A facile method to modify activated carbon fibers for drinking water purification

The safety of drinking water plays a vital role in human health. Activated carbon fibers (ACF) have been widely used in the field of water purification. However, current filter elements of water purifier made by ACF have an unqualified pH change which fails to meet sanitary soak standard and low COD removal rate. Considering the perspective of converting surface functional groups and adjusting composition of ACF, a facile method via flushing followed by calcination in humid nitrogen atmosphere was used to modify ACF. The effects of some parameters including washing method, type of flushing water, flushing time, water content of calcined sample, calcination temperature and time were investigated, and possible mechanism of reducing pH change of soaking solution was clarified by characterizing the ACF samples before and after flushing and calcinations using Boehm titration, XPS, TG/DTA-MS, BET, FTIR and IC analysis. 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. 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 calcination process. The pH changes of all the modified ACF (M-ACF) and filter elements of water purifier made by the M-ACF under optimized modification conditions met sanitary soak standard and COD removal rate obviously increased. This economical and practical modification method for solving unqualified soaking pH change and low COD removal problems of ACF filter elements of water purifier has great significance in the field of drinking water purification.