Bentonitas modificadas com NiO aplicadas na fotodegradação do corante aniônico vermelho de remazol RB

Abstract

This work aimed to synthesize inorganic/inorganic hybrids based on bentonites modified with nickel oxide (NiO), using different nickel precursor salts, by the coprecipitation method. The synthesized hybrids were characterized by XDR, FTIR, solid state UV-vis, SEM, EDS and FRX showing the formation of the desired hybrids for application in the photodegradation of anionic dyes. In the synthesis of the hybrids, a sodium bentonite with a cation exchange capacity (CTC) of 88 cmol (+) / kg was used, which was reacted by heating and constant stirring with two nickel precursors (nickel nitrate and nickel acetate), the agent precipitant used was ammonium hydroxide and after the co-precipitation process the hybrids obtained were calcined at 500ºC for 3 h and further characterized. The XRD patterns of NiO synthesized without bentonite demonstrated that the non-calcined solids formed Ni(OH)2 and only after the calcination process the formation of NiO was obtained. The results of the XRD patterns of the NiO/bentonite hybrids showed that there was a predominance of the characteristic peaks of montmorillonite in relation to the NiO peaks, due to the overlapping of the montmorillonite peaks, which makes it difficult to identify the peaks related to the NiO phases. The EDS standards and the FRX analysis demonstrated the absence of NiO in the crude bentonite and its presence in both hybrids, with greater incorporation in the hybrid synthesized with nickel acetate, which shows the formation of the desired hybrids. Solid state UV-vis corroborated with FRX and EDS and presented characteristic bands of electronic transitions present in nickel, evidencing the presence of NiO in the hybrids. Subsequently, the synthesized hybrids were applied in the photodegradation of the anionic dye of remazol RB, in which the influence of different parameters on the process efficiency was evaluated, such as photocatalyst mass, medium pH and reaction time. The hybrids applied showed photodegradation potential, degrading approximately 52% of the dye, using pH 3, photocatalyst concentration of 1 g/L and initial dye concentration of 10 mg/L. The hybrid synthesized with nickel acetate as precursor showed higher photodegradation efficiency, tests with markers indicated predominance of indirect photocatalysis in the process and reuse tests showed stability of the photocatalyst in up to three application cycles.