Date of Award

May 2026

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Civil Engineering

First Advisor

Yeo Howe Lim

Second Advisor

Ali Alshami

Abstract

Arsenic contamination in groundwater represents a critical environmental and public health challenge due to its high toxicity and widespread occurrence in natural aquifers. Chronic exposure to arsenic, even at trace levels, is associated with severe health effects, including skin lesions and increased cancer risk. Conventional treatment technologies, such as adsorption using activated carbon or metal oxides, often suffer from limited selectivity, regeneration difficulty, and reduced efficiency under varying pH conditions. Therefore, developing advanced sorbent materials with high capacity, selectivity, and structural stability is essential for addressing arsenic pollution in decentralized water systems.Metal–organic frameworks (MOFs) have recently emerged as promising materials for water purification owing to their tunable pore structures, high surface areas, and functional versatility. Among them, zirconium-based MOFs such as UiO-66 are particularly attractive because of their excellent water stability and Zr–OH active sites favorable for arsenate binding. However, the powdered nature of most MOFs presents significant challenges for practical filtration applications, including clogging, high pressure drop, and regeneration difficulties. To overcome these limitations, this work first focused on integrating UiO-66 and UiO-66-NH₂ with granular activated carbon (GAC) to develop hybrid point-of-use filtration materials. The composite exhibited uniform MOF attachment on GAC surfaces, mitigating issues related to powder handling and mobility. Batch adsorption tests revealed that UiO-66–GAC outperformed UiO-66-NH₂–GAC under near-neutral pH, highlighting the influence of surface chemistry on arsenic affinity. Although tested under batch conditions, the granular form and structural stability of the composite suggest improved hydraulic performance and reusability in potential flow-through systems.

Building on these results, a second phase of this study focused on enhancing the intrinsic adsorption performance of the MOF itself. Pristine UiO-66 was modified through defect engineering and iron doping to generate Fe–UiO-66, synthesized using acetic acid modulation to induce missing-linker defects followed by Fe incorporation at those defect sites. Comprehensive characterization (FTIR, XRD, EDS, SEM, and XPS) confirmed a defect-rich framework with homogeneously distributed Fe centers. The Fe–UiO-66 exhibited a markedly improved arsenic adsorption capacity of 178 mg g⁻¹, compared to 88 mg g⁻¹ for pristine UiO-66, and maintained high performance across a broad pH range. Kinetic and isotherm analyses indicated that adsorption followed a pseudo-second-order model and the Freundlich isotherm, suggesting multilayer chemisorption on heterogeneous active sites.

Overall, this research presents a dual strategy for advancing MOF-based adsorbents for arsenic remediation: (1) immobilizing UiO-66 on GAC to enhance applicability in filtration systems, and (2) employing defect engineering and metal doping to improve adsorption performance. The findings provide a scientific foundation for developing decentralized, high-efficiency, and cost-effective point-of-use water treatment systems to mitigate arsenic contamination and protect public health.

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