Degradation of polyamide nanofiltration membranes by free chlorine and halide ions: Kinetics, mechanisms, and implications.

The kinetics of polyamide membrane degradation by free chlorine and halide ions (Br and Cl) were innovatively evaluated based on physicochemical properties and filtration performance, using water/solute permeability coefficient in addition to bromide incorporation as important indicators. The reaction rate constants for the reduced water and HBO permeability coefficient were 1-2 orders of magnitude higher at 0-1 h than 1-10 h. N-bromination and bromination-promoted hydrolysis are dominant degradation mechanisms at 0-1 h (reflected by the breakage of hydrogen bond, the increased Ca binding content, and the increased charge density), and ring-bromination further occurs at 1-10 h (reflected by the disappearance or weakening of aromatic amide band and the nearly constant hydrogen bond).

Removal of antibiotics and estrogens by nanofiltration and reverse osmosis membranes.

The separation behavior of a variety of emerging contaminants, including nine antibiotics and six estrogens commonly reported in natural environment, by four commercial nanofiltration and reverse osmosis (NF/RO) membranes at various water conditions (pH, concentration) was investigated. The contaminant rejection at pH 6.0 followed a decreasing trend of XLE (94%-100%) ≈ NF90 (88%-100%) ＞ NF270 (25%-85%) ＞ DL (16%-75%).