Sorption of chromate by clinoptilolite modified with alkylammonium surfactants

Clinoptilolite from Dyl1gówka (Poland) with an external cation exchange capacity (ECEC)of 16 meq/100 g determined by adsorption of alkylammonium ions was treated with hexadecyltrimethylammonium(C16) and dioctadecyldimethylammonium (2C18) bromides in amounts equivalent to 1.0 and1.5 ECEC. The productswere characterized using IR spectroscopy and C andNdeterminations. The sorptionof chromate on the modified mineral was measured spectrophotometrically as a function of pH, concentrationof Cr(VI) or the proportion of the sorbent to solution. The amount of chromate removed from thesolution continuously decreased with increasing pH in the range 1.3–10. At pH 2.6–3.1, the maximumadsorption of Cr(VI) by the organo-zeolites (103 and 124 mmol/kg) was observed for the samples modifiedusing a 1.5 ECEC surfactant concentration. Considerably lower adsorption values (37 and 46mmol/kg) wereobtained with sorbents prepared using a 1.0 ECEC concentration of the alkylammonium ions.