China Petroleum Processing & Petrochemical Technology ›› 2023, Vol. 25 ›› Issue (1): 10-22.

• Scientific Research • Previous Articles     Next Articles

Demulsification Behavior, Characteristics, and Performance of Surfactant Stabilized Oil-in-Water Emulsion under Bidirectional Pulsed Electric Field

Ren Boping1,3; Kang Yong2; Zhang Xianming1; Gong Haifeng1,3; Chen Ling1,3; Liu Yunqi3   

  1. 1. Engineering Research Center for Waste Oil Recovery Technology and Equipment, Ministry of Education, Chongqing Technology and Business University, Chongqing 400067, China;
    2. School of Chemical Engineering and Technology, Tianjin University, Tianjin 300350, China;
    3. State Key Laboratory of Heavy Oil Processing, China University of Petroleum (East China), Qingdao 266580, China
  • Received:2022-06-18 Revised:2022-07-15 Online:2023-03-30 Published:2023-03-30
  • Contact: Yong Kang
  • About author:Corresponding Author: Kang Yong; Tel./fax: +86 22 2740 3389; E-mail:

Abstract: As a novel electric demulsification method, bidirectional pulsed electric field (BPEF) was employed to demulsify the surfactant stabilized oil-in-water (SSO/W) emulsion for oil/water separation in this work. The demulsification behavior, characteristics, and stages under BPEF were explored. It was discovered that BPEF drove SSO/W emulsion to move and form vortexes, during which the oil droplets aggregated and accumulated to generate an oil droplet layer (ODL). ODL subsequently transformed into a continuous oil layer (COL) leading to the demulsification and separation of SSO/W emulsion. The conversion rate of ODL to COL was defined and used to evaluate the demulsification process and reflect the coalescence ability and transformation efficiency of dispersed oil droplets into COL. Furthermore, the effects of BPEF voltage, frequency, duty cycle, ratio of pulse output time, and surfactant type and content on the demulsification performance were examined. The optimal values of BPEF parameters for demulsification operation were 400 V, 25 Hz, 50%, and 4:1. O/W emulsion containing anionic surfactant was apt to be demulsified by BPEF, nonionic surfactant took the second place and cationic surfactant was the most difficult. A high surfactant content was not conducive to the BPEF demulsification. This work is anticipated to provide useful guidance for oil/water separation and oil recovery from actual emulsified oily wastewater by BPEF.

Key words: oil-in-water emulsion, surfactant, demulsification, bidirectional pulsed electric field