Selective leaching of iron from scrapped diamond alloy cutters and preparation of battery-grade iron phosphate

Discarded diamond alloy cutters contain plenty of elements such as iron, copper, and diamond. Efficient and comprehensive utilisation of these elements is an important technical problem in the recovery process. In this study, a selective leaching process of iron with high efficiency was used to separate iron from waste diamond cutters, and battery-grade iron phosphate was prepared using the iron-leached solution. The leaching efficiencies of Fe and Cu in the diamond alloy cutters were 99.57% and 0.003%, respectively at a leaching temperature of 80 C, leaching time of 39 h, liquid-to-solid ratio of 10:1, and sulphuric acid content of 1.3 times the theoretical amount. Battery-grade iron phosphate was prepared by purifying and oxidising the iron in the leaching solution using phosphoric acid as the precipitant at a pH value of 2–3. Analysis of the chemical composition of the prepared iron phosphate indicated that the impurity levels satisfied the requirements of the HG/T 4701-2021 standard. X-ray diffraction studies established the high purity and crystalline nature of the prepared iron phosphate, satisfying the requirements of battery-grade iron phosphate. Thus, the effective separation of iron from waste diamond alloy cutters and its high-value utilisation were simultaneously achieved.