针铁矿纤铁矿催化降解苯酚动力学速率及其反应产物研究

Catalytic decomposition products and kinetic rates of phenol by hydrogen peroxide with goethite and lepidocrocite

研究了针铁矿和纤铁矿在过氧化氢参与下对苯酚的催化降解的动力学速率与溶液pH关系,并用紫外吸收谱测定其反应产物的谱学特征,发现纤铁矿反应体系降解苯酚的速率大于针铁矿反应体系,其中又以pH=3.8的纤铁矿体系反应速率常数最大。当溶液pH=3～4时,苯酚可被完全降解,并有40%～60%有机碳(TOC)被矿化。当溶液pH=4～5时,苯酚可被转化为多酚类化合物,但基本上不被矿化。当溶液pH>5时,苯酚没有发生明显的转化和矿化。

Catalytic oxidation of phenol by H2O2 with goethite and lepidocrocite was investigated in an aqueous system at pH=3-6 under normal room temperature. The results of ultraviolet spectra and TOC analysis of products suggest that when solution pH〈4 the phenol was completely decomposed to carboxylic acids and about 50%-60% of TOC was mineralized. However as solution pH was in range of 4-5 the phenol was catalyzed to polyphenol such as catechol and hydroquinone, but was basically not mineralized for the reaction system with either goethite or lepidocrocite. When pH〉5 the phenol in solution was neither transferred to polyphenol nor be mineralized. Kinetic rate calculation shown that the rate constant of phenol decomposition in presence of lepidocrocite is usually larger than that of goethite under same condition, and largest rate was found at about pH=3.8 in presence of lepidocrocite. Actually the rate constants were depended on both of homogeneous and heterogeneous catalytic reaction in the system. Former depends on the contents of ∑Fe=Fe（Ⅱ）＋Fe（Ⅲ） in solution solved by H2O2 from iron oxides, which increase as solution pH descents. Later depends on the surface characteristics of iron oxide.