Effect of ultrasound power on HCl leaching kinetics of impurity removal of aphanitic graphite

Xiangning Bu; Zheng Tong; Muhammad Bilal; Xibing Ren; Mengqian Ni; Chao Ni; Guangyuan Xie

doi:10.1016/j.ultsonch.2023.106415

Effect of ultrasound power on HCl leaching kinetics of impurity removal of aphanitic graphite

Ultrason Sonochem. 2023 May:95:106415. doi: 10.1016/j.ultsonch.2023.106415. Epub 2023 Apr 20.

Authors

Xiangning Bu¹, Zheng Tong², Muhammad Bilal³, Xibing Ren², Mengqian Ni², Chao Ni², Guangyuan Xie²

Affiliations

¹ Key Laboratory of Coal Processing and Efficient Utilization (Ministry of Education), School of Chemical Engineering and Technology, China University of Mining & Technology, Xuzhou 221116, China. Electronic address: xiangning.bu@foxmail.com.
² Key Laboratory of Coal Processing and Efficient Utilization (Ministry of Education), School of Chemical Engineering and Technology, China University of Mining & Technology, Xuzhou 221116, China.
³ Department of Mining Engineering, Balochistan University of Information Technology, Engineering and Management Sciences (BUITEMS), Quetta, Pakistan.

Abstract

This study aimed to investigate the effect of ultrasonic power and temperature on the impurity removal rate during conventional and ultrasonic-assisted leaching of aphanitic graphite. The results showed that the ash removal rate increased gradually (∼50 %) with the increase in ultrasonic power and temperature but deteriorated at high power and temperature. The unreacted shrinkage core model was found to fit the experimental results better than other models. The Arrhenius equation was used to calculate the finger front factor and activation energy under different ultrasonic power conditions. The ultrasonic leaching process was significantly influenced by temperature, and the enhancement of the leaching reaction rate constant by ultrasound was mainly reflected in the increase of the pre-exponential factor A. Ultrasound treatment improved the efficiency of impurity mineral removal by destroying the inert layer formed on the graphite surface, promoting particle fragmentation, and generating oxidation radicals. The poor reactivity of hydrochloric acid with quartz and some silicate minerals is a bottleneck limiting the further improvement of impurity removal efficiency in ultrasound-assisted aphanitic graphite. Finally, the study suggests that introducing fluoride salts may be a promising method for deep impurity removal in the ultrasound-assisted hydrochloric acid leaching process of aphanitic graphite.

Keywords: Aphanitic graphite; Ash impurity removal; HCl; Leaching kinetics; Ultrasound.