Patent
AUSTRALIAN PATENT APPLICATION NO. 2006900739
According to Select Minerals Pty Ltd, nickel, cobalt and manganese may be simply, efficiently and rapidly recovered from laterites dominated by Asbolane by leaching the Asbolane with a dilute solution of sulphur dioxide in water at ambient conditions of temperature and pressure.
The process may be carried out at ambient conditions of temperature and pressure, i.e., at about 25°C and a pressure of 1 atmosphere. The much shorter leaching times and weaker solution acidity permit the use of stainless steel vessels for sulphurous acid leaching, while titanium or other exotic alloys are generally required to withstand corrosion in leaching with mineral acids. The weak acidity of the sulphurous acid leaching solution is also advantageous in any subsequent neutralization step since the demand for alkali or ammonia in the neutralization steps will be much smaller than that required in the case of a mineral acid leach. Following reaction of the sulphurous acid leach solution with the asbolane, the solution is separated from the residue by conventional procedures such as filtration or decantation, and will usually contain more than 80 percent, or more, of the nickel, cobalt and manganese. Separation and recovery of the nickel and cobalt from the manganese-free leach solution may be readily achieved by conventional methods.
