Sorption‐oxidation mechanism for the removal of arsenic (III) using Cu‐doped ZnO in an alkaline medium

Abstract

Abstract1‐D oxides Zn1‐xCuxO and spherical composites Zn1‐xCuxO/CuO were obtained by thermolysis of formate‐glycolate complexes Zn1‐xCux (HCOO)(OCH2CH2O)1/2 (0 ≤ x ≤ 0.15). The structural and property characteristics showed that Cu was introduced into the Zn site of the ZnO lattice to form the Zn0.95Cu0.05O solid solution. The concentration of copper in the precursors regulates the topological and structural features of the formation of Zn1‐xCuxO oxides, which determine their sorption and photocatalytic properties. The materials were tested in As3+ photooxidation reaction under UV and visible radiation. It has been established that Cu+ is an effective dopant in the composition of 1‐D oxide Zn1‐xCuxO (0 ≤ x < 0.1). The presence of Cu2+ in the shell of Zn1‐xCuxO/CuO composite reduces the photoactivity of the material. The maximum efficiency of arsenic extraction (up to 80% for Zn0.95Cu0.05O) was achieved from dilute arsenic‐containing solutions (3.8 mg/L As) and an adsorbent concentration of 0.8 g/L for 24 h. In saturated solutions (380 mg/L As) this value is reduced by a factor of 100. According to XPS data, the primary process is As3+ sorption on the catalyst surface followed by its oxidation to As5+. Using the EPR method it was found that singly charged oxygen vacancies associated with Cu in Zn1‐xCuxO are directly involved in the photostimulated oxidation of As3+.Practitioner Points Two types of Zn1−xCuxO photocatalysts were obtained by thermolysis of the Zn1−xСux(HCOO)(OCH2CH2O)1/2 complex (0 ≤ x ≤ 0.15) in air. Sorption of arsenic from dilute solutions reaches 80% on 1‐D oxide Zn0.95Cu0.05O. Sorption of As3+ on the catalyst surface is at primary process followed by its oxidation to As5+. Removal of As3+ from alkaline solutions occurs due to successful combination of sorption and photocatalytic properties of the 1‐D oxides Zn1−xCuxO.