Lan Qing, Li Fangbai, Liu Chengshuai, Li Xiang-Zhong
Guangdong Key Laboratory of Agricultural Environment Pollution Integrated Control, Guangdong Institute of Eco-Environmental and Soil Sciences, Guangzhou 510650, PR China.
Environ Sci Technol. 2008 Nov 1;42(21):7918-23. doi: 10.1021/es801220n.
The degradation of pentachlorophenol (PCP) in a heterogeneous system with maghemite (gamma-Fe2O3) and oxalate under UV illumination was investigated in this study. The results of adsorption experiments demonstrated competitive adsorption between PCP and oxalic acid on the surface of gamma-Fe2O3. The results of photodegradation experiments showed that the rate of PCP degradation strongly relied on the oxalic acid concentration and that an optimal tested initial concentration of oxalic acid (Cox(0)) of 0.8 mM was obtained under our experimental conditions. It was observed that a sufficient amount of oxalic acid can be adsorbed on the gamma-Fe2O3 to form various Fe(III)-oxalate complexes at Cox(o) = 0.8 mM. During the photoreaction, Fe(C2O4)2- and Fe(C2O4)3(3-) were found to be the dominant Fe(III)-oxalate complexes at different Cox(0), while Fe(C2O4)2(2-) was the dominant Fe(II)-oxalate complex at Cox(0) > or = 0.8 mM. The mechanism of H2O2 formation and consumption in the UV-irradiated gamma-Fe2O3/oxalate system was proposed and evaluated. Furthermore, six intermediates of PCP degradation were identified by GC/MS, HPLC, and IC analyses, respectively, and a possible pathway of PCP degradation in such a system was proposed.
本研究考察了在紫外光照射下，磁赤铁矿（γ-Fe₂O₃）和草酸盐组成的非均相体系中五氯苯酚（PCP）的降解情况。吸附实验结果表明，PCP和草酸在γ-Fe₂O₃表面存在竞争吸附。光降解实验结果显示，PCP的降解速率强烈依赖于草酸浓度，在我们的实验条件下，获得了0.8 mM的最佳测试初始草酸浓度（Cox(0)）。观察到在Cox(o) = 0.8 mM时，足够量的草酸可吸附在γ-Fe₂O₃上形成各种铁（III）-草酸盐络合物。在光反应过程中，发现Fe(C₂O₄)₂⁻和Fe(C₂O₄)₃³⁻在不同的Cox(0)下是主要的铁（III）-草酸盐络合物，而Fe(C₂O₄)₂²⁻在Cox(0)≥0.8 mM时是主要的铁（II）-草酸盐络合物。提出并评估了紫外照射的γ-Fe₂O₃/草酸盐体系中H₂O₂形成和消耗的机制。此外，分别通过气相色谱/质谱（GC/MS）、高效液相色谱（HPLC）和离子色谱（IC）分析鉴定了PCP降解的六种中间体，并提出了该体系中PCP降解的可能途径。
