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Self-cleaning surfaces have excelled in recent years in energy and environmental fields. In particular, in solar energy area, these surfaces are used to avoid soiling accumulation on photovoltaic (PV) modules. So far TiO 2 has been widely used due to its photocatalytic activity and photo-induced superhydrophilicity. However, this oxide has some limitations since it reduces the glass transmittance and it rapidly reestablish the water contact angle in dark environments. In order to circumvent these limitations, composites TiO 2 /SiO 2 have been proposed. For photovoltaic application, besides a good transparency in the wavelength region 300-1800 nm and self-cleaning properties, the coating should also present long durability and adequate adhesion to endure the outdoor conditions. Aiming at developing a coating with these properties, in this work, TiO 2 /SiO 2 composites containing different titanium content have been synthesized and compared with pure TiO 2 films in relation to adhesion, transparency and hydrophilicity. Both films have been deposited over low iron float glass substrates by sol-gel dipcoating technique and different calcination temperatures (400, 500, 600°C) and Si/Ti molar rates (Si 86 Ti 14 , Si 40 Ti 60 ) have been considered. TiO 2 /SiO 2 films showed higher transmittance in visible range compared with pure TiO 2 . TiO 2 /SiO 2 films showed superhydrophilic character before and after ultraviolet irradiation, with water contact angles near to 0°. Furthermore, as predicted, TiO 2 /SiO 2 films could keep the superhydrophilic character in dark environments, in contrast with pure TiO 2 films. Both TiO 2 and TiO 2 /SiO 2 films exhibited good adherence and it is shown that higher calcination temperatures and higher titanium content enhance such property. All films presented abrasion resistant property in contact with sponge and detergent. It has been demonstrated that high transmittance, self-cleaning and adherent composite has been obtained by a simple sol-gel route presenting good potential to be applied on photovoltaics systems.

SUMMARYZeolites are hydrated crystalline aluminosilicate minerals of natural occurrence, structured in rigid third dimension net that can be used as slow release plant-nutrient source. The main objective of this study was to evaluate the effects of plant growth substrate under zeolite application, enriched with N, P and K, on dry matter yield and on nutrient contents in consecutive crops of lettuce, tomato, rice, and andropogon grass. The experiment was carried out in a greenhouse, with 3 kg pots with an inert substrate, evaluated in a randomized block design with three replications. Treatments consisted of four types of enrichment of concentrated natural zeolite: concentrated zeolite (Z) only, zeolite + KNO 3 (ZNK), zeolite + K 2 HPO 4 (ZPK) and zeolite + H 3 PO 4 + apatite (ZP), and a control grown in substrate fertilized with a zeolite-free nutrient solution. Four levels of enriched zeolite were tested: 20, 40, 80, and 160 g/pot. Four successive crops were grown on the same substrate in each pot: lettuce, tomato, rice, and andropogon grass. Results indicated that N, P and K enriched zeolite was an adequate slow-release nutrient source for plants. The total dry matter production of above-ground biomass of four successive crops followed a descending order: ZP > ZPK > ZNK > Z.Index terms: stilbite, Lactuca sativa, Lycopersicum esculentum, Oryza sativa, Andropogon gayanus, slow-release fertilizer, growth substrate.(

This report describes the characterization of a sedimentary occurrence from the Parnaíba Basin, Brazil, containing the zeolite stilbite intertwined with smectitic clay mineral. The head samples from different sites present a wide content range of the zeolitic phase -15% to 50%. The use of simple separation techniques -conventional gravitic treatmentsyields concentrates containing about 67% of the zeolitic component. Assays with the amendments of these concentrates with plant nutrients yield release rates matching those reported for similar commercial products.

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