Alkali modified oak waste residues as a cost-effective adsorbent for enhanced removal of cadmium from water: Isotherm, kinetic, thermodynamic and artificial neural network modeling

[Display omitted] •Adsorbent dosage and initial Cd2+ concentrations have direct and indirect relationships with Cd2+ removal, respectively.•pH of solution and temperature have the highest and lowest influence on removal of Cd2+ from solution.•The Cd2+ removal efficiency onto the AOW surfaces increases enhancement of solution pH, significantly.•The AOW has higher ability than ROW to remove Cd2+ from aqueous solution, in all applied adsorbent dosages. Heavy metals are kind of toxic substances which are abundant in all municipal, agricultural, industrial and treated wastewaters. In this research, a comparative study was carried out for adsorptive removal of Cd2+ from aqueous solution using raw oak waste and NaOH-activated oak waste at different experimental conditions namely, pH of solution (2–8), contact time (5–240min), adsorbent dosages (0.1–10g/L) and initial Cd2+ concentrations (25–100mg/L). In addition, the experimental data of Cd2+ adsorption were fitted with different isotherm and kinetic models to determine the most appropriate model. Artificial neural network (ANN) model was also used to find the effect of each individual parameter on Cd2+ adsorptive removal. Based on the results of batch experiments, adsorbent dosages and initial Cd2+ concentrations had direct and indirect relationships with Cd2+ removal, respectively. Furthermore, among all applied isotherm and kinetic models, Langmuir isotherm model and Avrami fractional-order kinetic models could best-fitted with the experimental data of Cd2+ removal. The results of thermodynamic studies revealed that the adsorption of Cd2+ onto the surfaces of oak waste adsorbents is exothermic and spontaneous. Finally, according to the findings of ANN studies, this approach could model the role of each parameter on Cd2+ removal with high coefficient of correlation (>0.99). Accordingly, pH of solution and temperature had the highest and lowest influence on removal of Cd2+ from solution, respectively. The results implied that oak waste can be selected as a promising and environmentally friendly adsorbent for the effective remediation of water bodies containing heavy metals.