Novel fabrication of the recyclable Bi7O9I3/chitosan and BiOI/chitosan heterostructure with improved photocatalytic activity for degradation of dimethyl phthalate under visible light

Among the bismuth oxyhalides, bismuth oxide has the shortest band gap and high absorption power in the visible light region. Dimethyl phthalate (DMP) has been identified as endocrine-disrupting plasticizer and emerging pollutant, which was selected as the target pollutant to evaluate the efficacy of the studied catalytic process. In this work, Bi7O9I3/chitosan and BiOI/chitosan were efficaciously synthesized by the hydrothermal process method. Characterizing prepared photocatalysts was done by employing transmission electron microscopy, X-ray diffraction, scanning electron microscopy energy-dispersive spectroscopy, and diffuse reflectance spectroscopy. For this study, the test design was performed using the Box-Behnken Design (BBD) method in which the variables of pH, Bi7O9I3/chitosan dose, and dimethyl phthalate concentration were examined for the catalytic removal of dimethyl phthalate in the presence of visible light. Our detected results disclosed that the order of efficiency in DMP removal was as follows: Bi7O9I3/chitosan > BiOI/chitosan >Bi7O9I3 > BiOI. Also, the maximum pseudo-first-order kinetic coefficient for Bi7O9I3/chitosan was 0.021 (min)(-1). When the synthesized catalysts were exposed to visible light irradiation, the predominant active species were O-2(-) and h(+) for degradation of DMP. The study on the reuse of Bi7O9I3/chitosan showed that this catalyst could be reused 5 times without significant reduction in efficiency, which indicates the cost-effectiveness and environmental friendliness of using this catalyst.