Copper sulphide precipitation in a fluidised bed reactor

The feasibility of the removal of a single metal (copper) by sulphide precipitation from a synthetic stream was investigated in a seeded fluidised bed reactor. The use of sulphide was motivated by high sulphate levels in local acid mine drainage and the potential integration of the metal removal process with a biological sulphate reducing process that produces an aqueous sulphide stream. Results showed that high local supersaturation and complex reaction chemistry were responsible for inefficiencies in the system, resulting in the precipitation of very fine particles and the formation of stable, soluble copper polysulphide complexes. The influence of the sulphide to copper molar ratio, recycle flow rate, inlet copper flow rate and the inlet copper concentration on the copper conversion and removal efficiency were investigated using response surface methodology to map the response surface and optimise the laboratory system. The sulphide to copper molar ratio was the most influential factor. However, the derived models were unable to account for a significant portion of the observed variation, so an optimal reactor configuration could not be determined with a high degree of confidence.