Bioleaching Of Heavy Metals Research Articles

Tolerance levels of sulfur-oxidizing micro-organisms to Methylene blue and Remazol black B dyes during sewage sludge bioleaching

The present study was undertaken to investigate the tolerance levels of indigenous sulfur-oxidizing micro-organisms to Methylene blue (MB), Remazol black B (RBB), and mixture of both the dyes (DM) during bioleaching of heavy metals from sewage sludge. The experiments were performed with anaerobically digested sewage sludge at initial neutral pH of the sludge containing 0–35,000 mg/l of the MB, RBB, and DM. The results show that the bioleaching process was affected by the increase in concentration of MB, which decreased the growth of indigenous sulfur-oxidizing micro-organisms leading to the slow rate of decrease in pH and hence decreased solubilization of metals. Similar effects were observed on the activity of indigenous sulfur-oxidizing micro-organisms using RBB and a mixture (DM) of MB and RBB. The presence of RBB and DM were found to be more toxic as compared to MB at the same initial concentration of the dyes. At initial concentration of 30,000 mg/l, a drastic reduction in pH drop was observed with decreased solubilization of metals, irrespective of any dye. The results of the present study shall be useful to develop a suitable bioleaching process for the sludges contaminated with a variety of dyes.

Thermophilic bioleaching of heavy metals from waste sludge using response surface methodology

The bioleaching process is considered to be more efficient and environmentally friendly than conventional technologies for removal of heavy metals from waste sludge. The objective of this study was to develop an optimal thermophilic bioleaching process for the treatment of waste sludge containing high concentrations of heavy metals. In this study, two operating parameters, sludge solid content and sulfur (substrate) concentration, were studied based on a central composite design (CCD) for their metal solubilization and solid degradation performances. The optimal bioleaching operation conditions were then determined using the response surface methodology (RSM). The results indicated that an increase in sludge solid content range from 0.5% to 5.0% resulted in a decrease in the pH reduction rate due to the increase in buffering capacity. The rate of acidification corresponded to sulfur concentration until sulfur itself became inhibitory. At sulfur concentration beyond approximately 2.75%, the lower acidification rate was caused by a lower bacteria growth rate. Similar trends were also observed in the variations of ORP and sulfate concentrations during this thermophilic bioleaching process. At the optimum conditions of a sludge solid content of 0.5% and sulfur concentration of 2.5%, the thermophilic bioleaching process achieved the maximum solubilization of 97%, 99%, 99% and 78% for Cu, Zn, Ni and Pb, respectively. At the same time, the maximum SS and VSS destruction efficiency were 69% and 63%, respectively.

The change in activated sludge surface properties after heavy metals leaching

The change in colloid-chemical properties of natural sludge sol formed as a result of biological treatment of domestic wastewater in the process of heavy metals leaching induced by metabolizing heterotrophic (acidogenic and alkaligenic) chemotrophic biocoenosis was investigated. It was found that bioleaching of heavy metals involving heterotrophs results in hydrophobization of sludge colloids and reduces its negative charge. Heavy metals leaching also results in destabilization of sludge sol, maximum in biological processes. Exopolysaccharides significantly stabilizing sludge sol have a little effect on its stability after heavy metals have been leached.

Conditioning of sediment polluted with heavy metals using plants as a preliminary stage of the bioremediation process: a large-scale study

Purpose A bioremediation process for sediments contaminated with heavy metals has been developed based on two core stages: (1) conditioning of dredged sludge using plants; and (2) solid-bed bioleaching of heavy metals from the resulting soil-like material using microbially produced sulfuric acid. In laboratory and pilot-scale tests, reed canary grass (Phalaris arundinacea) was found to be best suited for the conditioning process. To demonstrate the feasibility of conditioning in practice, a study on a larger scale was performed.

Bioleaching of heavy metals from red mud using Aspergillus niger

Red mud (bauxite residue) is the main waste product of the alkaline extraction of alumina from bauxite with high amounts of metals. In this study, bioleaching of heavy metals from red mud by using the fungus Aspergillus niger was investigated. Bioleaching experiments were examined in batch cultures with the red mud at various pulp densities (1–5%, w/v) under various bioleaching conditions (one-step, two-step and spent medium bioleaching). It was shown that the main lixiviant excreted by A. niger was citric acid. The highest leaching ratios of most various heavy metals were achieved under spent medium leaching at 1% pulp density. The increase in red mud pulp densities resulted in a general decrease in leaching ratios under all bioleaching conditions. However, in the case of the spent medium leaching the decrease in leaching ratios was lowest. The Toxicity Characteristic Leaching Procedure (TCLP) tests showed that the leaching toxicity of the bioleaching residue was far below the levels of relevant regulations. The micromorphology of the red mud particles were changed by the fungal activity during bioleaching process.

