Nitrate removal from aqueous solutions by γ-Al 2 O 3 ultrafiltration membranes

In the framework of understanding the transport mechanism that governs the filtration of NO solution through a -Al O membrane with a nominal pore size of 5 nm at low ultrafiltration, a series of various types of nitrate solutions and operating conditions were investigated. The effect of filtration parameters such as pH, applied pressure and NO concentration on the selectivity and permeability of the membrane were studied using binary solutions (KNO , NaNO , Ca(NO ) and Mg(NO ) ) and ternary solutions ((NaNO + KNO ), (NaNO + Ca(NO ) ) and (Mg(NO ) + Ca(NO ) ). The experimental filtration results showed that high NO rejection was observed when pH was close to the point of zero charge of the membrane for both binary and ternary solutions. NO rejection increased with an increase of applied pressure. The rejection gradually decreased when the initial NO concentration increased. It appeared that the valency and hydrated radius of associated cation had a dramatic effect on NO rejection, with the divalent cations being more rejected than monovalent cations. In order to get to natural water complexity, three different samples of mineral water doped with NO from two different sources were studied at optimized operating conditions (25 ppm of NO and 6 bar). Experimental results demonstrated that NO rejection strongly depended upon the total mineralization and the presence of divalent anions in solution. In addition, the obtained results showed the potential use of -Al O ultrafiltration membrane for denitrificatoin of contaminated water especially in Moroccan agricultural areas.