The aluminum electrolysis industry continually and unavoidably produces hazardous solid waste in the form of carbon anode slag. Carbon anode slag poses a serious environmental pollution risk, and it must be disposed of in a harmless manner. On the other hand, it contains a few valuable resources, as well. In order for the aluminum electrolysis industry to develop in an environmentally friendly and high-quality manner, the harmless disposal of carbon anode slag and its resourceful utilization are of considerable importance. The selective comminution of carbon and cryolite particles in carbon anode slag can be effectively achieved with grinding pretreatment. However, the optimization study of grinding process parameters has yet to be investigated. Therefore, firstly, the mineralogical characteristics and existing mode of carbon anode slag from the perspective of mineralogical properties are analyzed in this study. Then, the effects of grinding time, grinding concentration, and steel ball diameter on the particle size of the ground product (γ_{−0.074 mm}) are investigated using response surface analysis. The results showed that the effect of grinding time was the most significant, followed by grinding concentration and steel ball diameter. In addition, the performance of the multi-stage flotation process for separating the −0.074 mm ground product was analyzed. Cryolite with a purity of 93.12% and a carbon product with an ash content of 10.67% could be simultaneously obtained through multi-stage flotation. It should be pointed out that the deep dissociation and efficient recovery of fine undissociated particles still need to be further explored.

One of the main electrolytic aluminum production costs is the consumption of carbon anodes, and carbon anode slag is a common hazardous waste in the aluminum industry. In this work, electrolytic aluminum carbon anode slag was separated by flotation. Using the selectivity index (SI) as an indicator, the influencing factors of the carbon slag flotation process were optimized, and the separation performance of carbon and cryolite in the carbon anode slag was investigated. The raw carbon anode slag was ground for 40 min to achieve dissociation of the cryolite from the carbon, the optimized SI value was then used to determine the optimal flotation test conditions. The test results showed that the SI value under the optimal grinding flotation was approximately four times larger than the value of direct flotation. This indicated that carbon anode slag had a better flotation selectivity under the grinding flotation, which significantly improved the flotation performance.