Effect of hydrophobically associating polymeric aluminum-polymer dual coagulant on coagulation of oily sewage from oilfields

Whether the oilfield sewage index can reach the reinjection specification is a crucial issue that is urgently need to be solved in polymer flooding systems. Thus the coagulability and floc morphology development of dual coagulants was systematically studied in different pH oily wastewaters. Acidification improved the deprotonation ability of coagulant. Hydrophobic associative polyaluminum silicate-poly dimethyl diallyl ammonium chloride (PASSC-PD) resolved the problem of excessive acid addition. The dual coagulants prepared not only preserved the high charge density of polyaluminum silicate (PASS) itself but also made it have the hydrophobic association and strong bridging ability. Besides, PASSC-PD was compared with hydrophobic associative polyaluminum silicate (PASS-C), PASS, and poly dimethyl diallyl ammonium chloride (PDMDAAC) pertaining to the polymer flooding oily sewage of Daqing Oilfield. The coagulation result demonstrated that PASSC-PD exhibited more advantageous turbidity and oil removal efficiencies than PASS-C, PASS, and PDMDAAC. The floc morphology result showed that adding dual coagulant made the petal-like floc of oily sewage larger at the pH value of 6. Furthermore relevant results evidenced that the coagulant had more successful fruits of turbidity removal of 96.5% and oil removal of 96.3% under weak acid conditions. These can satisfy the reinjection condition of oily sewage.