吸收协同高级氧化工艺处理低浓度含氰废气实验研究

Experimental study on the treatment of low-concentration cyanide-containing waste gas by adsorption coupled with advanced oxidation process

以乙腈作为含氰废气的典型组分,考察吸收协同不同高级氧化体系下低浓度乙腈的去除效率以及产物分配情况.研究结果表明:UV/PS和VUV/PS体系均能有效吸收并降解乙腈,在60 min内其脱除效率近100%,且矿化率近80%或以上.主要原因是吸收液中的过硫酸盐(PS)可以在紫外光的激发下产生大量的HO^(·)和SO_(4)^(·-),这些自由基可以促进乙腈和中间产物的氧化.同时实验还观察到乙腈中的氮元素主要被转化为NO^(-)_(3)和NH^(+)_(4),这说明乙腈的直接氧化和水解反应同时进行.NO^(-)_(3)的累积会竞争消耗反应体系中的自由基,这是其稳定性实验中乙腈矿化率下降的主要原因.此外,干扰离子Cl^(-)也会由于自由基的捕获作用抑制乙腈的降解.最后,根据产物的分析结果,提出了包含氧化与水解路径的乙腈总体降解反应途径.

Taking acetonitrile as the typical cyanide-containing waste gas,the removal efficiency and product distribution for low-concentration acetonitrile abatement in adsorption-advanced oxidation combined system were investigated.The experimental results revealed that both UV/PS and VUV/PS system were effective for the degradation of absorbed acetonitrile,where the removal efficiency was close to 100% with a mineralization rate of about 80%or above during the first 60 min reaction.The persulfate in the solution could be activated to generate a large amount of HO·and SO_(4)^(2-) radicals under ultraviolet light irradiation,promoting the oxidation of acetonitrile and the carbonaceous intermediates.Since the nitrogen of acetonitrile was observed mainly transformed into NO^(-)_(3) and NH+4,which indicated that both oxidation and hydrolysis of acetonitrile were proceeded.The accumulation of NO^(-)_(3) would consume free radicals in the absorption solution,thereby decreasing the mineralization rate in the stability test.Furthermore,the presence of Cl^(-) would also lower the mineralization rate due to the radical capture effect.Moreover,the possible reaction mechanism including oxidation and hydrolysis pathways for acetonitrile degradation were proposed base on the analysis of aqueous by-products.