Highly mesoporous K2CO3 and KOH/activated carbon for SDBS removal from water samples: Batch and fixed-bed column adsorption process

• Preparation of mesoporous activated carbon (AC) from cones biomass of pine tree.
• Highly porous structures of ACs give remarkable uptake capacity for removal of SDBS.
• Performance of porous carbon for removal of SDBS was related to their MPSD.
• Adsorption isotherm, kinetic and breakthrough curves were analyzed.
• The removal procedure was successfully applied for SDBS from river water sample.

This manuscript evaluates the behavior of activated carbon (AC) prepared from the cones biomass of Iranian pine trees, with high mesoporosity and a large specific surface area, as a high potential adsorbent for sodium dodecylbenzene sulfonate (SDBS) in batch and continuous systems. The AC samples were prepared from pine tree cones by chemical activation with different impregnation ratios of K2CO3 and KOH. The materials were characterized by Boehm titration, approximate elemental, SEM, FT-IR, TGA, XRF analyses and BET surface area measurement. In a batch process, the effects of various parameters such as adsorbent dose, pH, contact time and initial SDBS concentration and temperature were considered. Six different adsorption isotherms were applied to equilibrium data. Pseudo-first-order, pseudo-second-order and intraparticle diffusion models were used to estimate the adsorption kinetic data. The experimental data resulted in excellent fits with the Redlich-Peterson isotherm and that the pseudo-second-order described the best description of adsorption data. Thomas and Yan models were used in describing the experimental data in a continuous system. The thermodynamic parameters such as Gibbs free energy (ΔG°), enthalpy (ΔH°), entropy (ΔS°) and activation energy (Ea) were analyzed. The contrasting negative and positive values of ΔG° and ΔH°, respectively, indicated that adsorption was spontaneous and endothermic in nature, and the obtained Ea confirmed chemisorption of SDBS adsorption onto AC. The adsorptive behavior of AC was also investigated with different bed heights, flow rates and the initial concentrations of SDBS. These results, by the recovery of 88% after five successive cycles, indicated that the combination of sulfuric acid and ethanol with a ratio of 4:6 is suitable for desorbing SDBS from AC.