含氯离子苯酚废水高级氧化过程AOX生成研究

AOX FORMATION DURING THE ADVANCED OXIDATION OF PHENOL WASTEWATER CONTAINING CHLORIDE ION

难降解工业废水中普遍存在的高浓度Cl^(-)影响废水的高级氧化深度处理效果,并产生有害有机氯代副产物。以苯酚为目标污染物,研究了Cl^(-)存在下UV/PDS和UV/H_(2)O_(2)2种高级氧化技术处理苯酚过程中可吸附有机卤素(adsorbable organic halogens,AOX)的生成规律。结果表明:实验条件下(1000,10000 mg/L Cl^(-)),UV/PDS对苯酚的矿化效果优于UV/H_(2)O_(2),但UV/PDS出水中AOX浓度约为UV/H_(2)O_(2)的10倍;UV/H_(2)O_(2)体系在强酸性条件(pH=3)下更容易生成AOX,而UV/PDS体系的AOX生成量受溶液初始pH的影响并不显著;通过对4种氯自由基稳态浓度的模拟计算发现:随着Cl^(-)浓度从1000 mg/L升高至10000 mg/L,氯自由基总浓度在UV/H_(2)O_(2)和UV/PDS中升高了1~2个数量级,且UV/PDS体系中氯自由基浓度显著高于UV/H_(2)O_(2),这可能是导致不同条件高级氧化出水中AOX浓度显著不同的原因;同样地,处理含酚实际废水时,UV/PDS体系生成更多AOX,且废水中有机物组成及其结构对AOX生成的影响高于废水TOC浓度的影响。

The high concentration of chloride ions prevalent in refractory industrial wastewater affects the performance of advanced oxidation and generates harmful organochlorine by-products.In this study,phenol was selected as the target pollutant and the generation of adsorbable organic halogens(AOX)during its oxidation by two typical advanced oxidation processes,namely UV/PDS and UV/H_(2)O_(2),were investigated in the presence of Cl^(-).The results showed that UV/PDS was more effective than UV/H_(2)O_(2) in the degradation and mineralization of phenol under experimental conditions in the presence of 1000 mg/L and 10000 mg/L Cl^(-).However,the AOX concentration formed during UV/PDS oxidation was about 10 times higher than that in UV/H_(2)O_(2).The UV/H_(2)O_(2) process tended to form more AOX under strongly acidic conditions(pH=3),while the AOX generation in the UV/PDS process was not significantly affected by the initial pH.Simulations of the steady-state concentrations of the four chlorine radicals revealed that the chlorine radical concentration increased for 1~2 orders of magnitude,when Cl^(-)increased from 1000 mg/L to 10000 mg/L.The concentration in the UV/PDS system was significantly higher than that in UV/H_(2)O_(2),which may be an important reason for the significant difference in AOX observed in the two advanced oxidation processes under different conditions.Similarly,the UV/PDS generated more AOX when treating actual wastewater,and the effect of organic structure and composition in wastewater on AOX generation was stronger than the effect of TOC concentration in wastewater.