Toward Rapid Detection of Trace Lead and Cadmium by Anodic Stripping Voltammetry in Complex Wastewater Streams

Heavy metals (HMs), such as lead (Pb) and cadmium (Cd), in municipal wastewater (MWW) limit its use as an alternative water resource. Therefore, monitoring HM concentrations in MWW is critical to evaluating potential reuse applications. However, current metal detection methods rely on grab-sampling and analysis on complicated laboratory-based analytical chemistry instruments, limiting sampling frequency. Anodic stripping voltammetry (ASV) is a promising measurement alternative. However, HMs in MWW are found as complexes and/or sorbed onto particles, and are thus not detectable by ASV. In this study, we develop a processing method that enables the detection of HMs using ASV. In this method, HM-containing MWW is pretreated by either vacuum ultraviolet (VUV)/H2O2 (Cd) or a strong acid (Pb), which releases the bound HMs. HMs are then accurately detected and quantified using ASV by utilizing a bismuth subcarbonate/reduced graphene oxide nanocomposite incorporated in a Nafion matrix electrode. The resulting sensing process is able to detect trace concentrations of Cd and Pb in both synthetic and real MWW samples. Detection results were benchmarked against state-of-the-art metal detection methods, and were found to be highly accurate (>88%). This pretreatment and detection method enables utilities and end-users to frequently monitor HM concentrations in complex streams.