A novel interface-active cationic flocculant for the oil-water separation of oily wastewater produced from polymer flooding

Cationic flocculant has fast flocculation rate and high oil removal for treating oily wastewater produced from polymer flooding (OWPF), but its floc has strong adhesiveness, which is a problem for OWPF treatment in offshore oilfield. In this paper, we found that interface-active cationic flocculant can resolve this problem partly. Terpolymer (PDMXSCn) of diallyldimethyl-ammonium chloride (DM), sodium allylsulfonate (XS) and long-chain alkyl dimethyl propenyl ammonium chloride (CnDM) was prepared and its flocculation was evaluated. The PDMXSCI2 has an oil removal of 97.5% and viscous floc decrease of 40%. Zeta potential, interfacial dilational modulus and droplet-to-planar coalescence experiments showed that PDMXSCn can destroy the electric double layer of oil droplet and can weaken the interface film strength, which are the oil-water separation mechanism of PDMXSCn. The dynamic light scattering (DLS) results presented that PDMXSCI2 has very weak interaction with the partially hydrolyzed polyacrylamide in OWPF, which is the main reason why its floc had less adhesiveness than that of regular cationic flocculant PDM. (C) 2019 Elsevier B.V. All rights reserved.