Application of surfactant-modified montmorillonite in nitrophenol removal by adsorption

Quaternary ammonium salts (QASs) such as 1-methyl-di-nonyl-1 phenyl ammonium iodide (QAS1) and 1-methyl-di-dodecyl-1 phenyl ammonium iodide (QAS2) were newly synthesized by complete alkylation reaction for modification of sodium montmorillonite (Mt). The sodium montmorillonite was modified via an ion-exchange reaction with QAS1 and QAS2, and two organoclays, Mt1 and Mt2, have been obtained. The synthesized quaternary ammonium salts were analyzed by nuclear magnetic resonance spectroscopy (NMR). The organoclays (Mt1 and Mt2) were characterized by a range of methods including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The adsorption capacities of the synthesized organo-montmorillonites for the hydrophobic organic pollutant 4-nitrophenol (4-NP) have been evaluated. The distances between the organoclay layers showed a much better opening than that reported in the literature. The results show that the adsorption capacity increased in the order Mt2 > Mt1. The adsorption capacities of Mt1 and Mt2 for 4-NP were 77% and 81%, respectively.