Heikki Leinonen

Purification of metal plating rinse waters with chelating ion exchangers

A wide range of chelating ion exchangers was tested for their abilities to remove Zn, Ni, Cu and Cd from solutions simulating waste effluents from the metal-plating industry. The task was to reduce metal discharges to the environment so that metal-plating shops could keep up with the modern, more stringent regulations of waste effluents. The resins were tested by batch and mini-column experiments. Decontamination factors (DFs) as high as 700 and capacities up to 3.3 meq/mL were measured at the 5% breakthrough (BT) point in mini-column tests. Complexing agents, especially cyanide, considerably reduced the performance of the resins with only a few exceptions. Ammonium seemed to improve the ion-exchange performance of some chelating resins and capacities higher than the theoretical values, given by the manufacturer, were measured. Comparative experiments between chelating, strong acid and weak acid ion-exchange resins showed that the advantage of chelating exchangers over strong and weak acid exchangers is a very low metal BT level, even as low as 2 μg/L, which is very important, especially in the end-of-pipe polishing.

Ion-exchange of nickel by iminodiacetic acid chelating resin Chelex 100

The distribution coefficient (KD) of trace nickel on an iminodiacetate-chelating resin Chelex 100 increased with pH to a peak value close to 2 000 000 ml/g at pH of about 5. At higher pH values the KD dropped to 5000 ml/g due to competition of an unidentified complexing agent. In equilibrium of three-component Na/H/Ni ion-exchange system, H/Ni exchange was found to be dominant in the pH range up to 8 and in Na concentration up to 6 mol/l. The practical ion-exchange capacity for nickel was 2.15 mmol/g (4.3 meq/g).

Purification of metal finishing waste waters with zeolites and activated carbons

Sixteen zeolites and 5 activated carbons were tested for the removal of nickel, zinc, cadmium, copper, chromium, and cobalt from waste simulants mimicking effluents produced in metal plating plants. The best performances were obtained from 4 zeolites: A, X, L, and ferrierite types and from 2 carbon types made from lignite and peat. The distribution coefficients for these sorbents were in the range of 10,000-440,000 ml/g. Column experiments showed that the most effective zeolites for Zn, Ni, Cu, and Cd were A and X type zeolites. The activated carbons, Hydrodarco 3000 and Norit Row Supra, exhibited good sorption properties for metals in aqueous solutions containing complexing agents.

Purification of nickel and zinc from waste waters of metal-plating plants by ion exchange

Abstract A wide variety of chelating organic ion exchange resins and inorganic ion exchangers were tested for the removal of nickel and zinc from waste effluents from metal plating plants. Best performances were found to be exhibited by three chelating resins, sodium titanate and an active carbon impregnated with oxine. For most of these exchangers, the batch separation percentages were 99.9% or higher at pH above 5. Column experiments showed that the most effective exchanger for nickel was an inorganic ion exchanger, sodium titanate, and for zinc an aminophosphonate resin, Duolite ES 467.

Hydrolysis and H+/Na+ exchange by Chelex 100 chelating resin

Abstract Chelex 100 chelating resin, as supplied (mixed sodium/hydrogen form 43% /57%), was found to be readily hydrolyzable through hydronium ion exchange from water. Contact with deionized water in solution volume to exchanger weight ratios of 10–4000 brought sodium ions into solution with concentrations of 0.05–1.5 mM and increased the pH from 6.1 to 8.7–10.0. In addition to sodium and hydroxide, the exchanger was found to release chloride and carbonate ions. The two acetate groups vary substantially in their selectivities to hydronium ions, the corrected selectivity coefficients being 1.3 × 10 9 and 1.4 × 10 3 , respectively.

Advanced separation of harmful metals from industrial waste effluents by ion exchange

Advanced separation methods of harmful metals from industrial waste effluents, i.e., radionuclides from nuclear waste solutions, transition metals from metallurgical waste effluents, developed at the Laboratory of Radiochemistry, are discussed.

Ion exchange of zinc on an aminophosphonate-chelating resin

The distribution coefficient (KD) of trace zinc in 1 M NaCl solution on an aminophosphonate-chelating resin Duolite C467 increased with pH to a peak value close to 200 000 ml/g at pH about 6. At higher pH values the KD dropped to 25 000 ml/g due to competition of zinc hydrolysis. Increasing NaCl concentration up to about 1 M improved zinc uptake on sodium-form Duolite C467 since it prevented exchanger hydrolysis, but at higher concentrations KD decreased somewhat due to Zn2+Na+ competition. Also, increasing zinc concentration, from 6 x 10−7 M to 1 mM, improved zinc uptake, since the exchanger is less hydrolysable in zinc form. EDTA interfered strongly with zinc uptake when present at concentrations higher than 1 μM, sodium cyanide at concentration higher than 1 mM, citrate in concentrations higher than 10 mM while gluconate did not interfere at all.

Sorption of radiocobalt and other activation product radionuclides on titanium oxide material CoTreat

Abstract CoTreat is a commercial titanate material that is effective for the removal of 60Co and other activated corrosion product nuclides from nuclear waste effluents. A basic study has been carried out to investigate the uptake mechanism and selectivity of CoTreat material for trace sorption of 54Mn, 59Fe, 57Co, 63Ni, 65Zn and 110mAg. The analyses of the trace sorption isotherms indicate that except for 110mAg the uptake mechanism for the trace metal ions is surface complex formation. The selectivity of the material for the metal ions studied decreases in the order Fe>Ag>Mn>Co ≈Ni>Zn. Except for Fe, the selectivity thus decreases with the increasing tendency of the cations to hydrolyse.

SEPARATION OF CHROMIUM WITH A FIBROUS ION EXCHANGER

1 ABSTRACT For the separation of chromium from solutions sixteen commercially available ion exchanger were tested. Best performance was shown by a fibrous ion exchanger FIBAN AK-22, which has both carboxylic and imidazole functionalities on polypropylene fibres. It takes up very efficiently all forms of chromium, Cr3+ and C r 2 O 7 2 − at pH range of 3-4 and CrO 4 2 − at pH range of 6-9. Na+, Mg2+ and Ca2+ ions interfere with the chromium separation at concentrations higher than 0.1M and Fe2+ and Fe3+ ions at concentrations higher than 0.001M. From waste solutions from a metal plating plant FIBAN AK-22 removed chromium rather efficiently.

Hydrolysis of Chelex 100 Chelating Resin and its Effect on Nickel Ion Exchange

Chelex 100 chelating resin in sodium form was found to be significantly hydrolysable. Contact with de-ionised water in solution volume to exchanger weight ratios of 10-4000 yielded a conversion to hydronium form of 1 to 10%. Hydrolysis brought sodium ions into solution with concentrations of 0.05-1.5 mM and increased the pH from 6.1 to 8.7-10.0. Hydrolysis has a marked effect on the nickel ion exchange on Chelex 100 in dilute nickel solutions (<0.1 mM): hydrolysis controls the sodium ion concentration in the solution and the increasing pH diminishes the absorption of nickel.