含氯离子苯酚废水高级氧化过程AOX生成研究

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/H₂O₂ 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/H₂O₂,但UV/PDS出水中AOX浓度约为UV/H₂O₂的10倍;UV/H₂O₂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/H₂O₂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/H₂O₂,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。

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

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/H₂O₂, were investigated in the presence of Cl-. The results showed that UV/PDS was more effective than UV/H₂O₂ 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/H₂O₂. The UV/H₂O₂ 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/H₂O₂, 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.