Hydrophobic deep eutectic solvent-impregnated sponge for efficient phenol adsorption from aqueous media

In this work, a common household melamine sponge was impregnated with a novel hydrophobic deep eutectic solvent (HDES) and used for the removal of phenol from aqueous media. The HDES was prepared from trihexyltetradecylposphonium chloride as a hydrogen bond acceptor and dodecanoic acid as a hydrogen bond donor. The modified sponge characterization was performed using Fourier transform infrared (FTIR), thermogravimetric analysis (TGA), scanning electronic microscopy (SEM), and energy dispersive (EDX) to confirm the presence of the HDES in the sponge, and assess the microscopic morphology of DES impregnated foam. The phenol adsorption over the hydrophobic sponge was investigated using batch adsorption experiments to examine the influence of the HDES loading (0.025–0.125 g), contact time (5–420 min), initial concentration of phenol (62–1000 mg/L), and temperature (25–45 °C) on the removal performance and kinetics. The phenol adsorption efficiency was found to decrease with temperature and increase with the initial concentration of aqueous phenol solution, contact time, and HDES load. The phenol adsorption efficiency of the native sponge increased to 469 mg/g after the HDES was loaded. Freundlich adsorption isotherm is more applicable than the Freundlich adsorption isotherm model. The kinetic study confirmed that the adsorption of phenol on the hydrophobic sponge follows a pseudo-second-order model. Thermodynamic parameters represented the spontaneous adsorption of phenol on the hydrophobic sponge. Experimental results revealed that the modification of the surface of the melamine sponge with the reported HDES is an economical and efficient strategy for the adsorption of phenol from an aqueous solution.