Fenton Oxidation-hydrolysis Acidification Method For The Pretreatment Of Mercaptopropionic Acid Wastewater

Mercaptopropionic acid is an important fine chemical product,and much high content organic wastewater,which is produced during the production process,is treated difficultly.In order to solve the problem above,the pretreatment technology was studied in this research.Meanwhile,in view of Fe2+ in wastewater,the combined technology of Fenton oxidation and hydrolysis acidification was used for pretreatment of Mercaptopropionic acid wastewater.The contents of this study include:the optimal process parameter,treatment efficiency and kinetics analysis of Fenton oxidation technique,the optimal process parameter and treatment efficiency of hydrolysis acidification after Fenton oxidation,and the biochemical experiments of the effluent after Fenton oxidation-hydrolysis acidification.In this study,COD value is used as a major evaluation index of water quality.The optimal process parameters of Fenton oxidation technique by single factor experiments were:the total dosage of 30%H2O2 was 1/6 Qth(34.8mL/L)through 3 adding times,pH was 4 and the reaction time was 120 min.The removal efficiency of COD is 92.96%.The results of orthogonal experiment showed that the order of the main factors affecting effluent COD by Fenton oxidation was pH value,H2O2 dosage,reaction time,adding times.The optimal process parameters were:pH value was 4,the total dosage of 30%H2O2 was 1/6 Qth(34.8mL/L)through 3 adding times and the reaction time was 90 min,the removal efficiency of COD was 90%.Kinetics analysis showed that COD degradation by Fenton oxidation accorded with the pseudo-second-order reaction kinetics approximately.By analyzing and calculating the experimental datas,the kinetic model of the treatment of wastewater by Fenton oxidation was derived.The effects of the pH,volume load and hydraulic retention time on treatment efficiency of hydrolysis acidification after Fenton oxidation.Results showed that the optimal pH value was 7,the average COD removal rate was 9.3%,and the highest is 13.5%;under the optimal pH,the reactor was subjected to 5 load shocks,the removal efficiency of COD increased with the increase of influent COD concentration,nutrients and microbial activity,the highest removal efficiency of COD reached on the eighth day;and then decreased because of the decrease of microbial activity and degradation ability caused by the toxicity accumulate of wastewater.The COD efficiency increased rapidly with the increase of reaction time in the first 4 h,then increased slowly.The maximum COD removal efficiency(15.3%)was reached at the 24th h.After the pretreatment of Fenton oxidation and hydrolysis acidification,the concentration of COD was 3 820～4215 mg/L,the total removal efficiency was 91.5%,compared with the raw wastewater,which showed that the combined technology of Fenton oxidation and hydrolysis acidification was beneficial to biochemical treatment of wastewater.The results of the biochemical experiments showed that the effluent COD of anaerobic-aerobic reactor was 995-1054 mg/L,and the removal efficiency of COD was 97%.