Study On Treatment Of Bleaching Wastewater AOX With H₂O₂ Catalyzed By Metal Organic Framework Supported Phosphomolybdic Acid

Conventional chlorine-containing bleaching can produce adsorbable organic halides（AOX）,most of which are difficult to biodegrade,easy to enrich,and have significant carcinogenic and teratogenic effects on humans and animals.Fenton methods can be used to remove AOX compounds because it can produce strong oxidizing free radicals.However,iron sludge deposition and other problems limit the removal effect of Fenton method.Therefore,it is necessary to seek iron-free catalytic oxidation system to improve the treatment effect of AOX.In this study,AOX was degraded by PMA/H₂O₂catalytic oxidation system.The main contents are as follows:Using 4-chlorophenol（4-CP）to simulate AOX,the degradation of AOX was studied via phosphomolybdic acid（PMA）/H₂O₂ oxidation system.The effects of temperature,PMA concentration and H₂O₂ concentration on the degradation of 4-CP by PMA/H₂O₂ oxidation system were investigated.The changes of AOX content,chlorine ion content,total organic carbon,intermediate type and structure were analyzed.The mechanism of degradation of 4-CP by PMA/H₂O₂ catalytic oxidation system and its mineralization path were discussed.The results showed that the removal efficiency of 4-CP reached 100%.The release of chlorine ion was about 77.5%,the removal rate of AOX was 82.5%,and the removal rate of TOC was 44.74%.Aromatic compounds and aliphatic compounds were the main products in the oxidative degradation process of 4-CP.The degradation of 4-CP in PMA/H₂O₂ oxidation system underwent the aromatic dechlorination reaction and the ring-opening reaction of conversion from aromatic compounds to aliphatic compounds,among which dechlorination reaction was the main oxidative degradation reaction of 4-CP.The supported catalyst（PMA@Ui O-66）was prepared by encapsulating phosphomolybdic acid（PMA）with zirconium MOF（Ui O-66）and its structure was characterized by FT-IR,XRD,BET,SEM,TG,XPS and other means.The degradation of pulping and bleaching wastewater by PMA@Ui O-66 under H₂O₂action was analyzed and AOX changes in wastewater were discussed.The recycle and stability of supported catalyst were studied.The results show that the PMA is successfully loaded on the metal skeleton,which does not destroy the Ui O-66crystal structure of the metal skeleton.The supported catalyst had large specific surface area and pore size,which was conducive to the entry of pollutants into the active site.Under the action of PMA@Ui O-66/H₂O₂,the removal rate of AOX and TOC in bleaching wastewater can reach 55.65%and 60%respectively.After four cycles,AOX removal rate could till reach to 51.8%,and the structure of PMA@Ui O-66 did not change before and after the reaction.Phosphomolybdic acid（PMA）/H₂O₂ method can effectively remove chlorine organic pollutants in water.This study can be used as one of the potential treatment methods for AOX wastewater treatment.