Polymetallic nodules reveal the closest similarity with lateritic type land ores, thus most of the processing methods, which have been tested for nodules, are adaptations of the ones originally developed for laterites. The major impediment in the recovery of base metals (Ni, Co, Cu, Zn, Mo) is coexistence with large amounts of iron and manganese, as a basic component of nodules. There are two general types of processing technologies:
- Hydrometallurgical: mainly leaching (acidic – by hydrochloric/sulphuric acid or alkaline – by ammonia reagents) with or without reduction, followed by purification of the obtained solutions and separation of metals in the elemental or compound form
- Pyro-metallurgical: high temperatures pre-treatments (chlorination, sulphonation, reduction roasting, smelting) usually followed by hydrometallurgical metal separation
Technologies of polymetallic nodules (PN) processing with the main processes and types of products.