Equilibrium studies of ammonium exchange with Australian natural zeolites

Millar, Graeme J., Winnett, Abigail, Thompson, Travis, & Couperthwaite, Sara J (2016) Equilibrium studies of ammonium exchange with Australian natural zeolites. Journal of Water Process Engineering, 9, pp. 47-57.

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Abstract

This paper is concerned with the study of the equilibrium exchange of ammonium ions with two natural zeolite samples sourced in Australia from Castle Mountain Zeolites and Zeolite Australia. A range of sorption models including Langmuir Vageler, Competitive Langmuir, Freundlich, Temkin, Dubinin Astakhov and Brouers–Sotolongo were applied in order to gain an insight as to the exchange process. In contrast to most previous studies, non-linear regression was used in all instances to determine the best fit of the experimental data. Castle Mountain natural zeolite was found to exhibit higher ammonium capacity than Zeolite Australia material when in the freshly received state, and this behavior was related to the greater amount of sodium ions present relative to calcium ions on the zeolite exchange sites. The zeolite capacity for ammonium ions was also found to be dependent on the solution normality, with 35–60% increase inuptake noted when increasing the ammonium concentration from 250 to 1000 mg/L. The optimal fit ofthe equilibrium data was achieved by the Freundlich expression as confirmed by use of Akaikes Information Criteria. It was emphasized that the bottle-point method chosen influenced the isotherm profile in several ways, and could lead to misleading interpretation of experiments, especially if the constant zeolite mass approach was followed. Pre-treatment of natural zeolite with acid and subsequently sodium hydroxide promoted the uptake of ammonium species by at least 90%. This paper highlighted the factors which should be taken into account when investigating ammonium ion exchange with natural zeolites.

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ID Code: 91680
Item Type: Journal Article
Refereed: Yes
Keywords: natural zeolite, isotherm, ammonium, equilibrium, bottle-point
DOI: 10.1016/j.jwpe.2015.11.008
ISSN: 2214-7144
Subjects: Australian and New Zealand Standard Research Classification > ENGINEERING (090000) > CHEMICAL ENGINEERING (090400) > Water Treatment Processes (090410)
Divisions: Current > Schools > School of Chemistry, Physics & Mechanical Engineering
Current > Institutes > Institute for Future Environments
Current > QUT Faculties and Divisions > Science & Engineering Faculty
Copyright Owner: © 2015 Elsevier Ltd
Deposited On: 25 Jan 2016 04:10
Last Modified: 27 Jan 2016 03:47

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