Removal of arsenate from aqueous solution using nanoscale iron particles

Removal of As(V) using nanoscale iron particles was examined in batch reactors. Nanoscale iron particles, utilizing zero-valent iron with a diameter less than 100 nm as reactive materials, have been demonstrated to effectively remediate a wide variety of common environmental contaminants. In this study, characterization of nanoscale iron particles and their corrosion products was conducted using SEM-EDX, XRD, BET surface area analyzer and Laser Zee Meter. SEM-EDX results indicated adsorption of arsenic onto the iron surface, and XRD analysis found the formation of iron corrosion products including lepidocrocite, magnetite and/or maghemite at a reaction period of 7 d. Measurements of zeta potential revealed that the nanoscale iron particles have a zero point of charge at pH 4.4. Increasing adsorption amounts of arsenic with decreasing pH can therefore be attributed to the positive surface charge of the particles at lower pH. The maximum adsorption capacity of nanoscale iron particles determined by the Langmuir equation was about 38.2 mg/g. Normalization of the adsorption capacity to specific surface areas provides insight into the importance of iron types and the contact time of reactions in influencing arsenic uptake.