Combination of Na-modified zeolite and anion exchange resin for advanced treatment of a high ammonia–nitrogen content municipal effluent

Abstract

In this study, the exchange equilibrium and kinetic experiments of ammonia–nitrogen on the Na-form zeolite were conducted. The results indicated that the presence of humic acid have a negative effect on the equilibrium exchange capacity but have limited influence on the equilibrium time except shorten the sole intra-particle diffusion control time. The exchange equilibrium data could be well fitted by Freundlich model in the absence of humic acid but Langmuir model in the presence of humic acid. While the exchange kinetic data could be well described by pseudo-second-order kinetic model in both situations. An anion exchange resin exhibited high removal efficiency to humic acid and dissolved organic matter through kinetic results and fluorescence excitation-emission matrix (EEM) spectroscopy results. The use of the anion exchange resin prior to the Na-form zeolite improved the ammonia–nitrogen removal efficiency from 78% to 95% and increased the treatment volume of the Na-form zeolite from 51 BV (bed volume) to 76 BV. Both the resin and the Na-form zeolite could be successfully regenerated by the combination of alkaline and sodium chloride. Complete elution of ammonia–nitrogen was achieved when the mass percentage of sodium chloride and alkaline was 10% and 0.6% respectively.