KOH-activated tire pyrolysis char as an adsorbent for chloroorganic water pollutants

Activated carbons (ACs) produced from end-of-life tires with different tire pyrolysis char (TPC)-to-activator (KOH) ratios of 1:2, 1:3, and 1:4 were prepared and characterized. These materials were used as adsorbents for the removal of two common chloroorganic water contaminants such as 2,4-dichlorophenol (DCP) and 2,4-dichlorophenoxyacetic acid (2,4-D). The adsorption kinetics, equilibrium adsorption, and effects of solution pH were investigated. The adsorption of both adsorbates was found to be pH-dependent and preferred in acidic environments. The adsorption kinetics was evaluated using pseudo-first-order and pseudo-second-order kinetic models and mechanism - using Weber-Morris and Boyd models. Results demonstrated that the adsorption of DCP and 2,4-D on all ACs followed the pseudo-second-order model and was controlled by film diffusion. The Langmuir isotherm described the equilibrium data better than the Freundlich isotherm model. The maximum adsorption capacity of DCP adsorbed on AC1:2, AC1:3, and AC1:4 at equilibrium was 0.582, 0.609, and 0.739 mmol/g, respectively, while the maximum adsorption capacities for 2,4-D were 0.733, 0.937, and 1.035 mmol/g, respectively. The adsorption rate and efficiency were closely correlated with the porous structure of the tested adsorbents. The results showed that the activated carbons obtained from the scrap of end-of-life tires as raw materials could be used as a low-cost and alternative adsorbent for the removal of chlorinated organic pollutants from water.