Graphene oxide and chitosan co-modified ZnS as photocatalyst and adsorbent: preparation, characterisation, removal of acid orange 7, kinetic studies, and adsorption isotherms

This research presents the preparation of nanosized ZnS/chitosan/graphene oxide (ZnO/Ch/GO) via crosslinking ZnS with chitosan and graphene oxide. X-ray diffraction (XRD) technique proved the formation of Blended ZnS crystal phase with (1 1 1), (2 2 0), and (3 1 1) planes at 28.6, 47.7, and 56.5o (2 theta), respectively. The photodegradation and adsorption activities of the composite was studied in the removal of Acid Orange 7 (AO7), and then the effect of parameters such as pH, composite amounts, initial dye concentration, and contact time was investigated. The final results showed that by addition of ZnO/Ch/GO (0.02 g) to AO7 (10 ppm) at pH = 3, and 105 min contact time, the highest photodegradation (71.3%) and adsorption (95.81%) can be achieved. Ultimately, the kinetic studies indicated that photodegradation and adsorption of AO7 follow pseudo first order and second order models, respectively. In addition, the adsorption data matched perfectly with the Freundlich isotherm.