A Method For In Situ Generation Of Fenton's Reagent And Its Applications In The Treatment Of Refractory Organic Wastewater

Biological treatment is the preferred method for the industrial organic wastewater treatment,but refractory organic wastewater must be pretreated to improve its biodegradability before biochemical processing.As an advanced oxidation processes,Fenton's reagent oxidation processes is widely used in the refractory organic wastewater treatment.And electro-Fenton method has the greatest potential for industrial application because it could generate Fenton's reagent on site,but low working current,low current efficiency and electrode vulnerable contaminated result in that it is difficult to apply in real industrial applications.This paper proposed a method different from the electro-Fenton method,in situ generation of Fenton's reagent,which was expected to achieve the purpose of industrial applications.This paper presented a method for in situ preparation of H2O2 which was independent of the wastewater,low alkali-ratio and low ionic strength alkaline H2O2 electro-synthesis method was developed by drawing on the technique of cathodic reduction of oxygen to prepare alkaline H2O2,adapting to the required weak acidic environment of Fenton's reagent oxidation processing.Gas diffusion electrode modified by 2-ethyl anthraquinone as oxygen cathode reduction,cation exchange membrane as the diaphragm,the alkalinity of the cathode solution was controlled by acid anodic membrane process.When the current density was 750A·m-2,air flow rate was 1.3 times the amount of the theoretical oxygen and oxygen produced on anode return to the air chamber,after cyclic electrolysis for 8 hours at room temperature,alkaline H2O2 solution which alkali ratio was 0.23,the mass concentration was 1.5%was obtained in the 2.5wt%Na2S04 solution at pH 12.This article also introduced iron-carbon micro-electrolysis method for in situ generation of Fe2+,which could be quickly introduced into the biotin production wastewater as a representative of refractory organic wastewater through the iron-carbon micro-electrolysis reactor.After 3 hours cyclic reaction and 1 hour actual residence,under the conditions of initial pH 3.5 and Fe:C=1:1,10mmol·L-1 Fe2+ was introduced into the wastewater,while part of the COD was removed.Iron-carbon micro-electrolysis processing and low alkali-ratio and low ionic strength alkaline H2O2 electro-synthesis processing formed the method for in situ generation of Fenton's reagent.The processing conditions about the pretreatment of biotin production wastewater using in situ generated Fenton's reagent was studied.After considering influence of a single factor,optimal operating conditions were chosen:pH of iron-carbon micro-electrolysis inffluent was 3.5,micro-electrolysis contact time was 1 hour,and pH of micro-electrolysis effluent need not adjust,25 mmol·L-1 H2O2 preparated on site were added by a continuous dropping manner,the COD removal rate of the biotin production wastewater was more than 50%after reacting 1 hour at room temperature.Simulated aerobic biological treatment showed that the biodegradability of the biotin production wastewater pretreated by in situ generated Fenton's reagent had been greatly enhanced.Based on the laboratory studies,this paper also conducted a pilot scale study on the production site,designed and produced the pilot scale devices of the low alkali-ratio and low ionic strength alkaline H2O2 and the iron-carbon micro-electrolysis,constructed the pilot processing line that in situ generated Fenton's reagent used for pretreatment of biotin producton wastewater.After thirty days continuous operation,the results showed that the quality of effluent was stability,and compared with the original treatment process,whether quality of the effluent or processing speed had been significantly improved,reaching the local sewer standard of Fuyang.The results obtained from pilot scale stueies indicated that the method for in situ generation of Fenton's reagent was an effective technical means for the pretreatment of the refractory organic wastewater,fully equipped with the practical possibility and broad application prospects.