Removal of N-Nitrosamines and Their Precursors by Nanofiltration and Reverse Osmosis Membranes

Abstract

Rejection of selected N -nitrosamines, a group of probable human carcinogens, and their precursors by nanofiltration (NF) and brackish water reverse osmosis (BWRO) membranes was evaluated using a bench-scale cross-flow filtration apparatus. The tested nitrosamines included N -nitrosodimethylamine, N -nitrosomethylethylamine, N -nitrosopyrrolidine, N -nitrosodiethylamine, N -nitrosodi- n -propylamine, and N -nitrosodi- n -butylamine. The target nitrosamine precursors included secondary amines such as dimethylamine, methylethylamine, diethylamine, and dipropylamine. Rejection of nitrosamines varied greatly depending on the tested membranes (9–75% for NF membranes and 54–97% for BWRO membranes) and the molecular weight of nitrosamines. Experimental data obtained with the BWRO membranes matched well with an irreversible thermodynamic model coupled with film theory. The model further suggested that effective diffusion of nitrosamines through the BWRO membranes is responsible for the relatively low rejections o...