Levulinic Acid Production from Waste Corncob Biomass Using an Environmentally Benign WO3-Grafted ZnCo2O4@CeO2 Bifunctional Heterogeneous Catalyst.

Herein, a novel and environmentally benign solid catalyst was fabricated by grafting WO3 active species onto the ZnCo2O4@CeO2 support for efficient levulinic acid production from corncob waste biomass. The morphological, compositional, and textural properties of the designed catalyst were investigated using different characterization techniques to identify suitable catalyst formulation with enhanced catalytic activity and stability. The results demonstrated that WO3 active species were successfully loaded with uniform distribution onto the support to develop a robust catalyst with both acidic and basic sites. The experimental investigation showed that among the catalysts, WO3(10 wt %)/ZnCo2O4@CeO2 exhibited the best catalytic activity, providing a maximum levulinic acid yield of 78.49% at the optimal conditions of 6 wt % catalyst dosage, reaction temperature of 180 °C, and reaction time of 200 min. The presence of an optimum number of both acid and base active sites on the catalyst surface could lead to the highest catalytic activity of the synthesized catalyst. Finally, the reusability investigation indicated that the synthesized catalyst possessed sufficient recyclability of up to four times for the levulinic acid production from the selected biomass with negligible drop in the catalytic activity.

Synthesis of chitosan composite of metal-organic framework for the adsorption of dyes; kinetic and thermodynamic approach.

The iron metal-organic framework composite with chitosan (CS/MOF-235) was synthesized using a solvothermal method and its synthesis was confirmed by surface area, PZC, XRD, FESEM, XPS, TGA, TEM, EDX mapping and EDX analysis. The chitosan composite of the iron metal-organic framework (CS/MOF-235), MOF-235 and chitosan were used for the removal of methylene blue (MB) and methyl orange (MO) from aqueous solutions. The maximum adsorption capacities were found to be 2857-2326 mg/g for CS/MOF-235, 357 - 236 mg/g for MOF-235 and 209-171 mg/g for chitosan (CS) which reveal that the adsorption capacity of CS/MOF-235 is almost 8 and 14 times greater than MOF-235 and chitosan respectively. The adsorption selectivity of the (CS/MOF-235) towards the dye was in the order MO > MB. Moreover, hydrogen bonding, pi-pi bonding, pore-filling, electrostatic interactions and chemisorption were proposed as possible mechanisms for the removal of dyes onto CS/MOF-235. The intraparticle diffusion and Richenberg models confirmed that the adsorption process was jointly controlled by the pore and film diffusion. The negative values of the isosteric heat of adsorption (ΔH¯) fall with surface coverage indicating that a lesser amount of heat is required for the greater uptake of dyes.