Modification of ZnFe2O4 by conjugated polyvinyl chloride derivative for more efficient photocatalytic reduction of Cr(VI)

Abstract

This work reports the improvement of the photocatalytic activity of ZnFe2O4 by using the conjugated polyvinyl chloride derivative (CPVC) as a modifier. A facile multi-step method was adopted to synthesize ZnFe2O4 nanoparticles coupled with CPVC (ZnFe2O4/CPVC nanocomposites). Based on catalytic reduction of aqueous Cr(VI) under visible-light (λ > 420 nm) irradiation, the photocatalytic activities of the ZnFe2O4/CPVC nanocomposite products were evaluated, and compared with those of ZnFe2O4 nanoparticles and some previously reported visible-light photocatalysts. ZnFe2O4/CPVC-2% (which was synthesized with the mass ratio of PVC to ZnFe2O4 being 2%, and the heating temperature and time for transforming PVC into CPVC being 150 °C and 2 h, respectively) was found to have the highest photocatalytic activity, which is 2.9 times as ZnFe2O4. Moreover, larger dosage of photocatalyst, lower concentration and pH of Cr(VI) solution favored faster removal of Cr(VI) by ZnFe2O4/CPVC-2%. The boosted photocatalytic activity of ZnFe2O4/CPVC-2% was attributed to its larger specific surface area, and more efficient separation and transfer of photoinduced electrons and holes. Besides, ZnFe2O4/CPVC-2% has also good photocatalytic reusability (about 95% Cr(VI) can still be reduced in the fifth cycle), and can be largely recovered from the aqueous suspension by using a magnet. These features of ZnFe2O4/CPVC-2% render it a potential visible-light photocatalyst for application in Cr(VI) wastewater treatment.