Ebook: Microbial Synthesis of Chalcogenide Nanoparticles: Combining Bioremediation and Biorecovery of Chalcogen in the Form of Chalcogenide Nanoparticles

Recent years have seen a growing interest in the application of chalcogenide nanoparticles (NPs) (e.g. Se, Te, CdSe) in various industrial sectors including energy, petroleum refining and also in the field of biology and medicine. Moreover, due to the high toxicity of chalcogen oxyanions, their release in the environment is of great concern. Thus, emphasize was given in this book on the development of a novel microbial synthesis process of chalcogenide NPs by combining biological treatment of Se/Te-containing wastewaters with biorecovery in the form of Se/Te chalcogenides NPs.

Anaerobic granular sludge capable of reducing selenite to selenide in the presence of Cd was enriched for the microbial synthesis of CdSe NPs. It was evident that when Cd is present along with selenite, it reacts with aqueous selenide (HSe-) after selenite bioreduction to form CdSe. The formation of an alloyed layer of CdSxSe1-x at the interface between the CdSe core and CdS shell in the sludge was also observed. Distinct fingerprints of extracellular polymeric substances (EPS) extracts by size exclusion chromatography indicated a compositional change in the EPS matrix of anaerobic granular sludge performing selenite reduction in the presence of cadmium and synthesizing CdSe NPs. Studies also shows that EPS on the surface of chalcogenide NPs plays a major role in lowering the toxicity of NPs and make biogenic Se(0) NPs 10 times less toxic than chemogenic Se(0) NPs.

An UASB reactor was used for the first time for continuous removal of tellurite from synthetic wastewater and the recovery of Te as biogenic Te(0). As the majority of the biogenic Te(0) nanocrystals was trapped predominantly in the EPS surrounding the biomass, make it easier to separate and recovery by centrifugation.