Decontamination of 4-Chloro-2-Nitrophenol from Aqueous Solution by Graphene Adsorption: Equilibrium, Kinetic, and Thermodynamic Studies

4-Chloro-2-nitrophenol (4C2NP) is an important chemical widely used in the pharmaceuticals, herbicide, and pesticide industries. The ability of graphene to remove 4C2NP from aqueous solutions was performed as a function of contact time, amounts of adsorbent, pH, initial 4C2NP concentrations, and temperatures using a batch technique. Based on the results, the amount of 4C2NP adsorption increased with increasing initial concentration, whereas the alkaline pH range, higher graphene dosage, and higher temperature were unfavorable. Non-linear regression methods suggest that the isotherm data can be well described by the Freundlich isotherm equation. The adsorption kinetic data were analyzed using the non-linear rate equations of pseudo-first and pseudo-second order. It was found that the pseudo-second-order kinetic model was the most appropriate model, describing the adsorption kinetics. The observed changes in the standard Gibbs free energy (Delta G degrees), standard enthalpy (Delta H degrees), and standard entropy (Delta S degrees) show that the adsorption of 4C2NP by graphene is feasible, spontaneous, and exothermic in the temperature range 298-328 K.