Processes and methods for refining ferronickel alloy, and producing nickel sulfate or other nickel product, are provided, where the ferronickel alloy is treated with an oxidizing leach. The oxidizing leach may be, for example, a pressure oxidation (POX) leach or a leach with peroxide or copper (II) ions. The treatment may be in the presence of added copper, such as by providing a copper sulfate solution. Producing nickel sulfate may comprise removing copper and iron after the leach, removing impurities, and either crystallizing the nickel sulfate or precipitating/winning another nickel product.