Bionanomining of copper-based nanoparticles using pre-processed mine tailings as the precursor.

The bacterial synthesis of copper nanoparticles emerges as an eco-friendly alternative to conventional techniques since it comprises a single-step and bottom-up approach, which leads to stable metal nanoparticles. In this paper, we studied the biosynthesis of Cu-based nanoparticles by Rhodococcus erythropolis ATCC4277 using a pre-processed mining tailing as a precursor. The influence of pulp density and stirring rate on particle size was evaluated using a factor-at-time experimental design. The experiments were carried out in a stirred tank bioreactor for 24 h at 25 °C, wherein 5% (v/v) of bacterial inoculum was employed. The O2 flow rate was maintained at 1.0 L min-1 and the pH at 7.0. Copper nanoparticles (CuNPs), with an average hydrodynamic diameter of 21 ± 1 nm, were synthesized using 25 g.L-1 of mining tailing and a stirring rate of 250 rpm. Aiming to visualize some possible biomedical applications of the as-synthesized CuNPs, their antibacterial activity was evaluated against Escherichia coli and their cytotoxicity was evaluated against Murine Embryonic Fibroblast (MEF) cells. The 7-day extract of CuNPs at 0.1 mg mL-1 resulted in 75% of MEF cell viability. In the direct method, the suspension of CuNPs at 0.1 mg mL-1 resulted in 70% of MEF cell viability. Moreover, the CuNPs at 0.1 mg mL-1 inhibited 60% of E. coli growth. Furthermore, the NPs were evaluated regarding their photocatalytic activity by monitoring the oxidation of methylene blue (MB) dye. The CuNPs synthesized showed rapid oxidation of MB dye, with the degradation of approximately 65% of dye content in 4 h. These results show that the biosynthesis of CuNPs by R. erythropolis using pre-processed mine tailing can be a suitable method to obtain CuNPs from environmental and economical perspectives, resulting in NPs useful for biomedical and photocatalytic applications.

Bionanomining: biotechnological synthesis of metal nanoparticles from mining waste-opportunity for sustainable management of mining environmental liabilities.

Mining is an important activity for many countries, especially some in development, such as Chile, where it is a pillar of its economy. However, it generates large impacts that are undesirable for the population such as the generation of polluting solid and effluents with a high content of heavy metals and metalloids, which are traditionally accumulated in deposits. In recent years, bionanomining emerged as a cutting-edge scientific-technological development associated with the application of micro- and macro-organisms to generate nanotechnological products by using mining and industrial wastes and wastewaters. Biomass of many species of bacteria, plants, algae and fungi have the ability to reduce or oxidise cations, which can physically be deposited as nanometric materials such as the nanoparticles. Nanoparticles are materials that are increasingly used, and therefore, their demand increase, based on the high surface area characteristics to improve thermal, electrical and optical properties of materials, and metallic ones have also antimicrobial activity. This review addresses the biosynthesis of metal nanoparticles, focusing on mining waste recovery strategies, which is an emerging reality in mining countries. Transformation of potentially hazardous waste into a valuable product through techniques that are eco-friendly is an opportunity to develop sustainably depressed or polluted sites.