Search

Mixed anatase–rutile and pure anatase mesoporous TiO2 photocatalysts have been synthesized for the first time via a modified greener sol–gel approach at low temperature without the involvement of any acid or base. Non-ionic surfactant Brij-35 was used as a sacrificial agent for the synthesis. The effect of additives like dextran and silica nanoparticles on different physical parameters of catalysts was also studied. The chemical, electronic and physical properties of the as-synthesized catalysts were studied by FTIR, TGA, PXRD, DRS, SEM, EDAX, TEM, and BET techniques and the photocatalytic potentiality was also tested by photocatalytic degradation of methyl orange (MO) azo dye. The photocatalytic activity of the synthesized catalysts was found to be in the order TiO2/Brij-35/Si-NPs > TiO2/Brij-35 > TiO2/Brij-35/dextran. The higher photocatalytic activity of TiO2/Brij-35/Si-NPs provided direct evidence of the surface area-dependent photocatalytic activity. As a comparative study, the catalysts were also tested for other environmentally harmful dyes like Rhodamine B and Congo Red and were proven to be highly efficient catalysts for the photodegradation of these dyes.

A novel catalyst Ag/Triton X-705/SiNPs is synthesized by a modified sol–gel method without the use of an acid or a base as a catalyst for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in the presence of 0.1 M NaBH4 in aqueous media. The reduction time was found to be 30–35 seconds when the concentration of 4-NP was varied from 0.001 M to 0.009 M while maintaining a constant amount of the Ag/Triton X-705/SiNP catalyst at 0.006 g. Fe3O4NPs, dextran, and trimethylbenzene (TMB) were added separately to Ag/Triton X-705 hydrogels to modify their morphology and catalytic activities against the reduction of 4-NP to 4-AP. The as-synthesized monoliths were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), powder X-ray diffraction (PXRD) analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Brunauer–Emmett–Teller (BET) surface area analysis. The pseudo first order rate constant (k), energy of activation (Ea), and thermodynamic parameters viz. activation enthalpy (ΔH‡), activation Gibbs free energy (ΔG‡) and entropy of activation (ΔS‡) have also been determined. The turnover frequency (TOF) of the Ag/Triton X-705/SiNP catalyst was 9.66 × 1020 molecules per s and the catalyst was used up to nine cycles successfully with greater efficiency, making it a potential and leading candidate for the industrial conversion of 4-NP to 4-AP. We claimed that the Ag/Triton X-705/SiNP catalyst took almost minimum time for the reduction of 4-NP to 4-AP.

Composite gels of Ba/alginate(Alg)/carboxymethyl cellulose (CMC) were prepared by a dissipative convective process. Graphene oxide (GO) and Au nanoparticle (Au-NPs) were successfully encapsulated into the polysaccharide matrix. The resulting composite gels were characterized by Fourier transform infrared (FTIR) spectrometry, Raman spectroscopy, powder X-ray diffraction (PXRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The rheological and mechanical behaviors of the composite gels were also investigated. The composite gels were tested for the reduction of o-nitroaniline (o-NA), to 1,2-benzenediamine in the presence of NaBH4. Ba/Alg/CMC/GO/Au composite gels reduce o-NA within 3 min with a rate constant of 0.45 s−1 and the composite can be recycled for up to 4 successive cycles.