The Effect of Electrode Geometry and Fluid Flow on Electrodeposition of Pb2+ in Drinking Water

Abstract

The recent Flint Water Crisis (2014) and the failure of a lead leaching-prevention system in Newark (2018) raise concerns about health risk caused by heavy metals in water. To prevent damage from leaching of heavy metals in public water system, affordable heavy metal sensors that can continuously monitor water quality at the end point of water service lines (e.g., bathroom) for a long period are needed. We previously developed a sensor that utilized electrodeposition in a four-electrode system (anode, cathode, and two floating electrodes) to detect heavy metal ions (Pb2+, Zn2+, Cu2+, and Fe2+) in drinking water1. This sensor could detect low concentrations of heavy metal ions with 2 AAA batteries at a low per-sensor manufacturing cost (~$0.10/sensor) and a small footprint (~1 mm2). However, the response time of the sensor varied by days and the effect of fluid flow on the sensor performance has not been tested. In this presentation, we report our study about the effect of electrode geometry and fluid flow on the ability of the sensor to detect lead. We varied the number and shape of interdigitated electrodes as well as the gap width between electrodes, and we found we could reduce the response time from 103.8 ± 42.8 hr to 14.3 ± 3.2 hr. Scanning Electron Microscopy (SEM) revealed fractal and dendritic growth of the lead oxides deposited, hinting that the deposition occurs in a mass-limited condition. We also observed a differential growth speed of the lead oxides in electrode areas and a complete change of the spatial pattern of this deposition behavior in fluid flow condition. Lin, W., Li, Z. & Burns, M. A. A drinking water sensor for lead and other heavy metals. Anal. Chem. 89, 8748-8756 (2017).