Research On Multi-index Coupling Carbon Selection Method Of Activated Carbon For Drinking Water Treatment Adsorption

Activated carbon has been widely used in drinking water treatment.In actual process of carbon selection,iodine value and methylene blue value are often used to determine the quality of activated carbon,ignoring the influence of internal pore structure and surface functional groups.The correlation among multi-indexes of activated carbon was evaluated in this study.First the common characteristic organic compounds such as amino acids and antibiotics and some organic matters in a lake were selected for the adsorption of activated carbon.Then two modification methods were used to adjust the pore structure of activated carbon.Through adsorption test,associate the adsorption performance of activated carbon for organic matters with the multi-indexes of activated carbon.As a result,some suggestions on the selection of activated carbon in practical application are obtained.In the experiment,11 kinds of coal activated carbon and 4 kinds of wood activated carbon were selected,the iodine value of carbon was 439-1201mg/g,and the iodine number,methylene blue value and phenol adsorption value of wood carbon were higher.In the experiment,the multi-indexes of activated carbon mainly include iodine number,methylene blue value,phenol adsorption value,BET specific surface area,total pore volume,micropore volume,mesopore volume,average pore size,etc.The experimental data also show that S_BET/V value,a new technical index obtained by coupling,can better reflect the pore structure characteristics of activated carbon.Through the correlation analysis of multiple indicators,it was found that the iodine number and methylene blue value of activated carbon have a certain positive correlation with BET specific surface area.The phenol adsorption value was negatively correlated with the BET specific surface area and pore volume of activated carbon.For the carbon whose iodine value is greater than 900 mg/g,the iodine value and phenol adsorption value increase with the increase of S_BET/V_micropores and S_BET/V_meso-pores,respectively.The adsorption value of methylene blue was negatively correlated with S_BET/V_meso-pores.However,the rule of coal activated carbon with iodine value in 400-900 mg/g is opposite.The larger the pore volume of wooden activated carbon is,the greater the iodine value and methylene blue value of activated carbon become.The micropore volume of activated carbon is negatively correlated with the average pore size.The total pore volume and mesopore volume are positively correlated with the average pore size.By studying the assocoations between the adsorption performance of activated carbon for organic matter and multiple indexes,it is found that,in drinking water treatment,the activated carbon with a smaller S_BET/V value,a larger S_BET value and a larger proportion of mesopore volume had better adsorption performance.The S_BET values and pore volume of activated carbon should also be taken into consideration during carbon selection.The adsorption capacity is mainly affected by BET specific surface area of activated carbon.The test results show that the activated carbon with lower S_BET/V_meso-pores value,larger BET specific surface area and pore diameter should be selected in the treatment of perfluorooctanoic acid.When activated carbon mainly contains micropores,it may not be conducive to the diffusion and adsorption of PFOA in the pore structure of activated carbon.