Synthesis of a Micro-Crosslinked Polyacrylamide Flocculant and Its Application in Treatment of Oily Produced Water

A cationic polyacrylamide (PADO) with excellent flocculation performance was synthesized by the inverse emulsion polymerization of acrylamide benzyldimethyl[2-[(1-oxoallyl)oxy]ethyl]ammonium chloride (DBC) and vinyl siloxanes (VTEO). The structure and weight of PADOs were characterized by H NMR spectra and static light scattering. The impacts of the types and amounts of vinyl siloxanes were investigated to optimize the produced flocculant. When more crosslinking groups are present in the added vinyl siloxanes, the synthesized copolymer could achieve larger molecular weights through micro-crosslinking networks, which is beneficial to its flocculation performance. The PAD3O copolymer prepared by VTEO3 monomers with a mole fraction of 1.16% exhibited the best efficiency for oil removal, which balanced the large molecular weight and appropriate water solubility, optimizing the interactions with oily colloids from produced water. The flocculation performance of PADO copolymers prepared in this work has been compared with seven different commercial cationic polyacrylamides by treating simulated produced water. The PADO copolymers exhibited a higher oil removal rate with a lower dosage, which surpassed the performances of all commercial cationic polyacrylamides and successfully achieved high-efficiency water treatment. Moreover, the application performance was further evaluated by treating the practical produced water with complex composition generated from the site of the Bohai K platform. The deoiling rate of practical produced water could achieve 98% after 2 h at room temperature by adding 300 mg/L PAD3O copolymers. This work shows a potential candidate for efficient treatment of oily wastewater and provides an approach for future flocculant design.