Improvement of Nickel-Precipitation from Aqueous Nickel Solution by Sulfuration with Sodium Sulfides

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In order to recover nickel from waste plating solution, the precipitation of nickel by sulfuration was applied in the present study. Sodium sulfide (Na₂S), sodium disulfide (Na₂S₂) and sodium tetrasulfide (Na₂S₄) were employed as sulfurating agents and were compared in terms of their ability to form Ni precipitates. From the results, it was found that the initial nickel concentration of 100 mg/dm³ was reduced to 0.594–3.37 mg-Ni/dm³ in the filtrate by addition of sulfurating agents. The average specific filtration resistance of the slurry produced by addition of a sulfurating agent was smaller than that of nickel hydroxide slurry; in particular, the lowest specific resistance of the slurry was found to be produced by addition of sodium tetrasulfide at a controlled pH 7 ± 1. The low filtration characteristic of nickel sulfide precipitates obtained by addition of sodium tetrasulfide was attributed to their particle size.