| The control of disinfection by-products is a hot issue in the current drinking water safety.The control of chloroform,which is widely distributed and highly toxic,is particularly important.At present,the main adsorption method and the electrocatalytic degradation method have been used for the removal of chloroform,and the removal of low concentration of chloroform in water by a single method is poor,and the adsorption method and the electrocatalytic degradation method can be used in combination.The two methods complement each other and effectively improve the removal efficiency of low concentration chloroform in water.At the same time,the product is single and does not produce by-products.Therefore,the use of adsorption-electrocatalytic coupling in the removal of disinfection by-products will have a higher value.The test carried out high-temperature impregnation method on the surface of granular activated carbon(GAC)with nano-silver to prepare silver-loaded activated carbon(Ag-GAC).The physicochemical properties of GAC and Ag-GAC were determined by characterization analysis test methods such as BET analysis,SEM analysis,ICP analysis and CV analysis.Through single factor experiments,the silver adsorption,flow rate(ml/min),aspect ratio,time(h)and current density(mA/cm2)during the adsorption and electrocatalytic degradation tests were investigated for Ag-GAC adsorption degradation.The effect of chloroform on the performance of chloroform was obtained,and the effect of its adsorption and degradation of chloroform was obtained.The reaction process and mechanism were studied.On the basis of this,the effects of electrocatalytic regeneration and thermal regeneration and ultrasonic regeneration were compared.The experimental results show that the adsorption capacity of Ag-GAC is best when the flow rate is 75ml/min and the aspect ratio is 2.5.The average removal rate and total adsorption capacity are 47.9%and 88.07 ug/g,respectively,and then at 5mA/cm2.The electrocatalytic degradation at current density for 3 h can be completely regenerated.The average removal rate and total adsorption capacity of Ag-GAC after regeneration are increased by 33.9%and 24.2%,respectively.The adsorption test water sample was tap water,and the average concentration of chloroform was 30.82 ug/L.The study found that the flow rate is the main factor affecting the adsorption capacity of Ag-GAC.The adsorption capacity increases with the decrease of flow rate;the high aspect ratio does not affect the total adsorption amount,but the average removal rate can be improved by increasing the height to diameter ratio.The comparison test results show that the adsorption capacity of Ag-GAC is about 10%lower than that of GAC.It is considered that chloroform is a hard base,and the GAC after silver loading has soft acid properties.According to the soft and hard acid-base theory(HSAB),its adsorption performance is better.Neutral GAC has declined.The fitting analysis of the adsorption process found that the adsorption of chloroform by Ag-GAC was consistent with the Thomas model curve.In the electrocatalytic degradation test,the average concentration of chloroform was 30.82 ug/L.The results show that the current density is an important factor affecting the rate of electrocatalytic degradation.When the electrocatalytic degradation time is 3 hours and the chloroform content is 500 ug,the chloroform can be completely degraded by Ag-GAC when the current density is 5 mA/cm~2.The degradation rates at current densities of 1 mA/cm~2 and 2 mA/cm~2 were 73.5%and 87.6%,respectively.Comparative experiments show that the electrocatalytic efficiency of Ag-GAC is significantly higher than that of GAC.When electrocatalytic degradation is 5 hours,chloroform content is 500ug,and current density is 1mA/cm~2,the average degradation rate of Ag-GAC to chloroform can reach 88%.The average degradation rate of GAC is64%.It is considered that the nano-silver adsorbed by Ag-GAC is not occupied by chloroform,and desorption occurs during electrocatalytic degradation,thus making chloroform and catalyst nano The silver is in full contact to achieve rapid degradation.The regeneration test proved that the average removal rate and total adsorption capacity of Ag-GAC after thermal regeneration decreased by 27.61%and 24.31%,respectively,and the adsorption performance of Ag-GAC after ultrasonic regeneration decreased by 8.36%and 16.25%,respectively.The average removal rate and total adsorption amount of Ag-GAC after reduction and regeneration increased by 33.9%and24.2%,respectively.The regeneration effect of electrocatalytic degradation method is obviously better than that of thermal regeneration method and ultrasonic regeneration method. |
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