Nitrate removal from water by new polymeric adsorbent modified with amino and quaternary ammonium groups: Batch and column adsorption study

Abstract

A new polymeric adsorbent (NDQ) modified with amino and quaternary ammonium groups was synthesized for the purpose of nitrate removal from water. Sorption kinetic and isotherm experiments were carried out in a series of batch experiments. Batch adsorption isotherms indicated that the maximum monolayer adsorption capacity of NDQ for nitrate was 221.8mg/g which was higher than that of many other adsorbents reported in literature. Both ion-exchange and hydrogen bond played important roles in nitrate removal. The enthalpy change (−12.32 to −9.65kJ/mol) and free energy change (−2.7 to −0.76kJ/mol) indicated an exothermic and spontaneous adsorption process. Moreover batch adsorption kinetic curves indicated that both film and intra-particle diffusion processes were rate-limiting in the nitrate adsorption. It was observed that the adverse effect of co-existing anions on nitrate removal followed the order of ‘SO42− > HCO3– > Cl–’. In order to quantify the influence of operational conditions on the treatment efficiency, a series of fixed bed column experiments were conducted at different bed heights, flow rates and influent concentrations, and the breakthrough curves at various operational conditions were simulated and analyzed using different mathematical models. Finally, the adsorption–desorption assay showed a promising reusability of the NDQ.