Amphiphilic PA-induced three-dimensional graphene macrostructure with enhanced removal of heavy metal ions

Phytic acid (PA) induced graphene macrostructures were synthesized and investigated for the sorption characteristics and mechanisms of mercury. The as-synthesized graphene foam possessed large specific surface area and amphiphilicity. FTIR and XPS analysis revealed that the as-prepared graphene macrostructure retained oxygen-containing functional groups after hydrothermal reduction and also captured new phosphorus-containing groups because of the introduction of PA. Different experimental parameters, such as pH, PA fractions and contact time were applied to probe into the Hg(II) adsorption performance of as-synthesized macrostructure. Pseudo-second-order kinetic model and Langmuir isotherm model fitted well to the obtained sorption kinetic and isothermal data. The maximum adsorption capacity at pH = 7.2 for mercury was 361.01 mg/g. The dominant mechanisms for mercury removal were mainly ion exchange and surface complexation. Real application in river water and seawater exhibited very promising results, indicating its broad prospect in water purification.