Adsorption of CECs in the nanofiltration process

Adsorption is one of the main mechanisms of compounds of emerging concerns (CECs) rejection by a membrane process. CECs could be adsorbed not only by membrane but also by suspended solid during membrane filtration. In this study, the adsorption of five CECs by natural organic matter (NOM) and NF270 was investigated by using 96-h bottle and batch tests at 25°C, respectively. Humic acid (HA), which is the major ingredient of NOM, was added into Milli-Q water as NOM to simulate the natural water. HA added into the solution was found insolubility at pH 7 in this study. Adsorption of CECs by HA was strongly correlated with log K_ow of compound. Adsorption capacity was observed to be maximum with HA followed by NF. The study also found that the removal efficiency of CECs by NF could be affected by NOM present in the water. Micro-pollutants, such as CECs, could be adsorbed by HA and then be removed easily during the membrane filtration. Moderate existence of HA would be contributive for CECs removal, but too much HA would cause fouling phenomenon resulted in a worse removal efficiency.