An investigation of the electrodeposition of nickel-iron for a novel electrochemical stripping and recovery process

• Main Author: Lam, Kelven Jian Xiong
• Other Authors: Lim Teik Thye
• Format: Final Year Project
• Language: English
• Published: 2012
• Subjects: DRNTU::Engineering::Environmental engineering::Waste management
• Online Access: http://hdl.handle.net/10356/49779
• Institution: Nanyang Technological University

The electrodeposition of nickel-iron (Ni-Fe) alloys was studied under different conditions of metal ion concentration, pH, temperature, acid concentration, air agitation, presence of phosphorous and current density. The alloy deposits were investigated using SEM-EDS and the electrochemical behaviour was evaluated by potentiodynamic studies. It was found that anomalous codeposition was enhanced at low acid concentrations, due to the increased formation of an iron hydroxide film at the cathode. Ni selectivity was increased at the highest bath temperature of 80ºC, probably due to the inhibition of the formation of Fe intermediates at the cathode. The presence of air agitation enhanced Fe selectivity due to Fe reduction being under mass transport limitations. A high Ni2+-to-total Fe ratio (Ni2+:Fetot) led to Fe deposition and it is suspected that the concentration of Ni2+ is proportional to its catalytic effect on Fe deposition. Increasing current density led to an increase in Fe selectivity, due to high hydrogen evolution reaction (h.e.r) which accounted for a higher interfacial pH that favoured the formation of iron hydroxide film. The addition of 2g/L of phosphorous significantly decreased the anomalous behaviour by increasing Ni selectivity but also seem to enhance h.e.r which led to poor current efficiency for metal deposition. It was observed that h.e.r was most likely the dominating reaction when electrodepositing from all baths due to the high acidity of the baths and this is reflected in the cathodic polarization curves.