Construction Of A Coupling System Of Coal-Based Carbon Membranes With Electrochemical Advanced Oxidation And Its Synergistic Persulfate Activation For Phenolic Wastewater Treatment

In recent years,with the development of global economic,people suffer from a series of problems caused by water environment pollution.Phenolic wastewater,as the most common type of organic pollutant wastewater,poses a great threat to the water environment due to its recalcitrance and toxicity.Membrane separation technology is recognized to be one of the most potential methods for wastewater treatment with advantages of easy operation,low cost and environmental friendliness.However,traditional membrane separation depends on pore size sieving for pollutants separation which poses an insufficient interception capacity for small molecule organic pollutants.The development of coupling system with electrochemical advanced oxidation processes（EAOPs）and membrane separation can realize expansion of membrane function in which organic pollutants degradation can be achieved via electrochemical oxidation.Herein,the coupling system combined EAOPs with coal-based carbon membrane separation and its synergistic persulfate activation was designed for phenolic wastewater treatment.The treatment performance of phenolic wastewater by the coupling system was explored and the mechanism of coupling process on the improvement of membrane separation was also revealed.The main research results as following:（1）A coupling wastewater treatment system combined coal-based carbon membrane separation with anodic oxidation（CCM/AO）was developed.The enhancement on membrane separation performance by the assistance of AO was systematically studied.When the treatment of phenolic wastewater（100 ppm phenol）relies on membrane separation merely,permeate flux of the membrane and the removal efficiency of phenol was 119.8 L m^-2 h^-1 bar^-1 and 6.9%,respectively.However,an increasement on both permeate flux of membrane and phenol removal efficiency can be observed with the assistance of AO.The permeate flux of membrane and phenol removal efficiency was 1.8 and 13.2 times respectively higher than that of membrane separation.Gas chromatography-mass spectrometry（GC-MS）analysis revealed the degradation pathway of phenol in this coupling system.The product analysis illustrates that the treated phenol molecules were oxidized to generate catechol,hydroquinone and resorcinol,and then degraded to maleic acid,fumaric acid,oxalic acid and other organic acids,finally mineralized into CO₂ and H₂O via direct AO and indirect AO.（2）Based on the characteristics of H₂O₂ generation using coal-based carbon membrane as anode,a new wastewater treatment system coupled anodic Fenton and anodic oxidation with coal-based carbon membrane separation（anodic Fenton-CCM/AO）was constructed.It realizes an effective treatment of phenolic wastewater due to the·OH produced from H₂O₂via Fenton process.The results show that the treatment performance of the anodic Fenton-CCM/AO wastewater treatment system for phenolic wastewater treatment has been improved with the help of anodic Fenton process.The removal efficiency for 150 ppm phenol was less than 70%by CCM/AO while it increased to more than 90%by anodic Fenton-CCM/AO.The mechanism of H₂O₂ generation and phenol degradation in this wastewater treatment system were also explored.The formation of H₂O₂ in this system mainly based on the double electron oxidation of water in the process of water flowing through the coal-based carbon membrane.In addition,the improvement on phenolic wastewater treatment performance was attributed to the·OH produced from H₂O₂ via Fenton process.（3）A wastewater treatment system coupled cathodic Fenton and anodic oxidation with coal-based carbon membrane separation（cathodic Fenton-CCM/AO）was conducted using carbon felt as cathode material.It obtained an enhancement on phenolic wastewater treatment which was attributed to the electrochemical oxidation occurs on cathode.Under the optimal experimental conditions(p H=3,catalyst concentration 12 g L^-1,flow rate 1.33 m L min^-1,I=10m A),the removal efficiency of phenol with a concentration of 200 ppm maintain above 85%during the whole treatment process.The phenol degradation in this coupling system was mainly caused by·OH produced from AO and Fenton process.The effects of environmental factors on phenolic wastewater treatment and the treatment performance for different organic pollutants wastewater were investigated.It indicates that the cathodic Fenton-CCM/AO wastewater treatment system has the potential for practical wastewater treatment applications.（4）Based on the advantages of strong oxidation ability and long life of SO₄^·-,a wastewater treatment system coupled persulfate oxidation and electrochemical advanced oxidation processes with coal-based carbon membrane separation（PS-CCM/EAOPs）was constructed.It realized efficient treatment of phenolic wastewater due to the SO₄^·-for phenol oxidation.In addition,the mechanism persulfate activation and phenol degradation in this wastewater treatment system was revealed.The results show that the removal efficiency of phenol is improved due to the persulfate oxidation according to the results of phenolic wastewater treatment with and without persulfate addition.For the treatment of 200 ppm phenol,the removal efficiency of phenol was less than 70%without PS oxidation while it increased to more than 95%with PS oxidation.By analyzing the effect of quencher on phenolic wastewater treatment performance,it can be found that both SO₄^·-and·OH have an important impact on the treatment of phenolic wastewater.The SO₄^·-generated in this wastewater treatment system was caused by the activation of persulfate through the synergistic action of carbon felt,iron catalyst and electrochemical action,·OH was produced from electrochemical oxidation and persulfate oxidation.In conclusion,an efficient phenolic wastewater treatment can be realized by the design of CCM/AO and its further improvement.This study provides a new idea for the application of coal-based carbon membrane in the field of organic pollutant wastewater treatment,and provides theoretical guidance for the establishment of electrochemical-membrane wastewater treatment system.