Research progress in biohydrometallurgy of rare metals and heavy nonferrous metals with an emphasis on China

In the past decade, progress in the field of biohydrometallurgy had been significant. A total of 17 novel biomining microorganisms were discovered, and eight copper heap bioleaching plants and 11 gold biooxidation plants were established or expanded. In this review, it was summarized the physiological properties of the newly isolated biomining microorganisms and three novel microbial ecological methods for studying microbial community dynamics and structure. In addition, biohy- drometallurgy research on rare metals such as uranium, molybdenum, tellurium, germanium, indium, and sec- ondary rare metal resources, as well as heavy nonferrous metals such as copper, nickel, cobalt, and gold has been reviewed, with an emphasis on China. In future, further studies on bioleaching of chalcopyrite, rare metals, secondary resources from waste, and environmental pollution caused by resource utilization are necessary.

Research and development trends of hydrometallurgy:An overview based on Hydrometallurgy literature from 1975 to 2019

Modern hydrometallurgy has been developing for more than 100 years and the related articles keep piling up.Based on a bibliometric analysis of the articles in Hydrometallurgy,the most authoritative journal in the field of hydrometallurgy,we try to catch the research and development trends from a global perspective.Firstly,keywords burstness shows that rare earth,recycling,lithium,ionic liquid,and thorium are the hotspots in recent years,and the economic and technological reasons behind them were discussed in depth.Secondly,the proportion of biohydrometallurgy grows fast from 5%to 13%and the related articles are almost all about bioleaching.There are some new directions such as direct preparation of materials in hydrometallurgical processes and ion-imprinted techniques.Thirdly,the advanced instrument analysis methods such as XAFS(X-ray absorption fine structure),gene sequencing,and micro-CT promote the deep understanding of hydrometallurgy mechanism.Finally,the cooperation network and contribution of the main institutes were mapped.

Bioleaching of low-grade copper sulfide ores by Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans

The grown conditions of Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans were investigated,and then experiments were conducted to research the bioleaching behaviors of crude ore of copper sulfide and hand-picked concentrates of chalcopyrite by Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans.The experimental results show that the bacteria grow best when the temperature is(30±1) °C and the pH value is 2.0.The bacteria concentration is 2.24×107 mL-1 in this condition.It is found that the copper extraction yield is affected by the inoculum size and the pulp density and the extraction yield increases as the inoculum size grows.The bioleaching rates reach their highest point in sulfide copper and chalcopyrite with a pulp density of 5% and 10%,respectively.Column flotation experiments of low-grade copper sulfide ores show that the bioleaching recovery reaches nearly 45% after 75 days.

Influence of copper solvent extractant on microbial community structure of acidophilic microorganisms

The influence of different concentrations of copper solvent extractant ZJ 988 on the growth and activity of acidophilic microorganisms was studied and the microbial community structures were compared by 16S rRNA gene clone library analysis.The total bacteria numbers are reduced when 0.5%(volume fraction) extractant is added.The proportions of Acidithiobacillus ferrooxidans and Acidiphilium organovorum are increased,whereas the proportion of Leptospirillum ferriphilum is reduced.When the concentration of extractant is elevated to 1%,growth of all bacteria is inhibited.Clone library results reveal that the dominant bacteria in the culture solution with/without the extractant are At.ferrooxidans,A.organovorum and L.ferriphilum.The sensitivity order of the three bacteria to the extractant from the most to the least is found to be L.ferriphilum>At.ferrooxidans>A.organovorum.

MICROBE-METAL-INTERACTIONS FOR THE BIOTECHNOLOGICAL TREATMENT OF METAL-CONTAINING SOLID WASTE

In nature, microbes are involved in weathering of rocks, in mobilization of metals from minerals, and in metal precipitation and deposition. These microbiological principles and processes can be adapted to treat particulate solid wastes. Especially the microbiological solubilization of metals from solid minerals （termed bioleaching） to obtain metal values is a well-known technique in the mining industry. We focus here on non-mining minerai wastes to demonstrate the applicability of mining-based technologies for the treatment of metal-containing solid wastes. In the case study presented, microbial metal mobilization from particulate fly ash （originating from municipal solid waste incineration） by Acidithiobacilli resulted in cadmium, copper, and zinc mobilization of 〉80%, whereas lead, chromium, and nickel were mobilized by 2, 11 and 32%, respectively. In addition, the potential of HCN-forming bacteria （Chromobacterium violaceum, Pseudornonas fluorescens） was investigated to mobilize metals when grown in the presence of solid materials （e.g.,copper-containing ores, electronic scrap, spent automobile catalytic converters）. C. violaceum was found capable of mobilizina nickel as tetracyanonickelate from fine-grained nickel powder. Gold was microbially solubJlized as dicyanoaurate from electronic waste. Additionally, cyanide-complexed copper was detected during biological treatment of shredded printed circuit-board scraps. Water-soluble copper and platinum cyanide were also detected during the treatment of spent automobile catalytic converters.

Bioleaching of spent Ni-Cd batteries and phylogenetic analysis of an acidophilic strain in acidified sludge

Biohydrometallurgy is a novel method to recycle discarded batteries,in which sewage sludge is used as microorganisms and culture due to the presence of indigenous Thiobacilli.A two-step continuous flow leaching system consisting of an acidifying reactor and a leaching reactor was introduced to achieve the bioleaching of spent nickel-cadmium(Ni-Cd)batteries.The acid supernatant produced in the acidifying reactor by the microorganisms with ferrous ions as the substrate was conducted into the leaching reactor to dissolve electrode materials.The efficiency of a batch treatment of batteries was examined.The results showed that the complete dissolution of two AA-sized Ni-Cd batteries with 0.6 L/d acid supernatant took about 30,20,and 35 days for Ni,Cd,and Co,respectively.But the dissolution ability of the three metals was different.Cd and Co can be leached mostly for pH below 4.0 while the complete dissolution of Ni can be achieved for pH below 2.5.Meanwhile,a strain(named Thiooxidans.WL)accounting for the reduction of pH in the acidified sludge was isolated and sequenced.It was identified to be 100%similar to Acidithiobacillus ferrooxidans strain Tf-49 based on 16S rDNA sequence analysis.The relevant phylogenetic tree constructed indicates that the strain should be classified into genus Acidithiobacillus ferrooxidans.

Silver-catalyzed bioleaching for raw low-grade copper sulphide ores

This research was conducted to investigate the biooxidation and copper dissolution from raw low-grade refractory copper sulphide ores located in the Xinjiang Autonomous Region of China using adapted Thiobacillus ferrooxidans bacteria.In order to accelerate the bioleach-ing rate,the adapted mixed bacteria and silver ion catalyst were tested in the leach columns at laboratory scale.The overall acid consumption was 4.3kg sulphuric acid per kg of dissolved copper and was linearly related to the percent copper dissolution.The calculated copper dissolution rates obey the Shrinking Core Model.The relative activation energy of the whole biooxidative leaching stages was calculated to be 48.58kJ/mol.