Research On The Electrolyte Effects During Electrochemical Oxidation Processes

In recent years,with the development and progress of the society,the pollution of the scarce water resources caused by industrial and agricultural production becomes more and more serious,which brings a great threat to human health and ecological stability.So the investigations concerning new and efficient water treatment processes have been the focus of the environmental subjects.Among the various water treatment techniques,electrochemical oxidation processes have demonstrated wide research and application prospects due to their unique advantages.The two most important factors affecting the efficiency of electrochemical oxidation technology are the electrode materials and electrolytes employed.In terms of electrode materials,boron-doped diamond electrode(BDD)and Ti-based coating anodes(DSA)have been recognized as the most outstanding electrocatalytic electrodes in the field of water treatment.While in terms of electrolytes,sodium sulfate and sodium chloride have been regarded as the most important electrolytes.Numerous studies have demonstrated that there are certain reaction selectivities between the electrode materials and electrolytes,and BDD/Na2SO4 and DSA/NaCl are proved to be the best combinations.In this scenario,we have carried out some novel research works concerning the anode/electrolyte relationship,and the works conducted have been listed as follows:Part ?:Factorial design methodology was employed to examine the electrolyte effect on DSA electrode and the reaction selectivity between electrode and electrolyte.Four operating parameters(reaction time?flow rate?applied current density and supporting electrolyte concentration),and five types of electrolyte combinations(100%Na2SO4?75%Na2S04 + 25%NaCl?50%Na2S04 + 50%NaCl?25%Na2S04+ 75%NaCl and 100%NaCl)were chosen here to investigate the electrolyte effects from a statistical perspective,with Acid orange ?(AO ?)being taken as a target pollutant.The results obtained demonstrated that the Na2SO4 could strongly inhibit DSA electrolytic oxidation process,while NaCl favors the oxidation reaction.Some plausible explanations had been provided based on the results from electrochemical measurement and UV-vis spectra detection.Part II:A central composite rotatable design coupled with response surface methodology was implemented to investigate the electrolyte effect on BDD electrode and the reaction selectivity between electrode and electrolyte.In this section,four operating parameters that influenced the degradation efficiency of nitrilotriacetic acid(NTA)were investigated,including the initial solution pH value,flow rate,applied current density and concentration of supporting electrolyte.The influence of Na2SO4 and NaCl on various operating parameters of BDD technology was also examined in order to determine the optimal conditions of the degradation processes.It turns out that the electrolyte affects not only the choice of operating variables,but also lead to different reaction kinetics.Finally,liquid chromatography/mass spectrometry technology(LC/MS)was adopted to determine the main reaction intermediates,and the reaction pathway of NTA in chloride media also proposed.