Studying the Stability of Silver ions attached to a Cationic Exchange Resin Under Different Concentrations of Sodium Chloride (Saltwater) Solution

Abstract

Ion exchange resins (IERs) have a range of applications in the environmental field, especially in water treatment and engineering, such as water softening. Silver ions have been known inhibitors of bacterial growth in literature and have been shown as selective ions for certain IERs. The present study aims to investigate the stability of silver ions adsorbed onto a cationic exchange resin (Indion^® 220 Na) under different concentrations of sodium chloride (saltwater) solution so as to see whether such a resin could be effective for bactericidal treatment of wastewater over sustained periods of time at an industrial scale. Two batches of 22 cm³ of resin were generated using concentrated hydrochloric acid and then treated with 25% w/v silver nitrate solution. Stock solutions of sodium chloride were made with concentrations of 0 ppm, 30 ppm, 109 ppm, 898 ppm and 6110 ppm and the resin was treated with the same in a ratio of 10 cm³ of solution per gram of dry resin for seven days. Chemical analysis for silver retained on the resin was done using ICP-AES method and this was converted into percentage of silver retained with respect to the original amount of silver ions on the resin. While there was an overall decreasing trend of sliver retention with respect to concentration of sodium chloride solution, there were irregularities from concentration to concentration. For the range of concentrations typically obtained in domestic wastewater, silver retention decreased almost linearly with increase in concentration of sodium chloride solution, indicating the instability of silver ions on the particular resin.