The Influence of Metal-Organic Frameworks on Arsenic Removal from Contaminated Groundwater: Column Experiments and Predictive Field-Scale Simulations
Authors
Dechdacho, Porraket
Issue Date
2022
Type
Thesis
Language
Keywords
Arsenic removal , fractional advection dispersion equation , groundwater
Alternative Title
Abstract
Arsenic contamination in groundwater is a global health concern for decades. A long term exposure to arsenic can cause serious health problems such as skin and lung cancer. Over 200 million people around the world have experienced arsenic contamination exceeding the recommended drinking water standard of 10 μg/L. Multiple approaches to remove arsenic from water have been developed. However, the current arsenic removal technologies are often found to be inefficient, produce hazardous residues or require a complicated setup and maintenance. This work aimed to examine the al- alternative remediation using the MOFs (Fe-BTC), which has a high potential for arsenic removal. The saturated column experiments were conducted. Three sets of column mixtures including decomposed granite (DG), DG and compost, and DG, compost, and MOFs were tested to compare the arsenic removal in the presence of MOFs. Each column was saturated with the synthetic groundwater and 1 L of 10 mg/L As-spike solutions was injected. A significant pH drop was observed in the mixture with compost. It was likely caused by the H+ release from compost and water interaction. The water analysis showed that the compost and MOFs removed 9% and 54% of arsenic respectively but there was no removal in the DG column. The primary factor that caused high arsenic sorption by MOFs was the high surface area to volume ratio and abundantly accessible surface sites provided by its porous structure. The one-dimension advection-dispersion equation (1D ADE) analytical solution models coupled with retardation factor were performed. The 1D ADE could capture the DG C/C0 curve but it failed to model compost and MOFs because the average linear velocity is only appropriate for homogeneous media. In contrast, the space fractional advection-dispersion equation (sFADE) could successfully model the compost and MOFs. The a value also implied the relative heterogeneity of the column. The field-scale simulations were conducted to predict and compare the influence of MOFs and the commercial iron oxide nanoparticles as a permeable reactive barrier in basin-fill, carbonate-rock, and granitic-rock aquifers. The PHREEQC predicted that the MOFs was more efficient than nanoparticles under all conditions at different pH ranges. The granitic-rock aquifer showed the highest re- moval, which was possibly due to the enhanced arsenic adsorption onto phyllosilicate minerals in the presence of cations. The results from column experiment and simulations demonstrated that MOFs is efficient and feasible for contaminated groundwater remediation.