Adsorption of 2, 4 Dichlorophenoxyacetic Acid on Different Types of Activated Carbons Based Date Palm Pits: Kinetic and Thermodynamic Studies

Abstract

The removal of 2,4-dichlorophenoxyacetic acid (2,4-D) from waste water was studied by three activated carbon samples (AP21, AZ21 and AN13) prepared from date palm pits (DP) as a precursor and phosphoric acid, zinc chloride and sodium hydroxide as activating agents. Different techniques were used to characterize the solid adsorbents as N2-adsorption at −196°C, scanning electron microscopy (SEM), thermo gravimetric analysis (TGA) and FT-IR. The effect of various operating parameters such as initial concentration of 2, 4-D, contact time, temperature, adsorbent dosage, and pH were investigated. Equilibrium isotherms were used to identify the possible mechanism of the adsorption process. Characterization results showed that AN13 sample gave the heights surface area 498.9 m2/g and micropores volume 0.239 cm3/g. pHpzc, pH of the supernatant and FT-IR indicated the presence of different C-O function groups. It was shown that the adsorption of 2, 4-D on activated carbon samples could be best fitted to Langmuir equation with qm 80 mg/g in case of AN13. The kinetic data were also examined with applying pseudo-first-order and pseudo-second-order kinetics models and was found to follow closely the pseudo-second-order kinetic model. Thermodynamic parameters such as enthalpy changes (Δ H°), entropy changes Δ S° and free energy changes (Δ G°) were evaluated indicating that the nature of adsorption was found to be endothermic and spontaneous.