Nanotubes/nanorods-like structures of La-doped ZnO for degradation of Methylene Blue and Ciprofloxacin

Abstract

In this study, nanotubes/nanorods-like structures of Zn0.97La0.03O compound were synthesized at different pH values (pH = 8, 9, 10, 11, and 12), and the photocatalytic response for Methylene Blue (MB) dye and Ciprofloxacin (CIP) drug were investigated. It was verified that the pH variation directly impacts the ZnO crystal structure, morphology, optical and photocatalytic properties. The basic and alkaline pH values cause a decrease in the crystallite size and these differences may have contributed to the band gap energy values variations. Oxygen vacancy defects (VO, VO+, and VO++) were abundant in the La-doped ZnO samples, which also demonstrated to be formed from mesopores, as seen in N2 adsorption/desorption results. The photocatalytic response of the materials was verified in MB and CIP solutions under UV irradiation conditions. The sample synthesized at pH 9 (ZL9) demonstrated greater capacity to remove MB (91.45 %) and CIP (87.6 %) in typical pseudo-first-order kinetics. Using different inhibitors, it was observed that the •OH radicals were the species involved in the photocatalysis of pollutants for the ZL9 sample. In addition, this material demonstrated a satisfactory ability to remove pollutants even after three consecutive uses. This study demonstrates that pH is an important parameter to consider in the synthesis process of ZnO nanostructures, directly influencing the structural, optical, and morphological properties and the degradation of highly dangerous dyes and drugs.