Recent advances in biosynthesis of metal chalcogenides from wastewater: Scale-up technologies and industrial applications.

Microbial synthesis of metal chalcogenides from wastewater has emerged as a sustainable and environment friendly approach that simultaneously enables resource recovery and the production of high value nanomaterials. Chalcogenides are used in a wide range of industrial applications such as solar cells, biosensors, semiconductors and biomedical fields because of their exceptional catalytic, physical and optical properties. Microorganisms, including bacteria, fungi and archaea, have demonstrated remarkable potential to convert metal and chalcogen-rich wastewater into functional nanoparticles. Microbial synthesis of chalcogenides provides green alternative as compared to traditional chemical methods, which require toxic chemicals and expensive, harsh operating conditions. However, several challenges such as regulating particle size, composition and product yield, continue to hinder the scale-up of microbial synthesis from the laboratory to the industrial level. These challenges can be addressed by innovative bioreactor design, automation and advanced monitoring systems. Industrial applications of chalcogenides have grown rapidly with sulfur-based particles used in photovoltaic cells, selenium and tellurium-based materials in thermoelectric devices and imaging systems. This review summarizes recent developments in wastewater driven microbial synthesis of metal chalcogenide and highlights microbial mechanisms, scale up technologies and industrial applications. Particular focus is directed towards bioreactor configurations, immobilization techniques and factors that determine productivity and product quality. Finally, the review discusses current challenges and future research directions such as process optimization, life cycle assessment and discovery of novel microorganisms that are capable of producing broader range of metal chalcogenides with properties of specific industrial applications.