Explore the recycling of bioleaching functional bacteria and sulfur substrate using the sulfur-covered biochar particles

Background Bioleaching has been attracting attention recent years as an emerging sediment heavy metal pollution remediation technology. However, the use of sulfur powder as sulfur substrate causes the problem of “post-acidification”, and the free bioleaching functional bacteria which are susceptible to environmental impact during reactor operation cannot be used efficiently for multiple rounds. These problems can be solved if the sulfur substrate and the bioleaching functional bacteria can be recycled simultaneously after bioleaching. A new kind of sulfur substrate, the laboratory-made sulfur-covered biochar particles, were used in the bioleaching experiment, compared with sulfur powder and sulfur powder mixed with the surfactant rhamnolipid. Results The sulfur-covered biochar particles exhibited superior bioleaching performance, including faster acidification rate, SO 4 2- production rate and heavy metal bioleaching rate, and higher heavy metal solubilization percentage (Ni 33.76%; Cu 66.16%; Zn 65.494%), which was resulted from the acceleration of bioleaching reaction by the bioleaching functional bacteria immobilized on the biochar surface. Otherwise, the sulfur-covered biochar particles could be reused in the second round, and the heavy metal solubilization percentage (Ni32.84%, Cu69.93%, Zn67.17%) was comparable with that of the first round. Nevertheless, the sulfur content became the main limiting factor causing poor bioleaching performance during the third round. The sulfur mixed with the surfactant rhamnolipid did not show significant effect in promoting acidification and heavy metal solubilization due to high levels of organic matter and the impact of the low pH value. Conclusion The research indicated the laboratory-made sulfur-covered biochar particles could realize the dual immobilization of the bioleaching functional bacteria and the sulfur substrate to support their recycling and reuse in the second bioleaching round. In the future research, the way to maintain the reuse of the sulfur-covered biochar particle for more rounds will be explored.

Explore the recycling of bioleaching functional bacteria and sulfur substrate using the sulfur-covered biochar particles

Background Bioleaching has been attracting attention recent years as an emerging sediment heavy metal pollution remediation technology. However, the use of sulfur powder as sulfur substrate causes the problem of “post-acidification”, and the free bioleaching functional bacteria which are susceptible to environmental impact during reactor operation cannot be used efficiently for multiple rounds. These problems can be solved if the sulfur substrate and the bioleaching functional bacteria can be recycled simultaneously after bioleaching. A new kind of sulfur substrate, the laboratory-made sulfur-covered biochar particles, were used in the bioleaching experiment, compared with sulfur powder and sulfur powder mixed with the surfactant rhamnolipid. Results The sulfur-covered biochar particles exhibited superior bioleaching performance, including faster acidification rate, SO 4 2- production rate and heavy metal bioleaching rate, and higher heavy metal solubilization percentage (Ni 33.76%; Cu 66.16%; Zn 65.494%), which was resulted from the acceleration of bioleaching reaction by the bioleaching functional bacteria immobilized on the biochar surface. Otherwise, the sulfur-covered biochar particles could be reused in the second round, and the heavy metal solubilization percentage (Ni32.84%, Cu69.93%, Zn67.17%) was comparable with that of the first round. Nevertheless, the sulfur content became the main limiting factor causing poor bioleaching performance during the third round. The sulfur mixed with the surfactant rhamnolipid did not show significant effect in promoting acidification and heavy metal solubilization due to high levels of organic matter and the impact of the low pH value. Conclusion The research indicated the laboratory-made sulfur-covered biochar particles could realize the dual immobilization of the bioleaching functional bacteria and the sulfur substrate to support their recycling and reuse in the second bioleaching round. In the future research, the way to maintain the reuse of the sulfur-covered biochar particle for more rounds will be explored.

Explore the recycling of bioleaching functional bacteria and sulfur substrate using the sulfur-covered biochar particles

Background Bioleaching has been attracting attention recent years as an emerging sediment heavy metal pollution remediation technology. However, the use of sulfur powder as sulfur substrate causes the problem of “post-acidification”, and the free bioleaching functional bacteria which are susceptible to environmental impact during reactor operation cannot be used efficiently for multiple rounds. These problems can be solved if the sulfur substrate and the bioleaching functional bacteria can be recycled simultaneously after bioleaching. A new kind of sulfur substrate, the laboratory-made sulfur-covered biochar particles, were used in the bioleaching experiment, compared with sulfur powder and sulfur powder mixed with the surfactant rhamnolipid.Results The sulfur-covered biochar particles exhibited superior bioleaching performance, including faster acidification rate, SO 4 2- production rate and heavy metal bioleaching rate, and higher heavy metal solubilization percentage (Ni 33.76%; Cu 66.16%; Zn 65.494%), which was resulted from the acceleration of bioleaching reaction by the bioleaching functional bacteria immobilized on the biochar surface. Otherwise, the sulfur-covered biochar particles could be reused in the second round, and the heavy metal solubilization percentage (Ni32.84%, Cu69.93%, Zn67.17%) was comparable with that of the first round. Nevertheless, the sulfur content became the main limiting factor causing poor bioleaching performance during the third round. The sulfur mixed with the surfactant rhamnolipid did not show significant effect in promoting acidification and heavy metal solubilization due to high levels of organic matter and the impact of the low pH value.Conclusion The research indicated the laboratory-made sulfur-covered biochar particles could realize the dual immobilization of the bioleaching functional bacteria and the sulfur substrate to support their recycling and reuse in the second bioleaching round. In the future research, the way to maintain the reuse of the sulfur-covered biochar particle for more rounds will be explored.

