Arsenic removal using iron oxides: Application of magnetite nanoparticles and iron salts
Yean, Su Jin
Tomson, Mason B.
Doctor of Philosophy
Elevated levels of arsenic in groundwater have generated great attention worldwide because of its wide occurrences throughout the world and toxicity at low concentration. This work introduces a possible application at household levels to provide arsenic-safe water using nanoscale iron oxide (i.e., magnetite nanoparticles) and iron salts (i.e., ferric nitrate and ferric chloride) as adsorbents and coagulants, respectively. Recent publications illustrate that more than 70 million people are chronically exposed to arsenic-contaminated groundwater and suffer from skin lesions and cancers worldwide. A number of technologies (for example, ion exchange and membrane methods) are currently available to remove arsenic; however, each technique has drawbacks to be applicable in the developing countries. Therefore, it is crucial to develop a technology to treat arsenic-contaminated groundwater. Our results show an immediate reduction of arsenic concentration in solution to meet the maximum contaminant level of arsenic (10 microg L-1) in drinking water. Also, iron concentrations in solution are below the World Health Organization guideline value of 300 microg L-1. Contrary to previous results reported by other researchers, arsenic(III), known as more problematic in natural water, is also removed as effectively as arsenic(V) by using our method. When citrate, one of most common organic ligands in environments, is initially added to arsenic-containing solutions, the formation of iron oxides from iron salts is completely inhibited and resulting arsenic concentration remains the same as the initial arsenic concentration, indicating that arsenic removal does not occur. However, other common carboxylic acids such as tartarate, succinate, malate, formate, and tricarballylate, have a negligible impact on preventing the formation of iron hydroxides and resulting arsenic removal from solution. This work shows the efficient method to reduce high arsenic concentrations in groundwaters and better understanding of arsenic removal mechanisms using iron salts and iron oxides.