Effective Cd2+ removal from water using novel micro-mesoporous activated carbons obtained from tobacco: CCD approach, optimization, kinetic, and isotherm studies

Purpose This research aimed to develop activated carbons from tobacco by double (thermal-physical) and triple activations (thermal-chemical-physical) for high-efficiency removal of Cd 2+ . Methods The adsorbents were characterized by their chemical composition, point of zero charge (pH PZC ), SEM, FT-IR, BET, and BJH. The subsequent adsorption studies were conducted: optimal conditions (CCD on adsorbent dose versus pH of Cd 2+ solution), kinetics, equilibrium, thermodynamics, and desorption studies. Results The activated carbons have irregular and heterogeneous morphology, surface functional groups COO–, C–O, C–O–C, C=O and O–H, pH PZC of 11.11 and 10.86, and enhanced SSA (especially for CT NaOH + CO 2 = 103.40 g m −2 ). The optimal conditions for Cd 2+ adsorption occur using 4.0 g L −1 , pH from 3.0 to 7.0, with most of the Cd 2+ adsorbed in the first 10–20 min. The goodness of the fit found for pseudo-first order, pseudo-second order, intraparticle diffusion, Langmuir, Freundlich, Dubinin–Radushkevich, Sips, and Temkin suggest the occurrence of Cd 2+ chemisorption and physisorption in mono and multilayers. The values of ∆G°