for platelet and cauliflower-like MgAl-LDH, respectively. The pseudo-first-order and pseudo-second-order Lagergren kinetic models were studied for the understanding of the adsorption kinetics. The results depicted that anion exchange and the electrostatic interaction are the possible reasons of arsenic sorption on MgAl-LDH, but the ion exchange mechanism is found to be the dominant mechanism. The maximum adsorption capacity of cauliflower-shaped MgAl-LDH was found to be slightly higher than platelet structure, but overall maximum arsenic adsorption uptake values of both in situ growth structures have found to be exceeded the mostly reported MgAl-LDH maximum adsorption capacities.
... chlorophenol by sonolysis were studied byKu et al. (2005), which was enhanced by the presence of H 2 O 2 . The decomposition rates of 3-chlorophenol by sonolysis were found to be higher than those for 2-and 4-chlorophenol for most experiments, suggesting that the ring structure of 3chlorophenol provides more sites available for free radical attack.Kitis et al. (2005) evaluated the oxidative destruction of free cyanide with H 2 O 2 and copperimpregnated pumice as a heterogeneous catalyst. For all of the three natural pumices tested in this study with various particle size fractions, the use of copper-impregnated pumices and peroxide together significantly enhanced both the initial rate and extent of ...
... This result supports the previous finding that iron coating increases the surface areas of the largest size fractions through modification of pore structures and sizes, and suggests that the largest fractions are more effectively coated with iron oxides. This finding is consistent with our previous work (Kitis et al., 2005) in which copper impregnation was more effective for the larger size fractions (250-1000 lm) of pumices. Iron contents of the original and coated samples were 0.7-11.5 and 5.4-23.1 mg Fe g À1 , respectively. ...
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Natural pumice particles were used as granular support media and coated with iron oxides to investigate their adsorptive natural organic matter (NOM) removal from waters. The impacts of natural pumice source, particle size fraction, pumice dose, pumice surface chemistry and specific surface area, and NOM source on the ultimate extent and rate of NOM removal were studied. All adsorption isotherm experiments were conducted employing the variable-dose completely mixed batch reactor bottle-point method. Iron oxide coat- ing overwhelmed the surface electrical properties of the underlying pumice particles. Surface areas as high as 20.6 m2 g􏰁1 were achieved after iron coating of pumice samples, which are above than those of iron coated sand samples reported in the literature. For all particle size fractions, iron coating of natural pumices significantly increased their NOM uptakes both on an adsorbent mass- and surface area- basis. The smallest size fractions (<63 lm) of coated pumices generally exhibited the highest NOM uptakes. A strong linear correlation between the iron contents of coated pumices and their Freundlich affinity parameters (KF) indicated that the enhanced NOM uptake is due to iron oxides bound on pumice surfaces. Iron oxide coated pumice surfaces preferentially removed high UV-absorbing fractions of NOM, with UV absorbance reductions up to 90%. Control experiments indicated that iron oxide species bound on pumice surfaces are stable, and potential iron release to the solution is not a concern at pH values of typical natural waters. Based on high NOM adsorption capacities, iron oxide coated pumice may be a promising novel adsorbent in removing NOM from waters. Furthermore, due to prefer- ential removal of high UV-absorbing NOM fractions, iron oxide coated pumice may also be effective in controlling the formation of disinfection by-products in drinking water treatment.
... The samples were crushed and sieved into 20-40 mesh (0.4-0.8 mm). Pumice samples were coated by CuSO 4 5H 2 O (1N) solution according to Kitis et al and Rezaee et al methods [14,15] with some modification. They were washed by distilled water several times, then dried and pretreated in HCl (1M) solution for 24 hr and then the samples were rinsed out with distilled water and put in distilled water for 24 hr. ...
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... 7,8 As an economic and environmental-friendly method, biohydrometallurgy is attracting more and more attention. Considering that SCN À consists of S, C and N, which are all necessary elements for the growth of the living beings, it can provide a carbon source, nitrogen source and sulfur source for microorganisms under aerobic conditions, and generate such metabolites as SO 4 2À , CO 2 , and NH 4 + . 9 Hence, high-load SCN À in the wastewater can be biodegraded efficiently under the condition that dissolved oxygen and hydraulic retention time (HRT) are sufficient. ...
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As one of the inorganic pollutants with the highest concentration in the waste water of gold tailings using biohydrometallurgy, thiocyanate (SCN⁻) was effectively degraded in this research adopting a two-stage activated sludge biological treatment, and the corresponding degradation pathway and microbial community characteristics in this process were also studied. The results showed that SCN⁻ at 1818.00 mg L⁻¹ in the influent decreased to 0.68 mg L⁻¹ after flowing through the two-stage activated sludge units. Raman spectroscopy was used to study the changes of relevant functional groups, finding that SCN⁻ was degraded in the COS pathway. Based on 16S rRNA high-throughput sequencing technology, the microbial diversity in this system was analyzed, and the results indicated that Thiobacillus played a major role in degrading SCN⁻, of which the abundance in these two activated sludge units was 32.05% and 20.37%, respectively. The results further revealed the biological removal mechanism of SCN⁻ in gold mine tailings wastewater.
... In this sense, in recent years pumice stone, in both natural and modified forms, has been used for the removal of fluoride [23], azo dyes [22], phenol and 4-chlorophenol [3], heavy metals [26], SO 2 [29] and natural organic matter [16]. To improve the adsorption capacity of the naturally-occurring adsorbents, various metals such as aluminium [13], iron, manganese [8] and copper [17] have been used. ...
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In the present paper, the removal of ethidium bromide (EtBr) from aqueous solutions in a batch system using natural (NP) and aluminium-coated pumice (ACP) as alternative low-cost adsorbents was investigated. The maximum adsorption capacity, qm (mg/g) was 58.82 and 76.92 mg/g for NP and ACP, respectively, operating at an initial pH of 8, an adsorbent dose of 8 g/L, a contact time of 210 min and an initial EtBr concentration of 30 mg/L. The equilibrium data of both adsorbents fitted the Freundlich isotherm model, indicating the heterogeneity of the adsorbent surface. In addition, the adsorption rate of both adsorbents was well described by the pseudo-second-order kinetics model. This indicated chemisorption was the rate-controlling step of the adsorption process which occurred by ion exchange. Within the performed study, a three-layer artificial neural network (ANN) model was also developed to predict the efficiency of EtBr removal. Computational results clearly demonstrated that the ANN model was able to predict the combined effect of initial pH, adsorbent dose, contact time and initial EtBr concentration on the adsorption efficiency with a very high determination coefficient (R2 = 0.98) and a low relative error (RE = 0.037).
