Magnetite nanoparticles for removal of arsenic from drinking water
Shipley, Heather J.
Tomson, Mason B.
Doctor of Philosophy
Arsenic has become a major contaminant of concern due to the increased knowledge of its toxicological and carcinogenic effects on human health, causing the maximum contaminant level (MCL) to be lowered from 50mug/L to 10mug/L in the United States. Lowering the MCL requires improving current methods or developing new ones to remove arsenic from the drinking water. Currently, there are many methods to remove arsenic, such as coagulation iron salts, ion exchange, and membranes. These methods can be expensive, have poor removal efficiency, and produce a large amount of waste. In this research, magnetite nanoparticles are evaluated as arsenic sorbents due to there magnetic properties for removal, minimal production of waste, and high surface area. Also, in this work, the kinetics of adsorption was examined along with the competitive adsorption of other ions (chloride, phosphate, sulfate, silica, and bicarbonate) in solution. Equilibrium was reached in about two hours for arsenate and arsenite; however, approximately 90% of the arsenate and arsenite was adsorbed within thirty minutes with 0.5g/L Fe3O4. The arsenate and arsenite equilibrium concentrations are similar which demonstrates the affinity of magnetite nanoparticles for both arsenite and arsenate. This work presents a model which predicts the amount of arsenic adsorbed by magnetite nanoparticles in the presence of several ions using a modified rate equation. To test the viability this arsenic removal method, it was tested on spiked arsenic tap water and arsenic contaminated groundwater from Brownsville, TX. In each case, the treatment goal of less than 10mug/L was reached with minimum residual iron in the water. Therefore, these results suggest that using magnetite nanoparticles is a feasible process to remove arsenic from the drinking water. This process could be applied as a household treatment system for developing and developed countries.
Environmental science; Environmental engineering