An experimental design study of photocatalytic activity of the Z-scheme silver iodide/tungstate binary nano photocatalyst.

A binary AgI/ Ag 2 WO 4 photocatalyst was fabricated and characterized by SEM, XRD, UV-Vis DRS, and FT-IR. It was then used to photodegrade sodium ceftriaxone (CTX) in an aqueous solution. The band gap energies of 2.95, 2.78, and 2.62 eV were obtained by the Kubelka-Munk model for Ag 2 WO 4 , AgI, and AgI/Ag 2 WO 4 catalysts. The samples have pH PZC values of 6.9, 4.2, and 6.6, respectively. The synergistic photocatalytic activity of the coupled system depended on the AgI:Ag 2 WO 4 mole ratio and grinding time (optimums:mole ratio of 4:1 and time 30 min). The experimental design was used for optimizing the conditions and a quadratic model well-processed the data based on the model F value of 131.87 > F 0.05,14,13  = 2.55 and LOF F value of 0.78 < F 0.05,10,3  = 8.78. The optimized RSM run included the irradiation time of 85 min, 3.5 mg/L of CTX sample at pH 9, and a catalyst dose of 1.0 g/L. Under the optimized conditions, about 63% of CTX molecules were photodegraded. In the study of the scavenging agents, the direct Z-scheme mechanism accumulated electrons in the CB-AgI and the holes in the VB-Ag 2 WO 4 level, as stronger reducing and oxidizing centers than the accumulated electrons and holes of the type (II) heterojunction mechanism. Compared to a CTX oxidation potential of about 0.06 V, the direct Z-scheme mechanism is more favorable to reduce or oxidize it.