Manganese (manganese)

Manganese (Mn) is a heavy metal and essential trace nutrient that becomes a problem at elevated levels: it stains water and fixtures (black/brown deposits) at low concentrations, imparts taste, and is neurotoxic at high chronic exposure (manganism, a Parkinson-like condition). Its effluent discharge limit is 2 mg/L across most discharge modes.

Manganese enters effluent from steel and ferroalloy manufacture (manganese is a key steel alloying element), battery manufacture (manganese dioxide is the cathode in alkaline and zinc-carbon cells, and lithium-ion NMC cathodes contain manganese), mining, and metal finishing. For recyclers, the two most relevant sources are battery recycling and metal/steel recycling.

The battery recycling connection is significant: alkaline and zinc-carbon batteries use manganese dioxide, and the increasingly important lithium-ion NMC (nickel-manganese-cobalt) chemistry contains manganese as a valuable cathode metal. Manganese in lithium-ion black mass is therefore both an effluent parameter to control and a metal to recover, alongside nickel and cobalt. In steel scrap recycling, manganese is present as a steel alloying element.

The practical relevance, especially for lithium-ion battery recyclers, is that manganese is part of the valuable metal mix in black mass (Li, Ni, Co, Mn) that hydrometallurgical recovery targets, while dissolved manganese in process effluent must be controlled to 2 mg/L. Manganese is removed from effluent by oxidation followed by precipitation (it precipitates as the dioxide/hydroxide once oxidised and pH-adjusted), and in battery recovery the same manganese is captured as a product in the leach-and-recover circuit. As with the other battery metals, controlling manganese in effluent and recovering it as product are two sides of the same well-designed process.