Experimental and Numerical modeling on dye adsorption using pyrolyzed mesoporous biochar in Batch and fixed-bed column reactor: Isotherm, Thermodynamics, Mass transfer, Kinetic analysis

Adsorbents derived from agro-waste can be a feasible substitute for the synthesis of the activated biochar for the removal of pollutants from their aqueous solution. ZnCl2 was used to activate the pyrolyzed biochar, derived from sugarcane bagasse. Physical characterizations of synthesized activated pyrolyzed biochar were analyzed by XRD, FTIR, and SEM. From the BET analysis, the surface area of activated pyrolyzed biochar was determined as 51.733 m(2)/g. Investigations on the adsorption of Malachite Green (MG) dye using activated biochar was studied in batch and fixed-bed system. Isotherm study suggested that the Freundlich isotherm model (R-2=0.9955) provided the best fit to the equilibrium adsorption and the biosorption capacity obtained as 90.1mg/g at 30 degrees C. Experimental data showed well in accordance with the pseudo-second-order kinetic model. The thermodynamic study indicated the spontaneous and exothermic nature of reactions involved. Boyd's film diffusion model was used with the kinetic data of the Batch adsorption experiment to evaluate the diffusion mechanism and ratelimiting step. The derived value of the average effective diffusion coefficient (D-e) was 0.014 x 10(-7) m(2)/s. The Yoon-Nelson and Thomas model ware well fitted with the experimental data obtained from column adsorption study. The dispersion coefficient and mean pore velocity for adsorbent columns were estimated using the breakthrough curves at various experimental conditions. Adsorption Kinetic parameters for MG dye were estimated using the solute transport model by combining convective flow and hydrodynamic dispersion with a two-site adsorption model and coupled with inverse modeling of breakthrough curves.