Study On Degradation Characteristics Of Organic Matter In Bio-Treated Effluent Of Coking Wastewater By Persulfate

Residual refractory organic in coking wastewater after biochemical treatment is a main issue to affect the depth reuse.In this article,there use of bio-treated effluent of coking wastewater is the main target of treatment,selecting the actual coking wastewater as the main objects of this study the oxidation system was established in the persulfate center.The optimal system（C/UV/PS system）was selected to study the molecular weight distribution of organic matter and the change of hydrophobic and hydrophobic organic matter content in the wastewater before and after advanced treatment.The oxidation mechanism was also discussed.In addition,quinoline,a typical refractory organic matter in coking wastewater,was selected as the main research object.The optimum system was selected under various catalytic oxidation systems.The main types of free radicals in the oxidation system were analyzed and the degradation pathway of quinoline was discussed.By the experiments we find that:（1）There exist more organic compounds of refractory aromatic organic matter in bio-treated wastewater and those are mainly organic matter of MW<1 kDa,the next is such organic matter of MW>100 kDa.The types of organic matter of hydrophobic-acid fraction and hydrophobic-neotral fraction played a predominate role.（2）The optimal oxidation conditions determined in the three oxidation systems were:C/UV/PS system,initial pH,iron ore and PS investment of 3 g·L^-1 and 2 g·L^-1,ultraviolet irradiation power of 300W,Under the optimal conditions,COD、UV₂₅₄、DOC and color removal rate could reach 74.9%、93.5%、84.1%and 80.1%in 90 minutes.In the oxidation reaction,the ore catalyst and ultraviolet light cooperate to oxidize refractory substances,and their main activities are as follows.Free radicals are·SO^-₄ and·OH,both of which play an oxidative role at the same time.（3）The results also showed that C/UV/PS system was more effective in removing organics of MW>10kDa,the share of MW<1kDa organics increased after treatment,C/UV/PS system was also effective in removing hydrophobic and transphilic fraction compounds（from 75%to 58%）,and the share of hydrophilic substances increased（from22.4%to 28.6%）after treatment.（4）Combining factors of reaction effect and cost,the degradation experiments of quinoline were carried out in the five systems of C,PS,UV,UV/PS and C/UV/PS.The optimum reaction conditions were determined as PS dosage of 10.5 mmol/L^-1,pH of 7,ultraviolet irradiation power of 300 W,reaction time of 30 min,and the operation of UV/PS process under these conditions.There are at least two types of active radicals,·SO₄^-and·OH.Under neutral conditions,·OH and·SO₄^-mainly cause the ring opening of benzene ring to produce a series of by-products mainly consisting of pyridine ring.