Equipment for Ion Exchange

The size of the plant is a further factor that may lead the designer to consider other options besides die conventional fixed bed. A very smaU plant may be comprised of overtfesigned fixed beds b simplify operation and require no instrumentation. On die other himd, the use of continuous ion exchaiige may significantly reduce the capital cost of a large plant. 

The above mentioned factors, combined with the fact that high flow rates obtainable in packed beds give faster reaction rates, have led to the development of presem-day plants. In general, clear dilute solutkms are treated in fixed or moving packed beds while turbid effluents and ore slurries are handled in fluidized beds or stirred tanks. 

The basis of ion-exchange plant design is the superficial velocity of liquid feed passing through the vessels, sometimes termed the empty-bed velocify . Once the fype of resin bed—either fixed, fluidized, or stirred— has been selected, a design velocity from the feasible range for that fype must be assumed. 

The cross-sectional area of the vessels is calculated directly from the specified total througiqwt and the superficial velocify. If this is larger than current practice, then parallel streams rmst be considered. 

The pressure drop over the resin bed may be an importaM variable in fixed beds while in other techniques it is not relevant in comparison with pressure losses incurred in pumpiiig liquid ttuough the pipework. The superficial velocity is one of the main variiMes in the pressure-drop and bed-expruision calculations. 

---

Equipment for ion exchange is selected on the basis of the method to be used for regenerating the spent resin. Regeneration has to be carried out with the minimum disruption of the process and at a minimum cost. At its simplest, equipment may consist of a vessel containing the liquid to be treated, possibly fitted with stirrer to ensure good mixing. Ion... 

Dowex monosphere 550A (OH) anion-exchange resin (60 mL) equipment for ion-exchange chromatography rotary evaporator. 

Bitumen processes can be held either as batch or as continuous operations. In the fust case, the steps of drying and mixing the dried material in molten bitumen are involved, whereas in continuous operation, the spent material is introduced as slurry to equipment that continuously mixes the bitumen at the same time. Then, the bitumen mixture flows into a suitable storage container and is solidified upon cooling. Neilson and Colombo (1982) have presented the main features of the process for ion-exchange resin wastes. 

Ion exchange resins are used widely as heterogeneous catalysts of processes that require acid or base catalysis, for example, hydration of propylene to isopropanol, reaction of isobutylene with acetonitrile, and many others. The same kind of equipment is suitable as for ion exchange, but usually regeneration is not necessary, although some degradation of the resin naturally occurs over a period of time. 

The older classic low speed LPLC methods are often used for biochemical separations, because they are very simple, modest in instrumentation, and therefore cheap. They can be realized in every laboratory without special equipment. Also, ion exchange materials for these purposes need not be so finely and carefully prepared nor stand high pressure, and are usually inexpensive. The most important materials... 

Application, recovery, and regeneration equipment and techniques would resemble those described for carbon and for ion-exchange sorbents. Limitations occur because of desorption sensitivity to oxidation. Thermal desorption is too hazardous for use with flammable sorbates. Effluent desorption seems to have some potential. 

The 163-N facility contains demineralization equipment, including ion exchange units, regeneration tanks, treatment tanks (for pH adjustment) that are part of the elementary neutralization unit (ENU), acid and caustic-materials storage tanks, a heater, and a degasifier (DOE-RL 1990). 

The purified commercial di-n-butyl d-tartrate, m.p. 22°, may be used. It may be prepared by using the procedure described under i o-propyl lactate (Section 111,102). Place a mixture of 75 g. of d-tartaric acid, 10 g. of Zeo-Karb 225/H, 110 g. (136 ml.) of redistilled n-butyl alcohol and 150 ml. of sodium-dried benzene in a 1-litre three-necked flask equipped with a mercury-sealed stirrer, a double surface condenser and an automatic water separator (see Fig. Ill, 126,1). Reflux the mixture with stirring for 10 hours about 21 ml. of water collect in the water separator. FUter off the ion-exchange resin at the pump and wash it with two 30-40 ml. portions of hot benzene. Wash the combined filtrate and washings with two 75 ml. portions of saturated sodium bicarbonate solution, followed by lOu ml. of water, and dry over anhydrous magnesium sulphate. Remove the benzene by distillation under reduced pressure (water pump) and finally distil the residue. Collect the di-n-butyl d-tartrate at 150°/1 5 mm. The yield is 90 g. 

The detection and determination of traces of cobalt is of concern in such diverse areas as soflds, plants, fertilizers (qv), stainless and other steels for nuclear energy equipment (see Steel), high purity fissile materials (U, Th), refractory metals (Ta, Nb, Mo, and W), and semiconductors (qv). Useful techniques are spectrophotometry, polarography, emission spectrography, flame photometry, x-ray fluorescence, activation analysis, tracers, and mass spectrography, chromatography, and ion exchange (19) (see Analytical TffiTHODS Spectroscopy, optical Trace and residue analysis). 

Disadvantages of these continuous countercurrent systems are associated primarily with the complexity of the equipment required and with the attrition resulting from the transpoiT of the ion exchanger. An effective alternative for intermediate scale processes is the use of merry-go-round systems and SMB units employing only packed-beds with no movement of the ion-exchanger. 

---