Natural zeolite/PVC beads for the removal of ammonium ions from water: Wettability, particle size, strength, hydrophilicity and equilibrium behaviour

Abstract

This study developed an improved method for removing ammonium ions from water using natural zeolite/PVC beads. Research gaps relating to the impact of particle size, wettability, robustness, hydrophobicity and equilibrium behaviour were addressed. It was surmised that manipulation of the formation of natural zeolite/PVC beads will improve the performance of these composite materials. First it was noted that water-saturated sorbents exhibited higher ammonium ion exchange rates than dried beads. An air nozzle was proposed as a potential solution for controlling particle size. To control bead particle size, a range of airflow rates passed through an optimised 3D printed nozzle design. Bead diameters from below 0.5 mm up to 2 mm were obtained, with higher airflow rates promoting the growth of smaller beads. 0.5–1 mm beads also were characterised by lower attrition rates compared to larger ≈ 2.7 mm particles (54 to 57 % change) and had almost the same kinetics exchange rate as their regular unbound zeolite powder counterparts (0.4 to 13.5 % difference). The equilibrium data was in the shape of a linear isotherm, which suggested that the ammonium ions were equally dispersed throughout the sorbent and the aqueous solution. Finally, the use of amphipathic copolymer (Pluronic F127) improved the exchange kinetics of the dry beads (42 to 160 % change) but also weakened the structural integrity of the zeolite composites (284 to 647 % change depending on the analysed composites).