Key points
- SGS piloted high-pressure acid leaching on CCZ polymetallic nodules and achieved 99% nickel recovery, mid-90s recovery for cobalt and copper, while selectively rejecting manganese, iron, and aluminum into the leach residue.
- Three hydrometallurgical routes are under consideration for nodule processing: smelting plus acid leaching (TMC), reductive acid leaching with sulfuric acid and SO2 gas recycling (GSR), and the Cion process using ammonia-ammonium carbonate lixiviant (LowKey Minerals).
- Analysis of 13 critical mineral projects commissioned since 2009 shows eight experienced prolonged ramp-up periods after startup, with material handling consistently identified as an operational challenge.
- Processing all manganese from nodules into sulfate would exceed market capacity; a 60,000-ton-per-year nickel plant would produce roughly 5 million tons of manganese sulfate annually.