... Photo Fenton-type reaction Direct Blue 71 (DB71), Acid Green 25 (AG25), and Reactive Blue 4 (RB4) [191] Copper oxide Electro Fenton-type reaction Cyanide [192] Photo Fenton-type reaction Phenol [202] Copper-impregnated pumice Fenton-type reaction Cyanide [203] [219] tannins (polyphenols), condensed tannins, flavonoid-based, steroids (some of the steroids are esterified with fatty acids), and triterpenes. The catalysts based on Cu showed the best performance in terms of TOC reduction (52.7%) in contrast to catalyst based on Fe (the degree of mineralization was only about 30%). ...
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Download full text from: http://www.tandfonline.com/eprint/aNCmI277yWMU23EMNCyq/full This review examines in detail all components involved in heterogeneous Fenton-type reactions, with special focus on copper species supported on alumina for H2O2 decomposition, their redox chemistry, and their practical advantages over traditional Fenton for the degradation of recalcitrant organic compounds. Several aspects for a deeper comprehension of the properties of γ-Al2O3 as support for catalytic applications are discussed. Iron-free systems stability after calcination and catalyst performance during the oxidation reaction are evaluated to solve the disadvantages of iron-based system. Copper species supported on alumina for H2O2 decomposition in Fenton-like reactions are examined, with special focus on their redox chemistry and practical advantages over traditional Fenton system for recalcitrant compounds degradation. Characterization techniques for the elucidation of the structures, compositions, and chemical properties of both the solids used in heterogeneous catalysis, and the adsorbates and intermediates present on the surfaces of the catalysts during reaction are explained. Global indicators for chemical characterization of wastewaters and measurement of catalytic efficiency are described.
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The adsorption of cobalt ions from aqueous solutions onto Nevsehir and Kayseri pumice was investigated in this study. Pumice samples were activated at 873 K for 2 h before contact with cobalt ions. In order to develop the predictive regression models all experiments were performed according to statistical designs. The concentrations of cobalt "ons were measured by UV-Vis spectrophotometer. The maximum removal efficiencies of 60 and 80 % have been obtained experimentally using Nevsehir pumice and Kayseri pumice, respectively. The goal of modeling was analyze the influence of sorbent dosage and initial cobalt concentration on sorption efficiency in case of Nevsehir and Kayseri pumice sorbent. The contour response surface plot was drawn for spatial presentation of regression equation. The experiments with radioactive 60Co were performed to test Kayseri pumice ability to remove radioactive compounds. The results showed that Nevsehir and Kayseri pumice can be used as efficient sorption materials for cobalt ions.
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Background and purpose: Lead is a toxic heavy metal that is considered major environmental contaminants and all its compounds are important in terms of toxicity in humans. So, the aim of this study was to the efficiency survey of pumice powder to lead removal from the aquatic environment. Material and Methods: In the beginning of this study, the powdered form of pumice was prepared, then the batch experiments were performed at room temperature in the variety of conditions including different contact times, various adsorbent dosages, pH=7, agitation periods=200 rpm and concentration of lead (50 mg/L). Obtained data were fitted to Langmuir and Freundlich isotherms and the pseudo first and second order and the intraparticle diffusion reaction kinetics. Results: The results showed that lead is most absorbed so its maximum removal was obtained 100%, Correlation coefficients indicate the following order to fit both isotherms: Freundlich and Langmuir for lead (R2=0.995, R2=9) respectively and second-order reaction kinetics. Also, the removal efficiency has significant difference by increasing the adsorbent dose and contact time (R2 < 0.001). Conclusion: Note that the separation coefficient (RL) and adsorption intensity was obtained in the favorable range 1-0, so the pumice is the effective adsorbent for lead removal from the aquatic environment.
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Metal oxides possess exceptional physicochemical properties which make them ideal materials for critical photocatalytic applications. However, of major interest, their photocatalytic applications are hampered by several drawbacks, consisting of prompt charge recombination of charge carriers, low surface area, inactive under visible light, and inefficient as well as expensive post-treatment recovery. The immobilization of metal oxide semiconductors on materials possessing high binding strength eliminates the impractical and costly recovery of spent catalysts in large-scale operations. Notably, the synthesis of green material (ash, clay, foundry sand, and pumice)-based metal oxides could provide a synergistic effect of the superior adsorption capacity of supporting materials and the photocatalytic activity of metal oxides. This phenomenon significantly improves the overall degradation efficiency of emerging pollutants. Inspired by the novel concept of "treating waste with waste", this contribution highlights recent advances in the utilization of natural material (clay mineral and pumice)- and waste material (ash and foundry sand)-based metal oxide nanocomposites for photodegradation of various pollutants. First, principles, mechanism, challenges towards using metal oxide as photocatalysts, and immobilization techniques are systematically summarized. Then, sources, classifications, properties, and chemical composition of green materials are briefly described. Recent advances in the utilization of green materials-based metal oxide composites for the photodegradation of various pollutants are highlighted. Finally, in the further development of green materials-derived photocatalysts, we underlined the current gaps that are worthy of deeper research in the future.
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The continuous discharge of cyanide-containing effluents to the environment has necessitated for the development of environmentally benign treatment processes that would result in complete detoxification of the cyanide-containing wastewaters, without producing additional environmental toxicants. Since biological detoxification of hazardous chemical compounds has been renowned for its robustness and environmental-friendliness, the ability of the Exiguobacterium acetylicum (GenBank accession number KT282229) and Bacillus marisflavi (GenBank accession number KR016603) to co-metabolise thiocyanate (SCN⁻) and free cyanide (CN⁻) under alkaline conditions was evaluated. E. acetylicum had an SCN⁻ degradation efficiency of 99.9 % from an initial SCN⁻ concentration of 150 mg SCN⁻/L, but the organism was unable to degrade CN⁻. Consequently, B. marisflavi had a CN⁻ degradation efficiency of 99 % from an initial concentration of 200 mg CN⁻/L. Similarly, the organism was unable to degrade SCN⁻; hence, this resulted in the evaluation of co-metabolism of SCN⁻ and CN⁻ by the two microbial species. Optimisation of operational conditions was evaluated using response surface methodology (RSM). A numeric optimisation technique was used to evaluate the optimisation of the input variables i.e. pH, temperature, SCN⁻ and CN⁻ concentrations. The optimum conditions were found to be as follows: pH 9.0, temperature 34 °C, 140 mg SCN⁻/L and 205 mg CN⁻/L under which complete SCN⁻ and CN⁻ degradation would be achieved over a 168-h period. Using the optimised data, co-metabolism of SCN⁻ and CN⁻ by both E. acetylicum and B. marisflavi was evaluated, achieving a combined degradation efficiency of ≥99.9 %. The high degradative capacity of these organisms has resulted in their supplementation on an active continuous biological degradation system that is treating both SCN⁻ and CN⁻.
