Application of fungal copper carbonate nanoparticles as environmental catalysts: organic dye degradation and chromate removal

Biomineralization is a ubiquitous process in organisms to produce biominerals, and a wide range of metallic nanoscale minerals can be produced as a consequence of the interactions of microorganisms with metals and minerals. Copper-bearing nanoparticles produced by biomineralization mechanisms have a variety of applications due to their remarkable catalytic efficiency, antibacterial properties, and low production cost. In this study, we demonstrate the biotechnological potential of copper carbonate nanoparticles (CuNPs) synthesised using a carbonate-enriched biomass-free ureolytic fungal spent culture supernatant. The efficiency of the CuNPs in pollutant remediation was investigated using a dye (methyl red) and a toxic metal oxyanion, chromate Cr(VI). The biogenic CuNPs exhibited excellent catalytic properties in a Fenton-like reaction to degrade methyl red, and efficiently removed Cr(VI) from solution due to both adsorption and reduction of Cr(VI). X-ray photoelectron spectroscopy (XPS) identified the oxidation of reducing Cu species of the CuNPs during the reaction with Cr(VI). This work shows that urease-positive fungi can play an important role not only in the biorecovery of metals through the production of insoluble nanoscale carbonates, but also provides novel and simple strategies for the preparation of sustainable nanomineral products with catalytic properties applicable to the bioremediation of organic and metallic pollutants, solely and in mixtures.