Comparison of the effects of two flocculants on the interaction between dispersed phases in produced water during air floatation-flocculation

The branched amphiphilic copolymer of N-(3-dimethylaminopropyl) methacrylamide and polyether macromonomer (DA) can gather a large number of oil droplets and bubbles together to form oil aerated flocs, and cooperate with air-flotation cyclone separation device to achieve efficient oil-water separation. In this paper, the effects of DA and linear cationic flocculant polymethylacryloxyethyl trimethylammonium chloride (PDMC) on interaction between dispersed phases in produced water were studied from the microscopic point of view, and the reason why oil aerated flocs can be formed under the action of DA was analyzed. Firstly, the aggregation behaviors of the dispersed phases (including oil droplets and bubbles) in water were studied intuitively by microfluidic experiment. Then, the interaction between oil droplets and the interaction between oil droplet and bubble were studied by optical tweezers and oil-coated bubbles experiments, respectively. The experimental results showed that both the efficiencies of oil droplets coalescence and oil droplet-bubble adhesion of DA were 5 times higher than that of PDMC at concentration of 500 mg/L. DA can enhance the attraction force between oil droplets while PDMC cannot. The film drainage time of oil droplet-bubble adhesion of DA was 3 times shorter than that of PDMC. The increasing temperature and salinity had the negative effect on the film drainage oil droplet-bubble adhesion of DA. In addition, the type of attraction force between oil droplets under action of DA still needs analysis and the generation reason needs molecular dynamics simulation study. The research results of this paper can give a guide to the development of DA type flocculants.