Removal of aqueous arsenic using iron attached to immobilized ligands (IMLIGs)

The present study describes the synthesis of the iron(III) salt of a commercially available immobilized ligand, IMLIG, Octolig-21 and its use to remove arsenic from aqueous solutions. The synthesis 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, and treatment with dilute sodium hydroxide converted the composite to the hydroxide. Using standard test water containing 300 ppb As and column chromatography, reduction of the arsenic concentration to 3 ppb or less in the effluent was achieved, using a pair of columns (4.5 cm id; 1780 mL and 2019 mL, respectively) in tandem. Subsequently, the Fe(III)-Octolig composite was tested for capacity, and it was calculated that with an input of 50 ppb As, it could take up to a year for the effectiveness to be exhausted.

Keywords:

• Arsenic
• Bangladesh
• Drinking water
• Toxicity
• Arsenic removal
• Immobilized ligands.

Acknowledgments

We gratefully acknowledge the input of Mr. Karl Zuelke in the design and Mr. Kelly O'Connell, Metre-General, Inc. in the fabrication of the large-scale chromatography apparatus. We thank Dr. Patricia M. Dooris, CEP of Dooris & Associates, LLC for a sample of groundwater.

Notes

*Control run: Octolig-21.

* BDL = Below detection limit.

** Value for column 1 (1780 mL only).