Basic Research Of Phenolic Wastewater Electrolysis Under High Gravity Field

Phenolic wastewater becomes one of difficult problems in wastewater treatment all overthe world, because of its toxicity, complicated composition, degradation-resistant, high CODvalue, poor biochemical degradability. The treatment of phenolic wastewater has receivedattention both at home and abroad extensively. Among all kinds of treatment methods,electrolysis method has the advantages of mild condition, no secondary pollution, greenenvironmental protection. It is known as one of the most promising approach in21st century.But the bubbles which are produced by hydrogen evolution and oxygen evolution sidereaction adhering to the surface of electrode will lead to low utilization rate of electrode, highcell voltage, large energy consumption and poor mass transfer efficiency. The strongcentrifugal force which is produced by high gravity technology can make these bubblesrapidly separated from electrode and electrolyte solution, decrease cell voltage, enhance masstransfer efficiency, reduce the reaction time, improve the treatment effect, reduce energyconsumption. Therefore, high gravity technology is used to strengthening electrolysis process,to treat phenolic wastewater, in order to decrease cell voltage and reduce energy consumption.The degradation of phenol, the selection of electrode, electrode kinetics process, highgravity strengthening electrolysis mass transfer process, high gravity electrolysis equipmentwere analyzed. Iron was used as anode, stainless steel as cathode, high gravity multistageconcentric cylinder electrolytic device as electrolysis equipment for this study.Through the research of high gravity factor, voltage, electrolysis time, liquid circulationflow, phenol initial concentration on removal rate of phenolic wastewater of electrolysis underhigh gravity. The results showed that phenolic removal rate increased with the increase of high gravity factor down after rising first, with the increase of voltage flat after rising first,with the increase of electrolytic time. With the increase of liquid circulation flow decreaseafter high, with the increase of phenol initial concentration increases after the first cut. Thenthe optimum process parameters what were phenolic initial concentration of3000mg/L, highgravity factor of34.48, voltage of10V, liquid circulation flow rate of60L/h, electrolysis timeof30min were chosen. Under the condition of this process, phenolic removal rate was26.4%,COD removal rate was36.19%, B/C was improved from0.015to0.17which was less than0.3, but biodegradability was greatly improved.The result of dynamics of electrolyzing phenolic wastewater under high gravity showedthat the reaction follows first order kinetics reaction model, the reaction rate expression wask=0.663exp(10.39×10~3/RT), activation energy was10.39×10~3J/mol. The theoreticalbasis was provided for the practical application of this method.In order to improve the effect of wastewater treatment, electrolyte strengtheningelectrolysis under high gravity was used with phenolic initial concentration of3000mg/L.Comparison of different electrolyte, NaCl was chosen as electrolyte. The results showed thatthe phenolic removal rate reduced with the increase of NaCl concentration after rising first,with the increase of super gravity factor decrease after rising first, increases with the increaseof voltage, electrolytic increases with time.Then through the research of high gravity factor, voltage, electrolysis time, NaClconcentration on removal rate of phenolic wastewater of electrolyte strengthening electrolysisunder high gravity, the most suitable process parameters what were electrolyte concentrationof0.03mol/L, high gravity factor of34.48, voltage of5V, liquid circulation flow of60L/h,electrolytic time of30min was obtained. Under the process conditions, phenolic removal ratewas42.79%, COD removal rate was55.81%, B/C was increased from0.17to0.31, and therequirement of biochemical treatment was reached.Economic analysis of conventional electrolysis, electrolysis under high gravity and electrolyte strengthening electrolysis under high gravity was given. The results showed thatpower consumption by electrolysis under high gravity was1/3than by conventional condition,and electrolytic time was4/15than by conventional condition. Power consumption byelectrolyte strengthening electrolysis was1/9than by conventional condition, and electrolytictime was2/15than by conventional condition. Electrolyzing30min, power consumption werethe same under three conditions, but phenolic removal rate was3to6times higher byelectrolysis under high gravity and electrolyte strengthening electrolysis under high gravitythan conventional condition, and COD removal rate was6to9times.To sum up, the using of high gravity technology and electrolyte improve the treatmenteffect of phenolic wastewater. It is expected to solve the problems of high energyconsumption and long electrolysis time in conventional condition. It provided a technicalmethod which was more economic and effective. The theoretical basis and practicalfoundation for electrolysis industrial application under high gravity was provided.