Water quality testing with the United Nations High Commissioner for Refugees (UNHCR) in Ali Ade Refugee Camp, Djibouti reveals elevated vanadium levels as high as 100�g/L (Canadian guideline for vanadium is 15ug/L). Vanadium is listed under candidate contaminant list 2 under USEPA. Chronic exposure to inorganic vanadium can cause several adverse effects including neurological and circulatory issues. Iron oxides are well known for their sorption capacity and their efficiency in removing heavy metals from solution. However, there are relatively few studies that focus on vanadium interaction with iron oxides. Hematite and goethite, two of the most naturally abundant and thermodynamically stable iron oxides, were chosen for this study. The objective of this study is to optimize and quantify vanadium uptake by hematite and goethite. Hematite and goethite nanoparticles were synthesized in the lab. Batch experiments with vanadium and hematite or goethite were prepared and the pH, conductivity and, initial vanadium concentrations were varied. All samples were rotated for 3 hours, filtered, and analyzed by ICP. Nano-particulate goethite and hematite are able to effectively remove vanadium from solution at a range of pH and initial vanadium concentrations. Maximum vanadium uptake was observed between pH 3-4 for both goethite and hematite. By mass, hematite has a higher removal rate than goethite over a range of pH values. The pH edge curves suggest a different sorption mechanism and/or different vanadium species uptake at pH 5-6 and 8-9. This is likely due to a speciation change from VO2+ to either VO(OH)3, V10O26(OH)4-, or VO2(OH)2-, depending on the initial vanadium concentration. Vanadium chemistry is complex and this study elucidates its adsorption behavior with iron oxides. Future studies will focus on pilot-scale field studies in Djibouti. This study lays the groundwork for what could be an effective means of removing vanadium from drinking water.

Aqueous vanadium removal using iron oxide nanoparticles

247th National Meeting (2014)

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