Effect and mechanism of modification treatment on ammonium and phosphate removal by ferric-modified zeolite

ABSTRACT

In this study, the reason for the decline of ammonium sorption capacity by zeolite after ferric modification and the effect of modification treatment on ammonium and phosphate removal by ferric-modified zeolite were studied. Modification treatment media (Na salt and HCl) and Na concentration (0.1 and 0.9 mol/L) have been investigated. Zeolites have been characterized by SEM, XRD, BET and XRF; meanwhile, CEC and pHpzc have been also determined. Equilibrium batch sorption for ammonium and phosphate individually and kinetics batch sorption for ammonium were conducted. The results showed a decline in sorption capacity or diffusion coefficients for ammonium but an increase for phosphate after ferric modification. The decrease of surface negative charge was the main contributor for the former, but iron loading did not well account for the latter. The performance of 0.1 mol/L Na modification treatment was better than other treatments for ammonium sorption and equal to HCl modification treatment for phosphate sorption, and the enhancement extent increased for ammonium but declined for phosphate when Na concentration increased. The advantage of Na modification treatment for ammonium was due to the enhancement of textural properties and high exchange rate with ammonium.

GRAPHICAL ABSTRACT

KEYWORDS:

• Ferric-modified zeolite
• ammonium
• phosphate
• modification treatment

Acknowledgements

The authors acknowledge the support from adjunct professor Pan Huanying of Experimental Teaching Model Center of Ground Water and Environment.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the National Undergraduate Innovation Experiment Project [number 201510491043]; China University of Geosciences Open teaching laboratory Project [number SKJ2016001].