Polyethyleneimine/activated carbon paper-based material for low-concentration hexavalent chromium removal

Abstract In this study, softwood pulp, activated carbon powder, and polyester fiber were prepared into activated carbon paper-based materials (ACPBM) by papermaking. Then the polyethyleneimine (PEI) is loaded on the activated carbon paper-based material by dipping to prepare a high-performance, green PEI/activated carbon composite paper-based adsorbent material (PPCA) to remove low concentrations of Cr(VI) in water. The surface characteristics of the ACPBM and PPCA were analyzed by SEM, EDX, BET, and FT-IR, which showed that PEI had been successfully loaded on the surface of ACPBM. It was found that when the impregnated PEI concentration is 1%, the adsorbent dosage is 3 g·L-1, the contact time is 180 min, the concentration of initial Cr(VI) is 5 mg·L-1 , and the pH is 2, the maximum adsorption capacity for Cr(VI) can reach 1.58 mg·g-1. The process of PPCA adsorption of Cr(VI) conformed to the Freundlich isotherm model and the quasi-second-order kinetic model, indicating that the adsorption is multi-molecular layer adsorption with the adsorption mechanism of ion exchange and electrostatic attraction. In adsorption thermodynamics, ΔH0>0, ΔG0<0, and ΔS0＞0, indicating that the process of adsorbing Cr(VI) by the 1%PPCA is an endothermic entropy increase reaction that can proceed spontaneously. This study shows that a green, recyclable, and degradable high-performance PPCA adsorbent has been prepared through traditional papermaking processes and physical impregnation methods, which has a significant removal effect on low-concentration hexavalent chromium ions and can be industrialized.