title: Extra-framework cation release from heulandite-type rich tuffs on exchange with NH(4)(+).
abstract: The outgoing cations of Greek heulandite-rich tuff samples (heulandite type-III, 91wt.%, mica 4wt.%, feldspar 5wt. %, CEC 2.22meq/g) were analysed upon exchange with ammonium acetate using atomic absorption spectrometry (AAS). The kinetic curves of each cation were investigated over a total time of contact of 720h with sampling at frequent intervals. The materials were examined by powder X-ray diffraction, SEM-EDS, and AAS. The sorption ability was measured using the ammonium acetate saturation method. It was found that Ca(2+) presents an unexpected extra-framework release and a surprisingly high degree of exchange (90%). The exchange of Mg (57%) is also worthy of note whereas the behavior of K(+) showed an expected rapid initial release. The behavior of Na(+) must be similar. However, its lower concentration in the zeolitic material minimizes its overall significance somewhat. On the other hand, Ca(2+) and Mg(2+) release is kinetically much slower, compared to that of alkali metal ions, and this phenomenon indicates that different exchange energies are needed till final equilibrium.
authors.affiliation: School of Geology, Aristotle University, Thessaloniki, Greece. kantira@geo.auth.gr
authors.forename: N
authors.initials: N
authors.lastname: Kantiranis
authors.forename: K
authors.initials: K
authors.lastname: Sikalidis
authors.forename: A
authors.initials: A
authors.lastname: Godelitsas
authors.forename: C
authors.initials: C
authors.lastname: Squires
authors.forename: G
authors.initials: G
authors.lastname: Papastergios
authors.forename: A
authors.initials: A
authors.lastname: Filippidis
mesh_terms: D000085:Acetates / Q000737:chemistry*; D002118:Calcium / Q000737:chemistry*; D002412:Cations / Q000737:chemistry*; D007700:Kinetics; D008855:Microscopy, Electron, Scanning; D012964:Sodium / Q000737:chemistry*; D013054:Spectrophotometry, Atomic; D013997:Time Factors; D018707:Volcanic Eruptions / Q000032:analysis*; D014961:X-Ray Diffraction; D017641:Zeolites / Q000737:chemistry*
chemical_list: D000085:Acetates; D002412:Cations; D017641:Zeolites; D012964:Sodium; C018824:ammonium acetate; D002118:Calcium