Zeolite 4A (LTA) has been successfully synthesized by a hydrothermal method, where kaolin was used as silica and alumina source. The synthesized zeolite was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), laser granulometry, and FTIR spectroscopy. XRD data from the Rietveld refinement method confirmed only one crystallographic phase. Zeolite A morphology was observed by SEM analysis, and it showed well-defined crystals with slightly different sizes but with the same cubic shape. Particle size distribution of the crystals was confirmed by laser granulometry, whereas FTIR spectroscopy revealed significant structural differences between the starting material and the final zeolite product used as water softener.

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Hierarchical silica porous materials have been successfully synthesized using polystyrene nanospheres as macropore template, triblock copolymer Pluronic F127 as mesopore template, tetramethyl orthosilicate as silica source and ethanol as cosurfactant. The obtained materials were characterized by XRD, TG-DTA, N 2 adsorption, SEM, TEM and AFM. These materials consist of a system of macropores with diameters of ca. 300 nm whose walls are filled with mesoporous material with average pore diameter 10 nm. The materials are also integrated with non-crystalline micropores. The XRD pattern indicates one sample with structure Fm 3m, which consists of the mesopores organized in a face-centred cubic arrangement. The hierarchical porous material created after template extraction by solvent washing exhibited a BET surface area of 277 m 2 g À1 . Following calcination the material has a BET surface area of 469 m 2 g À1 . Such properties give these materials potential for a wide range of applications in which high surface area combined with a well-defined system of pores at different length scales are required, such as adsorption, catalysis and enzyme immobilization.

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Parabens are widely used as preservatives in food, pharmaceutical, and cosmetic products. These compounds are known for their estrogen agonist activity. This research investigates the synthesis of micro- and mesoporous silica from coal fly ash at different pH values (13, 11, 9, and 7) as well as its use as an adsorbent for the removal of parabens. The materials were characterized, and X-ray fluorescence (XRF) analysis revealed that the fly ash acid treatment reduced the presence of aluminum, iron, and calcium oxides and also that silica synthesized at lower pH values (7 and 9) showed a higher SiO2 content. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses revealed microporous silica formation for silica synthesized at pH 13 and mesoporous silica at pH 7, 9, and 11. Adsorption tests were performed with materials, and FA-AT7 showed a higher adsorption capacity. The effect of factors (A) adsorbent mass, (B) initial paraben concentration, and (C) agitation rate on the adsorption process was studied for the FA-AT7 adsorbent using a factorial experimental design. Standardized Pareto charts revealed a negative effect of factor A, positive effect of factor B, and negative interaction effects of factors A–B for all studied parabens. Isotherms and multicomponent kinetic studies were performed. A linear type-III isotherm was obtained, and adsorption equilibrium was reached at approximately 10 min.