Conclusion
Our excellent results on Cd2+ removal allow us to state that tobacco use as a raw material for adsorbent development is a renewable and eco-friendly technique, allowing the production of highly effective activated carbons and providing an adequate destination for this waste.
Methods
The adsorbents were characterized by their chemical composition, point of zero charge (pHPZC), SEM, FT-IR, BET, and BJH. The subsequent adsorption studies were conducted: optimal conditions (CCD on adsorbent dose versus pH of Cd2+ solution), kinetics, equilibrium, thermodynamics, and desorption 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 Cd2+.
Results
The activated carbons have irregular and heterogeneous morphology, surface functional groups COO-, C-O, C-O-C, C=O and O-H, pHPZC of 11.11 and 10.86, and enhanced SSA (especially for CT NaOH + CO2 = 103.40 g m-2). The optimal conditions for Cd2+ adsorption occur using 4.0 g L-1, pH from 3.0 to 7.0, with most of the Cd2+ 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 Cd2+ chemisorption and physisorption in mono and multilayers. The values of ∆G° < 0 kJ mol-1 indicate that the observed phenomena are energetically favorable and spontaneous; the values of ∆H° < 0 and the effective desorption rates (58.52% and 44.64%) suggest that the adsorption of Cd2+ is ruled mainly (but not only) by physical interactions.
Supplementary Information
The online version contains supplementary material available at 10.1007/s40201-021-00740-8.