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Background: Xylene is a volatile organic compound That cause central nervous system disorder and suspected cancer. Concern of occupational exposure to volatile organic compounds (VOCs) has been increasing. Thus before being discharged to the environment, it must be treated from polluted air stream. Methods: The research study is of the experimental type and was carried out on a laboratory scale. The experimental equipmen including of an air compressor, silicagel filters and activated charcoal, Syringe Pump, an ozone generation and a fixed bed reactor. The sampling, xylene analyzing in samples were done with 1501 Niosh Manual Analytic Method by GC equipped with FID detector The performance of catalytic ozonation process was compared with that of single adsorption and ozonation in removal of several concentration of xylene under the similar experimental conditions. Results: The results indicated that the catalytic ozonation concentration increased from 50 to 200 ppm, absorption break point and removal of xylene from hybrid reactor decreased from 12 to 8 h, while this time was between 9 and 5 h for pumice. When pumice and ozone come together, their synergistic effects increased on xylene degradation. Also the efficiency of absorbent decreased with the concentration increase of xylene. Conclusion: With regard to high efficiency of catalytic ozonation process and increasing the xylene removal, the catalytic ozonation process is suggested as a promising and alternative technology for elimination of VOCs from the polluted air stream.
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In this work, volcanic rocks were used as particle electrodes to construct a volcanic rock three-dimensional (3D) electrode reactor. In a wide pH range (3 ∼ 11), volcanic rocks can degrade norfloxacin (NOR) at low voltage (4 V) within 40 min. In acidic environment, the NOR removal was greater than 85%. Volcanic rock also showed excellent electrocatalytic activity when treating ofloxacin, methylene blue and other pollutants. After six cycles, the weight loss rate of volcanic rocks was 3.87%. Volcanic rocks had high mechanical strength stability. There were hydroxyl radicals (·OH) and superoxide radical (O2·⁻) produced in the volcanic rock 3D system. The volcanic rock surface was the main location of NOR degradation. The possible degradation mechanism and the degradation pathway of NOR were proposed. In addition, volcanic rock also showed excellent effects in actual surface water treatment.
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Background: Shortage of fluoride in water sources leads to numerous health problems. Also excess fluoride concentration is a more serious threat for health of community. Thus investigating of various physical, chemical, and biological processes for excess fluoride reduction from water supplies is considerable. This study aimed to reduce fluoride ion concentration from aqueous solutions by adsorption process by iron-coated pumice. Methods: Firstly, the pumice pieces were grinded and sized. After several preparation stages pumice particles were covered by 0.5 N iron nitrates (III) solution. Then the effect of parameters including pH (2-10), reaction time (5-120 min), initial fluoride concentration (3– 20 mg/L), and the adsorbent dose (0.1-1.5 g/L) on removal efficiency of fluoride were investigated in a batch system. Finally adsorption isotherms and kinetics models were determined. Results: The results showed that the removal of fluoride increased by increasing of reaction time and adsorbent dose, and reduced by increasing of initial fluoride concentration. The Iron coated pumice exhibited the best performance for fluoride removal (84.3%) at fluoride concentration 3 mg/L, adsorbent dose 0.5 g/L, pH= 6, and contact time 30 min. The adsorption equilibrium data fitted well with the Langmuir model (R2= 0.9989), and kinetic adsorption study showed that pseudo-second order kinetic is more favorable. Conclusion: According to results, the iron-coated pumice is an efficient, low cost and available adsorbent that can be considered for eliminating of fluoride ions from aqueous solutions.
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Background & Objectives: Phenol is one of the hazardous pollutants in industrials effluent. This pollutant is very toxic to human and the environment. The purpose of this study was investigation of phenol adsorption capacity with egg shell waste from aqueous solution. Methods: The eggshells were dried at 70◦C and for 12 hr in oven and then shells were crushed. The surface characteristics and quantitative elemental information were studied with SEM and XRF analysis. Then the Freundlich and Longmuir adsorption isotherms and Kinetic models were applied to description of the experimental data. Results: The maximum adsorption took place in first 60min of reaction and at pH 9. With increasing the temperature the pollutant adsorption was decreased. Also absorption characteristics of this pollutant on eggshell accommodated with Freundlich isotherm (R2=0.996). Phenol removal kinetics were fitted with both pseudo-first order and pseudo-second order kinetic models. Conclusion: The presented results demonstrate clearly that eggshell is a potentially useful material to be used for the removal of phenol from aqueous solution and industrial wastewater.
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The influence of the curing conditions (ambient curing or heat-curing), and concentration of the activating agent (8, 10, 12, 14, 16, 18 and 20 Molar sodium hydroxide solution) on the properties of alkali-activated lightweight mortars (AALWMs) containing ground granulated blast furnace slag (GGBFS) as sole binder is reported in this study. AALWMs are exposed to elevated temperatures (150, 250 and 500 °C) at the age of 28 days. The investigated properties of AALWMs at ambient and high temperatures are the unit weight (Uw), ultrasonic pulse velocity (Upv), flexural strength (fs), compressive strength (fc) and the analyses of X-ray powder diffraction (XRD) and scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS). The best strength results have been achieved on the ambient–cured AALWMs activated with 8M NaOH solution.
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This work is dedicated to the removal of free cyanide from aqueous solution trough oxidation with hydrogen peroxide H2O2 catalyzed by copper-oxide nanoparticles. Effects of initial molar ratio [H2O2]0/[CN−]0, catalyst dose, temperature, pH and the catalyst stability on cyanide removal have been investigated. The use of copper-oxide has improved the reaction rate showing thus a catalytic activity. The cyanide removal efficiency was increased from 60% to 94% by increasing in the dose of catalyst from 0.5 g/L to 5.0 g/L. Increasing the temperature from 20 °C to 35 °C promotes cyanide removal and the four successive times re-use of catalyst shows a good stability. Kinetics of cyanide removal was found to be of pseudo-first order with respect to cyanide. The rate constants have been determined.
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The problem of the production of tar along with the syngas in gasification processes limits the diffusion of this technology. In this work the tar abatement capacity of four bed materials was investigated. The bed materials, namely activated carbon, aluminium oxide, olive residue char and pumice stone, listed in order of decreasing surface area were chosen to investigate its effect on the abatement capacity. Furthermore, the deactivation of these materials with time on stream was measured and the results were used to develop a kinetic model. The tar abatement capacities were highly influenced by the surface area, activated carbon presents a removal capacity of about 97 % while pumice stone of 80 %; correlation between surface area and tar abatement capacity was found.
