Adsorption Characteristics of Organic Pollutants on Montmorillonites Modified by Quaternary Ammonium Surfactants with Organic Counterions

Na-montmorillonite (Na-Mt) modified by quaternary ammonium surfactants containing different organic counterions [OMt-QAS·Y^-, Y = CH₃CO₃ ^-, CH₃ (CH₂)₃COO^-, CH₃CH(OH)COO^-, and HCOO^-] was prepared for enhancing the adsorption capacity of 2, 4-dichlorophenol/cibacron brilliant yellow 3G-P. Compared with Na-Mt, whose adsorption efficiency for 2,4-dichlorophenol/cibacron brilliant yellow 3G-P was only 58/1.85 mg/g, the adsorption efficiency of OMt-QAS·Y^- was greatly improved, with OMt-QAS·CH₃CO₃ ^- having the highest adsorption capacity of 152.85/116.17 mg/g. The kinetic and isotherm studies indicate that all adsorption processes fit well to the pseudo-second-order model and Freundlich model, respectively. The hydrophobicity of counterions and their affinity with the aliphatic chains had an effect on the interlayer spacing and point of zero charge of OMt-QAS·Y^-, which in turn affected their adsorption properties.