Effect of pH on surface hydration of coal particles and its attachment with oily bubbles in flotation

ABSTRACT

The pH of flotation slurry directly affects the surface potentials of mineral particles and bubbles, and therefore the hydration of coal surface and the mineralization process of flotation. In this paper, the effect of pH on the surface potential, hydration degree, and floatability of lignite particles was studied, wherein Einstein’s dispersion viscosity theory was adopted to calculate the hydration degree, and DLVO theory was used to estimate the interaction between coal particles and oily bubbles. The effect of pH on the lignite floatability was evaluated in terms of induction time and oily-bubble flotation results. The results showed that with increasing pH, the zeta potentials of coal particles and oily bubbles decrease, causing a 37.89% increase in the coal surface hydration from pH 3 to pH 11. As a result, the energy barrier for attachment between the coal particles and oily bubbles reaches the maximum value of 2.669 × 10⁻¹⁶ J at pH 11, resulting in low attachment efficiency. Correspondingly, the combustible matter recovery of oily-bubble flotation is significantly decreased from 57.76% to 28.00%.

KEYWORDS:

• Lignite
• oily-bubble flotation
• surface hydration
• DLVO theory
• interaction potential energy

Acknowledgments

This study was supported by the National Natural Science Foundation of China (Grant No. 51774284, 51574235).

Additional information

Funding

This work was supported by the National Natural Science Foundation of China [Grant No. 51574235,51774284].

Notes on contributors

Dongjiao Gui

Dongjiao Gui, Master, graduated from China University of Mining and Technology.

Songjiang Chen

Songjiang Chen, PhD in Minerals Processing Engineering, graduated from China University of Mining and Technology. Doctor Songjiang Chen is now a lecturer affiliated to Xi'an University of Science and Technology. His research interests focus on coal cleaning and flotation. The focus of his current research is on flotation colloid and interface science, including air/oily bubble–particle interaction and reagent–particle interaction.

Shiwei Wang

Shiwei Wang got his doctorate degree of Minerals Processing Engineering from China University of Mining and Technology, and he is now an associate professor of School of Chemistry and Materials Engineering, Liupanshui Normal university.

Xiuxiang Tao

Xiuxiang Taois senior professor of China University of Mining and Technology, and he is the leader of mineral processing engineering. His research interests embrace low-rank coal cleaning/flotation, coal desulfurization, biological beneficiation,biotransformation of coal, et al.

Liang Chen

Liang Chen, Master, graduated from China University of Mining and Technology.

Rang Wang

Rang Wang is a master student majoring in minerals processing engineering of China University of Mining and Technology.