Degradation of inhibitory substances in sludge by Galactomyces sp. Z3 and the role of its extracellular polymeric substances in improving bioleaching

This study sought to elucidate the effect and mechanism of Galactomyces sp. Z3 in improving the bioleaching of heavy metals from sludge. Results showed that co-inoculation of Galactomyces sp. Z3 and two Acidithiobacillus strains (Acidithiobacillus ferrooxidans LX5 and Acidithiobacillus thiooxidans TS6) reduced the period required for sludge bioleaching by 4.5days compared to Acidithiobacillus alone. Further, removal efficiencies of Cu, Zn and oxidation rate of Fe2+ and S0 were higher in co-inoculation system than the Acidithiobacillus alone. Galactomyces sp. Z3 consumed the acetate, propionate, iso-butyrate, butyrate, and iso-valerate in sludge from the initial concentrations of 109.50, 28.80, 7.70, 34.30, and 18.40mg/L to 10.20, 0.61, 0.63, 19.40 and 1.30mg/L, respectively, after 12h in the co-inoculation system, significantly lower than the concentrations observed in the Acidithiobacillus alone. Meanwhile, the surfactant properties of the extracellular polymeric substances produced by the Galactomyces accelerated the rate of sulfur oxidization by A. thiooxidans.

Transformation of heavy metals and the formation of secondary iron minerals during pig manure bioleaching by the co-inoculation acidophilic thiobacillus

Bioleaching of heavy metals from pig manure using a mixture of harmless iron- and sulfur-oxidizing bacteria in an air-lift reactor was conducted. The transformation of heavy metals and the formation of secondary Fe minerals during bioleaching were also investigated in the present study. The removal efficiencies of Zn, Cu, and Mn from pig manure were 95.1%, 80.9%, and 87.5%, respectively. Zn mainly existed in the form of Fe–Mn oxides in fresh pig manure; most of the pig manure-borne Cu was in organic matter form; Mn existed mainly in Fe–Mn oxides, carbonates, and residual forms. The pig manure can be applied to land more safely after bioleaching because the heavy metals mainly existed in stable forms. The removal efficiencies Zn, Cu, and Mn had good relationships with pH and oxidation reduction potential during bioleaching. A mixture of jarosite and schwertmannite was found in the bioleached pig manure, which might have an adverse effect on the solubilization efficiency of toxic metals from pig manure. The bioleaching process using a mixture of harmless iron- and sulfur-oxidizing bacteria was shown to be a very feasible technology for the removal of heavy metals from pig manure.

Removal of Cu, Zn and Pb from mine tailings by bioleaching: effects of initial pH

The presence of heavy metals in mine tailings poses potential threats to environment and human health. The paper reports an investigation of the effects of initial pH on bioleaching of heavy metals (Cu, Zn and Pb) from mine tailings by indigenous sulphur-oxidising bacteria.

Preliminary bioleaching of heavy metals from contaminated soil employing indigenous Penicillium Chrysogenum strain F1

Bioleaching is an environment-friendly and economical technique to remove heavy metals from contaminated soil. The objective of this work is to find out an indigenous strain to remedy soil contaminated by Zn, Pb, Cu and Cd. A strain which was selected from the soil of a local smelting industry was found to be able to produce many organic acids and degrade pH value of the liquid medium. The fungus strain is identified as Penicillium Chrysogenum (P. Chrysogenum) by sequencing 18srDNA and ITS. Bioleaching condition using P. Chrysogenum is optimized. Glucose is the best carbon source for P. Chrysogenum and inorganic nitrogen is better than organic nitrogen. In addition, neutral solution and room temperature are fit for P. Chrysogenum to bioleach. In the one-step bioleaching, the bioleaching ratios are 39.95% for Zn, 9.4% for Pb, 34.89% for Cu and 49.59% for Cd, which are 53.89% for Zn, 14.44% for Pb, 55.53% for Cu and 62.81% for Cd in the two-step bioleaching. The efficiency of two-step bioleaching is better than the one-step bioleaching. P. Chrysogenum is effective in removing heavy metals from the contaminated soil.

