Selective recovery of Nickel from electroplating rinse bath wastewater by an integrated Donnan Dialysis/precipitation process

The purpose of this work is to experimentally assess the application of a hybrid process, Donnan Dialysis (DD)/precipitation, for the selective separation and recovery of Nickel ions from Nickel electroplating rinse bath effluent. The primary objectives include facilitating water and Nickel reuse while protecting environmental resources. The separation of Ni (II) via an ion-exchange membrane was investigated experimentally. Operational parameters, such as the type of cation-exchange membrane, initial Nickel (II) concentration, and counter-ion concentration, were systematically studied to understand their impact on the productivity and selectivity of DD process. Simultaneously, the feasibility and efficiency of Ni (II) recovery from the receiver compartment through the precipitation process, forming Ni3(PO4)2, were examined. Results indicate that, under optimal conditions and with an initial Ni (II) concentration of 200 mg/L or less, the removal efficiency reached 90% after 24 hours of dialysis. Significantly, the type of cation-exchange membrane emerged as a crucial factor influencing Ni (II) removal. Additionally, employing PO43- as a precipitation reagent in a stoichiometric ratio yielded an excellent Ni recovery performance of 99%. Consequently, the treated effluent (feed compartment) becomes suitable for recycling in a new electroplating operation, while the solution obtained in the receiver compartment can be reused for another DD cycle process after Ni (II) recovery as Ni3(PO4)2. Importantly, this hybrid method produces a valuable Ni3(PO4)2 precipitate of excellent quality.