Purification Of Natural Waters By Electro Advanced Oxidation Processes With Solid Polymer Electrolytes

With the growing economy,plastics and medicines are widely used in our daily life.Plasticizers and antibiotics,which are important components,have been widely concerned for their potential adverse effects on public health.Many countries have issued relevant policies to control their pollution,but unfortunately,they have also been detected in natural waters.In recent years,EP（Electro-Peroxone）and EF（Electro-Fenton）technologies have become the focus of research in EAOPs（Electro advanced oxidation processes）because of their advantages of low cost and high efficiency.Compared with the traditional peroxidation technology,H₂O₂ can be generated in situ by 2e-ORR reaction in the EP system,avoiding the potential safety hazard brought by transportation and storage.Meanwhile,EP has better degradation effect and lower energy consumption for pollutants.Compared with the traditional Fenton reaction,H₂O₂ is also generated in situ by 2e-ORR reaction at the cathode,avoiding potential safety hazards,and Fe³⁺produced after catalytic completion can be partially reduced to Fe²⁺through the cathode,which slows down the generation of iron sludge.However,when they are used to remove refractory organic matter in natural water,a large number of supporting electrolytes（such as Na₂SO₄,KCl,Na Cl,Na₂Si O₃ and so on）are often added to the treated water in order to reduce energy consumption and improve the treatment effect.Although organic pollutants that are difficult to degrade are treated,the addition of large quantities of these supporting electrolytes will also change the water environment.In view of this problem,this paper uses solid polymer electrolytes（SPEs）combined with EP and EF technology to degrade plasticizer and antibiotic in natural water,respectively.The specific research of this paper is as follows:（1）Plasticizers degradation by Electro-peroxone combined with solid polymer electrolytesDimethyl phthalate（DMP）was used as the target pollutant to evaluate the efficiency of the EP-SPE system in a simulated natural water environment.The results show that the EP-SPE system has good performance for DMP in natural water.When O₃ is 40 mg·L^-1 and the current density is 10 m A·cm^-2,the EP-SPE system can achieve 100%of DMP mineralization.Compared to the conventional EP system（not）adding salt compounds（CEP-（N）AS）,pollutants mineralization was increased from～70%to 100%while the energy consumption was reduced by 2.3（7.4）times in EP-SPE system.The main ROS in the system were O₃,·OH and O₂^·–by electron spin resonance（EPR）spectroscopy.Their transient concentrations and contributions to plasticizer degradation were also determined by low concentration probe method.Furthermore,tests of variety of SPEs and natural waters demonstrated universal applicability of EP-SPE.Additionally,EP-SPE did not show any performance deterioration after 15 runs.Therefore,this work provides a feasible technology for plasticizer purification in natural water.（2）Antibiotics degradation by metal-free Fenton combined with solid polymer electrolytesIn this study,nitrogen-doped graphite felt（c PANI/GF-8）was obtained by calcination after polyaniline was loaded on graphite felt by electrodeposition.The as synthesized electrode was used for in-situ electro-generation and activation of H₂O₂ to·OH radicals for degradation of organic pollutants without metal catalyst.A metal-free Fenton system with solid polymer electrolytes was constructed to degrade antibiotics in natural water.The results showed that the EF-SPE system could degrade CBZ by 95%in 120 min at p H=5.6（neutral）,and had a good degradation effect in p H=3～9.Compared with EF-（N）AS system,the energy consumption is reduced by 2（7.4）times.EPR spectra confirmed the existence of·OH in EF-SPE system,and XPS proved that graphite nitrogen and pyridine nitrogen were the sites of electro-generation and activation of H₂O₂ to·OH,respectively.Tests in natural water showed that the EP-SPE was universally applicable and degraded by only 5%after five runs.