Resource Utilization of Residual N,N-Dimethylformamide for Enhanced Adsorption Removal of Aromatic Compounds from Wastewater: Mechanism and Influencing Factors

Abstract

Residual N,N-dimethylformamide (DMF) complicates industrial wastewater treatment, but no studies have reported its potential to enhance the removal of coexisting aromatic compounds. This study verified this conjecture via investigating the adsorption behavior of five aromatic compounds (benzene, toluene, xylene, aniline, and phenol) in five real waters (pharmaceutical, dye, petrochemical, natural, and ultrapure water) by regulating DMF concentrations. Turning point concentrations of DMF were found between promoting and inhibiting pollutant removal. Optimizing DMF concentration promoted pollutant removal by 43.4%, with similar enhancements for five aromatic compounds in real wastewater. This enhancement correlated positively with surface tension and negatively with dissolved organic carbon in wastewater. Kinetic and adsorption isotherm analyses showed optimal turning points of DMF-enhanced adsorption capacity, removal rate and preferential adsorption for aromatic compounds, despite competitive and synergistic adsorption between DMF and pollutants. Hierarchical clustering and structural equation modeling revealed that the enhancement is primarily driven by the hydrophilicity, surface tension, and solubilization ratios of pollutants. The DMF-enhancing effect is evidenced by the decrease in the total interaction energy barrier calculated by EDLVO, and transitions in the water contact angle and zeta potential. This study presents a feasible technique for the enhanced purification of wastewater containing surfactants and hydrophobic compounds.

Keywords: Waste utilization, Surfactants, Enhanced adsorption, Aromatic compound, Petrochemical wastewater