Woo Hyoung Lee
University of Central Florida, USA
Woo Hyoung Lee, P.E. is an assistant professor in the Department of Civil, Environmental, and Construction Engineering at the University of Central Florida. He received his PhD in environmental engineering from the University of Cincinnati in 2009. He has published more than 17 papers in reputed journals and is serving as an editorial board member of the Austin Journal of Biosensors & Bioelectronics. His current research interests include electrochemical environmental microsensors for biofilm and corrosion investigation, electrocoagulation for emulsion breaking, and greywater reuse.
Orthophosphate is used as a corrosion inhibitor in drinking water utilities by forming a microscale passivating surface layer onmetal pipes of distribution systems. However, phosphate consumption by metal pipes and the associated role of phosphate on water chemistry dynamics of metal oxidants remain unclear. A previous cobalt-based potentiometric phosphate microelectrodeshowed oxygen interference, limiting its use in environments where oxygen gradients are found. The limit of detection (LOD) was relatively high for drinking water application.This research presents two enhanced amperometric cobalt-based sensors that lack oxygen interference with an improvedLOD: a cobalt-based microelectrode (~15 µm of tip diameters) and a nano-textured phosphate sensor. For the microelectrode, at an applied potential of -400 mV (vs. Ag/AgCl), the sensor showed an excellent linear response to various phosphate concentrations (10-2 to 10-8 M), with a sensitivity of 18 pA/pCand an improved LOD of 0.31 ppb,and was not affected by the presence of oxygen. A novel Cu-Co based nano-structured sensor was fabricated by pulsed electroplating Cu-Co alloy on the surface of a gold electrode. The amperometric response without oxygen interference of the Cu-Co nano-structured phosphate sensor was found at -250 mV with a sensitivity of 14.7±0.3 mA/log[H2PO4- ]. The enhanced phosphate microelectrode was successfully applied for quantifying and evaluating the phosphate effect on the corrosion kinetics of ductile iron coupons in simulated drinking water systems by measuring phosphate microprofiles. The cobalt-based phosphate sensorswill greatly improve our understanding of phosphate’s impact on drinking water pipelines andvarious water systems.