Preparation and characterization of a novel and recyclable InVO4/ZnFe2O4 composite for methylene blue removal by adsorption and visible-light photocatalytic degradation

Abstract

A novel magnetic InVO4/ZnFe2O4 composite with the synergistic effect of adsorption and photocatalytic activity has been prepared using a hydrothermal method and characterized by a series of analytical techniques. The addition of ZnFe2O4 not only improves the adsorption capability in the case of more active sites and positive zeta potential but also broadens the absorption range and promotes visible light harvesting. The optimum activity was found at a mole ratio of ZnFe2O4:InVO4 = 3:1 (IZ-4). The removal rate for methylene blue (MB) under the synergistic effect of adsorption and photocatalytic reaches 88.74%, which is 6.87 times and 14.11 times that of the pure InVO4 and ZnFe2O4, respectively. Furthermore, the adsorption kinetics and isotherm investigations indicate that the adsorption process followed the pseudo-second-order kinetic and Langmuir isotherm models. The maximum adsorption capacity of MB as 97.12 mg/g is achieved on the IZ-4 composite, which is better than the adsorbents reported previously. A type-II heterojunction between InVO4 and ZnFe2O4 based on the results of Mott-Schottky (M-S) plots is proposed to facilitate the charge transfer and improve the photocatalytic activity. In terms of the experimental results of N2 adsorption/desorption, zeta potential and photoluminescence emission spectra, a possible mechanism of MB removal is discussed. The InVO4/ZnFe2O4 composite with a synergistic effect of adsorption and photocatalytic degradation increases the active adsorption sites and promotes the separation of photogenerated electron and holes, thereby improving the MB removal performance.