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This work investigates the removal of cyanide as a noxious pollutant in the gold processing effluent (Aq-Dara mine, Takab, Iran) using H2O2, H2O2+Fe(II) (Fenton), H2O2+Cu(II), NaClO and Ca(ClO)2 oxidants. Implementation of purification operation was carried out with the parameters change including pH, oxidant dosage, temperature and time of the reaction. The results show the oxidants have the highest efficacy at pH 10-12, while the Fenton process has the highest efficiency at pH 8. The results confirm that Ca(ClO)2 is the best oxidant due to less time, low reaction rate, high degradation of cyanide and low cost. The obtained results of response surface methodology optimization show that cyanide degradation has a direct relation with temperature, amount of oxidant, time and catalyst dosage parameters and has an inverse relation with pH. Also, the cyanide elimination efficiency is more than 99.5% and residual cyanide less than Environmental Protection Agency standards and 40% of the consumed water be compensated by the effluent treatment and its return to the factory's processing circuit.
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This study investigated the performance of ZrO2-pumice/H2O2-catalysed ozonation (O3/H2O2/Zr-pumice) system in the decolourisation of Rhodamine B (RhB) dye from aqueous solutions. Fourier-transform infrared spectroscopy, Scanning Electronic Microscope, X-ray fluorescence, X-ray diffraction, Brunauer-Emmett-Teller surface area, and Barrett-Joyner-Halenda pore size and volume analyses were employed to characterise the Zr-pumice. Central composite design-response surface methodology (CCD-RSM) and artificial neural network (ANN) approaches were employed to model the association between operating variables and RhB removal. CCD-RSM method suggested a reduced second-order polynomial model with R² = 0.9998, and ANN method developed an ANN model with R² = 0.9948. The levels of operating variables were displayed to be optimum at pH = 9.31, reaction time = 20 min, Zr-pumice = 0.9 g/L, RhB = 100 mg/L and H2O2 = 4.6 mmol/L, according to CCD-RSM and genetic algorithm approaches. Synergistic effect assessment revealed about 51.9% increase of removal efficiency in the hybrid system of O3/H2O2/Zr-pumice. The findings related to HO• radical-scavenging test illustrated that the major contribution of removal occurs through radical mechanism. Maximum TOC removal was determined to be 64.4% for RhB solution, and the BOD5/COD ratio increased from 0.08 to 0.56 after 150 min reaction time for a textile industry wastewater sample. Reusability test demonstrated that the Zr-pumice has a reasonable recyclability capacity even after five cycles of reuse. In conclusion, the O3/H2O2/Zr-pumice hybrid system can be suggested as a potential process in the treatment of dyeing wastewaters.
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Nanotechnology’s rapid development of nanostructured materials with disruptive material properties has inspired research for their use as electrocatalysts to potentially substitute enzymes. Herein, a novel electrocatalytic nanomaterial was constructed by growing gold nanograss (AuNG) on 2D nanoassemblies of gold nanocubes (AuNC). The resulting structure (NG@NC) was used for the detection of H2O2 via its electrochemical reduction. The NG@NC electrode displayed a large active surface area, resulting in improved electron transfer efficiency. On the nanoscale, AuNG maintained its structure, providing high stability and reproducibility of the sensing platform. Our nanostructured electrode showed excellent catalytic activity towards H2O2 at an applied potential of -0.5 V vs Ag/AgCl. This facilitated H2O2 detection with excellent selectivity in an environment like human urine, and a linear response from 50 µM to 30 mM, with a sensitivity of 100.66±4.0 μA mM-1 cm-2. The NG@NC-based sensor hence shows great potential in nonenzymatic electrochemical sensing.
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The adsorption capabilities of multiwalled carbon nanotubes (MWCNTs) with and without the embedded carboxyl group for the removal of parts per million levels of hexavalent chromium were examined as a function of several parameters, namely contact time, pH of initial solution, initial concentration of Cr (VI), adsorbent dosage as well as temperature of solution. Adsorption isotherms have been utilized to explain the adsorption mechanism. Ion exchange, intra‐particle diffusion, and electrostatic interactions are found to be the fundamental mechanisms describing the adsorption of Cr(VI). The maximum adsorption capacities of Cr(VI) ion by raw MWCNTs and functionalized MWCNTs were found to be 84.75 and 78.13 mg/g, respectively, as calculated by the Langmuir adsorption isotherm model. This is with regard to the electron‐rich atoms inside the functional group which repels the negatively charged dichromate ions. Kinetic studies were performed, and the data was found in good agreement with the pseudo‐second‐order. This article is protected by copyright. All rights reserved.
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The purpose of this research was to develop a novel ethylene scavenger by combining pumice and potassium permanganate (KMnO4) to preserve fruit and vegetables. The study showed that pumice with smaller particle sizes and lower relative humidity (RH) were favorable to ethylene adsorption. The optimal ratio was 1 g of pumice (<5 μm) to 100 mg of KMnO4 with approximately 620 μL/g of ethylene adsorption capacity within 24 h at lab room RH (30%). Further, this novel ethylene scavenger restricted the ethylene production rate of avocados to 0 μL/kg/h for nine days, and simultaneously, the carbon dioxide (CO2) production rate remained below 25 mL/kg/h. In addition, the firmness of avocados preserved by the novel ethylene scavenger was 4.04 × 10⁵ N/m² on the 9th d. The results confirmed that the shelf life of avocados was extended by 1 week at 25 °C under the preservation of the novel ethylene scavenger.
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The photocatalytic oxidation of free cyanides in aqueous suspensions containing polycrystalline TiO2(anatase) powders irradiated in the near-UV region has been investigated. The rate of cyanide photooxidation has been studied by varying the following operative parameters: (i) initial cyanide concentration; (ii) catalyst concentration; (iii) initial pH; (iv) power of irradiation; and (v) chloride ion concentration in the reacting mixture. Under the used experimental conditions the photoreaction proceeded at a measurable rate until the complete disappearance of cyanides. The kinetics of cyanide photooxidation is affected by the catalyst concentration, the chloride ion concentration, and the power of irradiation while it is independent of the initial cyanide concentration and the pH. The detrimental effect of chloride ions on cyanide photooxidation rate is not determined by a competition mechanism of chloride ions with cyanide ions or oxygen molecules for adsorption on active sites. Chloride ions affect the photoreaction rate by lowering the concentration of dissolved oxygen to values for which oxygen may become a rate limiting reactant. The Langmuir–Hinshelwood kinetic model well fits all the photoreactivity results. The reaction pathway was also investigated; cyanate, nitrate, and carbonate were found to be the main oxidation products. A mass balance on nitrogen was also successfully carried out. Specific experiments were carried out in a particular setup for measuring both the photon flow absorbed by the reacting suspension and the cyanide photoreaction rate; for these particular conditions the quantum yield value was calculated.
