The process of recovering nickel sulfate from waste batteries includes the following key steps: pretreatment, leaching, extraction and separation, and subsequent refining and purification. The following is the detailed process flow introduction:

Pretreatment

Waste batteries need to be pre-treated before recycling, including dismantling, crushing and screening operations. For waste lithium ternary batteries, the battery shell is usually removed first and the electrode materials are separated. The purpose of pretreatment is to enrich the valuable metal components in the battery for subsequent leaching operations.

Leaching

Leaching is one of the key steps in the recovery of nickel sulfate, the purpose of which is to dissolve the nickel and other valuable metals in the battery into the solution. Commonly used leaching methods include acid leaching and reducing acid leaching. In the acid leaching process, sulfuric acid (H₂SO₄) is usually used as the leaching agent, and reducing agents (such as sodium bisulfite NaHSO₃ or hydrogen peroxide H₂O₂) are added to reduce the valence of the metal ions and improve the leaching efficiency. For example, nickel, cobalt, manganese and other metals in ternary lithium batteries can be dissolved by the following reaction: MeO2+H2SO4+NaHSO3→MeSO4+Na2 SO4+H2O where Me represents nickel (Ni), cobalt (Co), manganese (Mn) and other metals.

Extraction and separation

The leach solution contains a variety of metal ions, which need to be separated from nickel and other metals by extraction and separation processes. Commonly used extractants include P204 and P507. The extraction process is usually divided into the following steps:

Saponification: React the extractant (e.g. P507) with alkali to change it from hydrogen type to sodium type to improve the extraction efficiency.

Extraction: The leach solution is subjected to a multi-stage countercurrent extraction with the saponified extractant to load metal ions such as nickel into the organic phase.

Back-extraction: Use sulfuric acid solution to back-extract the nickel ions loaded in the organic phase into the aqueous phase to obtain nickel sulfate solution.

Refining and purification

The nickel sulfate solution obtained after extraction and back-extraction may still contain a small amount of impurities, which need to be further refined and purified. Commonly used refining methods include precipitation method, ion exchange method and so on. For example, by adjusting the pH of the solution, the impurity ions can be precipitated and removed to obtain a high purity nickel sulfate solution.

Environmental protection measures

In the recycling process of waste batteries, pollutants such as acidic wastewater, waste gas and waste residue will be produced. In order to reduce the impact on the environment, it is necessary to take appropriate environmental protection measures:

Wastewater treatment: Neutralization, precipitation, filtration and other methods are used to treat the acidic wastewater and remove the heavy metal ions in it.

Waste gas treatment: collect and purify the waste gas generated in the extraction process to prevent harmful gas emissions.

Waste residue treatment: reliable disposal or resource utilization of solid wastes such as leaching residue.