Solubilization Of Cu Research Articles

Augmentation in bioleaching potential of indigenous Bacillus sp. ISO1 for metals recovery from waste computer-printed circuit boards.

The bio-cyanidation process of various cyanogenic microorganisms is found to be a sustainable and effective method for metals recovery from primary and secondary sources. This process has surpassed the limitations of the chemical cyanide treatment process; thus, prioritized as a promising approach for e-waste "urban mining" strategies. The main focus of the study was to enhance the bioleaching capacity of indigenous Bacillus sp. ISO1 and to implement optimized parameters in large-scale bioleaching operations. The assessment of various amino acids unveiled that like other cyanogenic microorganisms Bacillus sp. ISO1 also preferred glycine as a prime precursor for cyanide synthesis, as maximum metal solubilization was achieved with glycine amino acid. Other amino acids influenced the bacterial growth but not significantly affected the biocyanidation process. The evaluation and optimization of methionine as a lixiviant stimulator demonstrated that the addition of 1 mg/L methionine effectively enhance the production of glycine-utilizing cyanide lixiviant, that led to a significant solubilization of Cu (86%), Au (75%), and Ag (63%) metals. Furthermore, the kinetics of metal solubilization and operating conditions were explored at increased volume (i.e., 3 L working volume) of bioleaching medium to assess the industrial scale potential of this potent bacterial strain with optimized parameters such as temperature, pH, pulp density, and inoculum size. The significant recovery of Cu (˃ 60%) and other metals at this substantial volume suggested the implementation of a bioleaching process with this potent bacterial strain at industrial scale operations.

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

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

Effects of inoculation with plant growth-promoting rhizobacteria from the Brazilian Amazon on the bacterial community associated with maize in field

The objective of this study was to investigate the effects of the inoculation with the plant growth-promoting rhizobacteria Bacillus thuringiensis RZ2MS9 and Burkholderia ambifaria RZ2MS16, both from the Brazilian Amazon, on the bacterial community of the rhizobiome and leaves of maize grown in field. For comparison, we analysed the effects of inoculating Azospirillum brasilense Ab-V5, a strain that is commercialized as inoculant for maize, as well as the combinations RZ2MS16 + Ab-V5 and RZ2MS9 + Ab-V5. The treatment RZ2MS9 + Ab-V5 yielded the highest plant height and stalk diameter, which were significantly different from the non-inoculated control (p < 0.05). The core microbiome of maize was mainly composed of the bacterial classes Gammaproteobacteria, Betaproteobacteria, Actinobacteria, Alphaproteobacteria, Cytophagia, and Bacilli. Overall, the inoculation process had no effect either on the composition of the maize-associated bacterial community or on the total bacterial biomass. However, we detected significant differences in the richness and in the community structure among the plant niches analysed. Linear discriminant analysis identified that the class Actinobacteria, and the order Actinomycetales were enriched in leaf and root of plants treated with RZ2MS16 + Ab-V5 and in rhizosphere of plants treated with RZ2MS9 + Ab-V5. Functional analysis of the soil samples revealed significant differences in the abundance of predicted genes encoding proteins related to respiration and solubilization of Cu, Mg, and K among treatments. Furthermore, the NMDS ordination showed association between different functional gene categories and some plant traits. Our findings contribute to understanding the efficacy of microbial inoculants for maize in field conditions.

Removal of metals and phosphorus recovery from urban anaerobically digested sludge by electro-Fenton treatment

