An equilibrium ion-exchange study on the removal of NH4 + ion from aqueous effluent using clinoptilolite

N. P. Hankins, S. Pliankarom, N. Hilal

Research output: Contribution to journalArticlepeer-review


The present work, of concerns an equilibrium study of naturally occurring clinoptilolite as an ion-exchange medium; the clinoptilolite has been used for the removal of the NH4+ ion from a model aqueous effluent of the Landfill Leachate Assisted Froth Flotation (LLAFF) process. The other principal cations involved were sodium and calcium, and the anion was chloride. A number of experimental tests with constant ionic strength in solution were conducted; these were performed to further validate the feasibility of using clinoptilolite to remove NH4+ ion from the LLAFF effluent. The experimental data obtained were well described by the law of mass action. A binary-component equilibrium study revealed a value for the binary separation factor αNH4+, Na+ of 5.5; this value was relatively unaffected by the total salinity under the experimental conditions. Values for the intra-particle diffusion coefficient and the maximum ion-exchange capacity were also obtained; the latter was affected by total salinity. Results from the binary-component and multi-component studies have revealed the selectivity of clinoptilolite for ammonium over other cations under the compositional conditions of the model LLAFF effluent: The selectivity sequence is K + > NH4+ > Na+ > > Ca2+. The factors that influence the selectivity of clinoptilolite for NH4+ in LLAFF effluent have been ascertained; in particular, it has been found that small quantities of Ca2+ in the effluent have a deleterious effect on both selectivity toward ammonium and ammonium ion-exchange capacity.

Original languageEnglish (US)
Pages (from-to)3639-3663
Number of pages25
JournalSeparation Science and Technology
Issue number15
StatePublished - 2004


  • Ammonium ion removal
  • Aqueous effluent
  • Clinoptilolite
  • Competing cations
  • Ion-exchange equilibrium
  • Mass action
  • Selectivity sequence
  • Separation factor

ASJC Scopus subject areas

  • General Chemistry
  • General Chemical Engineering
  • Process Chemistry and Technology
  • Filtration and Separation


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