Abstract
A process for recycling Ni2+ in Ni-plating wastewater was investigated. This study employed Mg alloy flash waste to reduce the Ni2+ in the wastewater into metallic Ni. Fine second-phase Mg17Al12 in a network is the critical point for promoting the reduction reaction of Ni2+. The microstructures of the Mg alloy flash scrap and the die-cast Mg alloy scrap waste fulfilled the requirement. The Mg17Al12 is like a catalyst for the quick reduction of the Ni2+ ions into pure Ni metal. Contrarily, pure Mg (not containing Mg17Al12 particles) and gravity-cast AZ91D Mg alloy (having coarse Mg17Al12 particles) were not suitable for being used for the Ni2+ wastewater treatment. Based on the above results and discussion, using the Mg alloy flash scrap waste for treating the laboratory-made Ni2+-containing wastewater, the wastewater initially with ∼5600 ppm of Ni2+ ions could be reduced to ∼20 ppm in 2 h. When applying the Mg alloy flash scrap for the Ni plating wastewater from industry, the concentration of Ni2+ was able to be reduced from ∼16,670 ppm to ∼1434 ppm in 10 min for the wastewater at 90 °C.
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