Modification Of Activated Carbon Fiber For Water Purification

The health and safety of drinking water plays a vital role in human health.Activated carbon fiber(ACF)has been widely used in the field of water purification due to its rich micropores,large specific surface area,large adsorption capacity,and fast adsorption and desorption.However,filter elements of water purifier made by ACF have the problem about pH change during sanitary safety soak which fails to meet Sanitary Standards for Drinking Water Quality,the COD removal rate is low,and the effect of selectively removing micro-trace heavy metals is not ideal.So,it is necessary to modify it by an effective method.In this paper,the ACF was modified via flushing followed by calcination method for the problem that the ACF have an unqualified pH change in the sanitary safety soaking experiment and low COD removal rate.Considering the perspective of converting surface functional groups and adjusting composition of ACF,the effects of washing method,type of flushing water,flushing time,water content of calcined sample,calcination temperature and time were investigated.When deionized water or pure water is used as flushing water,under optimized conditions with flushing time is no less than 2 min,water content of calcined sample is no less than 10%,calcination temperature is 700-1000 °C and calcination time is no less than 2 min,the modified ACF(F-ACF)soaking pH change meets the "Sanitary Standards for Drinking Water Quality"(2001).The possible mechanism of reducing pH change of soaking solution was clarified by characterizing the ACF samples before and after modification using Boehm titration,XPS,TG/DTA-MS,BET,FTIR and IC.The results show that some ions and fire retardants in ACF were effectively removed and surface functional groups were converted from acidic to basic ones by this method.Meanwhile,water in ACF was found to play an important role in promoting the release of gases and facilitating the conversion of functional groups in the process of calcination.The filter elements of water purifier made by the F-ACF also met the requirements,COD removal rate obviously increased and residual chlorine removal also maintains a high level,the result has been put into practical use.The ACF is modified by polydopamine method due to the effect of selective removal of micro-trace heavy metals is not ideal.The effects of stirring time,the concentration of ferric chloride,dopamine and calcium hardness on the adsorption performance of lead ions were studied.Under the optimized conditions of stirring time of 60 min,ferric chloride concentration of 5 mM and dopamine concentration of 0.5 g/L,the modified ACF(P-ACF)can make the lead ions effluent concentration for the initial concentration of lead ionic water of 150 ppb meet the requirements of hygienic standards for drinking water(GB5749-2006).Samples were analyzed by SEM,Zeta potential,XPS,BET and FTIR,the results showed that polydopamine modification did not affect the specific surface area and pore size distribution of ACF,which is beneficial to simultaneously exert the chelation of heavy metal by rich functional groups such as hydroxyl and amino groups in polydopamine and the adsorption of heavy metal on the large specific surface area and abundant micropores of ACF to improve the ability of removal lead ions selectively.