Degradation Of High Saline Surfactant Wastewater By Electrochemical Oxidation And Its Combined Process

Nonylphenol ethoxylate?NP_nEO?is a widely used non-ionic surfactant.Nonylphenol?NP?and short chain NP_nEO?n?3?are the biodegradation products of NP_nEO,which have endocrine disrupting properties and are more toxic than parent NP_nEO.Industrial salts such as nitrate,chloride and sulfate are widely used in the chemical industry.The high concentration of salt inhibits the activity of microorganisms in activated sludge,which further increases the difficulty of NP_nEO biodegradation.Electrochemical oxidation process has the advantages of strong oxidation and mild reaction conditions,and the salt can effectively improve the mass transfer of electrochemical oxidation in high salinity wastewater.This paper mainly investigated the treatment efficiency and corresponding mechanisms of high salinity NP₄₀EO wastewater using electrochemical oxidation process and electrochemical oxidation combined with UV irradiation process.The content and results of this thesis are summarized as follows:1. The treatment effect and mechanism of high salinity NP₄₀EO wastewater in electrochemical oxidation process were studied.Electrochemical oxidation had a good removal effect on the chemical oxygen demand?COD?in high salinity NP₄₀EO wastewater,and the active chlorine generated by the electrochemical process participated in the oxidation of organic pollutants.Electrochemical oxidation treatment of high salinity NP₄₀EO wastewater with graphite as anode had better treatment effect.In high current density or acidic conditions,the COD removal rate was higher in the reaction system.The plate distance had no effect on the COD removal rate.The higher COD removal rate was achieved with NaCl as electrolyte in wastewater,and the highest COD removal rate was achieved when NaCl concentration is 0.25 M,but the higher mineralization of wastewater was achieved with Na₂SO₄ as electrolyte.In the study of NP₄₀EO degradation pathway,first,the C-O bong and C-C bond of NP₄₀EO were attacked,the ethoxylate chain and the alkyl chain were shortened,then the benzene ring was attacked,the benzene ring was opened,and finally these intermediate products were further degraded into CO₂ and H₂O.In the electrochemical oxidation treatment of high-salt NP₄₀EO wastewater reaction system,the best operating parameters for the lowest energy consumption were graphite as the anode,current density of 30 m A/cm²,plate distance of 2.0 cm,NaCl concentration of 0.50 M,initial pH value of 3.0,and the lowest energy consumption was 47.5 k Wh·kg^-1 COD.2. The treatment effect and mechanism of high salinity NP₄₀EO wastewater in electrochemical oxidation combined with UV irradiation process were studied.Electrochemical oxidation combined with UV irradiation had a good synergistic effect,which is better than a single treatment process.In the electrochemical oxidation combined with UV irradiation system,organic pollutants were degraded by anode oxidation and indirect electrochemical generation of active chlorine,UV/chlorine system also played a role in the degradation of pollutants.With the increase of current density or UV irradiation intensity,the COD removal rate in wastewater gradually increased.UV irradiation intensity had a greater influence on the COD removal rate,the COD removal rate reached87.9%under the irradiation intensity of 1680?W/cm².The NaCl concentration had little effect on the COD removal in wastewater.The initial pH value had little effect on the treatment effect,but the reaction system could achieve a better treatment effect at acidic condition.Electrochemical oxidation combined with sunlight irradiation also had a good effect on the degradation of high salinity NP₄₀EO wastewater.