Abstract
The use of additives in the precipitation of nickel with hydrogen is known to influence the
particulate processes and, by extension, 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 ethylene maleic
anhydride 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. Ethylene maleic
anhydride acted as a growth inhibitor and an anti-agglomerating agent, thus acting as a
reduction catalyst by maintaining the available surface area for reduction. The system was
dominated by agglomeration at low concentration (2–5 mg/L) of ethylene maleic
anhydride while breakage became the dominant particulate process at higher
concentration (7–10 mg/L), as validated by scanning electron micrographs.