Surface modification of a zeolite and the influence of pH and ionic strength on the desorption of an amine

The adsorption of stearyldimethylbenzylammonium chloride (SDBAC) on the clinoptilolite-heulandite rich tuff in dependence on the applied temperature was studied. The maximal amount of sorbed SDBAC was 123 mmol/kg in the case of thermally treated zeolite tuff (100 °C) and a warm surfactant solution (80 °C). The amount and properties of water adsorbed on the organo-zeolite (OZ) as well as the bonding between the organic species and the zeolite were investigated by DTA, TG, DTG and IR analyses. During gradual heating in an oxidizing atmosphere, the ad- sorbed organic material was oxidized, giving rise to significant exothermic peaks. The adsorption of water vapor decreased with increasing SDBAC loading up to 75 mmol/kg of zeolite, which can be ascribed to an intensification of the hydrophobic characteristics of the surface. With loadings above the 75 mmol/kg, the adsorption of water vapor increased. Desorption of SDBAC from the organo-zeolite under en- vironmentally relevant conditions: distilled water, pH 3 and 10 buffers, as well as aqueous NaCl and CaCl2 solutions, was investigated. OZs with loadings up to their external cation exchange capacity value (75 mmol/kg) were stable under all of the applied conditions.