Adsorption equilibrium, kinetics and thermodynamics of dichloroacetic acid from aqueous solution using mesoporous carbon

Abstract

The presence of disinfection by-products, such as trihalomethanes and haloacetic acids in water, is believed to be harmful to human health. In this work, mesoporous carbon was synthesized with the evaporation-induced self-assembly method and employed to evaluate the effects of initial concentration, contact time, pH and temperature on the removal of dichloroacetic acid in batch experiments. Adsorption equilibrium was established in 480 min and the maximum adsorption (350 mg/g) of dichloroacetic acid on the mesoporous carbon was observed to occur at 308 K and pH 3.0. Freundlich and Langmuir isotherms were used to analyse the equilibrium data at different temperatures; kinetic data were fitted to the pseudo-first-order and pseudo-second-order models and found that the adsorption capacity, mass transfer coefficient and diffusivity of dichloroacetic acid were directly affected by the physical and chemical parameters. In addition, the various thermodynamic parameters, such as Gibbs free energy (Δ G), enthalpy (Δ H=54.35 kJ mol−1) and entropy (Δ S=258.36 J mol−1 K−1) were calculated to analyse the adsorption process. The experimental results indicated that the mesoporous carbon was an excellent adsorbent for dichloroacetic acid removal from aqueous solutions.