Synthesis, characterization and photocatalytic applications of ZnS/g-C3N4 nano-heterostructures

In this study, g-C3N4, ZnS nanoparticles, and ZnS/g-C3N4 nanocomposite were fabricated and these synthesized samples were used as photocatalysts for photodegradation of rhodamine B, diclofenac, and trimethoprim contaminants in aqueous solution under visible light irradiation. The structural, morphological, and electrochemical features of g-C3N4, ZnS nanoparticles, and ZnS/g-C3N4 nanocomposite were characterized by using XRD, FTIR, SEM-EDX, TEM, UV-DRS, PL, EIS and BET techniques. Compared to pure ZnS and g-C3N4, the ZnS/g-C3N4 nanocomposite exhibited extremely high photocatalytic activity for the photodegradation of rhodamine B, diclofenac and trimethoprim contaminants due to the decrease of photogenerated hole-electron recombination rate via increases of the photogenerated electron transmission at its interface. Furthermore, the effects of pH, catalyst dosage, and different water sources on the photocatalytic performance of nanocomposite were investigated in detail. The radical scavenger studies indicated that superoxide radicals played a main role in the photodegradation of all contaminates whereas the holes acted as secondary species. According to the obtained data from experiments, a plausible mechanism was proposed for the photodegradation of contaminants. In addition, the kinetic studies showed that the pseudo-first-order kinetic model was determined to fit well the obtained experimental results, and reaction rate constants were calculated using this model. The ZnS/g-C3N4 nanocomposite demonstrated excellent reusability and stability for photodegradation of rhodamine B, diclofenac, and trimethoprim contaminants after four times cycle.