Bioleaching of heavy metals from a contaminated soil using indigenous Penicillium chrysogenum strain F1

Bioleaching of heavy metals from contaminated soil using Penicillium chrysogenum strain F1 was investigated. Batch experiments were performed to compare leaching efficiencies of heavy metals between one-step and two-step processes and to determine the transformation of heavy metal fractions before and after bioleaching. The results showed that two-step process had higher leaching efficiencies of heavy metals than one-step process. When the mass ratio of soil to culture medium containing P. chrysogenum strain F1 was 5% (w/v), 50%, 35%, 9% and 40% of Cd, Cu, Pb and Zn were removed in one-step process, respectively. The two-step process had higher removals of 63% Cd, 56% Cu, 14% Pb and 54% Zn as compared with one-step process. The results of the sequential extraction showed that the metals remaining in the soil were mainly bonded in stable fractions after bioleaching. The results of TEM and SEM showed that during bioleaching process, although the mycelium of P. chrysogenum was broken into fragments, no damage was obviously observed on the surface of the living cell except for thinner cell wall, smaller vacuoles and concentrated cytoplasm. The result implied that P. chrysogenum strain F1 can be used to remove heavy metals from polluted soil.

Column Bioleaching of Arsenic and Heavy Metals from Gold Mine Tailings by Aspergillus fumigatus

AbstractA column bioleaching experiment was carried out to compare the effectiveness of the fungus Aspergillus fumigatus to bioleach arsenic (As) and heavy metals from the tailings using two different methods. In the first method, which is named as distribution method (DM), the fungus was distributed in the column by means of vertical and horizontal layers of coarse sand. In the other method, named as surface applied method (SAM), the fungus was cultivated on the surface of the tailings, which was covered with a few centimeters of coarse sand. Results showed that in the DM, oxalic acid production was stimulated and maximum removal of As, Fe, Mn, and Zn was 53, 51, 81, and 62%, respectively. However, Pb removal was low (8%), which might be due to the precipitation of Pb as its oxalates. On the other hand, the maximum removal of As, Fe, Mn, Pb, and Zn were 22, 28, 37, 64, and 34%, respectively, for the SAM. Results of the sequential extraction study showed that the DM was effective in removing the water soluble, exchangeable, carbonate, and Fe/Mn oxide fractions of As, Fe, Mn, and Zn. Our study suggested that A. fumigatus has a potential to be used in remediation of heavy metal contaminated sites. Distributing the fungus throughout the entire tailings columns improved the bioleaching of heavy metals by the fungus.

Influence of Sulfur Concentration on Bioleaching of Heavy Metals from Industrial Waste Sludge

The bioleaching process, including acidification and solubilization of heavy metals, is a promising method for removing heavy metals from industrial waste sludge. Solubilization of heavy metals in industrial waste sludge is governed by adding elemental sulfur. A sulfur concentration exceeding 0.5% (w/v) inhibits sulfate production and the activity of acidophilic bacteria. Sulfate production was described well by a substrate inhibition expression in Haldane's kinetics. After 15 days of bioleaching, 79 to 81% copper, 50 to 69% lead, and 49 to 69% nickel were solubilized from sludge with a sulfur concentration of 0.5 to 1.0% (w/v). Experimental results indicated that the optimal sulfur concentration for the maximum solubilization rate of copper and nickel was 0.5% (w/v) and 1.0% (w/v) for lead. The profiles of denaturing gradient gel electrophoresis confirmed that indigenous acidophilic Acidithiobacilli (A. thiooxidans and A. ferrooxidans) existed and were the dominant species in the bioleaching process.

