Bioextraction Of Metals Research Articles

Fighting Climate Change with Synthetic Biology

Fighting Climate Change with Synthetic Biology

Study effects of conventional flotation reagents on bioleaching of zinc sulfide

Although flotation and bio-extraction of metals from its products are extensively investigated, there are few studied which evaluated the effects of reagents on bioleaching process. Both structure and concentration of flotation reagents are effective factors on microorganism activities. In this study, Kendall’s tau (τ) as a statistical method was used to statistically access the effect of typical sulfide flotation surfactants (collectors: potassium amyl-xanthate, potassium isobutyl-xanthate, sodium ethyl-xanthate, potassium isopropyl-xanthate, and Dithiophosphate), and frothers: pine oil and methyl isobutyl carbinol) on the bioleaching of Zn sulfides in a mixed culture (Leptospirillum ferrooxidans, Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans). To consider both structure and concentration of these reagents, their molarities were used for the statistical evaluations. The Kendall assessments indicated that by increasing in the molarity of reagents, the pH value (the most effective factors of bioleaching) was increased (τ: 0.56) while the ORP value (τ: −0.54), Fe3+Fe2+ ratio (τ: −0.51) and numbers of oxidizing bacteria (τ: −0.38) in the solution were decreased. Therefore, as a result of these multi-interactions, by increasing the molarity of reagents, Zn recovery was decreased (τ: −0.45). These results potentially can be used for selection of flotation reagents when bioleaching would be the metallurgical metal extraction method.

Bio-Extraction of Metals as Secondary Resources from E-Waste

Electronic waste is widespread across the globe comprises wide range of elements, growing exponential recent years and even categorized as hazardous if the elements like lead, mercury, arsenic, cadmium, selenium, and hexavalent chromium etc. are present beyond the permissible quantities. They may also be important secondary resources if processed in eco-friendly manner for secured supply of contained metals. Bio-extraction of metals from E-waste with microbes such as bacteria and fungi is being increasingly explored to meet the twin objectives of resource recycling and pollution mitigation. This review focuses on the biological extraction techniques including an assessment has been made to quantify the different E-waste and their metal compositions, microbes used, metal leaching efficiency etc. and proposes that the biological recovery allows the cycling of metals by a process close to natural biogeochemical cycles reducing the demand for resources such as ores, energy, or landfill space.

Control and optimization in the bio-extraction of metals from primary ores before the new mineral processing techniques

The bioleaching is a biochemical process that is based on the capacity that certain microorganisms have to transform insoluble elements present in certain sulphide minerals in soluble elements and easy to be extracted from the lecheate in conventional downstream processes. The leaching microorganisms are characterized by a unique capacity to grow in environments virtually uninhabitable for the majority of microorganisms, as they live in places with extremely low pH and in temperature that can vary between 25 to 80°C. In a process of leaching sulphide minerals it is used to obtain a flotation concentrate so as to recover a large part of the metal of interest bearing sulphide minerals. However, the bioleaching of metal sulphide bearing ores is not an easy task taking into consideration that the metal sulphide minerals are not that available to be oxidized being frequently encapsulated in the gangue minerals, which imposes a barrier to the sulphide minerals oxidizing agent (i.e., Fe3+ ion) and microorganisms to act. With the advent of the HPGR (High pressure grinding rolls) and the electrodynamic fragmentation (SELFRAG), micro-fractures are created, and, in addition, with the possibility of monitoring and controlling the bioleaching parameters (i.e., pH, Eh, ore bed temperature, ionic strength etc.) the bio-extraction of metals, out of sulphide bearing ores, will definitely enhance such process.

BIOLOGICAL EXTRACTION OF METALS: THE RATE-CONTROLLING STEP

Abstract Although an enormous amount of work has been done in the area of biohydrometalJurgy, the influence of the inert solid matrix on metal extraction, and consequently the rate-controlling mechanism have not been fully understood. Actually, most studies have mainly focused on the bioextraction of metals from high-grade mineral concentrates. Such an approach is important in elucidating the diffusion and reaction phenomena that are taking place on the surface of the mineral. In reality, however, the mineral is embedded within an inert solid matrix which will have significant effects on diffusion and chemical reaction rate processes. In this work, a detailed experimental kinetic study was conducted to incorporate this factor in an attempt to quantify the rate-controlling mechanism involved. The biological dissolution of pyrite in the presence of acidophilic Thiobacillus ferrooxidans was investigated in a batch experiments on three distinct mine waste rocks. The experiments were conducted on two particle ...