Removal of toxic pollutants using tannery sludge derived mesoporous activated carbon: Experimental and modelling studies

Abstract Safe disposal of tannery activated sludge is a major challenge faced due to its complex nature. The present work focuses on the conversion of the tannery sludge biomass into mesoporous nano-activated carbon through carbonization and physical activation methods The prepared material was characterized by FE-SEM, EDAX, FT-IR, TGA, surface area, pH ZPC and surface functionality. The biomass derived activated carbon possesses specific surface area, mean pore diameter, total pore volume and zero point charge of 187.21 m 2 /g, 3.24 nm, 0.152 cm 3 /g and 7.80 respectively. The adsorbent was used for the removal of Malachite Green (MG), hexavalent chromium (Cr(VI)) and 2,4-Dichlorophenoxyacetic acid (2,4-D) from aqueous phase. Preliminary studies on the effect of pH, adsorbent load, concentration, kinetics of adsorption and adsorption dynamics were optimized using Response Surface methodology (RSM). Analysis of variance (ANOVA) showed high values of determination coefficient (R 2 ) for the three pollutants. viz., MG dye (R 2  = 0.9914), Cr (VI) (R 2 = 0.9882) and 2,4-D (R 2 = 0.9838). The monolayer adsorption capacity of the adsorbent was 231.34 mg/g, 86.26 mg/g and 20.09 mg/g, respectively for MG, Cr(VI) and 2,4-D. The adsorption data fitted well with Langmuir isotherm and the kinetics followed the pseudo second order model. The thermodynamic studies showed the adsorption process to be endothermic, spontaneous and favourable.