Separation of lead from high matrix electroless nickel plating waste solution using an ion-selective immobilized macrocycle system

Separation of trace levels of lead from concentrated-matrix electroless nickel plating (ENP) waste solutions is required to meet the increasingly stringent environmental regulations. A solid phase extraction (SPE) system using a molecular recognition technology (MRT) gel was used for the selective separation of trace levels of lead (Pb) from the waste discharge of ENP operations, followed by subsequent analysis with inductively coupled plasma optical emission spectrometry (ICP-OES). Two SPE-MRTs, AnaLig® Pb-01 and AnaLig® Pb-02, packed in 3mL polypropylene cartridges were used to treat the synthetic metal-waste solutions that were used to simulate the typical metal mixture in ENP bath waste. The fortified solutions contained 100-1000 μgL^-1 of Pb in an HNO₃ matrix with pre-added Ni, Cu and other interfering elements (1000mgL^-1). After the sample treatment, the SPE-MRT cartridges were washed with water and 0.1M nitric acid, followed by elution with 0.03M EDTA. The matrix elements (e.g., Ni, Cu) were completely removed at the washing step, while the 'captured' Pb was quantitatively eluted, as determined by ICP-OES measurements. The detection limit of the proposed method was 2.6 μgL^-1. 'Real' samples from commercial ENP operations were used to assess the validity of this method, and almost quantitative Pb recovery was observed. The excellent Pb selectivity of the SPE-MRT system indicates the potential of the proposed technique for trace-level Pb separation from the Pb-containing high matrix aqueous waste discharge.