Removal of Organic Compounds Containing a Benzene Ring from Water by Adsorptive Micellar Flocculation

Abstract

The removal of low-molecular-weight benzoic acid (benzoic acid, p-toluic acid, and salicylic acid)-derived and aniline (aniline, 4-chloroaniline, and 2,6-dimethylaniline)-derived organic compounds through adsorptive micellar flocculation (AMF) with anionic surfactants (sodium dodecyl sulfate, SDS) and aluminum sulfate was demonstrated. The interactions between SDS and the organic compounds were studied using 1H nuclear magnetic resonance (NMR) spectroscopy. Batch AMF experiments were conducted to study the influence of several factors on target pollutant removal. For benzoic acid derivatives, the removal rate was improved by increasing the SDS and Al concentrations, while increases in the concentrations of the organic pollutant tended to decrease the removal rate. The highest removal efficiencies were observed with p-toluic acid (95.4%) > salicylic acid (84.5%) > benzoic acid (76.5%) under weakly acidic conditions due to the greater hydrophobicity of p-toluic acid and the complexation of the Al salts and the salicylic acid. The removal rates of the aniline derivatives were positively related to the SDS concentration and negatively related to the pH. At a pH of 3.0, the highest removal rates of aniline, 4-chloroaniline, and 2,6-dimethylaniline (91.3%, 98.0%, and 97.6%, respectively) were observed. For aniline compounds, charge neutralization between the SDS anions and aniline cations dominated the removal process. These findings provide new insights for the development of further applications of AMF for the removal of benzoic acid and aniline derivatives.