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Deep bed sand filters are used extensively in drinking water and wastewater treatment. In this study, sand and pumice were used as a filtration media under rapid filtration conditions and performance results for both were compared. Turbidity removal performance and head losses were investigated as functions of filtration rate, bed depth and particle size. Under the same experimental conditions such as 750 mm bed depth, 7.64m3/m2.h flow rate and, 0.5−1.0 mm grain size, turbidity removal rates for sand and pumice were found to be 85–90% and 98–99%, respectively. Furthermore, the head loss for sand and pumice were found to be 460 mm and 215 mm, respectively. The results obtained have shown that pumice has a high potential for use as a filter bed material.
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The used carbon cathodes ('Spent Pot Lining', SPL) from aluminium smelting are typically contaminated with F-, CN- and Na+ which must be removed before disposal to produce material which satisfies environmental guidelines in respect of maximum rates of ion release. Leaching of powdered and crushed carbon samples in aqueous solution were studied in the presence and absence of ultrasound. First, it was demonstrated that the total leaching of F-, CN- and Na+ from the carbon powder could be accomplished after approximately 20 min of sonication using ultrasound. Second, carbon particles (< 5 mm) showed leaching characteristics under ultrasound which were in good quantitative agreement with the National River Authority (NRA) test under silent conditions; the former being a much more rapid (approximately 1 h compared to 24 h for the NRA test) but equivalent method to the latter standard test. Third, the removed CN- ions were found to be destroyed in the presence of ultrasound, possibly via the oxidative action of hydrogen peroxide generated by the sonication of water.
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The adsorption of Cu, Zn and Ni on to formaldehyde cross-linked Saccharomyces cerevisiae immobilized on pumice stone was investigated. Maximum adsorption was occurred at pH 6 for all elements studied. The effect of mixing time and the initial concentration of metal ion on the adsorption of metal ions were also investigated. 1 mol 1-1 of HCl, KCl (pH 2) and NaCl (pH 2) solutions were tested for desorption and 1 mol 1-1 of KCl (pH 2) solution was found to be appropriate for the desorption of all metals studied. The desorption was 89.2% for Cu, 89.8% for Zn and 87.0 for Ni. The metal capacity of immobilized cell biomass (quantity of metals accumulatad by one gram biomass) was found as 2.09, 2.24 and 3.18 mg g-1 dry cell biomass for Zn, Cu and Ni, respectively.
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Immobilized cells play an important role in removing organic and inorganic compounds taken from domestic sources and industrial plants. Biofilm or fixed film reactors are widespread form of immobilized cells for wastewater treatment. In this paper, a fixed film column reactor was used with Paracoccus denitrificans (hetetrophic microorganisms), which were immobilized on pumice as filling material. Artificial components were used for the preparation of the feeding solution and the effect of different carbon sources (ethanol, methanol, acetic acid, glucose) on the nitrate removal rate was examined. The best nitrate removal rate was observed at the optimum C/N ratio of 3 and with methanol as carbon source.
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Trials were conducted to optimize slow sand filtration by varying filter material, depth of the filter bed and flow rate. Recirculated nutrient solutions from Dracaena marginata and Aglaonema commutatum pot plants grown hydroponically in expanded clay on ebb/flow benches were inoculated with Xanthomonas campestris pv. pelargonii as the test organism. Four completely separated systems were used each consisting of one hydroculture bench (approx. 3 m2) and one filter unit (approx. 0.2 m2 filter surface). Granulated rockwool in comparison to sand, pumice or anthracite has been shown to be the most efficient filter material. The efficiency of a rockwool filter with a depth of 90 cm was only slightly and not significantly higher than that of a 60 cm filter. However, both efficiency rates were significantly higher than that of a 30 cm filter. The differences of the mean efficiency rates at flow rates of 100, 200 and 300 L/m2h were not as high as expected (99.76, 99.41 and 98.85 % respectively). A regression analysis revealed a significant correlation of -0.5 between flow rate and efficiency rate.
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Chemical replacements for cyanide have been investigated for decades; however cyanide remains the exclusive lixiviant of choice in the mining industry due to a combination of its availability, effectiveness, economics and ability to use it with acceptable risk to humans and the environment. About 90% of the significant gold producing operations worldwide currently utilize cyanide for gold and silver extraction. Despite the number of cyanide-related mining operations, there have been no documented accounts during the previous three decades of the death of humans due to cyanide as a direct consequence of major mining-related environmental incidents. Major mining-related environmental incidents have not been concentrated in any geographic location, may occur regardless of the size of the company and do not occur more frequently with a specific type of mining activity. The main aspects of cyanide management that should be addressed at mining operations include transportation of cyanide to site, process solution conveyance, worker health and safety training, water management and treatment, emergency response and preparedness, workplace and environmental monitoring, and community relations. If these aspects of cyanide management are integrated into an overall cyanide management plan, dramatic reductions in risk and potential incidents at mine sites will be realized.
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Cyanide (CN -) is a toxic species that is found predominantly in industrial effluents generated by metallurgical operations. Cyanide's strong affinity for metals makes it favorable as an agent for metal finishing and treatment and as a lixivant for metal leaching, particularly gold. These technologies are environmentally sound but require safeguards to prevent accidental spills from contaminating soils as well as surface and ground waters. Various methods of cyanide remediation by separation and oxidation are therefore reviewed. Reaction mechanisms are given throughout. The methods are compared in regard to their effectiveness in treating various cyanide species: free cyanide, thiocyanate, weak-acid dissociables and strong-acid dissociables.
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A series of pumice supported nickel catalysts used in the CO hydrogénation reaction were characterised by X-ray photoelectron spectroscopy. Qualitative and quantitative analysis of the XPS peaks have shown the effect of the calcination conditions on the chemical state of the nickel before hydrogenation and the particle size of the metal after reduction. Calcination at high temperature determined enrichment of sodium ions on the surface of the support and also on the metal particles. After exposure to the gas mixture CO/H2, formation of nickel carbides and other carbon species was checked. The correlation found between the surface atomic ratio Na/Si and the activity and selectivity of the catalysts in the hydrogenation of CO substantiated the role of the alkali ions naturally present in the pumice support.
