Abstract
Iron oxides/oxyhydroxides, namely maghemite, iron oxide-silica composite, akaganeite, and ferrihydrite, are studied for AsV and AsIII removal from water in the pH range 2–8. All sorbents were characterized for their structural, morphological, textural, and surface charge properties. The same experimental conditions for the batch tests permitted a direct comparison among the sorbents, particularly between the oxyhydroxides, known to be among the most promising As-removers but hardly compared in the literature. The tests revealed akaganeite to perform better in the whole pH range for AsV (max 89 mg g−1 at pH0 3) but to be also efficient toward AsIII (max 91 mg g−1 at pH0 3–8), for which the best sorbent was ferrihydrite (max 144 mg g−1 at pH0 8). Moreover, the study of the sorbents’ surface chemistry under contact with arsenic and arsenic-free solutions allowed the understanding of its role in the arsenic uptake through electrophoretic light scattering and pH measurements. Indeed, the sorbent’s ability to modify the starting pH was a crucial step in determining the removal of performances. The AsV initial concentration, contact time, ionic strength, and presence of competitors were also studied for akaganeite, the most promising remover, at pH0 3 and 8 to deepen the uptake mechanism.
Highlights
The arsenic toxicity depends on its chemical nature, as inorganic arsenic compounds are more dangerous than organic ones
AsV uptake (89 mg g−1 at pH0 3 and 52 mg g−1 at pH0 8) when compared with ferrihydrite, both in acidic and basic environments, thanks to the capability to decrease the initial pH, where the surface charge is high and positive
Concerning the AsIII removal, elevated and steady uptake in the pH0 range 2–8 was found for ferrihydrite (≈95% at 100 mg L−1, qe = 144 mg g−1 at 500 mg L−1 and pH0 8), which was higher than akaganeite (≈80% at 100 mg L−1, qe = 91 mg g−1 at 500 mg L−1 and pH0 8)
Summary
Ethylenediaminetetraacetic acid (98%), poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol), and sodium (meta) arsenite (90%) were purchased from. Iron (III) chloride tetrahydrate (99%) was purchased from. Arsenic (V) standard for ICP (1000 mg L−1 ) was purchased from Fluka (St. Louise, MO, USA). Sodium arsenate dibasic heptahydrate (98%) was purchased from Sigma (St. Louise, MO, USA). Ammonium hydroxide solution (28–30%) and iron (III). Nitrate nonahydrate (98%) were purchased from Sigma-Aldrich (St. Louise, MO, USA). Glacial acetic acid (99.9%), nitric acid (Normatom 67–69%), sodium acetate (99.2%), sodium hydroxide (99.4%), and anhydrous sodium sulphate (99.2%) were purchased from VWR (Leuven, Belgium)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
