Integrating multi-method approaches for the green separation and retrieval of nickel and phosphorus from spent electroless nickel plating solutions

Abstract

The spent electroless nickel plating (SENP) solution comprises abundant complexed nickel, hypophosphite, and phosphite ions, alongside scant organic additives. In this study, we introduced an innovative method that uses a combination of alkali and heat treatment-activated PMS to disrupt the nickel ion complexation, facilitating hypophosphite and phosphite oxidation, and the alkali acts as a precipitant for nickel. Consequently, nickel and phosphorus precipitated sequentially, enabling their efficient separation and recovery. With a 4 g L⁻¹ PMS dose, the hypophosphite (H₂PO₂⁻) and phosphite (HPO₃²⁻) conversion rates reached 100% and 99.69%, respectively. After the precipitation and separation of the concentrated SENP solution, residual nickel and phosphorus levels significantly dropped to 10.91 mg L⁻¹ and 12.29 mg L⁻¹, respectively. Subsequently, capacitive deionization (CDI) concurrently removed nickel and phosphorus to comply with emission standard GB39731-2020. Under optimal conditions, nickel and total phosphorus removal efficiency reached 96.69% and 93.62%, respectively, and the residual concentration decreased to 0.36 mg L⁻¹ and 0.78 mg L⁻¹, respectively. This innovative, streamlined strategy was proposed for the green treatment and recovery of nickel and phosphorus resources from spent electroless nickel plating solutions.