Cyclodextrin decorated with quaternary ammonium salt and hydrophobic chain as green demulsifier for the demulsification of oily wastewater

Currently, most of the industrial demulsifiers are based on petrochemical-derived raw materials, which have the disadvantages of dangerous and complicated synthesizing process, low demulsification efficiency (DE) and significant environmental harm. To tackle these challenges, this study focused on synthesizing a green cationized amphiphilic cyclodextrin demulsifier (CDPA) decorated with quaternary ammonium salt and hydrophobic chain, which exhibits effectively treats oily wastewater at ambient temperature and low concentration. The bottle tests revealed that the light transmittance and the corresponding oil removal efficiency of CDPA was 93.1 % and 99.4 %, respectively. In addition, CDPA consistently maintained an excellent DE in wide pH range (3–11) and high salinity conditions. The possible demulsification mechanism of CDPA was explored in detail and the results showed that CDPA could quickly adsorb and replace natural surfactants, leading to form an unstable composite film and initiating the demulsification process. Furthermore, the positive charge of CDPA also facilitated electrostatic neutralization with the oil droplets, thereby attenuating the strength of the interfacial film.