Benzalkonium chloride and sulfamethoxazole adsorption onto natural clinoptilolite: effect of time, ionic strength, pH and temperature.

The influence of different physical factors on the adsorption of the cationic surfactant benzalkonium chloride (BC) and the model drug sulfamethoxazole by a purified natural clinoptilolite (NZ) has been studied in order to employ zeolite-surfactant-drug composites as drug deliverer. It has been demonstrated that the adsorption of BC and sulfamethoxazole onto NZ depends of the time, the temperature, the ionic strength and the pH of the aqueous medium. The optimal conditions for the preparation of the zeolite-surfactant and zeolite-surfactant-drug composite materials are established. The results of the composite characterization support the presence of BC and sulfamethoxazole, as well as the structural stability of NZ during the treatments performed. The release experiments in acid medium demonstrate that the adsorption of sulfamethoxazole is reversible. It is also confirmed that the drug release profile corresponds to a diffusion or zero-order mechanism as a function of the compression pressure.

Acid natural clinoptilolite: structural properties against adsorption/separation of n-paraffins.

The employment of an acid natural clinoptilolite (AZH-1) in the adsorption and separation of n-paraffins has been evaluated. Natural clinoptilolite, NZ, was the raw material used to prepare the sodium-exchanged clinoptilolite (AZ) starting from which the AZH-1 sample was obtained by acid treatment. The structural stability of the samples after the applied treatments was demonstrated. The nitrogen adsorption experiments indicated that the acid sample has a homogeneous porous distribution and a considerable increase in the micropore volume with respect to NZ and AZ. The employment of the inverse gas chromatography at infinite dilution (IGCID) allowed studying the adsorption and separation of n-paraffin mixtures on AZH-1. It was also confirmed that the diffusion on AZH-1 took place in an unblocked structure through the A channel of ten members with minimal interactions. The IGCID results demonstrated the capacities of the acid Cuban natural zeolite in the adsorption and separation of n-paraffin mixtures.

Adsolubilization of drugs onto natural clinoptilolite modified by adsorption of cationic surfactants.

The combined adsorption onto purified natural clinoptilolite (NZ) of the cationic surfactant benzalkonium chloride (BC) and the model drugs metronidazole and sulfamethoxazole has been studied in order to design systems for the storage and release of drugs. The equilibrium adsorption of benzyldimethylalkylammonium chloride surfactants with hydrocarbon chain lengths corresponding to 12, 14 and 16 carbon atoms (BC12, BC14 and BC16) onto NZ from aqueous solutions was compared to that of BC. The effect of exchangeable cations on the NZ structure and that of acid-base pre-treatment of NZ on the adsorption capacity of BC was evaluated. It was shown that the nature of the exchangeable cations had little influence on the adsorption of BC onto NZ, and that acid-base treatments of NZ led to a decrease in the amount of surfactant adsorbed. The results indicated that the adsorption of the less polar drug, sulfamethoxazole, was enhanced by the presence of BC12 at the solid-liquid interface, whereas the uptake of metronidazole was independent of the surfactant adsorption.