Effect and mechanism of microemulsion on low-rank coal flotation by mixing AEO-3 and diesel oil

ABSTRACT

Low-rank bituminous coal has a low degree of metamorphism, a high oxygen content, and poor hydrophobicity. When using a conventional collector, it renders a low yield of clean coal, making it difficult to improve the quality via flotation. In this work, a type of diesel microemulsion (C1) was prepared using primary alcohol ethoxylate (AEO-3), which was adopted to conduct flotation. The results demonstrated that compared with a conventional diesel collector, the yield of clean coal was increased by 44.37%; the content of tailing ash was increased by 37.60%; the combustible recovery rate was improved by 55.65%, respectively; and the flotation kinetic constant was increased by 0.505. The addition of AEO-3 could significantly reduce the surface tension and generate smaller emulsion droplets, which could also adhere to coal particles, easily enhancing their hydrophobicity. An X-ray photoelectron spectroscopy analysis and its contact angle verify a significant enhancement in the hydrophobicity of the coal surface. More importantly, a molecular dynamic simulation revealed that adding AEO-3 could augment the electrostatic interaction between the collector (diesel) molecules and coal particles, as well as reduce the mean square displacement, i.e., the adsorption strength between the collector molecules and coal particles. On the other hand, the microemulsion could improve the hydrophobicity and floatability of coal particles and enhance the wrap angle of particle-bubble. And accelerating the generation of stable mineral flocculation, which was the main reason for the faster flotation process.

Graphical Abstract

(1) The adsorption and flotation behaviors of LRC with AEO-3 were explored.

(2) Microscopic adsorption mechanism of AEO-3 on LRC was investigated by MSD.

(3) The changes in functional group content after coal particles with different collectors.

(4) the interaction between the bubbles and samples could be monitored while simulating the adhesion time of the particles and bubbles.

KEYWORDS:

• Low-rank coal
• surfactant
• diesel oil
• microemulsion
• bubbles

Chinese   Library Classification:

• TD 94 Document Code: A

Acknowledgments

Financial support from Chinese national key research and development program-funded projects (2019YFC1904302) and Research project supported by shanxi scholarship council of chian (2020-045). The authors greatly appreciate the support and assistance of these institutional personnel.

Disclosure statement

No potential conflict of interest was reported by the author(s).

CRediT authorship contribution statement

Zhonghua Xue: Conceptualization, Study experiments, Data curation, Formal, analysis, Investigation, Project administration, Validation, Visualization, Writing - original draft.

Lianping Dong *: Funding acquisition, Formal analysis, Investigation, Methodology, Project administration, Resources, Validation, Writing - review & editing.

Bo Hao: Conceptualization, Methodology, Validation, Writing-review & editing.

Minqiang Fan: Methodology, Resources, Validation, Writing-review & editing.

Weiwang Chen: Validation, Writing - review & editing.

Chongyi Yang: Investigation, Resources.

Haipeng LI: Resources, Writing - review & editing.

Sijie LI: Investigation, Writing - review & editing.

Hongli Yang: Investigation, Project administration.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Additional information

Funding

This work was supported by the Projects funded by the national key research and development plan [2019YFC1904302]; Research Project Supported by Shanxi Scholarship Council of China [2020-045].