A Study on the Optimization of the Preparation of Recycled-Rare Earth Polishing Powder

To realize the efficient recovery and utilization of rare earth resources, this study systematically investigates the preparation process of recycled-rare earth polishing powder using rare earth intermediates (purified from waste polishing slag) as raw materials. This work focuses on two core stages: precursor synthesis and high-temperature calcination. During the precursor preparation stage, the particle size of the precursor was controlled by optimizing the ball milling process (with a ball milling time of 1 h, a ball-to-material ratio of 3:1, and 2 mm zirconia balls), yielding an optimal D50 of 6.5 μm. The Ce/La ratio was modulated by adding cerium carbonate (the conventional ratio is 65:35, which can be adjusted as needed within the range of 65:35–80:20). Furthermore, fluorine (3–7%) and a small amount of praseodymium were incorporated to enhance the polishing performance. In the high-temperature roasting stage, single-factor tests were conducted to determine the optimal staged heating rates (below 400 °C: 5 °C/min; 400–700 °C: 3 °C/min; above 700 °C: 1.5 °C/min) and a holding time of 4 h at 950 °C. Under these optimized conditions, the resulting polishing powder exhibits a material removal rate exceeding 350 mg·h−1 and maintains stable performance over three consecutive polishing cycles. This study demonstrates that by regulating the chemical composition and physical parameters of the precursor, as well as optimizing the high-temperature roasting process, recycled-rare earth polishing powders with tailored performance characteristics can be custom-manufactured. This approach balances the polishing ability and production cost, thus providing technical support for the industrial production of recycled-rare earth polishing powder.