平行板双介质阻挡放电处理水相中氯酚的脱氯机理

用平板介质阻挡放电等离子体技术和脉冲辐解方法研究了等离子体条件下水相中的4 氯酚脱氯的机理.研究结果表明,4 氯酚在等离子体中的脱氯近似为表观一级反应;4 氯酚的脱氯率与等离子体的电压和电极间距呈线性关系;溶液的pH值随着处理时间的增加而下降.用脉冲辐解方法得到的瞬态吸收光谱显示,在近中性和酸性条件下,4 氯酚主要经由4 氯酚的OH加合物进一步转化而脱氯;在碱性条件下,4 氯酚直接经过氯代酚氧自由基而进一步脱氯,脱氯率比中性或酸性的高.在等离子体条件下,水相中4 氯酚的脱氯主要是与·OH自由基作用的结果.4 氯酚在等离子体中脱氯后的产物为较易生物降解的酚类和有机酸类.

Dechlorination mechanism of chlorophenol in aqueous solution using low-temperature plasma

Dechlorination mechanism of 4-chlorophenol in aqueous solution in plasma has been studied by means of flat dielectric barrier discharge(DBD) and pulse radiolysis. The dechlorination of 4-chlorophenol is a pseudo first order reaction and its rate is in linear with the voltage and electrodes space. As processing time goes on, the pH value of the solution declines. It is implied by the transient absorption spectrum that, under neutral and acid conditions, 4-chlorophenol is first transformed into OH-adduct, and then dechlorinates through further reactions; while under alkaline condition, 4-chlorophenol dechlorinates by creating chlorinated phenoxyl radical directly, giving a better dechlorination rate than that under neutral and acid conditions. It is primarily the reactions between ·OH radical and 4-chlorophenol that contribute to the dechlorination of 4-chlorophenol in aqueous solution in plasma. Phenols and organic acids which are more biodegradable are the main products of 4-chlorophenol treated by DBD plasma.