A novel approach to treating nickel-containing electroplating sludge by solidification with basic metallurgical solid waste

Nickel-containing electroplating sludge is a solid waste generated during the treatment of electroplating wastewater, often managed through solidification with materials such as cement and lime. This paper presents a novel approach for solidifying nickel-containing electroplating sludge using basic metallurgical solid waste. A mathematical model was employed to determine the kinetics of Ni2+ leaching, yielding the kinetic equation α(t) = 0.97*(1-exp(-0.19*t)). Rapid leaching occurred in the initial 10 minutes, reaching a concentration of 86.78 mg/L, followed by a slower release, peaking at 104.54 mg/L within 40 minutes. Through the solidification of electroplating sludge with basic waste materials, it was found that the inclusion of 2.0% lime, 12.2% sintering dust, and 2.5% steel slag resulted in Ni2+ leaching concentrations of 0.28, 0.41, and 0.61 mg/L, respectively, all meeting the discharge standard of <1.00 mg/L. Phase analysis indicated that the main constituents of the solidified products were C-S-H and CaSO4, with no detectable change in the crystallinity of Ni2+ before and after solidification. Thermodynamic calculations further demonstrated that under basic solidification conditions, Ni2+ transforms from NiSO4 to Ni(OH)2. Microscopic morphology analysis revealed that the encapsulation of Ni2+ by C-S-H and CaSO4 led to the densification of the porous microstructure of the electroplating sludge, achieving effective solidification.