Amine-functionalised magnetic graphene-oxide nanosheets for the adsorption and reduction of Cr(VI) in water

We amine-functionalised a graphene-oxide nanosheet via the Schiff-base reaction, forming aminated graphene oxide (PNGO). To improve the adsorption efficiency and simplify the separation procedure, we applied amine-modified magnetic Fe3O4 nanoparticles (NFe3O4) to the PNGO surface. The resulting NFe3O4@PNGO exhibited exceptional adsorption capabilities for Cr(VI) anions at pH = 2, reaching an optimal adsorption capacity of 865.6 mg/g. Crucially, NFe3O4@PNGO can rapidly reduce the concentration of a Cr(VI) solution from an initial 5 mg/L to beneath the safe drinking water standard of 0.05 mg/L, established by the World Health Organisation (WHO), in under 20 s. The interaction mechanism between NFe3O4@PNGO and Cr(VI) was explored through controlled experiments and comprehensive characterisation. Cr(VI) adsorption on NFe3O4@PNGO conformed to the Langmuir isotherm model and the pseudo-second-order kinetic model. Furthermore, NFe3O4@PNGO exhibits excellent recyclability and demonstrates outstanding Cr(VI) removal performance in actual industrial wastewater, highlighting its potential for practical applications in efficient industrial wastewater treatment.