Zeta potential of unexpanded and expanded perlite samples in various electrolyte media

In this study, electrokinetic properties of unexpanded (UEP) and expanded (EP) perlite samples have been extensively investigated as a function of concentration of various electrolytes such as NaCl, KCl, LiCl, NaNO3, NaCH3COO, MgCl2, CaCl2, BaCl2, NaCO3, Na2SO4, AlCl3, FeCl3, CoCl2, CuCl2, and Pb(NO3)(2). The zeta potential measurements have been performed to determine the isoelectric point (iep) and potential determining ions (pdi). Although pH strongly altered the zeta potential of perlite samples, perlite samples do not yield any isoelectric point in the pH ranges of 2-11. Both of the perlite samples remain negatively charged in the pH ranges studied. The expanded perlite has a more negatively charged surface than the unexpanded perlite. Monovalent cations or anions and divalent anions are indifferent electrolytes for both perlite samples whereas MgCl2,CaCl2, BaCl2, CoCl2, CuCl2, Pb(NO3)(2), AlCl3 and FeCl3 change the interface charge from negative to positive for the expanded perlite but the potential determining ions for unexpanded perlite are CaCl2, BaCl2, AICl(3), and FeCl3 metal ions. (c) 2005 Elsevier Inc. All rights reserved.