Equilibrium studies of ammonium exchange with Australian natural zeolites
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- 作者：Graeme J. Millar ; graeme.millar@qut.edu.au" class="auth_mail" title="E-mail the corresponding author ; Abigail Winnett ; Travis Thompson ; Sara J. Couperthwaite
- 关键词：A ; Temkin isotherm parameter (L/mmol or L/mg) ; α ; exponent represented the inherent energy heterogeneity of the adsorbent surface ; ARE ; average relative error ; bT ; Temkin constant related to the heat of adsorption (J/mol) ; C0 ; initial concentration of ammonium ions in solution (mg/L or mmol/L) ; CeorCe ; NH4+ ; equilibrium concentration of ions in solution (mg/L or mmol/L or meq/L) ; E ; energy of adsorption (J/mol) ; EABS ; sum of the absolute errors ; eq ; equivalents ; Ɛ ; adsorption potential (J/mol) ; H
- 刊名：Journal of Water Process Engineering
- 出版年：2016
- 出版时间：February 2016
- 年：2016
- 卷：9
- 期：Complete
- 页码：47-57
- 全文大小：2271 K
文摘
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 in uptake noted when increasing the ammonium concentration from 250 to 1000 mg/L. The optimal fit of the 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.