Kinetic and Thermodynamic Studies of Phenolic Compounds' Adsorption on River Sediment

Phenolic compounds have increasingly attracted global concerns in recent years due to their strong bioaccumulation and potential toxicity. In this study, the adsorption of 2, 4-Dichlorophenol (2, 4-DCP), 2, 4-Dinitrophenol (2, 4-DNP) and 2, 4-Dimethyphenol (2, 4-DMP) on sediment at different temperatures was studied. Adsorption isotherms fitted well to the Freundlich model and the adsorption capacity was increased when the temperature increased from 5°C to 25°C. It was found that the adsorption process could be modeled well using pseudo-second-order kinetic equation. The thermodynamic parameter ΔG° for 2, 4-DCP, 2, 4-DNP and 2, 4-DMP varied between -8.82 and -13.68, -4.9 and -8.05, and -7.52 and -10.55 kJ/mol, respectively, with ΔH° (kJ/mol) and ΔS°(J/(mol·K)) measuring 55.397 and 0.2263, 40.121 and 0.1585, and 38.012 and 0.16, respectively. The calculated thermodynamic parameters suggested that adsorption of the three selected phenolic compounds was a spontaneous (ΔG°& 0), endothermic (ΔH°> 0), and entropy-driven reaction (ΔS° > 0). The thermodynamic data also suggested that the three selected phenolic compounds to sediment were closed to chemisorption because ΔH° was around 40.