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China Surfactant Detergent & Cosmetics ›› 2025, Vol. 55 ›› Issue (12): 1534-1543.doi: 10.3969/j.issn.2097-2806.2025.12.005

• Basic research • Previous Articles     Next Articles

Mechanism of enhanced low-rank coal flotation using a nanoemulsion collector based on zwitterionic/nonionic surfactants

Yingying Wang1,2,Zhenchao Ma2,Zhe Li2,*(),Yibo Kong2,Xinyi Zhao2,Yaowen Xing2,Xiahui Gui2   

  1. 1 China Coal Tianjin Design Engineering Co., Ltd., Tianjin 300131, China
    2 State Key Laboratory of Coking Coal Resources Green Exploitation, China University of Mining and Technology, Xuzhou, Jiangsu 221116, China
  • Received:2025-08-14 Revised:2025-12-25 Online:2025-12-22 Published:2026-01-23
  • Contact: *E-mail: zheli@cumt.edu.cn. E-mail:zheli@cumt.edu.cn

Abstract:

The abundant oxygen-containing functional groups and pore structures on the surface of low-rank coal (LRC) have restricted its flotation efficiency. Compared with traditional hydrocarbon oil collectors, emulsion collectors are an effective method to improve the dispersion performance and improve their adsorption and hydrophobic modification effect on LRC surface. In this work, a series of nanoemulsion collectors which were synergistically stabilized with zwitterionic and nonionic surfactants were prepared by low-energy emulsification method, using erucic acid amidopropyl betaine (EAB-40) and fatty alcohol polyoxyethylene ether (AEO-7) as surfactants, and diesel oil as oil phase. The influences of the contents of EAB-40 and AEO-7 on the droplet size and microscopic dynamic stability of nanoemulsions were systematically studied through dynamic light scattering (DLS) and multiple light scattering (MLS). The mechanism for nanoemulsions to enhance flotation was investigated through LRC flotation tests and the measurements of particle-bubble and particle-droplet adhesion/detachment forces. The results showed that when the mass ratio of EAB-40∶AEO-7 was 1∶4 (nanoemulsion collector #1), the droplet size of the nanoemulsion was the smallest (D50=307 nm), and the combustible matter recovery of LRC flotation could reach the maximum of 92.24%. Compared with traditional diesel collector, nanoemulsion collector #1 could significantly improve the hydrophobicity of LRC surface, enhance the adhesion/detachment interactions between coal particle and bubble and between coal particle and collector, and thus significantly improve the LRC flotation performance. The mechanism was that the EAB-40 at the surface of nanoemulsion droplets had both positively and negatively charged groups, which could both enhance the adsorption of collectors onto LRC surface and the hydrophobic modification of LRC surface through electrostatic attraction; however, when the EAB-40 content was too high, it would lead to excessive adsorption of surfactants and reduce the surface hydrophobic modification and the flotation performance to a certain extent. This research might be helpful to improve the theoretical basis and provide technical support for the development of novel collectors for LRC flotation.

Key words: low-rank coal, flotation, nanoemulsion collector, zwitterionic surfactant, non-ionic surfactant, adhesion force, detachment force

CLC Number: 

  • TQ423