1 - Graphene and reduced graphene oxide in bioreactors

Abstract

The toxicity of graphene and reduced graphene oxide in activated sludge is studied in this paper. The bioreactors fed with nanomaterials showed a reduction in performance in terms of chemical oxygen demand, ammonia, and phosphate elimination. Despite the increasing accumulation of nanomaterials in the sludge, these reactors reached a constant state of nutrient removal after about 8days, which corresponded to the recovery of specific groups of ammonia-oxidizing bacteria and phosphate-accumulating bacteria. These findings suggested that first exposure to nanoparticles can have a brief effect on biological therapy, but that certain bacteria that are less susceptible to these nanomaterials may be able to thrive in the presence of these nanomaterials. Deep sequencing of the 16S rRNA gene revealed that graphene and reduced graphene oxide had varied effects on the microbial populations in activated sludge. Graphene oxide had the most impact on nutrient removal, gene abundance, and alterations in microbial community structures of the two nanomaterials studied. These structures are especially beneficial in a variety of applications, from boosting reaction rates to being employed in nanodevices. Nanoparticles can be used in practically every aspect of modern chemical engineering and medicine, from sensing to chemical therapies to diagnosis.