To our knowledge, this work presents the first application of electro-Fenton (EF) process to sludge washing. Suspensions of anaerobically digested sludge (0.50 wt%) from a municipal wastewater treatment facility were electrolyzed with addition of Na2SO4 and Fe2+ at pH 3.0, using a stirred tank reactor with a boron-doped diamond (BDD) or RuO2-based anode and an air-diffusion cathode that produced H2O2. The effect of the sludge content in suspensions and applied current density (j) was examined. High quantities of Cr, Pb, Cd, Zn, Fe and P were leached at pH 3.0, whereas Cu showed the opposite trend. Aeration only enhanced Pb and Zn leaching, whereas the use of Fenton's reagent with 15 mM H2O2 solubilized 16.0% Cr, 23.0% P, 42.6% Fe and 56.0% Pb, with total leaching of Cd, Cu and Zn. EF with BDD anode at high j caused total precipitation of Cr, Pb and Fe, 40% Cd leaching and total solubilization of Cu and Zn. The RuO2-based anode enhanced the entrapment of Cr, Fe and P in the solid fraction of the sludge, but promoted a high transport of Cd, Cu and Zn to the liquid phase. P recovery was about 74%–79% in all EF treatments. The soluble organic carbon increased in most cases except for EF with BDD, where it decreased markedly, in agreement with the high oxidation power of this anode. The sludge dewaterability was largely improved in all treatments, attaining up to 97%, consistent with the scission of many extracellular polymeric components.

Metal biorecovery in acid solutions from a copper smelter slag

Slags from metallurgical processes represent a potential resource of metals but also waste materials that have not been successfully beneficiated to date. For this study, a bulk slag sample from a copper smelter was evaluated under chemical and bacterial leaching conditions to test the solubilization of Cu and Zn in acidic, sulfate-rich solutions. Fayalite, magnetite and glassy silicates as well as Cu-sulfides and sphalerite were the major phases of the slag. The acid demand of the slag was satisfied with a 24h contact time with sulfuric acid. A mixed mesophilic culture capable of oxidizing iron and sulfur and dominated by Acidithiobacillus thiooxidans, A. ferrooxidans, and Leptospirillum ferriphilum was used for bioleaching. The maximum extent of Zn leaching was 14%, contrasted with 83% Cu in experiments with an initial pH of 2.1–2.2, 10% pulp density, 10gL−1S0 addition, 5% inoculum, and 25d contact time. Biological S0 oxidation was an important source of acid in bioleaching experiments. Ferric iron did not enhance the solubilization of Cu and Zn appreciably.

β-Cyclodextrin assisted solubilization of Cu and Cr complexes of flavonoids in aqueous medium: A DNA-interaction study

Cu and Cr complexes of three flavonoids (morin, quercetin and 6-hydroxyflavone) were synthesized and included in beta-cyclodextrin (βCD) with the objective of improving their pharmacokinetic profiles. Then binding with ds.DNA was studied to monitor their interactive tendencies at physiological conditions. The binding constants and other thermodynamic data from UV–vis spectroscopy and cyclic voltammetry revealed Cr–flavonoid–βCD to interact with ds.DNA at pH-7.4 through electrostatic mode of binding while Cu–flavonoid–βCD can intercalate into DNA. The strong binding propensity of Cu–flavonoid–βCD with ds.DNA encourages their application as anticancerous agent.

Chemical Leaching of Antimony and Other Metals from Small Arms Shooting Range Soil

Military small arms shooting range (SASR) soils are heavily polluted by metals like copper, lead, antimony, and zinc. This study was carried out to define efficient operating conditions to solubilize these metals by a chemical leaching technique. The comparison of different leaching reagents (HCl, H2SO4, CH3COOH, and EDTA) has revealed that sulfuric acid leaching coupled with the addition of sodium chloride is the most interesting option for the solubilization of Cu, Pb, Sb, and Zn from the finest fractions (<125 μm) of SASR soil. The initial metal contents of the soil sample were 1,760 mg Cu kg−1, 43,300 mg Pb kg−1, 780 mg Sb kg−1, and 355 mg Zn kg−1. The important operational parameters for leaching ([H2SO4], [NaCl], pulp density, reaction time, and temperature) were also studied. The optimum leaching conditions identified were 1 M H2SO4 and 4 M NaCl with a 10 % (w/v) soil pulp density at ambient temperature. In these conditions, 83, 75, 61, and 72 % of Cu, Pb, Sb, and Zn were respectively solubilized after only 1 h of treatment. The use of five successive leaching steps and two washing steps removed 96, 99, 84 and 86 % of Cu, Pb, Sb, and Zn respectively from the soil.

