WANG Bing1a ，WANG Xiaofei1 ，PENG Gang1a ，YUAN Xiaoyan1 ，LIU Dan2 ，SHEN Xiangfeng3 ，GUO Shouwu1，4
1a. School of Materials Science and Engineering，1b. Shaanxi Key Laboratory of Green Preparation and
Functionalization for Inorganic Materials， Shaanxi University of Science and Technology， Xi’an 710021， China；
2. Jiangsu Jinrun Environmental Protection Engineering Co. ， Ltd. ， Yixing 214200， China；
3. Jiangsu Xingwanghong Construction Engineering Co. ， Ltd. ， Yixing 214200， China；
4. School of Electronic Information and Electrical Engineering， Shanghai Jiao Tong University， Shanghai 200240， China
Abstract
Objective To improve the performance of natural graphite raw materials and expand their application scope， a composite molten salt purification method is employed to purify the natural graphite raw materials， and the process parameters are optimized， aiming to improve production efficiency while reducing energy consumption and production costs.
Methods The components of the natural graphite raw materials were analyzed. High-purity graphite was prepared at room temperature using a dilute hydrochloric acid leaching method， with NaOH， Na2CO3， Li2B4O7， Na2B4O7， and Li2CO3 serving as the molten salt components. The effects of inorganic salt types， composite molten salt formulations， calcination temperatures， and the mass of natural graphite raw materials on the purity of purified graphite were studied. Moreover， a comparative analysis of the microscopic morphologies of the natural graphite raw materials and the purified graphite was performed.
Results and Discussion After two rounds of optimization experiments， NaOH， Na2CO3， and Na2B4O7 were selected as the formulation components of the composite molten salt. When the mass fraction of natural graphite raw material was 95.77 % and the mass was set at 4 g， the respective masses of NaOH， Na2CO3， and Na2B4O7 were optimized to 1.0， 0.5， and 1.0 g， with a calcination temperature of 700 ℃. Under these conditions， the mass fraction of purified graphite reached as high as 99.965%， with a mass ratio of NaOH to graphite of 1：5.5， and a composite molten salt to graphite mass ratio of 2.5：4. These parameters achieved an optimal balance between the equipment performance， production efficiency， and processing costs. The characteristic peaks in the X-ray diffraction （XRD） patterns of the purified graphite were highly consistent with the （002）， （004）， （100）， and （110） crystal planes referenced in the graphite standard PDF card （PDF#41-1487）， indicating that the composite molten salt method effectively removed impurities while preserving its crystalline structure. The purified graphite particles still maintained their ellipsoidal morphology， though with significantly diminished white substances on the particle surface and notably smoother surfaces， demonstrating the efficacy of the purification process in impurity elimination.
Conclusion The composite molten salt method synergistically enhances the reaction with minerals by leveraging the advantages of individual salt components， effectively reducing alkali consumption while improving graphite purity. In terms of industrial production， this method simplifies the operational procedures， and its efficient alkali treatment process significantly reduces the difficulty of the subsequent acid treatment process.
Keywords：composite molten salt method； natural graphite； purification； process parameter
Get Citation:WANG Bing， WANG Xiaofei， PENG Gang， et al. Process parameter optimization for natural graphite purification via composite molten salt method［J］. China Powder Science and Technology， 2025， 31（5）： 1-9.
Received: 2024-11-26 .Revised: 2025-05-22,Online: 2025-06-14
Funding Project: 国家自然科学基金项目，编号： 52272302。
First Author: 王冰（1998—），男，硕士生，研究方向为天然石墨提纯。E-mail：364367776@qq.com。
Corresponding Author: 王晓飞（1985—），男，讲师，博士，硕士生导师，研究方向为纳米能源材料。E-mail：wangxiaof@sust.edu.cn。
原晓艳（1985—），女，教授，博士，硕士生导师，研究方向为碳基材料。E-mail： yuanxiaoyan@sust.edu.cn。
DOI：10.13732/j.issn.1008-5548.2025.05.016
CLC No: TB4； TQ324.8 Type Code: A
Serial No: 1008-5548（2025）05-0001-09
