Effect of fatty acids on the structure and performance of cellulose acetate nanofiltration membranes in retention of nitroaromatic pesticides

Effects of addition of amphiphilic fatty acids (palmitic, oleic, and linoleic acids) were investigated on morphology and performance of cellulose acetate (CA) nanofiltration membranes. Water contact angle and zeta potential measurements, FTIR-ATR, SEM, AFM, and mechanical tests were applied to characterize the membranes. Performance of the membranes was examined in retention of a series of nitroaromatic pesticides (i.e. nitrophenols as one of the most important pollutants). p-Nitrophenol (PNP), 2,4-dinitrophenol (DNP), 3,5-dinitrosalicylic acid (DNSA), 2-methyl-4,6-dinitrophenol (DNOC), and 4-nitrophenyl phosphate disodium salt hexahydrate (NPP) were selected with different acidity and hydrophobicity as nitroaromatic pesticides. The treated membranes revealed considerably higher pure water flux and permeation compared to CA membrane. Performance of separation was strongly influenced by kind of nitrophenols and solution pH. Rejection of NPP, DNSA, DNP, and DNOC increased by increasing of the solution pH and additives concentration. However, rejection of PNP molecules increased by increment of concentration of additives similar to other nitrophenols, PNP molecules revealed different behavior by alteration in the solution pH. Comparison in efficiency showed that modified membranes upon addition of palmitic acid represent higher rejection of nitrophenols. Performance of the membranes was compared with commercial NF45 membrane proving the superior efficiency of CA modified membranes.

► Nanofiltration cellulose acetate membrane was treated by addition of fatty acids. ► Treated membranes represented structures with thinner top-layer and more porosity. ► Performance of the membranes was investigated in removal of nitrophenols. ► Filtration experiments carried out under different solution pHs. ► Treated membranes revealed higher flux and rejection compared to untreated CA.