Synergistically constructed polyamine/nanosilica/graphene composites: preparation, features and removal of Hg2+ and dyes from contaminated water

Abstract

A simple method was developed to construct graphene–nanosilica composites. Polyethyleneimine (PEI), which is a synthetic polyamine functionally analogous to bio-polyamines in organisms, was used as a template/scaffold/catalyst to direct nanostructured silica formation, i.e., PEI hybridised silica (PEI@SiO₂). Due to the cationic nature and reducibility of PEI, the hybrid PEI@SiO₂ surface instantly adsorbs the negatively charged graphene oxide (GO) at room temperature, leading to PEI@SiO₂@GO composites. The GO was further reduced in situ into reduced grapheme oxide (rGO) to form PEI@SiO₂@rGO at 90 °C. The PEI@SiO₂@GO showed a high removal efficiency of 96% for Hg²⁺ from a 10 ppm solution; PEI@SiO₂@rGO could decolorise organic dyes (rhodamine B or methyl blue) from solution after 30 min. Unlike previously published methods for producing graphene–inorganic composites, this method is general to other polyamine–silica (or metal oxide) systems and has the synergistic efficiency to target GO without additional surface modification and reductants.