Enhanced photocatalytic activity of ZrO2-CdZrO3-S nanocomposites for degradation of Crystal Violet dye under sunlight

Abstract

In this research binary and ternary nanocomposites of ZrO2-CdZrO3 and ZrO2-CdZrO3-Sxy with various sulfur contents (xy: 20%, 10%, and 5%) and synthesized through a two-stage hydrothermal method followed by solid-state approach. Since sulfur has structural and electronic properties similar to oxygen, it is a suitable replacement of oxygen in the structure. Moreover, due to the chemical interaction of sulfur on the surface of ZrO2-CdZrO3 with Zr and O atoms, it infers oxygen vacancies and lowers the band-gap energy. It also the increased specific surface area and creation of hierarchical pores led to have improved photocatalytic activities. The XRD analysis confirmed the formation of nanocomposites. FE-SEM, TEM, EDX and Map techniques were employed to identify the morphology and chemical composition of synthesized materials. FT-IR result exhibited the peak position and vibration modes related to metal oxides and metal sulfides in ZrO2-CdZrO3-Sxy nanocomposites. The specific surface area was determined by BET. The optical properties were investigated by DRS analysis and the band-gap energy (Ebg) was determined via Tauc plots. Based on the results, upon sulfur incorporation the edge absorption band of nanocomposites was shifted towards the visible area and Ebg showed a reduction from 4.99 eV for ZrO2-CdZrO3 to 2.00 eV for ZrO2-CdZrO3-S20. Photocatalytic performance and kinetics studies of the synthesized nanocomposites were evaluated in the degradation of Crystal Violet (CV) toxic dye under natural sunlight. The results revealed that the highest efficiency was observed for ZrO2-CdZrO3-S20 compared with ZrO2-CdZrO3 (95% vs. 19%) in the first 30 min of irradiation. Photodegradation rate of CV by ZrO2-CdZrO3-S20 nanocomposites followed the pseudo-second-order kinetic with R2 = 0.9119. The CV degradation rate by ZrO2-CdZrO3-S20 nanocomposites with a rate constant of K = 830.10−4 min−1 was much faster than ZrO2-CdZrO3 with K = 20.10−4 min−1. The effect of different scavengers such as EDTA, IPA, and H2O2 on CV degradation was examined and active species of superoxide and hydroxide involved in degradation proses were identified. Moreover, ZrO2-CdZrO3-S20 maintained 96.5% of its efficiency after 5 runs of CV degradation. The mineralization efficiency of the CV solution by TOC was obtained 78.36%.