Towards a circular nickel-plated steel (NPS) industry
A method to selectively dissolve nickel coatings from NPS in ammoniacal solutions
Muawya Elayyan Mohammad Hindi (TU Delft - Mechanical Engineering)
Y. Yang – Mentor (TU Delft - Team Yongxiang Yang)
Neslihan Dogan – Graduation committee member (TU Delft - Team Yongxiang Yang)
A.J. Wittebrood – Mentor (TATA Steel Nederland Technology BV)
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Abstract
A patent pending ammonia-based hydrometallurgical method is developed to selectively leach nickel coatings from the Nickel-Plated Steel sheets (NPS). The leaching process starts with the removal of the passive nickel oxide film by Na2S2O3.5H2O addition into the solution, followed by the dissolution of the metallic nickel. Leaching stops due to the passivation of the diffusion region between the coating and the steel. The experiments were conducted using two different ammoniacal systems, the NH3-(NH4)¬2S2O8-Na2S2O3.5H2O and the NH3-(NH4)¬2SO4-Na2S2O3.5H2O system, resulting in leaching efficiencies of 98% and 91% respectively.