Spectroscopic analysis of the bioleaching of chalcopyrite by Acidithiobacillus caldus

The formation and consumption of elemental S were investigated in the bioleaching of chalcopyrite within and without a CE dialysis membrane in Acidithiobacillus caldus cultures. The bacteria were supplemented with tetrathionate outside the membrane. XPS analysis showed that monosulfide species and elemental S were formed on CuFeS2 surface regardless of the enclosure in the dialysis membrane. They diminished over time in the inoculated systems. In the membrane enclosure, colloidal S partially dissolves and can pass the dialysis membrane for bacterial oxidation to sulfuric acid. Anaerobic pre-oxidation of CuFeS2 by Fe3+ produced S-rich deposition on mineral surface. The solubilization of Cu from membrane-enclosed pre-oxidized chalcopyrite in the A. caldus culture was much slower as compared to direct contact with bacteria. The difference is attributed to slow diffusion through the dialysis membrane as well as clogging caused by polymerized S on the inside of the membrane.

Effects of aging on the digestive solubilization of Cu from sediments

Solubilization of particulate Cu by different solutions, mimicking digestive fluids of deposit-feeders, was quantified in stable isotope 65Cu-spiked sediments (with 3 days-2 months Cu-sediment contact time or aging). Copper solubilization generally decreased with prolonged aging. However, such decrease became less evident after 1 month and equilibrium of Cu in sediments could be reached after 2 months. Aging effects on Cu solubilization can be explained by the changes in Cu geochemical fractionation with aging: Cu generally transferred from more mobile phases (carbonate and Fe–Mn associated) to more refractory phases (organic associated and residual phase). Besides Cu geochemical fractionation, digestive fluid composition and different Cu solubilization pathways involved, as well as sedimentary organic content, could all affect the digestive solubilization of Cu and its change with aging. Our results emphasize the necessity of considering Cu aging in laboratory sediment toxicity experiments, and in risk assessment of Cu contaminated sediments.

Surface complexation of Cu on birnessite (δ-MnO 2): Controls on Cu in the deep ocean

Hexagonal birnessite (δ-MnO 2) is a close analogue to the dominant phase in hydrogenetic marine ferromanganese crusts and nodules. These deposits contain ∼0.25 wt.% Cu which is believed to be scavenged from the overlying water column where Cu concentrations are near 0.1 μg/L. Here, we measured the sorption of Cu on δ-MnO 2 as a function of pH and surface loading. We characterized the nature of the Cu sorption complex at pH 4 and 8 using EXAFS spectroscopy and find that, at pH 4, Cu sorbs to birnessite by inner-sphere complexation on the {0 0 1} surface at sites above Mn vacancies to give a three to fourfold coordinated complex with 6 Mn neighbors at ∼3.4 Å. At pH 8, however, we find that some Cu has become structurally incorporated into the MnO 2 layer by occupying the vacancy sites to give 6 Mn neighbors at ∼2.91 Å. Density functional calculations on CuMn 18 O 24 ( OH ) 30 ( H 2 O ) 3 - 4 and CuMn 18 O 21 ( OH ) 33 ( H 2 O ) 3 - 1 clusters predict a threefold coordinated surface complex and show that the change from surface complexation to structural incorporation is a response to protonation of oxygens surrounding the vacancy site. Consequently, we propose that the transformation between sorption via surface complex and vacancy site occupancy should be reversible. By fitting the Cu sorption as a function of surface loading and pH to the formation of the observed and predicted surface complex, we developed a surface complexation model (in the basic Stern approximation) for the sorption of Cu onto birnessite. Using this model, we demonstrate that the concentration of inorganic Cu in the deep ocean should be several orders of magnitude lower than the observed total dissolved Cu. We propose that the observed total dissolved Cu concentration in the oceans reflects solubilization of Cu by microbially generated ligands.

