Preparation of core/shell-structured ZnFe2O4@ZnIn2S4 catalysts and its ultrafast microwave catalytic reduction performance for aqueous Cr(VI)

Irresponsible discharge of hexavalent chromium (Cr(VI)) containing industrial wastewater is a serious environmental issue, and a great risk to human health. In this work, a novel class of microwave (MW) responsive core/shell-structured ZnFe2O4@ZnIn2S4 (ZFO@ZIS) catalysts were prepared for aqueous Cr(VI) reduction. These catalysts exhibited “unexpectedly” high MW catalytic activity. The one with the ZFO:ZIS molar ratio = 1:3 led to 100 % Cr(VI) reduction within 15 min in a solution with the Cr(VI) concentration as high as 100 mg/L, which is superior to in the cases of using other photocatalysts previously reported. More significantly, the ZFO@ZIS catalysts exhibited an excellent Cr(VI) reduction ability even at a pH value as high as 6, close to that of industrial wastewater, demonstrating additionally their great feasibility. The excellent MW catalytic activity of the composite catalysts can be attributed to the MW induced “hot spots” effect. The MW responsive ZFO@ZIS core/shell-structured catalysts developed in this work can be a promising candidate for high efficiency catalytic reduction of Cr(VI) in wastewater.