Investigation for the development of a waste water-free ion exchange procedure for the decolorization of sugar solutions

The regeneration of ion exchange resins used for decolorization in the sugar industry requires a considerable surplus of sodium chloride, which for the most part goes into the eluate. The resultant waste water is heavily contaminated both organically and inorganically and is therefore ecologically harmful. The recycling ion exchange eluate, as a regenerant, helps to solve the waste water problem in a suitable and practicable manner. Because the eluate is mixed with wash water it is necessary to evaporate them in order to recover the initial volume of the regenerant. Additionally, approximately 85 % of colorants have to be eliminated from these eluates. The process developed is able to remove the colouring matter of the concentrated eluates to a great extent by the addition of lime and carbon dioxide. If calcium chloride is used instead of sodium chloride for the regeneration of ion exchange resins, the decolorization of eluates is optimized. For the first time it is possible to regenerate ion exchange resins in a complete waste water-free decolorization process. As can be seen in the cost analysis, the application of this process in sugar refineries is capable not only of avoiding damage to the environment but also of improving the economic efficiency. The use of waste water-free decolorization plants may be profitable to beet sugar factories if they meet the requirements. Therefore it is necessary to study the conditions with care in each individual case.