Effects of Energy Source Concentration on Bioleaching of Heavy Metals from Undigested Sewage Sludge by Using Iron-Oxidizing Bacterium

The objective of the present study was to optimize the energy source addition required for bioleaching of heavy metals from undigested sewage sludge after secondary treatment. Bioleaching was conducted in a batch system with both inoculation of iron-oxidizing bacteria and the addition of FeSO4 ⋅7 H2 O in the range of 0–17.5 g L−1 . The results showed that the pH of the sludge decreased with an increase in the ferrous iron concentrations and reached the maximum acidity of pH 2.1–3.0 for treatments receiving both bacterial inoculation and substrate addition. This led to a significant solubilization of metals from the solids fraction of sewage sludge. However, solubilization behavior differed for different metal species. Solubilization of Zn was not affected by the concentration of the substrate in the range of 7.5–17.5 g L−1 , whereas solubilization of Cu and Cr was highly dependent on substrate concentration. After 10 days of bioleaching the following heavy metal solubilization efficiencies were obtained: ...

Bioproduction of Ferric Sulfate Used during Heavy Metals Removal from Sewage Sludge

Toxic metals removal from wastewater sewage sludge can be achieved through microbial processes involving Acidithiobacillus ferrooxidans. The oxidation of ferrous ions by A. ferrooxidans, cultured in sewage sludge filtrate, was studied in both batch and continuous flow stirred tank reactors. Sewage sludge filtrate containing natural nutrients (phosphorus and nitrogen) was recovered as effluent following the dehydration of a primary and secondary sludge mixture. Batch and continuous flow stirred tank reactor tests demonstrated that A. ferrooxidans were able to grow and completely oxidize ferrous iron in a culture medium containing more than 80% (v v(-1)) sewage sludge filtrate with 10 g Fe(II) L(-1) added. Toxic levels were reached when total organic carbon in the sewage sludge filtrate exceeded 250 mg L(-1). The ferric iron solution produced in the sludge filtrate by A. ferrooxidans was used to solubilize heavy metals in primary and secondary sludge. The solubilization of Cu, Cr, and Zn yielded 71, 49, and 80%, respectively. This is comparable with the yield percentages obtained using a FeCl(3) solution. The cost of treating wastewater sewage sludge by bioproducing a ferric ion solution from sewage sludge is three times less expensive than the conventional method requiring a commercial ferric chloride solution.

CHARACTERIZATION OF AN INDIGENOUS IRON-OXIDIZING BACTERIUM AND ITS EFFECTIVENESS IN BIOLEACHING HEAVY METALS FROM ANAEROBICALLY DIGESTED SEWAGE SLUDGE

The objective of the present study was to isolate the indigenous iron-oxidizing bacterium and compare its effectiveness in bioleaching of heavy metals from fresh anaerobically digested sludge and aged sludge which had undergone a storage period in a sludge holding tank. An acidophilic iron-oxidizing bacterium Acidithiobacillus ferrooxidans strain ANYL-1 was successfully isolated from the sludge collected from a wastewater treatment plant at Yuen Long district in Hong Kong. It was a Gram negative, non-motile rod shaped bacterium which used ferrous iron, elemental sulfur or thiosulfate as energy source, but did not utilize tetrathionate or glucose as energy source. The optimal temperature and pH for its growth and iron oxidation were 30-35°C and pH 2.0-2.5, respectively. When it was used in the bioleaching of anaerobically digested sewage sludge, an inhibition on metal solubilization was observed in fresh sludge except for Zn whose dissolution was solely a chemical process. Compared to the 3 and 4 days required for solubilization of Cu and Cr respectively from the sludge sample collected after the sludge holding tank (Sludge SHT), 6 days were required to bioleach Cu and Cr from fresh sludge (Sludge AD). The fresh sewage sludge posed an unfavorable condition for bioleaching of heavy metals from anaerobically digested sludge as reflected by the prolonged bioleaching time. Therefore, further studies were needed to understand the inhibitory effects in the fresh anaerobically digested sludge and develop measures to remove it in order to improve the heavy metal bioleaching efficiency.

Identification of inhibitory substances affecting bioleaching of heavy metals from anaerobically digested sewage sludge.

