Influence of Organic Cations Sorption on the Point of Zero Charge of Natural Zeolite

Abstract

In this paper, the results of the surface modification of natural zeolite with different amounts (2, 5 and 10 mmol M(+)/100 g) of octadecyldimethylbenzyl ammonium ions (ODMBA) are presented. The obtained organozeohtes were denoted as OZ-2, OZ-5 and OZ-10. The degree of ion exchange was followed by determination of amounts of inorganic cations released from zeolite. Results confirmed that reaction between ODMBA and starting zeolite has occurred via ion exchange mechanism. The obtained value for point of zero charge, pH(pzc), of natural zeolite was 6.8 +/- 0.1, while for OZ-2, OZ-5 and OZ-10 pH(pzc) was 7.0 +/- 0.1. Below the pH(pzc), the surfaces of materials are positive while at pH values higher than pH(pzc) their surfaces are negative. Compared to the pHpzc of natural zeolite, no significant differences in pH(pzc) was observed for all three organozeolites indicating that obtained products have similar functional groups with similar acid and basic characteristics as starting zeolite. The pH(pzc) was not dependent on the amount of ODMBA ions at the zeolitic surface and the value of pH(pzc) for all investigated sorbents is the same for all three electrolyte concentrations indicating that the pH(pzc) of each material is independent of the ionic strength of KNO(3).