N and P removal from wastewater using rice husk ash-derived silica-based Fe-ZSM-5 zeolite

Abstract

N and P are essential elements for crop-based food production. With increasing ammonia and phosphate fertilizers used in agricultural land, water pollution in nearby waterbodies is also increasing from respective runoffs. In this study, ZSM-5 (Zeolite Socony Mobil-5), zeolite having Si/Al ratio of 22, with and without iron-incorporated was hydrothermally synthesized using extracted silica by alkali-acid treatment from rice husk ash. The synthesized zeolites were characterized using XRD, SEM, EDS, N2-sorption, XPS and STEM. Batchwise sorption studies of NH4+-N and PO43--P from synthetic solutions were carried out. Enhanced N and P adsorption capacities were found for Fe-ZSM-5 zeolites. Notably, a 3-fold better P-sorption ability was found for Fe-ZSM-5 compared to Na-ZSM-5. A regeneration study using 0.5 M NaCl solution was carried out and Fe-ZSM-5 zeolite retains 97% and 88% of N and P-removal ability. The simple synthesis step, utilization of waste rice husk, and excellent N and P removal capabilities suggest that the synthesized Fe-ZSM-5 zeolite is an excellent choice for sustainable adsorbent for water pollution control.