Photocatalytic degradation of humic acid using a novel visible-light active α-Fe2O3/NiS2 composite photocatalyst

Abstract

The effects of a-Fe2O3/NiS2 composite for the humic acid removal were systematically studied and compared with the synthesized a-Fe2O3 and NiS2. The obtained mesoporous composite has a stacked plate-like surface, active at a visible light region with a bandgap of 2.49 eV, and has a lower rate of recombination compared to the a-Fe2O3 but higher than the NiS2. The highest humic acid removal (93.7%) was achieved by the a-Fe2O3/NiS2 composite followed by the a-Fe2O3 (88.7%) and NiS2 (86.4%) at optimum conditions of 0.1 g L-1 catalyst loading, pH 5, and 30 mg L-1 initial humic acid concentration. The mineralization achieved 96.8% and the catalyst was stable up to the fourth cycle. These encouraging results were due to the better adsorption capacity of the composite, being active in visible light, and quenching of the photoluminescence that led to effective separation of subsequent reduction in the rate of recombination of the charged carriers.