Pranjal Saikia

Large-scale synthesis of ceria-based nano-oxides with high CO oxidation activity

We report large-scale synthesis of high surface area nano-oxides of Ce0.8M0.2O2/Al2O3 (M = Tb and Hf) possessing cuboctahedral shape of 3–5 nm size, which exhibit excellent oxygen storage capacity (OSC) and superior CO oxidation activity in comparison to the most advanced ceria–zirconia/alumina catalyst supports employed in the existing three-way-catalytic converters (TWCs).

Highly efficient catalytic reductive degradation of various organic dyes by Au/CeO 2 -TiO 2 nano-hybrid

AbstractHighly improved catalytic reductive degradation of different organic dyes, in the presence of excess NaBH4 over Au/CeO2-TiO2 nano-hybrid as the catalyst is reported in this study. CeO2-TiO2 nanocomposite was prepared by a facile co-precipitation method using ultra-high dilute aqueous solutions. Small amount of Au (only 1 wt%) was loaded onto the nanocomposite material by deposition-precipitation with urea (DPU) method to fabricate the ternary Au/CeO2-TiO2 nano-hybrid. The catalysts were characterized by the representative techniques like XRD, BET surface area, ICP-AES, UV-Vis diffuse reflectance spectroscopy, TEM and XPS. The Au/CeO2-TiO2 nano-hybrid along with NaBH4 exhibited remarkable catalytic activities towards all the probed dyes, namely Methylene Blue, Methyl Orange, Congo Red, Rhodamine B and Malachite Green, with a degradation efficiency of ∼100% in a short reaction time. The degradation reaction followed pseudo-first-order kinetics with respect to the concentration of the dye. Different parameters that affect the rate of the reaction are discussed. A plausible mechanism for methylene blue degradation has also been proposed. Graphical AbstractNanosized Gold particles stabilized on CeO2-TiO2 nanocomposite exhibits tremendous catalytic activity in the reductive degradation of various organic dyes with Au/CeO2-TiO2 nanocatalyst possesses good stability and reusability which reveals the potential for its practical applications.

Enhanced Catalytic Activity of Supported Gold Catalysts for Oxidation of Noxious Environmental Pollutant CO

Noble metal nanomaterials have attracted mounting research attention for applications in diverse fields of catalysis, biology, and nanotechnology. In the present study, we have undertaken a detailed investigation on synthesis, characterization, and catalytic activity studies for CO oxidation by nanogold catalysts supported over CeO2 and CeO2-ZrO2 (1 : 1 mole ratio). The support systems were prepared by modified, simple precipitation technique and the Au supported samples were synthesized using deposition-precipitation with urea method. The physicochemical characterization was performed by XRD, ICP-AES, BET surface area, FT-IR, UV-Vis DRS, Raman Spectroscopy, TEM, and XPS techniques. Au/CeO2 catalyst showed more than 80% CO conversions at 30°C, whereas Au/CeO2-ZrO2 exhibited ~100% CO conversion at that temperature. The catalytic performance of Au catalysts is highly dependent on the nature of the support.

Kinetic and thermodynamic studies for fluoride removal using a novel bio-adsorbent from possotia (Vitex negundo) leaf

BackgroundPossotia leaf powder (PLP), a novel biosorbent obtained from a locally available wild plant with environment friendly and low cost nature, has found to be effective to remove fluoride from fluoride contaminated drinking water.MethodsThe kinetic and thermodynamic parameters for the adsorption have been studied. Its fluorideabsorption efficiency is found to be nearly 75% at natural pH range and is affected by the parameters likecontact time, absorbent dose, solution temperature and initial fluoride concentration.ResultsThe optimum contact time and absorbent dose were found to be 120 min and 3gm/L, respectively.Langmuir, Freundlich and Temkin isotherm are studied through this experimental data and found to be well followed. The adsorption kinetics data were fitted to pseudo first order, pseudo second order, and intraparticle diffusion models and was best fitted for pseudo second order model.ConclusionsThe thermodynamic study points out the efficiency of this bio-adsorbent at low temperatureindicating the physical nature of adsorption with weak adsorbent-adsorbate force of attraction. By studyingenthalpy, entropy and Gibb’s free energy via van’t Hoff plot, it was observed that the adsorption process wasfavorable and exothermic in nature.