Effect of Added Complexing Anions on Cation Exchange of Cu(II) and Zn(II) with a Strong-Acid Resin

Abstract

Ion exchange is widely used for the recovery and separation of metals from process and waste streams in chemical process industries. The effect of added complexing anions such as EDTA, NTA, and citrate on the cation exchange of Cu 2+ and Zn 2+ with strong-acid Purolite NRW100 resin was studied at 298 K, with the metals in solution in excess over the complexing anions. Experiments were performed as a function of solution pH (1.0-6.0), concentration of metals (4.5-22.5 mol/m 3 ), and concentration ratio of complexing anions to metals (0-1). It was shown that the rate of metal exchange decreased when the complexing anions were present. The addition of EDTA and NTA decreased the amount of metal exchange throughout the entire pH range studied, but it was the case for the citrate system only at high pH (>4). In the absence of complexing anions, the Langmuir equation could be used to correlate the exchange isotherms at a given pH on a macroscopic basis. However, a proposed chemical model that takes into account possible solid-liquid exchange reactions and solution chemistry could be used to describe the metal exchange equilibria in the presence of complexing anions.

Ion exchange recovery of Ni(II) from simulated electroplating waste solutions containing anionic ligands

“…3a). Such a pH dependence is slightly different from that observed in an equimolar Cu(II)-citrate system [16]; in which the dominant species are free Cu 2+ ions at pH < 4.0 and the species CuL − at pH > 6.8. Between pH 4.0 and 6.8, the neutral species CuHL dominates.…”

Removal of chelated copper from wastewaters by Fe2+-based replacement–precipitation

“…As a result, the routine precipitation process becomes ineffective and unfeasible because of the wellknown stability of these heavy metal chelates (Gyliene et al 2002;Juang and Wang 2002).…”

Purification of dilute hydrofluoric acid by commercial ion exchange resins

“…Some metals form cationic, anionic and neutral fluorides complexes leading to cationic, anionic or amphoteric behaviour in HF matrices. The influence of complexing agents on the performance of ion exchange of metals has been widely studied in the literature [15][16][17][18][19]. The rate of metal exchange in cation resins decreases when the complexing anions are in excess (e.g.…”

“…The rate of metal exchange in cation resins decreases when the complexing anions are in excess (e.g. fluoride in HF matrices), thus leading to use anion exchange resins or chelating exchangers to remove metals [18]. Among impurities, transition metals can form stable complexes due to their electronic structure [19].…”