Effect of double carbon chains on enhanced removal of phenol from wastewater by amphoteric-gemini complex-modified bentonite

A novle amphoteric-gemini complex-modified bentonite was prepared with a gemini surfactant ethylene bis (tetradecyl dimethyl ammonium chloride) (EB) on the basis of the bentonite modified by amphoteric modifier dodecyldimethyl betaine (BS). The surface and structural characteristics of modified bentonite were characterized by X-ray diffraction (XRD), specific surface area (SBET), scanning electron microscopy (SEM), Fourier infrared spectroscopy (FTIR), total carbon (TC) and total nitrogen (TN). In addition to studying the enhanced effect of gemini surfactants on phenol adsorption by kinetics and equilibrium adsorption, the influences of modification ratio, pH, temperature and ionic strength were investigated. Results showed that BS + EB complex modification increased the interlayer spacing (IS), TC and TN of bentonite (BT), and SBET decreased with the increase in its total modification ratio. The adsorption of phenol on modified bentonite reached equilibrium in 20 min, and the adsorption capacities were in the order of BS+50 EB (BS+50% CEC EB)>BS+100 EB > BS+150 EB > BS+25 EB > BS > BT. The adsorption capacities of phenol on BS + EB complex modified bentonite (CMB) increased by 9.98-15.96 and 1.19-3.35 times compared with those on BT and BS single modified bentonite (SMB), respectively. The phenol adsorption capacities decreased with the increases in temperature and pH, while it increased with the augment in ionic strength. This study revealed that double carbon chains increased the organic carbon content more effectively than single carbon chains at low complex modification ratios, thus promoting the adsorption of phenol by hydrophobic partitioning on the bentonite surface.