Abstract
The use of additives in the precipitation of nickel with hydrogen is known to influence the
particulate processes and by extension the powder properties such as morphology,
microstructure and particle size distribution. Controlling these properties is crucial for some
downstream processes. The present study assesses the effect of calcium lignosulphonate on the
particulate processes taking place during the reduction of nickel ammine sulphate solutions by
hydrogen gas. Reactions were carried out in an autoclave operated at 28 bar and 180°C under
stirring conditions of 850 rpm. Particulate processes were studied by analysing the particle size
distribution and the corresponding normalized moments. These were further validated by
scanning electron microscopy and nitrogen physisorption analyses. The powder phase
identification and purity were determined by means of X-ray diffraction and X-ray
fluorescence respectively. Calcium lignosulphonate acted as a reduction catalyst, growth
promoter and by extension agglomerating agent. At 2, 5 and 7 mg/L of calcium
lignosulphonate, the system was found to be dominated by breakage while agglomeration was
more pronounced at 10 mg/L, as validated by scanning electron micrographs. Furthermore the
use of calcium lignosulphonate resulted in the increase of the reduction rate, indicating that this
additive acted as a growth promoter.