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Niobium-based metal oxides are emerging semiconductor materials with barely explored properties for photocatalytic wastewater remediation. Brazil possesses the greatest reserves of niobium worldwide, being a natural resource that is barely exploited. Environmental applications of solar active niobium photocatalysts can provide opportunities in the developing areas of Northeast Brazil, which receives over 22 MJ m2 of natural sunlight irradiation annually. The application of photocatalytic treatment could incentivize water reuse practices in small and mid-sized textile businesses in the region. This work reports the facile synthesis of Nb2O5 catalysts and explores their performance for the treatment of colored azo dye effluents. The high photoactivity of this alternative photocatalyst makes it possible to quickly obtain complete decolorization, in less than 40 min of treatment. The optimal operational conditions are defined as 1.0 g L−1 Nb2O5 loading in slurry, 0.2 M of H2O2, pH 5.0 to treat up to 15 mg L−1 of methyl orange solution. To evaluate reutilization without photocatalytic activity loss, the Nb2O5 was recovered after the experience and reused, showing the same decolorization rate after several cycles. Therefore, Nb2O5 appears to be a promising photocatalytic material with potential applicability in wastewater treatment due to its innocuous character and high stability.

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The most useful method of hybrid material preparations consisted in grafting a desired agent on the surface or by employing the sol-gel process under experimental control procedure by using catalyst or template molecules [1]. The grafting methodology takes into account a post-synthesis of a precursor support by attaching normally a molecule containing the functional moieties to the solid surface whose modification by incorporating organic groups is most commonly carried out by silylation. The majority of members of this class of hybrids available for immobilization with silylating agents, are inorganic polymeric natural or synthetic supports. There are large silanol group populations on their surfaces, which act as convenient points to anchor organic functionalization. In this context silica gel has been one of the most explored surfaces as shown by special investigations performed on analytical applications on preconcentration and retention of heavy cations from solutions [2-4], chemically bonded phases in chromatography [5] and adsorption of biological compounds [6]. However, other inorganic supports have been used as suitable supports for silylation by including metallic oxides, glasses, natural and phyllosilicates [7][8][9][10][11][12][13][14].Framework layers of most natural clay minerals are generated by a combination of octahedral and tetrahedral sheets, normally classified in two hydrous phyllosilicates groups that have the inorganic structural arrangement in 1:1 or 2:1 layers. The first natural layered structure consists of single tetrahedral coordinated [Si 2 O 5 ](OH) 2 layer, which is connected to an edge-shared octahedral M(OH) 6 sheet where M is normally Mg 2+ or Al 3+ [15]. The 2:1 layered material contains one octahedral sandwiched by two tetrahedral layers and in both cases the oxygen atoms are responsible for connecting the sheets. Isomorphous substitutions by cations of comparable radii are possible both in the tetrahedral and in the octahedral clay layers. These features illustrate the great versatility of the kind of compound, in particular this is explored in the present investigation: the synthesis and characterization of inorganic-organic hybrid resulting from reaction of chloropropyl trimethoxysilane of the general formula (CH 3 O) 3 Si(CH 2 ) 3 R, where R=CH 2 CH 2 CH 2 Cl and its subsequent interactions with aliphatic diamines. Experimental Materials ChemicalsThe silylating agent chloropropyl trimethoxysilane (Aldrich) was employed as received. All other reagents such as xylene (Merck) and ethanol (Merck) were used without previous purification. Ethylene, butyl and hexyldiamine (Aldrich) were used without treatment. The vermiculite sample was obtained from União Brasileira de Mineração, a Company from the municipality of Santa Rita (Paraíba, Brazil). Chemical analyses of the sample were performed by AAS using a PerkinElmer 5100 Model instrument with an air-acetylene flame. The samples were digested in a mixture of HF-HCl. Analysis and Calorimetry, Vol. 87 (2007) 3, 771-774 Silyla...