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Three identical anaerobic fluidized bed reactors containing different biomass support media were fed a distillery wastewater at various hydraulic retention times and COD loadings. The support media used were sepiolite, pumice stone and sand; particle diameter was around 0.5 mm in all cases. Start-up of the reactors was achieved within 63 days using a regime that included stepped increases in influent COD concentration and substitution of methanol for part of the wastewater COD. No significant differences in performance between reactors were observed during this period. Six different steady states at hydraulic retention times between 0.5 and 2.48 days were studied. Results obtained at these steady states showed similar performances in all three reactors except at HRT of 0.5 days, when the reactors containing sepiolite and pumice stone achieved better COD removal efficiencies and higher methane yields than the sand-containing reactor. It was concluded that sepiolite and pumice stone would be excellent solid supports in biological fluidized bed processes and have a lower energy consumption than the one demanded when using a sand support.
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The sixth region of Chile hosts the giant El Teniente porphyry copper deposit and several polymetallic districts exploited in small mine works; the latter are situated and processed in a predominantly agricultural area. This mining activity has a potential for environmental damage caused by infiltration of mineral processing slurries. As possible low-cost material for environmental applications, a local common clay and pumice were tested in 1:1 mixtures for the retention of Cu, As, Mo and Fe in mine waste waters and mineral processing slurries (pH range 3–6). In batch filtrations, simulating a single spillage of slurry, copper levels were reduced from >1100 to
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This technical note examines the difficulty of measuring specific gravity and estimating void ratio in pumice because of its vesicular nature and soft grains. Pumice particles each contain a dense network of fine holes, some of which may be interconnected and open to the surface, while others are isolated inside the particle. This paper examines different ways of measuring the specific gravity, and the influence of particle size on the results. The void ratio measure by conventional methods invariably includes some of the internal void space, and therefore will give an incorrect value for the effective volume of the particles. The resulting specific gravity is likely to be higher than the true value, leading to an underestimate of solid volume and an overestimate of void ratio. The tests conducted do not resolve the question of the appropriate specific gravity value to be used in calculating the void ratio.
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Two series of pumice-supported palladium catalysts (W = washed, U = unwashed) were prepared by the reaction of [Pd(CâHâ)â] with the support, followed by reduction using Hâ. W catalysts were washed before reduction to eliminate unreacted [Pd(CâHâ)â]. U catalysts did not undergo this treatment. Microstructural characterization of the catalysts was performed by small-angle X-ray scattering (SAXS), wide-angle X-ray line broadening, and transmission electron microscopy (TEM). Line-broadening analysis revealed the presence of lattice imperfections, such as growth stacking faults and microstrains in the fcc structure of palladium. The average particle size values determined by SAXS were confirmed by TEM analysis and were employed to calculate the percentage of palladium exposed (catalyst dispersion). W catalysts showed well-dispersed spheroidal particles, whereas the U series displayed agglomerates. 38 refs., 9 figs., 2 tabs.
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Porous lavas, more precisely pumice stone, are promising supports for TiO2 used as a photocatalyst. TiO2 deeply penetrates into pores that favours its retention. Its deposition is convenient and facile and the photocatalytic activity is not significantly affected by the erosion of the surface. The immobilization of TiO2 on pumice stone gave better results for the photocatalytic degradation of 3-nitrobenzenesulfonic acid than conventional sol–gel dip-coating on cement and red brick. A layer of pumice stone as pellets, fixed on a cement layer and impregnated with TiO2 is used in a thin film fixed bed reactor, for the photocatalytic treatment of water.
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Pumice-supported copper–palladium catalysts prepared from organometallic precursor have been tested in the hydrogenation of phenylacetylene and in the hydrogenation/isomerization of the but-1-ene. The structure and catalytic behaviour of the bimetallic catalysts depended on the different temperatures of reduction. The presence of CuO or Cu metal in an alloyed state with Pd influenced the two reactions. The system containing CuO is the most active and selective towards the formation of the monoalkene in the hydrogenation of the highly unsaturated hydrocarbon. The system containing Cu partially alloyed with Pd is more active and selective towards the isomerization of the but-1-ene. The performance in the two reactions is discussed in terms of the electronic effect prevailing when CuO is present and in terms of the geometric ensemble size variation prevailing with the Cu–Pd system.Copyright 1999 Academic Press.
Article
The aim of this study was to obtain a catalyst or support material from a natural pumice that could then be used in the hydroisomerization of n-pentane. Acid treatment of the raw material with HCl was found to extract a larger amount of cations than NH4Ac (Ac = acetate), yielding a product with a better developed texture and structure. The total number of protons present in the solution affects potassium extraction, while sodium is affected by both factors of concentration and volume of dissolution independently. The specific area of the material (meters squared per gram) obtained depends on the treatment conditions, and it value can be calculated by means of the treatment condition variables or by the total number of moles of the cations extracted. The treatments could be carried out by working at and above ambient temperatures and with and without fresh acid replacements. The optimum treatment for obtaining a catalytic support was 10 mL/g of pumice of 3 M HCl for 10 h with three replacements of fresh acid working at 70 °C.
Article
An XPS study has been performed on samples of monometallic catalysts of palladium and platinum and on bimetallic Pd-Pt catalysts supported on pumice. A negative shift of about 0.5 eV in the Pd 3d and Pt 4f binding energies of the catalysts relative to the energies of the same levels in the pure metals suggested an increase in the electron density in both metals. A quantitative XPS analysis indicated that the supported metals did not modify the surface atomic composition of pumice. In the bimetallic catalysts the variation in the Pd 3d/Pd MNN intensity ratio over the different Pd/Pt atomic fractions has been attributed to surface segregation of the metal present in smaller amount.
Article
In order to investigate the surface structure of pumice, an amorphous aluminosilicate, samples of pumice and of standards of silica and alumina have been studied by x-ray photoelectron spectroscopy (XPS). The effect of a mild acid leaching was also considered. The analysis of the Si 2p, Al 2p and O 1s photoelectron peaks and the Si KLL and O KLL Auger peaks indicated that pumice is formed by tetrahedral silica with some units being replaced by aluminate, AlO2−. The acid treatment decreases the alkali and the aluminate ions. X-ray photoelectron spectra of the valence band of pumices and of standards of Al2O3 and SiO2 agree with the core-level results. To support the conclusions from the XPS study, magic angle spinning (MAS) 27Al nuclear magnetic resonance (NMR) of pumice was used. The spectrum is indicative of tetrahedrally coordinated aluminium.
