| Electrochemical technologies have outstanding advantages include high versatility,and amenability,as well as safety,as they are performed at ambient conditions.Electrochemical technologies have extensive prospects in treating industrial wastewater.In this study,a novel electrochemical/persulfate hybrid technology for practical wastewater treatment was constructed through developing the dual-functional Ti@CuO-Co3O4 electrocatalytic membrane cathode material with excellent abilities of nitrate electrocatalytic reduction and persulfate electrochemical activation.And this technology was used to treat wastewater containing a large amount of nitrate and refractory organic pollutants,for example,the simulation bio-treated water discharged from farms,the coking wastewater and the bio-treated effluent of landfill leachate,and synchronously realized the removal of refractory organics and nitrate in the sewage.The key conclutions summarized from this research are as following:（1）Using porous titanium as the substrate,the Ti@CuO-Co3O4 cathode was successfully prepared by sol-gel method.And the Ti@CuO-Co3O4 cathode realized the rapid activation of persulfate and effectively promoted the electrochemical catalytic reduction of nitrate.The performance of the Ti@CuO-Co3O4 cathode in reducing nitrate and activating persulfate is 3times and 12%than that of the Ti cathode,respectively.The electrocatalytic membrane can adapt to the flow-through mode electrochemical system,which can effectively improve the mass transfermation of pollutents.In the flow-through mode electrochemical system,the reduction efficiency of nitrate was increased by more than 50%,and 0.2-0.5 m M persulfate（PMS）was fully activated（activation efficiency>99%）when passed through the Ti@CuO-Co3O4 electrocatalytic membrane at the conditions of 0.58 m3/m2·h and 10 m A/cm2.（2）The EPR experiment results showed PMS activated in Ti@CuO-Co3O4 cathode can produce a large number of hydroxyl radicals as well as sulfate radicals,which can strengthen the oxidation ability of the electrochemical system eliminating organic contaminents.And at the same time,a great number of[H]generated on Ti@CuO-Co3O4 cathode during the electrolysis,which could significantly promote the electrocatalytic reduction of nitrate and the electrochemical activation of PMS.When PMS and nitrate were present in the electrochemical system simultaneously,the low concentration of PMS could promote the reduction of nitrate.For one reason,the electrochemical system became acidic with the introduction of PMS,which is conducive to the reduction of nitrate.For another reason,the introduction of PMS reduces the reduction potential of nitrate on the Ti@CuO-Co3O4 cathode.However,the higher concentration of PMS may compete with nitrate for adsorption in the surface of cathode and the reaction with[H],and thus weakened the reduction of nitrate.（3）The outcomes from experiments treating with practical wastewater showed that the dosage of persulfate,the strategy of dosing and the mass transfer condition are important factors affecting the resultant of practical wastewater treatment.With the increase of persulfate dosage,the elimination efficiency of organic matters and nitrate in the practical wastewater can be effectively improved in the electrochemical system of Batch as well as the Flow-through mode.The addition method of small amounts in many times can further improve the organics（30%increase）and nitrate（100%increase）removal efficiency.The improvement of mass transfer conditions increased the removal efficiency of COD and nitrate in the practical effluents by 3.3 times and 1.8 times,respectively.The introduction of PMS into the Flow-through mode electrochemical system,the COD and nitrate removal efficiencies in the practical watewater further increased by 40%and 75%,which fully demonstrated the feasibility and effectiveness of Ti@CuO-Co3O4 electrocatalytic membrane/persulfate coupling technology in practical wastewater treatment. |
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