Degradation Of Cellulose In Ethanol Wastewater By UV/PS Advanced Oxidation

With the rapid growth of the demand for fuel ethanol in the world,the key breakthrough of ethanol production technology with straw and other cheap cellulose as raw materials,availability of raw materials,green environmental protection and other multiple advantages,the production of cellulosic ethanol will gradually become industrialized,and the treatment and resource utilization of its wastewater will become increasingly prominent.The wastewater from cellulosic ethanol production contains not only small molecular organic acids(lactic acid,formic acid,acetic acid,butyric acid,etc.)produced in the fermentation process,but also soluble lignin,cellulose,hemicellulose,furfural,phenol and other biodegradable organic substances produced in the hydrolysis process of cellulose raw materials.The water quality characteristics are more complex.At present,the commonly used method is to use anaerobic and aerobic biological method for treatment,but this method covers a large area,long experimental period,many uncertain factors,high cost,and some difficult to degrade organic matter can not achieve better treatment effect.Advanced oxidation technology has the advantages of simple operation,fast reaction speed,good degradation effect,low cost and so on.The treatment effect of organic matter is more obvious and widely used in wastewater treatment.Therefore,in this study,based on advanced oxidation technology,ultraviolet(UV)/persulfate(PS)system was used to treat the refractory organic matter produced in the production process of cellulosic ethanol,and a good treatment effect was obtained.The main contents of this study include qualitative and quantitative analysis of the residual persulfate after advanced sulfate oxidation treatment by spectrophotometry,rapid digestion method to determine the contribution of residual persulfate to COD,so as to eliminate the interference of residual persulfate on COD detection.Single factor experiments were carried out on the refractory cellulosic substances(lignin,cellobiose and xylose)in cellulosic ethanol wastewater using UV/PS system under five conditions of different reaction systems,reaction temperature,initial pH,dosage of persulfate and reaction time.The experimental studied on the treatment characteristics of cellulosic ethanol reduction wastewater was carried out,the optimal process conditions were investigated and analyzed.The first-order reaction kinetics was analyzed,and the UV/PS system was optimized to achieve better treatment effect.The persulfate was quantitatively analyzed by spectrophotometry.352 nm and 420 nm were determined as the wavelengths for the determination of persulfate anions,so as to ignore the spectral interference from reagent matrix.After persulfate activation treatment of water samples,if the solution contains a relatively high concentration of persulfate ions(0-25 g/L),the concentration determination method is to determine the absorbance value at 352nm after the water sample is diluted at an appropriate multiple.The linear equation is y=0.0214x-0.0013,R2=0.9992.If there is a low concentration of persulfate(0～2.5 g/L)in the water sample,the absorbance should be measured at 420 nm under the condition of undiluted water sample.The linear equation is y=0.2556x-0.006,R2=0.9993.The linear equation between persulfate concentration and COD consumption is y=18.83894x-7.11549,R2=0.99926.UV/PS advanced oxidation method was used to treat refractory cellulose substances,the following conclusions were drawn:UV/PS advanced oxidation method had good degradation effect on lignin,cellobiose and xylose.Through the further experiment and the optimum reaction conditions for degradation of cellulose material respectively:the best reaction system for the degradation of lignin was UV/PS system,50℃ was the optimum reaction temperature,pH=4 was the best initial pH,5 g/L was the best persulfate dosing amount and 24 h was the optimal reaction time.The best reaction system for degradation of cellobiose was UV/PS system,50℃ was the optimum reaction temperature,pH=3 was the best initial pH,5 g/L was the best persulfate dosing amount and 12 h was the optimal reaction time.The best reaction system for degradation of xylose was UV/PS system,50℃ was the optimum reaction temperature,pH=4 was the best initial pH,15 g/L was the best persulfate dosing amount and 24 h was the optimal reaction time.The wastewater from cellulosic ethanol reduction was degraded by ultraviolet/persulfate advanced oxidation method and the composite system respectively,the following conclusions were drawn:the best reaction system was UV/PS system,50℃ was the optimum reaction temperature,pH=6 was the best initial pH,10 g/L was the best persulfate dosing amount,20h was the optimal reaction time and the COD degradation rate was 94.16%.Different reaction systems,temperature,initial pH and dosage of persulfate were used to degrade wastewater from cellulosic ethanol reduction,which all fit the pseudo-first-order reaction kinetics equation.In the optimization experiment of the composite system by alkali+UV-activated persulfate advanced oxidation technology,the optimal reaction conditions were as follows:2 g/L was the dosage of NaOH,50℃ was the optimum reaction temperature,pH=6 was the best initial pH,6 g/L was the best persulfate dosing amount,20 h was the optimal reaction time,the COD degradation rate was 97.59%.By adding a small amount of alkali activator,the usage amount of persulfate was reduced and the degradation effect was very good.