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Several advanced oxidation processes for the destruction of cyanide contained in waste waters from thermoelectric power stations of combined-cycle were studied. Thus, oxidation processes involving ozonation at basic pH, ozone/hydrogen peroxide, ozone/ultraviolet radiation and ozone/hydrogen peroxide/ultraviolet radiation have been carried out in a semi-batch reactor. All these methods showed that total cyanide can be successfully degraded but with different reaction rates, and the decrease in the total cyanide concentration can be described by pseudo-first order kinetics. The influence of pH and initial concentration of hydrogen peroxide was studied to find the optimal conditions of the oxidation process. Experimental results of the single ozone treatment indicated that total cyanide is destroyed more rapidly at higher pH (12), while ozonation combined with H2O2 and/or UV is faster at pH 9.5. The optimum concentration of H2O2 was 20.58 × 10−2M because an excess of peroxide decreases the reaction rate, acting as a radical scavenger. The total cyanide degradation rate in the O3/H2O2(20.58 × 10−2M) treatment was the highest among all the combinations studied. However, COD reduction, in the processes using UV radiation such as O3/UV or O3/H2O2/UV was about 75%, while in the processes with H2O2 and/or O3/H2O2 was lower than 57% and was insignificant, when using ozone alone. Copyright © 2003 Society of Chemical Industry
Article
Pumice-supported nickel catalysts, prepared by the method of slow homogeneous precipitation with urea, were analysed by x-ray photoelectron spectroscopy (XPS). By comparison with similarly prepared silica- and alumina-supported nickel catalysts, a preferential interaction of Ni2+ with Al3+ of the support has been determined. A quantitative XPS analysis indicated large segregation of nickel to the surface. The treatment with H2 at 673 K and 1073 K produced a partial reduction of Ni+2 to Ni0. The extent of the reduction was largest at 1073 K and in this case the reduced Ni in the metallic phase was detectable by x-ray diffraction. A decrease of the Ni 2p/Si 2p intensity ratio occurring in the lower temperature H2-treated catalysts was attributed to diffusion of nickel as Ni2+, as a consequence of a solid-state reaction between nickel ions and support oxides, whereas the decrease of the intensity ratio in the high-temperature reduced catalysts was attributed to sintering of the nickel particles and to diffusion of nickel atoms interacting with oxygen vacancies of the support.
Article
The main objective of this work was to determine the effectiveness and kinetics of hydrogen peroxide in destroying cyanide in the tailings slurry from a gold mine with low sulphide and heavy metal content. The impacts of catalyst (Cu) and hydrogen peroxide concentrations, temperature and pH on the extent and rate of weak acid dissociable (WAD) cyanide destruction were investigated. Experiments were conducted using the variable-dose completely mixed batch reactor bottle-point method. Both the rate and extent of CNWAD destruction generally increased with increasing peroxide doses for either absence or presence of Cu catalyst. Catalyst addition was very effective in terms of not only enhancing the cyanide destruction rate but also significantly reducing the required peroxide dosages to achieve CNWAD concentrations of about 1 mg/l, independent of the temperatures tested (10, 20 and 30 °C). The initial cyanide destruction rates increased between 1.2 and 3 folds with the addition of 30 mg/l of Cu. Kinetic experiments showed that in most cases little CNWAD destruction occurred after a reaction time of 2–4 h. The impact of slurry pH on cyanide destruction varied depending upon the dosages of Cu catalyst. Relatively lower peroxide dose/CNWAD ratios required to achieve less than 1 mg/l of CNWAD may be due to lower heavy metals and sulphide content of the ore, resulting in lower peroxide requirement for metal bound cyanides. During cyanide destruction, nitrate was initially formed as a by-product and then possibly converted to other some volatile nitrogen-containing species, as supported by the mass balance calculations.
Article
The removal of Sr, Cs, U and Th ions from aqueous solution by means of natural pumice stone was studied using energy dispersive X-ray fluorescence spectroscopy (EDXRF) as an analytical tool. The results indicate the usefulness of pumice powder and the removal efficiency was found to be in order of Th>Sr>Cs ions, which is altered by the pH of the solution.
Article
Silver-palladium bimetallic clusters were synthesized on pumice by the reduction of aqueous solution of metal salts with different Pd:Ag ratios. Used as bimetallic catalysts, in hydrogenation reactions, in situations where molecules can undergo several different reactions, they eliminate undesired reactions and maximize the desired ones. To characterize the structure of these bimetallic catalysts and control if the two metallic elements do mix or not to each other to form an alloy, the structure of the Ag-Pd bimetallic clusters was investigated by means of X-ray-absorption fine-structure spectroscopy (XAFS) and anomalous wide angle X-ray scattering (AWAXS) experiments performed at the European Synchrotron Radiation Facility (ESRF) using the GILDA and the BM16 beamlines. A correlation between Ag and Pd was found but not a clear evidence of alloying.
Article
Two series of pumice-supported palladium and palladium–copper catalysts, prepared by impregnation with different palladium and copper precursors, were tested for the hydrogenation of aqueous nitrate and nitrite solutions. Measurements were performed in a stirred tank reactor, operating in batch conditions, in buffered water solution at atmospheric pressure and at 293 K. The activities of the catalysts were calculated in terms of nitrate and/or nitrite removal. With the monometallic Pd/pumice, the reduction of nitrite is highly selective; only 0.2% of the initial nitrite content is converted to ammonium ions. The activity in terms of turn over frequency (TOF) is higher as compared to a catalyst of Pd on silica. Addition of copper to the palladium catalyst is essential for the reduction of nitrates, although it decreases the nitrite reduction activity and increases the production of ammonium ions. Nitrate reduction appears to be structure-insensitive and a volcano-type dependence of the activity versus the overall Cu atomic weight percentage is observed for the two series of catalysts.
Article
In the history of Turkey the first use of cyanide for gold recovery has been at the Ovacik Gold Mine. During one-year test period, this mine has successfully been mining and processing after a complicated and extensive environmental impact procedure. In Turkey about 2500 ton of sodium cyanide are used with about 240 ton of sodium cyanide being used at this mine annually. During the test period, it has been shown that an effluent quality (CNWAD) between 0.06 ppm (min) and 1 ppm (max) was achievable after cyanide destruction with the Inco Process. It was also found that treated effluent values (CNWAD) of process water (decant) were between 0.04 ppm (min) and 0.59 ppm (max). This paper presents a review of the cyanidation and cyanide destruction processes at the Ovacik Gold Mine.
Article
An easy method is proposed to immobilize TiO2 for photocatalytic transformations of organic pollutants in aqueous solution. It consists of impregnation of pumice stone pellets with commercially available TiO2. Pumice stone is a soft material, but this disadvantage can be eliminated by fixing pellets on a hard surface (cement or polycarbonate) and using a thin-film fixed bed reactor. Examples of application are given with 3-nitrobenzenesulfonic acid (3-NBSA), Acid Orange-7 (AO-7, a dye) and real wastewaters collected after biological treatment.
