Succinic acid-assisted modification of a natural zeolite and preparation of its porous pellet for enhanced removal of ammonium in wastewater via fixed-bed continuous flow column

Abstract

Inspired by the development of adsorption techniques, an adsorbent for ammonium (NH4+-N) removal, featuring high selectivity towards NH4+-N, high adsorption capacity, simplicity of use, low cost and environmental friendliness, have attracted great attention in recent years. During this work, a natural zeolite with a lower nSi/nAl ratio of 4.2 was selected as the modified substrate. Various modification agents including NaOH, succinic acid (SA) and NaCl were performed to modify the zeolites successively. Due to succinic acid-assisted modification, plenty of carboxylate groups were distributed on the surface of zeolite as active adsorption sites. The modified zeolite (CMZ) shows a significant NH4+-N adsorption capacity which is much higher (10-fold) than that of natural zeolites. Moreover, CMZ also shows high selectivity for NH4+-N among several cations including Na+, Ca2+ and Mg2+. The NH4+-N adsorption kinetics and isotherms of CMZ fit the pseudo-first-order and Langmuir model, confirming a chemical monolayer adsorption process. After ten regeneration times, CMZ maintained the high NH4+-N adsorption capacity of around 14.55 mg g−1 showing outstanding stability and reusability when reused for water treatment. In addition, a modified porous zeolite pellet (MPZP) was further prepared. MPZP holds a relatively lower wear rate of 0.1% at the continuous flow rate of 50 BV h−1, suggesting high flushing resistance and long service life.