8-Hydroxyquinoline-5-sulfonic Acid (HQS) Impregnated on Lewatit MP 600 for Cadmium Complexation: Implication of Solvent Impregnated Resins for Water Remediation

Abstract

The impregnation of 8-hydroxyquinoline-5-sulfonic acid (HQS) onto an anionic strong base resin Lewatit MP 600 is described. The procedure was carried out by mixing HQS with Lewatit MP 600 in water, instead of in organic solvents generally used in solvent impregnated resins (SIRs). The maximum impregnation is 0.95 mmol of HQS/g of Lewatit MP 600. The HQS-impregnated resin was used in a flow injection system incorporating a mini-column for cadmium chelation. Measured cadmium breakthrough curves were used to study the influence of various impregnated HQS, the influent concentration of cadmium, and the packed HQS-Lewatit MP 600, on cadmium binding. By increasing the impregnated HQS from 0.098 to 0.830 mmol/g of Lewatit MP 600, column capacity increased from 11.29 to 52.57 mmol Cd/L of HQS-Lewatit MP 600. Increasing the influent concentration of Cd reduced the column capacity due to a concurrent increase of competing anion (ClO₄ ⁻). This in turn reduced the stability of cadmium complex in the resin phase. Varying the amounts of HQS-Lewatit MP 600 packed in a mini-column caused variations in Cd binding. A 450 mg quantity of 0.95 mmol HQS/g of Lewatit MP 600 can remove cadmium from an initial value of 1 ppm to 30 ppb (detection limit of our instrument). Cadmium and partially impregnated HQS can be eluted by 2 mol/L HNO₃ and the resin can be regenerated to impregnate HQS for further cadmium complexation.

Keywords:

• Ion exchange resins
• Permeable reactive barriers
• Water quality

Acknowledgments