Continuous ion-exchange

Continuous ion-exchange separation technology, which adopts counter-current processing in a rotating turntable, is currently making an impact and 70% of the world s lysine manufacture units use this technology. 

Continuous ion-exchange units are also available in which ion exchange and resin regeneration both occur constantly. In this case both the resin bed and the fluid being purified are in motion. Continuous units are usually more economical than batch units when the rate of ion removal exceeds 1 lb/min (0.5 kg/min).39... 

FIG. 16-66 Himsley continuous ion-exchange system. (Himsley and Farkas, Operating and Design Details of a Truly Continuous Ion Exchange System Soc. Chem. Ind. Corn., Cambridge, England, July 1976. Used by permission of the Society of Chemical Industry.)... 

Continuous inkjet (CIJ) printing, 9 222 Continuous ion-exchange systems,... 

Setter, N. J., Googin, J. M. and Marrow, G. B. USAEC Report Y-1257 (9th July 1959). The recovery of uranium from reduction residues by semi-continuous ion exchange. 

The ion-exchange process has been used effectively in the field of waste disposal. The use of continuous ion exchange and resin regeneration systems has further improved the economic feasibility of the applications over the fixed-bed systems. One of the reported [1] special... 

The economic break between fixed bed and continuous operation has been estimated as ion concentrations of 0.57V, or flow rates above 300 gpm, or when three or more parallel beds are required to maintain continuous operation. The original application of continuous ion exchange was to treatment of radioactive wastes, but some installations of ordinary water treating have been made. 

Resin requirements for two extremes of ion concentration are analyzed in Example 15.3. The high concentration stream clearly is a candidate for continuous ion exchange. 

Finally, one of the first continuous ion-exchange plants installed used a weak-acid resin to recover copper from rayon-fibre spinning solutions. In the Bemberg or copper(II) ammonium process,357 the spinning takes place in an addic copper sulfate solution, and the fibre is then washed in ammonia solution. The wash water contains as much as 30% of the copper required for the spinning operation and its recovery is important in economic and environmental terms. The copper is extracted as the cationic amine complex by the weak-acid resin, and is then stripped from the resin with the acidic spinning solution. Zinc is recovered in a similar manner from vicrose rayon-spinning operations. 

Detoxification of hydrolysates was accomplished in a continuous ion-exchange bench-scale unit. The resins used were Dowex 1 (50/100 mesh, density 0.71 g/cm3), weak basic anion exchanging, and Dowex-50W (50/ 100 mesh, density 0.80 g/cm3), strong acidic cation exchanging. 

From the liquid stream, about 88% of the acetic acid is removed in a continuous ion-exchange unit, simultaneously with the entire amount of sulfuric acid. 

MacDonald S.E.M., Continuous Ion Exchange Adsorption for the Dolorourization of Sugar, Proc. of Workshop on Separation Processes in the Sugar Industry, Sugar Processing Research Institute, 29-54, 1996. 

---