Effect of sulphur concentration on bioleaching of heavy metals from contaminated dredged sediments

The sulphur‐based bioleaching process using sulphur‐oxidizing bacteria (SOB) has been demonstrated to be a feasible technology for removing heavy metals from contaminated sediments, but the excess sulphur application will lead to the re‐acidification of bioleached sediments. The objective of the present study was to examine the effect of sulphur concentration on the bioleaching of heavy metals from contaminated sediments, with the ultimate purpose of minimizing the sulphur addition. The results showed that the inoculation of 7% of indigenous SOB, containing 3.6 × 108 colony forming units (CFU) mL−1, and addition of elemental sulphur as a substrate (0.5 to 7.0 g L−1) resulted in a sharp decrease in sediment pH from an initial pH 8.0 to pH 1.4–2.4 and an increase in ORP (oxidation–reduction potential) from −10 mV to 500 mV within 10 days of bioleaching. Although the increase in sulphur concentration enhanced the rates of pH reduction and ORP elevation, the bioleaching process with the addition of 3.0 g L−1 of sulphur was already sufficient to reach conditions of acidity (pH < 2.0) and ORP (500 mV) necessary for a satisfactory removal of metals, and, at day 10, 71.8% of Cu, 58.2% of Zn, and 25.3% of Cr were removed from the sediments. During the bioleaching process, Zn removal increased with a reduction in pH, whereas the removal of Cu and Cr increased not only with a reduction in pH but also with an increase in ORP. Results of sequential selective extraction indicated that the final levels of metal removals were dependent on their speciation distribution in the original sediments, and after bioleaching those unremoved metals in the bioleached sediments mainly existed in the residual fraction.

Bioleaching of heavy metals from sewage sludge by indigenous iron-oxidizing microorganisms using ammonium ferrous sulfate and ferrous sulfate as energy sources: A comparative study

The potential of indigenous iron-oxidizing microorganisms enriched at initial neutral pH of the sewage sludge for bioleaching of heavy metals was investigated at initial neutral pH of the sludge using ammonium ferrous sulfate (FAS) and ferrous sulfate (FS) as an energy sources in two different sets of experiments. After 16 days of bioleaching, 56% Cu, 48% Ni, 68% Zn and 42% C were removed from the sludge using ammonium ferrous sulfate as an energy source. On the other hand, 64% Cu, 58% Ni, 76% Zn and 52% Cr were removed using ferrous sulfate. Further, 32% nitrogen and 24% phosphorus were leached from the sludge using ferrous sulfate, whereas only 22% nitrogen and 17% phosphorus were removed using ammonium ferrous sulfate. The BCR sequential extraction study on speciation of metals showed that using ammonium ferrous sulfate and ferrous sulfate, all the metals remained in bioleached sludge as stable form (F4 fraction). The results of the present study indicate that the bioleached sludge would be safer for land application. Also, the fertilizing property was largely conserved in the bioleached sludge using both the substrates.

Biological leaching of heavy metals from a contaminated soil by Aspergillus niger

Bioleaching of heavy metals from a contaminated soil in an industrial area using metabolites, mainly weak organic acids, produced by a fungus Aspergillus niger was investigated. Batch experiments were performed to compare the leaching efficiencies of one-step and two-step processes and to determine the transformation of heavy metal chemical forms during the bioleaching process. After the one or two-step processes, the metal removals were compared using analysis of variance (ANOVA) and least-significance difference (LSD). A. niger exhibits a good potential in generating a variety of organic acids effective for metal solubilisation. Results showed that after the one-step process, maximum removals of 56%, 100%, 30% and 19% were achieved for copper, cadmium, lead and zinc, respectively. After the two-step process, highest removals of 97.5% Cu, 88.2% Cd, 26% Pb, and 14.5% Zn were obtained. Results of sequential extraction showed that organic acids produced by A. niger were effective in removing the exchangeable, carbonate, and Fe/Mn oxide fractions of Cu, Cd, Pb and Zn; and after both processes the metals remaining in the soil were mainly bound in stable fractions. Such a treatment procedure indicated that leaching of heavy metals from contaminated soil using A. niger has the potential for use in remediation of contaminated soils.

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: ...