Significant inhibitory effects of the filtrate medium of anaerobically digested sewage sludge on iron oxidation by Acidithiobacillus ferrooxidans ANYL-1 were observed in our preliminary experiments, indicating the presence of inhibitory substances in anaerobically digested sewage sludge. The objectives of the present study were to identify the possible inhibitory substances and to evaluate their impacts on metal solubilization during bioleaching of sewage sludge. The results showed that the concentrations of total reducing sugars, all tested metal ions, and anions were too low to suppress iron oxidation, and only organic acids, especially acetic and propionic acids, were found at concentrations higher than their inhibitory levels. The presence of 10.8 mM acetic acid and 9.88 mM propionic acid in sewage sludge (sludge N) led to long lag periods of 6 and 7 days for solubilization of Cu and Cr, respectively, as compared to a lag period of only 1 day in the control and another sludge (sludge S) with a low level of organic acids. Meanwhile the leaching time for maximum solubilization of Zn also extended to 6 days in the presence of organic acids as compared to 3 days in the control. Acetic and propionic acids posed an unfavorable bioleaching condition for anaerobically digested sewage sludge; therefore, further studies are required to explore the means to remove the inhibitory effects to improve the heavy metal bioleaching efficiency.

Biological processes: The effects of initial pH, percentage inoculum and nutrient enrichment on the solubilization of sediment bound metals

Biological solubilization of metals in highly contaminated sediments (Lachine Canal, Montreal, P.Q., Canada) was tested in 500 mL batches. The biological process uses the leaching capacity of Thiobacilli. Batch experiments were performed to determine the influence of initial pH, the percentage of inoculum, and the addition of nitrogen and phosphate on the efficiency of the process. Similar metal recoveries were obtained at either of the initial pH values (pH 4.0 and pH 4.5). The addition of 20% inoculum (v/v) appears to result in acceptable yields over a short time period (24–48 hours). Solubilization of Cu is strongly correlated with the presence of bacteria (r2 increase with time up to 0.90 after 53h). In the case of Zn (within first 6 hours) and Pb (at the beginning), the chemical environment appears to be the main factor controlling solubilization of these elements (r2 up to 0.99). The addition of nutrients had no affect on the production of Thiobacilli, but the addition of NH4 reduced the solubilization of Zn, Pb (r2 up to 0.90) and at the beginning, the solubilization of Cu (r2=0.67). While the addition of PO43- diminished the solubilization of Zn, Pb and Cu (r2 up to 0.96). Upon addition of substrate (FeSO 4.7H2), the growth of Thiobacilli already present in the sediments is favored. The application of this process to sediments appears feasible, as Zn and Cu levels were at acceptable levels following treatment. Further studies are necessary to improve the removal of Pb.

Strategies to maximize the microbial leaching of lead from metal-contaminated aquatic sediments

Different strategies designed to increase the removal of Pb were tested during the application of a biological remediation procedure to treat highly-contaminated aquatic sediments. The use of FeCl 2 instead of FeSO 4·7H 2O as a substrate for thiobacilli bacteria did not interfere with the biological solubilization process which occurred in sediments acidified to pH 4 with H 2SO 4. With FeCl 2, twice as much Pb was solubilized (5 mg Pb l −1) compared to the same strain acclimated to FeSO 4·7H 2O. With FeCl 2, the solubilization of other trace metals (Cu,Zn) was similar to that obtained with the strain acclimated to FeSO 4·7H 2O. If the sediments were acidified with HCl, rather than H 2SO 4, then the solubilization of Pb increased to 11 mg Pb l −1: this was five times greater than when a strain acclimated to FeSO 4·7H 2O was used in sediments acidified with H 2SO 4. Theoretical calculations with MINEQL + (chemical equilibrium program) predicted 10.8 mg Pb l −1 under similar conditions. This biological solubilization process was generally poorly adaptable to changes in the source of acidity (i.e. HCl vs H 2SO 4). The solubilization of Cu remained relatively low (solubilization of only 35% after 72 h) since the inadequately low levels of sulphate prevented the Thiobacillus bacteria from properly developing. Finally, the higher concentration of chloride ions gained through an increased level of total solids (7% rather than 3% TS) did not increase the soluble concentration of Pb. The soluble concentration of Pb remained at 11 mg Pb l −1 (46%), whereas theory predicted a concentration of 24.1 (100%) mg Pb l −1. Most of the experimental results seemed to follow the theoretically predicted outcome for Pb solubilization. There is more work to do to optimize the process. However, this work reveals that it seems possible to develop an economical process for the removal of Pb from contaminated sediments.

