Removal of nuisance aqueous anions with Ferrilig

Abstract

The present study describes an improved synthesis of Ferrilig, an iron(III) salt of a commercially available immobilized ligand, IMLIG, called Octolig®. The resulting composite, called “Ferrilig” was used to remove arsenate, chromate, molybdate, and selenite ions from aqueous solutions by means of column chromatography. The synthesis of Ferrilig was accomplished by treating an aqueous suspension of Octolig®-21 with an equal weight of ferrous sulfate heptahydrate under nitrogen. The ferrous salt was then collected by sieving and allowed to oxidize to the iron (III) salt by exposure to air; treatment with dilute sodium hydroxide converted the composite to the hydroxide. Using 300 ppb As (as Na₂HAsO₄·7H₂O) and column chromatography, the arsenic concentration in the effluent was less than the detection limit (< 2 ppb). Chromium as sodium chromate, molybdenum as (NH₄)₆ Mo₇O₂₄·4H₂O, and selenium as Na₂Se0₃, were removed with fair success. The elements, their initial concentrations and their percentage removal (parenthetically) were: As (280 ppb, 99%), Cr (50.6 ppm, 95.5%), Mo (50.7 ppm, 94.6%), Se (258 ppm, 99.9%).

Keywords:

• Arsenic
• arsenic removal
• Bangladesh
• drinking water
• Ferrilig
• immobilized ligands
• Octolig®
• toxicity

Notes

∗Based on titration of a filtrate sample with 0.1781N KMnO₄.

∗∗Separate experiments.