Evaluation of Cement-Based Reactive Media for Contaminant Remediation
No Thumbnail Available
Authors
Meeting name
Sponsors
Date
Journal Title
Format
Thesis
Subject
Abstract
Water contaminated with heavy metals, arsenic, and other industrial pollutants poses a severe risk to human health. Reactive media present an opportunity to intercept contaminants but have high material or environmental costs. Cement-based media filters (CBFM) present an opportunity to use ubiquitous cement mixed with a recycled material to permanently remove contaminants. By engineering a mechanical and chemical matrix derived from cement, an enhanced filter media can be produced to target and treat a spectrum of contaminants. Mechanisms of removal are adsorption, diffusion, precipitation and coprecipitation. The highly alkaline pore water of the cement drives each mechanism to produce a compounding effect, unique to CBFM and previously unreported. Batch reactor and breakthrough testing were performed using CBFM and showed 30 and 40 times increase from equilibrium to flow-through systems. Ordinary portland cement was used as the control for all systems and was replaced by supplementary cementitious materials (SCMs) to evaluate the impact of substitution on contaminant removal. The control removed over 50% of most contaminants, but when various SCMs were used, removal improved to over 95% and was ion selective. Ion selectivity for the system was accomplished through the unique mineral phases formed during removal and mimicked accelerated natural processes. Scanning electron microscopy and X-ray diffraction were used to analyze precipitates and phase distribution in cement. Heavy metals were removed due to coprecipitation with calcium and then encapsulated by oolitic calcite. Arsenic, boron, sulfate, and chlorides were removed by ettringite phase, stabilized by the ion inclusions. The mineral formations present an advancement to previous systems like activated carbon because the removal mechanisms produce continuous additional removal not limited by the reactive media but rather by the pore volume required for crystal deposition. CBFM achieve high levels of removal using sustainable recycled media and concentrate the contaminants for future valorization. This study shows the successful development of CBFMs for remediation.
Table of Contents
Introduction -- Removal and breakthrough of lead, cadmium, and zinc in permeable reactive concrete -- Reuse of drinking water treatment waste for remediation of heavy metal contaminated groundwater -- Removal of arsenic from synthetic groundwater using sulfur enhanced cement-based filter media -- Industrial water treatment and remediation using cement-based filter media summary -- Summary
DOI
PubMed ID
Degree
Ph.D. (Doctor of Philosophy)