Graduation Year

2021

Document Type

Thesis

Degree

M.S.E.V.

Degree Name

MS in Environmental Engr. (M.S.E.V.)

Degree Granting Department

Civil and Environmental Engineering

Major Professor

James R. Mihelcic, Ph.D.

Committee Member

Jeffrey A. Cunningham, Ph.D.

Committee Member

Katherine Alfredo, Ph.D.

Keywords

Sustainable Development Goals, Self-Supply, Drinking Water, Adsorption, Surface Complexation

Abstract

This research sought to determine the lead leaching mechanism impacted by an inorganic scale observed from lead valve weights of the pitcher pump systems used in Tamatave, Madagascar. Based on previous research, these valve weights are considered to be a major source for high lead levels in pump water consumed by the residents. As a part of the study, Raman Spectroscopy, X-ray Fluorescence Spectroscopy (XRF) and Energy Dispersive Spectroscopy with Scanning Electron Microscope (SEM-EDS) were performed to address the objectives of this research. The pump component samples for the analysis were selected based on the amount and visual characteristics of the scale seen on the valve weights. The scale was identified to be hematite (α-Fe2O3) and base (uncoated valve weights referred as base) was identified to be lead base mineral, Matlockite (PbClF) by Raman analysis. However, Raman analysis did not seem completely accurate and consistent with the results from other two techniques; XRF and SEM-EDS analysis. The XRF results reported lead and iron to primary elements with its limitation to not detect elements with atomic number below 12. The scale was found to be uneven and thickness of the scale ranged between 35 – 410 μm as analyzed by SEM analysis. The major elements reported in the scale by SEM-EDS analysis were iron, lead, oxygen, and carbon. The lead concentration in the scale by SEM-EDS analysis was reported to range between 4 – 25% with restriction to measure up to the depth of 3 μm which less than XRF penetration depth to detect elements. The lead compound found in the scale was estimated to be in the form of hydrocerussite [Pb3(CO3)2(OH)2] and lead carbonate (PbCO3) from examination of lead solubility diagram. Furthermore, based on the literature review, possibilities of lead adsorption due to surface complexation with hydroxyl groups present on the scale was estimated to support the presence of lead range (4-25%) detected in the scale by SEM-EDS analysis. This research developed possible explanations for lead adsorption and complexation which can further be confirmed through XRD and ICP-MS analysis and specific complexation modeling. Furthermore, the ability to study the scale at greater depth than 3 μm could confirm the variation in lead concentration observed in the scale.

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