School of Chemical Engineering and Technology, China University of Mining & Technology
National Engineering Research Center of Coal Preparation and Purification, China University of Mining & Technology

废弃锂电池电极材料中石墨和钴酸锂等有价组分浮选分离是实现锂电池二次资源循环利用的环节之一，然而由于2者粒度较细，利用传统浮选技术难以对2者实现有效分离。将界面纳米气泡引入该浮选体系，通过冷水升温法诱导纳米气泡在固液界面成核，联合原子力显微镜(AFM)软物质成像技术、胶体探针技术、聚集体尺寸表征、颗粒−气泡相互作用可视化装置和浮选试验系统研究了界面纳米气泡强化电极材料浮选分离机理。原子力显微镜成像结果表明，通过原子力显微镜间歇接触成像模式分别在高定向热解石墨(HOPG)和氧化铝固液界面观测到了界面纳米气泡图像，冷水升温可有效诱导纳米气泡在固−液界面成核。利用原子力显微镜在接触模式下对界面纳米气泡进行了扫描，纳米气泡在原子力显微镜针尖推动下的兼并及擦除现象有力证明了纳米结构的气相本质。纳米气泡通过在颗粒间的桥接作用增加了颗粒间的最大黏附力分布：常温水条件下颗粒间最大黏附力在10 nN以内，纳米气泡存在时颗粒间最大黏附力高达110 nN，随矿浆pH的变化而有所不同。纳米气泡诱导石墨颗粒间形成了更大的聚集体，和常温水中相比，冷水升温条件下石墨颗粒聚集体尺寸增加了2～11 μm。纳米气泡在石墨颗粒表面成核及其诱导形成的石墨颗粒聚集体协同促进了颗粒与浮选气泡的黏附。浮选结果表明，在不同pH和氯化钠离子浓度的矿浆中纳米气泡均有效改善了石墨颗粒的浮选效果。

Flotation separation of valuable components including graphite and lithium cobalt oxide (LCO) from the waste electrode materials of lithium battery is a key link in the recycling of waste lithium battery, which is difficult to realize with some conventional flotation techniques due to the fine size of graphite and LCO. Interfacial nanobubbles induced by temperature increasing were introduced into the flotation system and the mechanism on improving the flotation performance of electrode materials by nanobubbles was studied by combining intermittent mode atomic force microscope (AFM) imaging technique, colloidal probe technique, agglomeration size analyzer, particle-bubble interaction visualization and flotation. The results show that the images of nanobubbles were captured at highly oriented pyrolytic graphite (HOPG) and alumina surface with intermittent mode AFM. The detachment and/or coalescence of nanoentities in the action of AFM tip at contact mode provided evidence supporting gaseous nature of these nanoentities. The maximum adhesion force between graphite and HOPG in-creased in the presence of nanobubbles between graphite and HOPG. The maximum adhesion force was lower than 10 nN in the room temperature water while up to 110 nN in the cold water, which varied with the pH variation in slurry. It was observed that the larger graphite agglomerations were induced by interfacial nanobubbles. The size of such graphite agglomerations increased by 2−11 μm in the cold water compared with that in the room temperature water. The nucleation of interfacial nanobubbles on graphite surface and the formation of graphite agglomerations synergistically enhanced the adhesion between graphite and fixed bubbles. The flotation results showed that the flotation performance was always improved with nanobubbles in all slurry with different pH values and ions concentrations.

国家自然科学基金资助项目(52204291，52225405)；江苏省自然科学基金资助项目(BK20221127)

李臣威，张雅婷，张海军. 界面纳米气泡强化锂电池电极材料浮选分离机理[J]. 煤炭学报，2023，48(8)：3277−3288.

LI Chenwei，ZHANG Yating，ZHANG Haijun. Enhancement effect of interfacial nanobubbles on flotation performance of electrode materials from lithium-ion batteries[J]. Journal of China Coal Society，2023，48(8)：3277−3288.