Shan Zheng, Wenjun Jiang, Yong Cai
Apr 1, 2014
Citations
1
Influential Citations
116
Citations
Quality indicators
Journal
Catalysis Today
Abstract
Aromatic organoarsenic compounds, 4-hydroxyl-3-nitrophenylarsenic acid (Roxarsone, ROX) and 4-aminophenylarsonic acid (p-arsanilic acid, p-ASA) are heavily used in agricultural applications and pose a risk to the environment. We have shown that ROX and p-ASA are readily degraded by UV TiO2 photocatalysis under a variety of conditions. The adsorptions of the target compounds onto the surface of TiO2 in the dark are accurately modeled by employing Langmuir adsorption isotherms. The kinetic models for the degradation indicate that degradation occurs at or very near the surface (liquid–solid interface). Under acidic and neutral conditions strong adsorption is observed and the degradation follows pseudo-zero order kinetics, while under alkaline conditions the observed degradation follows pseudo-first order kinetics. Our results employing different reaction conditions indicate that hydroxyl radical plays an important role in the mineralization of ROX and p-ASA to arsenate. While p-ASA does not undergo degradation in the absence of molecular oxygen, the observed degradation of ROX under such conditions demonstrates reductive processes also play an important role in the degradation of ROX. The arsenic mass balance was monitored and complete conversion to arsenate was achieved upon continued treatment. Our results demonstrate that TiO2 photocatalysis is an attractive process for the remediation of aromatic organoarsenic compounds.