Improving the biocidal activity of outdoor coating formulations by using zeolite-supported silver nanoparticles.

Zeolite/nanoparticle composites are synthesized and used as additive for waterborne formulations in replacement of traditional isothiazolinone-based biocides. Silver nanoparticles dispersed onto micrometer-sized crystals of A-type zeolite were prepared by thermal treatment or chemical reduction methods applied to the Ag-exchanged zeolite. The antifungal efficiency against Trichoderma sp. of waterborne outdoor coatings containing the supported silver nanoparticles, measured in terms of inhibition halo development, shows similar results to those obtained by using traditional organic biocides, the type, size and size distribution of the nanoparticles being the main factors affecting the biocidal action of the prepared coatings.

Chromium removal by zeolite-rich materials obtained from an exhausted FCC catalyst: Influence of chromium incorporation on the sorbent structure.

A spent FCC catalyst was converted into a zeolitic mixture, and the product obtained was afterward used as trapping material for Cr(III) species frequently found in aqueous solutions. Eventual changes in the sorbent structure produced by Cr incorporation were studied by different characterization techniques such as point of zero charge determinations (PZC), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), and infrared absorption (FTIR). The XRD and FTIR analyses indicated that chromium incorporation produces an amorphization of the material, and PZC measurements show no surface adsorption of charged chromium species. SEM and EDX analyses clearly show that after chromium sorption, the initial microspheroidal catalyst morphology was maintained, and the presence of chromium species was mainly detected in the outer microsphere surface, where the zeolite crystals were hydrothermally grown.

Modified silica matrices for controlled release of cephalexin.

SBA-15 type ordered silicas possessing amino groups attached onto their surfaces were prepared by using two different functionalization methodologies. These matrices were used for the cephalexin adsorption from aqueous solution and further kinetic study of its release into physiological solution. The materials were characterized by nitrogen adsorption/ desorption, scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), X-Ray photoelectron spectrometry (XPS) and thermo analytical methods (TG/DSC). UV-visible spectroscopy at 262 nm was used for quantitative determination of cephalexin present in liquid media. Results reveal that drug adsorption capacities and the corresponding release profiles are dependent on the number of loaded amino groups and their location, which in turn is determined by the functionalization procedure used. It was concluded that amino post-functionalization could enhance long-term cephalexin delivery in comparison with co-functionalization procedure.

Chromium removal from water using LTA zeolites: effect of pH.

The effect of pH changes on the ability of the synthetic zeolite NaA to remove Cr(3+) from water by ion exchange was investigated. The exchange rate was improved by working near neutrality. Despite of the occurrence of simultaneous adsorption, precipitation or cation exchange phenomena, spectroscopic analyses of samples taken at different contact times suggested the presence of an unique chromium environment in the solid phase. The increase in pH observed during the ion exchange favored polymerization-precipitation of chromium species present in solution, which, in turn, improved the metal removal capacity of zeolite NaA above the values expected for a pure cationic exchange reaction.