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Deposition of titanium over a silica support was performed by three methods: precipitation with TiCI, and ammonium hydroxide in aqueous solution; impregnation with titanium(iv) isopropoxide in isopropyl alcohol; grafting with a solution of TiCI, in hexane. Samples were characterized by BET, XPS, zeta potential, DRS, XRD, SEM and EPMA. The method of deposition influences deeply the morphology and dispersion of the coated oxide. With the precipitation method, TiO, is deposited at the external surface of the silica. Impregnation provides the best external superficial dispersion of titania allowing the formation of small crystallites at its surface. The grafting method gives the best internal TiO, dispersion with formation of large crystallites at the external surface of silica. A strong interaction is found between titanium and silicon. This work also draws attention to the many analytical techniques needed to characterize the Ti0,-coated supports.

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Carboxylic acids are an important natural component as a final product or intermediates for syntheses. They are produced in plants, animals and also as products from biotechnological processes. This review presents the use of single hydroxide particles and layered double hydroxides as alternative adsorbents to remove carboxylic acids from liquid media. The proposal to use hydroxide particles is based on its affinity to adsorb or intercalate carboxylic acids. Besides, the change in properties of the adsorbate-sorbate product evinces that this intermediate can be used as a vehicle to transport and release carboxylic acids. Additional examples will also be presented to prove that layered hydroxides are capable of removing non-ionic compounds from wine, milk and tomato. The use of layered compounds to remove active ingredients could reduce the number of separations steps, costs and reduce or eliminate solvents, thus encouraging the design of industrial processes of separation using hydroxides particles.

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