Enhancing Metal Removal by Coaddition of Fe2+ and S0 as Substrates of Acidithiobacillus Ferrooxidans for Sewage Sludge Bioleaching

Bioleaching of heavy metals from sewage sludge has been shown to be a promising technique for sludge decontamination in such a complex matrix. The effect of two types of substrates ( Fe2+ and S0 ) and their combination on metal removal efficiencies was studied in a batch system using Acidithiobacillus ferrooxidans. The results showed that the inoculation of A. ferrooxidans and coaddition of Fe2+ and S0 accelerated pH reduction and metal solubilization. After 4–10 days of bioleaching, the following removal efficiencies were obtained: Cr 80%; Cu 100%; and Zn 100%, which were the maximum that have been reported. The time required for Cr to reach the maximum was 10 days, whereas for Cu and Zn the time needed was only 4–6 days. Three different patterns of solubilization for Cr, Cu, and Zn were established as a function of pH and Fe3+ concentration. Cr required a threshold pH of around 2.0 to initiate its solubilization, whereas Cu solubilization was controlled simultaneously by pH and Fe3+ concentration. The p...

Effects of water-washing pretreatment on bioleaching of heavy metals from municipal solid waste incinerator fly ash

Previous studies demonstrated that the bioleaching of municipal solid waste incinerator fly ash by Aspergillus niger was an efficient “green technology” for heavy metals removal, however, it demanded a long operational period. In this study, water-washing was used as a fly ash pretreatment before the bioleaching process (one-step and two-step). This pretreatment extracted 50.6% of K, 41.1% of Na, 5.2% of Ca and 1% of Cr from the fly ash. Due to the dissolution of alkali chlorides which hold particles together, fly ash particles were smashed into smaller granules by the hydraulic flushing action caused by vibration. After the pretreatment, the lag phase and bioleaching period were reduced by 45 and 30%, respectively, in one-step bioleaching of 1% (w/v) fly ash. Meanwhile, the metals extraction yield both in one-step and two-step bioleaching was increased markedly, e.g. in two-step bioleaching, 96% Cd, 91% Mn, 73% Pb, 68% Zn, 35% Cr and 30% Fe was extracted from 1% water-washed fly ash, respectively. The reduction of the bioleaching period and improvement of metals extraction yield will likely allow the practical application of the bioleaching technology for heavy metals removal from fly ash.

Optimization of Fe2 + /solids content ratio for a novel sludge heavy metal bioleaching process

A novel bioleaching process, preincubation bioleaching (PB) has been recently developed in our laboratory for decontamination of heavy-metal-laden sewage sludge by removing the toxic low molecular weight organic acids using an isolated degradative yeast species. The objective of the present study was to optimize Fe2+ /solids content ratio required for removing heavy metals from sewage sludge by using this novel process at high solids content. Results from the present study showed that regardless of the Fe2+ /solids content ratio iron oxidation and sludge acidification could be achieved within 2 days confirming the effectiveness of PB in reducing the inhibitory organic acids. When PB was conducted at an elevated solids content of 3%, Fe2 +/solids content ratio could be reduced to 0.75:1, 1:1 and 1.25:1 for solubilization of Zn, Cu and Cr respectively. Under this optimized bioleaching conditions, the following solubilization efficiencies were obtained after 8 days of bioleaching: 100% Zn, 96% Cu, 60% Cr with no reduction in nutrient contents. Hence, bioleaching at elevated solids contents represents a more economical way for decontamination of heavy-metal-laden sewage sludge while preserving its fertility values.

Influence of Fe(II) addition on heavy metal bioleaching from sewage sludge with mixed inocula

The indigenous mixed inocula were cultured and enriched from the thickened waste sewage sludge for heavy metal bioleaching. The mixed inocula were then used for bioleaching, and 2 g/L sulphur was added. The influences of FeSO4?7H2O dosage on heavy metals (Zn, Cu, Pb and Cd) and nutrients (nitrogen and phosphorus) bioleaching were investigated. Results show that the addition of FeSO4?7H2O accelerates the bioleaching process. With the FeSO4?7H2O addition, pH of the sludge decreases and the Oxidation Reduction Potential (ORP) increases more rapidly. The presence of FeSO4?7H2O obviously increases the solubilisation of Zn, Cu and Cd, but has insignificant impact on the Pb solubilisation. FeSO4?7H2O also changes the nitrogen loss and the phosphorus loss. The suitable FeSO4?7H2O dosage is 5?10 g/L; higher dosages cannot accelerate the heavy metal bioleaching more. With the addition of 10 g/L FeSO4?7H2O and 2 g/L sulphur powder, 81.4% of Zn, 81.1% of Cu, 67.6% of Pb and 56.6% of Cd are solubilised from the sludge after 15-day bioleaching at 28?C and an agitating speed of 180 r/min.