Synthesis and Flotation Performance Evaluation of Polypropylene Glycol Grafted Poly N-[(3-dimethylamino)propyl]methacrylamide Copolymer

When cationic polymers are used as flotation agent in oil field to treat oily wastewater, viscous flocs are inevitably produced, which severely affect the oilfield production. In this paper, polypropylene glycol monomethyl ether (MPPG) was used to graft-modify poly N-(3-dimethylaminopropyl) methacrylamide (PDPM). Five types of copolymers (PPG-g-PDPM-X) with different theoretical grafting degrees of PPG (20 %, 40 %, 60 %, 80 %, 100 %) were prepared. Chemical structures and surface activities of these copolymers were investigated. The flotation performances of the synthesized PPG-g-PDPM-X and PDPM were evaluated and compared. It was found that PPG-g-PDPM-3 showed high oil removal efficiency and the stickiness of its flocs was significantly lower than that of PDPM flocs. Factors that can affect the flotation performance of PPG-g-PDPM-X were also studied. The results showed that both the interfacial activity and the conformation of PPG-G-PDPM-3 in water changed as the rising temperature and the increasing pH, resulting in a decrease in the oil removal rate. The oil removal rate of PPG-g-PDPM-3 increased with the increasing dosage, gas flow rate and flotation time. The recommended flotation conditions for PPG-g-PDPM-3 were as follows: 100 mg/L dosage at room temperature, 1.5 L/min gas flow and 15 min flotation time. The oil removal rate at this condition was 87.33 %. This paper provides a solution to solve the viscous flocs issue when cationic copolymers are used as the flotation agent. Meanwhile, the PPG-g-PDPM-3 is expected to have more interesting applications because it is temperature sensitive and pH sensitive.

Automated summary

This study investigates the modification of cationic polymers for treating oily wastewater in oil fields. It was found that modifying poly N-(3-dimethylaminopropyl) methacrylamide with polypropylene glycol monomethyl ether resulted in improved flotation efficiency. The synthesized copolymers showed lower stickiness of flocs and temperature and pH sensitivity, making them promising for future applications.