Synthesis of nano-silica-coated biochar from thermal conversion of sawdust and its application for Cr removal: kinetic modelling using linear and nonlinear method and modelling using artificial neural network analysis

In this study, sawdust-based nanocomposite was synthesized from sawdust biochar and surface coating of the biochar was done using silica nanoparticles. Removal of hexavalent chromium (Cr(VI)) was studied using the synthesized nanocomposite. The adsorption capacity of the coated biochar was found as 88.2 mg/g for chromium removal. The mechanism of adsorption process was estimated using both adsorption isotherm and kinetic models. The pseudo-second-order kinetic model was capable of showing the possible mechanism behind the adsorption process. Linear and nonlinear pseudo-second-order model was analysed and the result was compared and error analysis of this study with experimental results was done using correlation coefficient (r(2)) and chi-square (chi(2)) test. With higher r(2)and low chi(2)value 0.999 and 0.2947, respectively, the nonlinear form of pseudo-second-order kinetic model was able to describe the adsorption process more successfully than the linear form. Category 1 of the linear form was a good approximation with nonlinear analysis. The ANN model was also developed and the model was validated with the experimental study.