Following solvent extraction, reduction and precipitation are conducted on an industrial scale and typically involve oxalic acid and/or sodium oxalate [22,23], SO₂ gas [25], metabisulfite [29], or sodium sulfite [25]. Sodium sulfite reduction presents several drawbacks, including high energy consumption (operating at 75 °C), significant SO₂ emissions, environmental pollution, and the generation of sodium sulfate and sodium chloride, which can affect gold powder quality. In contrast, oxalic acid is favored for its rapid reduction, good selectivity, and ability to produce gold powder with a purity exceeding 99.99%, surpassing that of SO₂ [13].

For industrial silver leaching, sodium s