Lewatit® TP 208

Lewatit TP 208 is a weakly acidic cation exchange resin for the selective removal of alkaline earth cations. 

Lewatit® TP 208 is a weakly acidic cation exchange resin with chelating imino-diacetate groups for the selective removal of alkaline earth cations. In comparison to Lewatit® TP 207 and Lewatit® MonoPlus TP 207 this resin has a modified polymer structure and also a modified subsitution grade of the immino-diacetate groups to make it especially suitable for the adsorption of earth alkali ions in the presence of alkali ions. It is especially suitable for use in the final polishing of brine feed to chlorakali membrane cells ( traces of alkaline earth ions are removed after their normal precipitation by carbonates in the pH-range 7-11)

The operating capacity of Lewatit® TP 208 depends on the pH-value of the brine. At pH 11 it is approx.

threefold that achieved at pH 7. At pH 9 and calcium content 2-20 ppm, the operating capacity is approx.0.7. eg/l Lewatit® TP 208 (volume of hydrogen form). At a service flow rate of 20-30 BV/h, the residual calcium content of treated electrolysis brine is less than 0.02 ppm (20 ppb). Greater security can be achieved by operating two units of equal size in series (see our Technical Information SP IOW 4006e).

Lewatit® TP 208 has to be conditioned with caustic soda solution after every regeneration cycle/before every exhaustion cycle. After the conditioning it is in disodium form for the final polishing of chlorakali brine feed. Aside from its major application in brine purification Lewatit® TP 208 can be used for the removal or recovery of heavy metals out of process and waste water streams, especially in the absence of calcium and magnesium ions. Thereby, it removes heavy metal cations from neutralized aqueous solutions in the following order:

Copper > Vanadium (VO) > Uranium (UO2++) > Lead > Nickel > Zinc > Cadmium > Iron (II) > Beryllium > Manganese > Calcium > Magnesium > Stronitium > Barium >>> Sodium.

Lewatit® TP 208 does not remove heavy metals from solutions containing EDTA or NTA respectively. Only cadmium is removed from solutions containing cyanides. For the extraction of those heavy metals which follow the uranyl oxide ion in the selectivity sequence as shown above. Before commissioning a Lewatit® TP 208 unit, see our Technical Information OC/I 20343 e for laboratory tests. 

Business Unit : Liquid Purification Technologies

Applications:

• Catalysis and Chemicals Processing
• Chemical synthesis
• Chloralkali electrolysis
• Metal industry
• Hydrometallurgy

Synonyms:

• Weakly acidic chelating grade resin