Solubilization of Cu 2+ from copper ore by iron-oxidizing bacteria isolated from the natural environment and identification of the enzyme that determines Cu 2+ solubilization activity

Solubilization of Cu 2+ from copper concentrate by 67 strains of iron-oxidizing bacteria isolated from the natural environment was studied. In the case of static growth on copper concentrate (5%)-salt medium (pH 2.5) at 30°C, Cu 2+ solubilization activities of 65 strains including Thiobacillus ferrooxidans strains AP19-3, OK-2, OK-3, OK1–50, Funis and NASF-1 ranged from 2.5–3.5 mg Cu 2+/ml/33 d. In contrast, the activities of T. ferrooxidans strains KO-1 and NA-1 were quite low at 0.9 mg Cu 2+/ml/33 d. Nonbiological solubilization activity of Cu 2+ was 0.4 mg Cu 2+/ml/33 d. For identification of the enzymes that play a crucial role in biological Cu 2+ solubilization, the activities of the enzymes involved in iron and sulfur oxidations were compared among the strains described above. No significant differences in the growth on iron-salt medium and the levels of cellular iron oxidizing activity were observed. In contrast, a marked difference was observed in the cellular activity of an enzyme that was involved in the first step of sulfur oxidation in T. ferrooxidans, i.e., hydrogen sulfide: ferric ion oxidoreductase (SFORase). Strains Funis, OK1–50, NASF-1, OK-3, AP19-3, OK-2 which showed high Cu 2+ solubilization activity showed high SFORase activity (1.3–4.0 μmol Fe 2+/ml/4 h). In contrast, strains NA-1 and KO-1 which showed low Cu 2+ solubilization activity showed low SFORase activity (0.3–0.4 μmol Fe 2+/ml/4 h), suggesting that SFORase, but not iron oxidase, is the enzyme that determines the ability of T. ferrooxidans to solubilize Cu 2+ from copper concentrate.

Major factors influencing bacterial leaching of heavy metals (Cu and Zn) from anaerobic sludge

Anaerobically digested sewage sludges were treated for heavy metal removal through a biological solubilization process called bacterial leaching (bioleaching). The solubilization of copper and zinc from these sludges is described in this study: using continuously stirred tank reactors with and without sludge recycling at different mean hydraulic residence times (1, 2, 3 and 4 days). Significant linear equations were established for the solubilization of zinc and copper according to relevant parameters: oxygen reduction potential (ORP), pH and residence time ( t). Zinc solubilization was related to the residence time with a r 2 (explained variance) of 0·82. Considering only t = 2 and 3 days explained variance of 0·31 and 0·24 were found between zinc solubilization as a function of ORP and pH indicating a minor importance of those two factors for this metal in the range of pH and ORP experimented. Cu solubilization was weakly correlated to mean hydraulic residence time ( r 2 = 0·48), while it was highly correlated to ORP ( r 2 = 0·80) and pH ( r 2 = 0·62) considering only t of 2 and 3 days in the case of pH and ORP. The ORP dependence of Cu solubilization has been clearly demonstrated in this study. In addition to this, the importance of the substrate concentration for Cu solubilization has been confirmed. The hypothesis of a biological solubilization of Cu by the indirect mechanism has been supported. The results permit, under optimum conditions, the drawing of linear equations which will allow prediction of metal solubilization efficiencies from the parameters pH (Cu), ORP (Cu) and residence time (Cu and Zn), during the treatment. The linear regressions will be a useful tool for routine operation of the process.

Importance du pH et du potentiel doxydo‐réduction sur la solubilisation biologique des métaux dans des boues

Abstract Heavy metal removal was made in batch reactors (1,5 L) by the way of a biological solubilization process called bacterial leaching. Linear equations were established for the solubilization of Cu, Zn and Mn, according to relevant parameters: pH and oxido‐reduction potential (ORP). The relatively low importance of ORP in aerobic sludges compare to anaerobic sludges can be explain. Normal values of ORP in aerobic sludges are higher than all threshold values found for solubilization whereas it is the opposite for anaerobic sludges.