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In the current research, biodiesel production was investigated in the presence of solid catalysts of K 2 CO 3 /Al 2 O 3 by transesterification of rapeseed oil. The specifications of produced fatty acid methyl esters like viscosity and flash point were studied, and it was noted that they complied with the requirements of ASTM D6751. In addition, the kinetic and thermodynamic parameters were explored considering the temperature changes between 318.15 and 348.15 K. Mass transfer resistance (external diffusion or internal diffusion) over the catalyst was neglected with regard to theWeisz-Prater criterion and Mears criterion. The kinetic models containing Eley-Rideal, Langmuir-Hinshelwood, pseudo-first-order, pseudo-second-order, and -order models were investigated. Corrected Akaike information criterion was utilized to find the best model fitted with the experimental data. The greatest illustration for the K 2 CO 3 /Al 2 O 3 -catalyzed reaction was the nonlinear model with an order of = 1.287 and the activation energy of 12.12 kJ/mol. Using transition state theory (Eyring-Polanyi equation), the activation Gibbs free energy, activation enthalpy, and activation entropy were calculated at different temperatures. The equilibrium thermodynamic properties depicted that this process is endothermic and spontaneous toward biodiesel production and tends to be irreversible. K E Y W O R D Salumina, heterogeneous catalyst, kinetics, thermodynamic, transesterification 472

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In this study, novel chitosan-g-itaconic acid/bentonite (CTS-g-IA/BT) and chitosan/bentonite (CTS/BT) nanocomposites were synthesized for adsorption of methylene blue (MB) from aqueous solution. The process was pH-sensitive and maximum sorption was obtained at pH 6 (CTS-g-IA/BT) and 7 (CTS/BT) in 76 h agitation time using 0.03 g of nanocomposites for 50 mL of MB solution. The results showed that in pH less than 6, the adsorption capacity of CTS-g-IA/BT nanocomposite due to the existence of IA monomer is less than that of CTS/BT nanocomposite. The Fourier transform infrared spectroscopy (FTIR) spectrum of CTS-g-IA/BT revealed that both itaconic acid and BT present in the nanocomposite structure, and also the -OH groups of BT, -NH and -OH of CTS participated in nanocomposite formation. According to the FTIR results, a schematic diagram of the nanocomposite synthesis was presented. The kinetic results indicated that the adsorption of MB fitted well with the pseudo-second-order kinetic model. The equilibrium data followed Langmuir isotherm with the maximum adsorption capacity of 500 and 181.818 mg/g for CTS-g-IA/BT and CTS/BT nanocomposites, respectively. The negative values of Gibbs free energy change (ΔG) and the positive values of ΔH confirmed that the adsorption process is spontaneous and endothermic. The positive values of ΔS suggested the randomness of adsorption at interface.