Alkan Mahir, Demirbaş Ozkan, Doğan Mehmet
University of Balikesir, Faculty of Science and Literature, Department of Chemistry, 10100 Balikesir, Turkey.
J Colloid Interface Sci. 2005 Jan 1;281(1):240-8. doi: 10.1016/j.jcis.2004.08.036.
The present paper deals with the electrokinetic characterization of sepiolite. A series of systematic zeta potential measurements have been carried out to determine the isoelectric point (iep) and potential-determining ions (pdi), and the effect of mono-, di-, and trivalent electrolytes such as NaCl, KCl, LiCl, NaNO(3), NaCH(3)COO, MgCl(2), CaCl(2), BaCl(2), CoCl(2), CuCl(2), Pb(NO(3))(2), Na(2)CO(3), Na(2)SO(4), AlCl(3), FeCl(3), and Na(3)PO(4) on the zeta potential of sepiolite. Zeta potential has been calculated with the aid of Smoluchowski's equation. Sepiolite yields an isoelectric point at pH 6.6. The zeta potential for the sepiolite has ranged from +23.3 mV at pH approximately 2 to -22.4 mV at pH approximately 8 at 20 +/- 2 degrees C in water. The valency of the ions have proven to have a great influence on the electrokinetic behavior of the suspension. Monovalent cations were found to have a weak effect, while di- and trivalent cations made the zeta potential positive. Charge reversal was observed for divalent cations at 1 x 10(-2) M and for trivalent cations at 3 x 10(-4) M. As a result, it can be said that monovalent cations are indifferent ions when di- and trivalent cations are potential-determining ions.
本文论述了海泡石的电动特性。已进行了一系列系统的ζ电位测量，以确定等电点（iep）和电位决定离子（pdi），以及诸如NaCl、KCl、LiCl、NaNO₃、NaCH₃COO、MgCl₂、CaCl₂、BaCl₂、CoCl₂、CuCl₂、Pb(NO₃)₂、Na₂CO₃、Na₂SO₄、AlCl₃、FeCl₃和Na₃PO₄等单价、二价和三价电解质对海泡石ζ电位的影响。ζ电位借助于斯莫鲁霍夫斯基方程进行计算。海泡石在pH 6.6时产生等电点。在20±2℃的水中，海泡石的ζ电位在pH约为2时为+23.3 mV，在pH约为8时为-22.4 mV。已证明离子的价态对悬浮液的电动行为有很大影响。发现单价阳离子的影响较弱，而二价和三价阳离子使ζ电位为正。在1×10⁻² M时观察到二价阳离子的电荷反转，在3×10⁻⁴ M时观察到三价阳离子的电荷反转。因此，可以说当二价和三价阳离子是电位决定离子时，单价阳离子是无关离子。
