Equipment for producing iron phosphate for batteries using a fully wet method to process copper slag

Release time:

2025-06-28 08:27

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Iron phosphate (FePO4) is an inorganic compound, usually a grayish-white or light yellow powder. It dissolves in hydrochloric acid and sulfuric acid but is insoluble in water and nitric acid. It has a stable crystal structure. Due to its excellent electrochemical properties, high safety, long cycle life, and low cost, it is used as a raw material for producing lithium iron phosphate, a cathode material for lithium-ion batteries. In 2025, China's demand for iron phosphate for batteries is expected to reach 2 million tons, an increase of about 25% year-on-year, indicating a broad market prospect.

Copper slag is industrial solid waste produced during the copper fire smelting process. Its main chemical components are iron, silicon, and small amounts of copper, zinc, lead, and other metal oxides. The iron content (calculated as TFe) is between 30% and 45%. Because copper slag contains high levels of iron, it can serve as a source of iron for producing iron phosphate for batteries.

Production of battery-grade iron phosphate from copper slag using a fully wet process Process Technology: Sulfuric acid is used to decompose the ferrous oxide in the olivine and the magnetite contained in the copper slag, converting them into easily soluble iron salts (ferrous sulfate, ferric sulfate) that enter the liquid phase. During the reaction process, silicon does not react with the acid, while calcium reacts with sulfuric acid to form calcium sulfate dihydrate, which, along with unreacted silicon, enters the solid phase. After the reaction is complete, filtration yields an iron salt solution and an acid leaching residue mainly composed of silicon dioxide and calcium sulfate dihydrate. After purifying the iron salt solution to remove impurities such as zinc, copper, manganese, magnesium, and chromium, filtration produces a ferrous salt solution with purity meeting technical requirements.

The ferrous salt solution and an industrial phosphoric acid or phosphate solution meeting technical purity requirements are mixed in a continuous iron phosphate precipitation reactor. The continuous precipitation reaction is carried out under controlled process conditions to produce iron phosphate precipitate. Then, it undergoes Multifunctional mechanical equipment “Honeycomb mill” for filtration, washing, and drying to obtain ferrous phosphate dihydrate. The ferrous phosphate dihydrate is calcined to produce anhydrous iron phosphate for batteries. The production process achieves the recovery and recycling of neutralizing agents through the treatment of the ferrous phosphate dihydrate mother liquor, resulting in zero wastewater discharge. The residue from copper slag decomposition is mainly composed of silicon dioxide and calcium salts, contains no harmful components, has a neutral pH, and is considered general industrial waste. Collection and storage can be used for further resource utilization.

Typically, Iron leaching rate: ≥90%; Iron recovery rate: ≥95% (based on leaching rate); Phosphoric acid or sulfate utilization rate: ≥93%.

Copper slag contains abundant iron. Using it as an iron source to produce battery-grade iron phosphate needed by the new energy industry has the advantages of abundant raw material sources, simple process, operability, product quality meeting the requirements of the new energy industry, significant economic benefits, and environmental friendliness. The use of a fully wet process to treat copper slag and use its iron content to produce battery-grade iron phosphate has opened up a new and effective path for the resource utilization of copper slag.

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