Article
Organoclays can be prepared by modification of the surface with a cationic surface active compound and used for the immobilisation or separation of non-polar contaminants from polluted waters. In this work pumice is used instead of clay material. Batch system experiments were performed for the modification of pumice surface with hexadecyltrimethylammonium bromide. Modification of pumice and then the sorption of pesticide, Fenvalerate, from water have been traced by FT-IR spectroscopy.
Article
Iron oxide is an excellent, regenerable adsorbent, and often controls free metals through adsorption reaction. The utilization of heating process for coating iron oxide on sand surface allowed the media to be used in a packed column. Iron-coated sand was investigated for adsorbing metal ions and natural organic matter from water by batch and column experiments. Chemical analysis (energy dispersive analysis of X-ray, EDAX) was used for characterizing the copper and lead adsorption sites on iron-coated sand. From the batch experiment results, the copper and lead ions could be removed simultaneously by the iron-coated sand in the competition adsorption system. The interaction between copper, lead ions and iron oxide on sand surface was primarily the chemical bonds. The maximum adsorption capacities of iron-coated sand for copper and lead were 0.259 mg Cu/g-sand and 1.211 mg Pb/g-sand, respectively. The presence of humic acid led to increase the adsorption of copper and lead. Results from column experiments indicated that the copper ions, lead ions and humic acid could be removed completely before the breakpoint. Consequently, the iron-coated sand may be applied for the adsorption/filtration of metal ions and natural organic matters from water.
Article
Microbial destruction of cyanide and its related compounds is one of the most important biotechnologies to emerge in the last two decades for treating process and tailings solutions at precious metals mining operations. Hundreds of plant and microbial species (bacteria, fungi and algae) can detoxify cyanide quickly to environmentally acceptable levels and into less harmful by-products. Full-scale bacterial processes have been used effectively for many years in commercial applications in North America. Several species of bacteria can convert cyanide under both aerobic and anaerobic conditions using it as a primary source of nitrogen and carbon. Other organisms are capable of oxidizing the cyanide related compounds of thiocyanate and ammonia under varying conditions of pH, temperature, nutrient levels, oxygen, and metal concentrations. This paper presents an overview of the destruction of cyanide in mining related solutions by microbial processes.
Article
In gold mining, cyanide has been the preferred lixiviant worldwide since 1887. Although cyanide can be destroyed and recovered by several processes, it is still widely discussed and examined due to its potential toxicity and environmental impact. Biological treatment of cyanide is a well-established process and has been commercially used at gold mining operations in North America. Biological treatment processes facilitate growth of microorganisms that are essential for the treatment. The present review describes the advances in the use of biological treatment for the destruction of cyanide in gold mill effluents.
Article
Laboratory and fieldwork studies were carried out to evaluate the potential of pumice soil for use as a wetland substrate in wastewater treatment. The composition of pumice soil was analysed by x-ray fluorescence (XRF) and x-ray diffraction (XRD) techniques. Adsorption kinetic studies were carried out in a semi-batch recycle system. Fieldwork tests were carried out on Subsurface Flow Constructed Wetland (SSFCW) cells planted with Phragmites mauritianus and Vetiveria zizanioides. The results have shown that pumice soil composition contains among other elements Al, Ca, Fe and Mg, which are positive indicators for phosphorus adsorption. The main minerals observed by XRD were augite, hematite, and sodium titanium silicate. Phosphorus adsorption kinetics have shown that phosphorus is adsorbed on pumice soil following first order kinetics and the adsorption was highly influenced by mass transfer. Approximately 3% of the phosphorus was removed by plant uptake.
Article
The treatment of a cyanidation effluent containing thiocyanate, free cyanide, and complexed cyanide was continuously performed for a period of 6 months. Activated carbon, pozzolana, and a mixture of pumice stone and zeolite were tested as supports in fixed bed reactors. Activated carbon adsorbed the different forms of cyanide. In contrast, the other supports did not remove any pollutants from the effluent during an adsorption experiment. All supports successfully allowed fixation of bacteria. More than 90% of the thiocyanate was biologically decomposed into NH4+, CO2 and SO4(2-), even when increasing the feed flow-rate and the pollutant concentrations. Free and complexed cyanides were eliminated, probably through a combination of precipitation and biological degradation. The oxidation of ammonium into nitrate was only performed by the activated carbon-containing column and with the more diluted feeding. The nitrification process was inhibited in all reactors when the cyanide concentrations and feed flow-rates were increased.
The usage of pumice and the effect of legislation on pumice mining
  • N Gungor
  • M Tombul
Gungor, N., Tombul, M., 1997. The usage of pumice and the effect of legislation on pumice mining. First Isparta Pumice Symposium, Isparta, Turkey, pp. 85-90.
Pumice and volcanic cinder
  • R P Geitgey
Geitgey, R.P., 1994. Pumice and volcanic cinder. In: Carr, D.D. (Eds.), Industrial Minerals and Rocks. Society for Mining, Metallurgy, and Exploration, Littleton, CO, USA, pp. 803-813.
Cyanide treatment methods The Cyanide Guide
  • M M Botz
Botz, M.M., 2001. Cyanide treatment methods. In: Mudder, T.I. (Ed.), The Cyanide Guide. A Special Edition of the Mining Environmental Management, vol. 9, pp. 28-30.
Oxygen sensitivity of natural and synthetic organic macromolecule sorption by activated carbon The University of Michigan Filtration and retention of mineral processing slurries with pumice and common clay: low-cost materials for environmental appli-cations in the small-scale mining industry
  • T Mi Karanfil
  • U Kelm
  • V Sanhueza
  • C Guzman
Karanfil, T., 1995. Oxygen sensitivity of natural and synthetic organic macromolecule sorption by activated carbon. Ph.D. Thesis, The University of Michigan, Ann Arbor, MI. Kelm, U., Sanhueza, V., Guzman, C., 2003. Filtration and retention of mineral processing slurries with pumice and common clay: low-cost materials for environmental appli-cations in the small-scale mining industry. Appl. Clay Sci. 24, 35–42.
Cyanide detoxification with hydrogen peroxide using the Degussa process
  • H Knorre
  • A Griffiths
Knorre, H., Griffiths, A., 1984. Cyanide detoxification with hydrogen peroxide using the Degussa process. Proceedings of the Cyanide and the Environment Conference, Tucson, Arizona.
  • L Gunduz
  • A Sariisik
  • B Tozacan
  • M Davraz
  • I Ugur
  • O Cankiran
Gunduz, L., Sariisik, A., Tozacan, B., Davraz, M., Ugur, I., Cankiran, O., 1998. Pumice Technology, vol. 1. S (in Turkish).
Study of pumice supported palladium and platinum catalysts
  • Venezia