Adsorption behaviors of atrazine and Cr(III) onto different activated carbons in single and co-solute systems

Abstract

Three kinds of activated carbons (ACs) from apricot shells (AS), wood (W), and walnut shells (WS) were used for the adsorption of atrazine and Cr(III) in single and co-solutions. The elemental composition, Brunauer–Emmett–Teller (BET) surface area, pore volume, and surface functional groups of the used ACs were characterized by elemental analysis, surface area analyzer, and X-ray photoelectron spectroscopy. The adsorption kinetics of atrazine and Cr(III) are consistent with the pseudo-second-order model. The adsorption isotherms of atrazine follow the Freundlich model, whereas those of Cr(III) follow the Langmuir model. The maximum adsorption capacities for Cr(III) are found to be of the order: WAC > ASAC > WSAC. The adsorption capacities for atrazine and Cr(III) onto ASAC, WAC, and WSAC conform to the results of activation energy. The adsorption of atrazine and Cr(III) onto samples is an endothermic and spontaneous process. The pH value of solution minimally affects the adsorption of atrazine, while the adsorption amount of Cr(III) significantly increases with increasing pH value up to around 6. When Cr(III) and atrazine coexisted in the aqueous solution, the competitive adsorption was observed due to the different porosities and specific surface areas, affinities and active sites.