The effect of molecular structure on the properties of cationic polyacrylate and its flocculation‐flotation performance of oilfield oily wastewater treatment

Abstract

With the increasing amount of oily wastewater produced in the offshore oilfield, more efficient air flotation agent is needed to be developed. Cationic polyacrylate with amphiphilic structure has been found to be a type of potential efficient air flotation agent. However, the effect of molecular structure on its properties and performance was lack of research. In this paper, copolymers with tertiary amine as side group were synthesized by copolymerization of ethyl acrylate (EA) and tertiary amine monomers, and then a series of cationic polyacrylates were prepared by quaternization of tertiary amine with quaternization reagent.The effects of tertiary amine monomer type (including dimethylaminopropyl methacrylamide (DPM) and dimethylaminoethyl methacrylate (DEM)), quaternization reagent type (including 3-Chloro-1,2-Propanediol and 3-chloro-2-hydroxytrimethylammonium chloride) and quaternization degree on the cationic polyacrylate properties and its flotation performance were investigated. The experimental results showed that the flotation performance increased with the increasing hydrophilicity and cation degree of the hydrophilic unit in the cationic polyacrylate. When the tertiary amine monomer was DPM, quaternization reagent was 3-chloro-2-hydroxytrimethylammonium chloride, and theoretical quaternization degree was 100%, the oil removal of product PE-M-1.0 was the highest. When PE-M-1.0 dosage was 50 mg/L, gas flow was 1 L/min, flotation time was 10 min, its oil removal rate was higher than 95% in the range of 20-60 C. The results of zeta potential measurement and microfluidic experiment showed that PE-M-1.0 can increase the size of oil droplets by destroying the electric double layer on the surface of oil droplets and maintain the stability of bubbles, which was helpful for the improve of gas bubble-oil droplet collision probability and adhesion efficiency.

Preparation of Cationic Polyacrylamide Suspension and Its Application in Oilfield Wastewater Treatment

“…The main treatment processes are the gravity separation process, membrane separation process, air flotation process, and so on. The physical separation method has the advantages of simple operation and low cost, but there are obvious shortcomings including that the separation is not thorough enough [ 6 ]. The biological treatment method employs microorganisms in some wastewater organic matter decomposition into some relatively simple substances, mainly used in the treatment of oilfield wastewater with high water quality requirements; the disadvantage of the biological method is that it needs to be based on the characteristics of the sewage for the cultivation of special biological strains of bacteria, and sewage water quality changes need to be cultivated to produce different strains of biological bacteria [ 7 , 8 ].…”