Study On Treatment Of Desizing Wastewater By Combined Process Of Micro-electrolysis Material With Advanced Oxidation

Polyvinyl alcohol(PVA)has a wide range of application.PVA is used as a warp sizing slurry in the textile printing and dyeing industry,producing a large amount of PVA-contained printing and dyeing desizing wastewater,whose amount is large and composition is complex.This kind of wastewater characterizes high COD and poor biodegradability,becoming a priority to be treated among dyeing wastewater.PVA was the main target pollutant in printing and dyeing desizing wastewater in this study.Novel micro-electrolysis material was modified with pore-forming agent,The optimum pore-forming agent and its content were screened.Preparing scheme of material was made.Properties of modified micro-electrolysis material were characterized by N2 isothermal desorption curve,scanning electron microscope,X-ray diffraction and thermogravimetric analysis.Optimum technological parameters of modified micro-electrolysis material and Fenton reaction were determined with PVA simulated wastewater,respectively.Application prospect of modified material was evaluated by comparision with commercial available material.Degradations of PVA simulated wastewater under combined process of micro-electrolysis+coagulation and micro-electrolysis/Fenton+coagulation were compared,and the optimum combined process was employed to treat PVA desizing wastewater.Results showed sodium bicarbonate was used as pore-forming agent and the mass fraction was 2%,presenting better CODcr removal rate as well as was economic.The optimum preparing mass ratio of material components was Fe:Al:P:C:NaHCO3=50:50:40:20:3.The average pore size of the micro-electrolysis material increased from 5.46 nm to 8.44 nm,the volume of the total pores increased from 0.09 cm3/g to 0.11 cm3/g,and the specific surface area reduced from 65.69 m2/g to 53.72 m2/g after modification.The main components were Al,Fe and C.The optimum process parameters for treating PVA simulated wastewater by modified micro-electrolysis material were as follows:under aeration conditions,the micro-electrolysis time was 60 min,the initial pH was 5,and the dosage of the material was 465 g/L in one time.Modified materials showed better CODcr removal rate and effluent biodegradability increased from 0.18 to 0.35 under the optimum conditions compared with commercial micro-electrolysis material.The optimum process parameters for Fenton reaction were:the initial pH was 4,nH2O2/nCODCr=2:1,nH2O2/nFe2+=15:1,and the reaction time was 1 h,and the CODCr removal rate of the simulated PVA wastewater was 80.39%,the BOD5 removal rate was 18.33%,and B/C increased from 0.18 to 0.73 under the optimum process parameters.The best effect was obtained by micro-electrolysis/Fenton(successively)+coagulation process with CODcr removal rate of 70.73%and B/C of 0.44.The combined process was used to treat the coagulated effluent of the desizing wastewater,and after two days biochemical reaction,the effluent removal rate of CODcrand PVA were 82.96%and 60%.CODcr removal rate increased 33%compared with biochemical reaction directly,which further proved combined process improved the biodegradability of effluent.