Chelating agents to solubilize heavy metals from Oxisols contaminated by the addition of organic and inorganic residues

Phytoremediation is an attractive technique for soils contaminated with heavy metals, especially in conjunction with chelating agents to assist metal phytoextraction. Nevertheless, their studies in Brazil are rare. Thus, the objective of the present work was to evaluate the efficiency of the chelating agents EDDS and EDTA for the solubilization of heavy metals from two Oxisols contaminated by organic sources in Jaguariúna (LVJ) and inorganic sources in Paulínia (LVP), São Paulo State, Southeastern Brazil. First, the soil samples were fractionated and the DTPA method was used to quantify heavy metals available forms. The results indicated that the metals were highly available in the soil fractions and could be solubilized by the chelating agents. The soil was suspended for 24 h in a chelating agent solution (EDTA or EDDS) at rates of 0, 250, 500 and 750 mg kg-1 of soil. The concentration of solubilized heavy metals was determined in the resulting solution. The extent of metal solubilization varied according to soil type, the chelating agent added and the specific metal. The amount of iron solubilized, as compared to the total iron (LVJ) was 11% (EDTA) and 19% (EDDS). EDDS solubilized more Cu than EDTA in both soils but more Ni in LVJ, while EDTA solubilized more Zn in both soils but more Cd in LVP. Both EDTA and EDDS may be useful for phytoextraction from soils, although the iron content is an important factor regarding the phytoextraction of heavy metals with chelating agents in Oxisols.

Biomining in the Post-Genomic Age: Advances and Perspectives

Systems Microbiology is a new way to approach research in microbiology. The idea is to treat the microorganism or community as a whole, integrating fundamental biological knowledge with OMICS research (genomics, proteomics, transcriptomics, metabolomics) and bioinformatics to obtain a global picture of how a microbial cell operates in the community. The oxidative reactions resulting in the extraction of dissolved metal values from ores is the outcome of a consortium of different microorganisms. Therefore, this bioleaching community is particularly amenable for the application of Systems Microbiology. As more genomic sequences of different biomining microorganisms become available, it will be possible to define the molecular adaptations of bacteria to their environment, the interactions between the members of the community and to predict favorable or negative changes to efficiently control metal solubilization. Some key phenomena to understand the process of biomining are biochemistry of iron and sulfur compound oxidation, bacteria-mineral interactions (chemotaxis, cell-cell communication, adhesion, biofilm formation) and several adaptive responses allowing the microorganisms to survive in a bioleaching environment. These variables should be considered in an integrative way from now on. Together with recently developed molecular methods to monitor the behavior and evolution of microbial participants during bioleaching operations, Systems Microbiology will offer a comprehensive view of the bioleaching community. The power of the OMICS approaches will be briefly reviewed. It is expected they will provide not only exciting new findings but also will allow predictions on how to keep the microbial consortium healthy and therefore efficient during the entire process of bioleaching.

Enhanced heavy metal bioleaching efficiencies from anaerobically digested sewage sludge with coinoculation of Acidithiobacillus ferrooxidans ANYL-1 and Blastoschizomyces capitatus Y5

Prolonged bioleaching period was required to remove heavy metals from anaerobically digested sewage sludge in the presence of low molecular weight organic acids. The purpose of the present study was therefore to enhance metal solubilization efficiencies through introducing organic acid-degrading microorganisms into this artificial bioleaching system. An acetic and propionic acid-degrading yeast Blastoschizomyces capitatus Y5 was successfully isolated from a local Yuen Long sewage sludge and it could achieve optimum growth in synthetic liquid media containing 2,000 mg l-1 acetic acid or 1,000 mg l-1 propionic acid. When it was inoculated simultaneously with Acidithiobacillus ferrooxidans ANYL-1 into anaerobically digested sewage sludge, which contained 648 mg l-1 acetic acid and 731 mg l-1 propionic acid, both acids were completely decomposed within 24 hours. As a result, ferrous iron oxidation was greatly improved, resulting in enhanced metal solubilization. Compared with the 8, 10 and 12 days required for maximum solubilization of Zn, Cu and Cr for the control sludge, the bioleaching period was significantly shortened to 4, 5 and 8 days respectively for sludge receiving co-inoculation.