On the Uptake Mechanisms of Organics from Natural Water - Investigations with Strong and Weak Base Ion Exchangers and Their Corresponding Copolymers

In laboratory column experiments, ion exchange resins and the corresponding non-functionalized copolymers were compared in order to investigate the uptake mechanisms of organics during the water demineralization process. To improve the detection limit, C-14-labeled model substances (ß-alanine, starch, synthetic humic acid type M42) were used. These compounds are supposed to represent the TOC fractions of polysaccharides, neutrals/amphiphilics and humics following the LC-OCD method. The uptake was investigated depending on the salinity and pH, the concentration of the organics, and the loading temperature. The main results are:

• At neutral pH, a near 100 % removal of ß-alanine and starch by ion exchange and/or adsorption was observed, whereas humic acid was taken up by ion exchange to an extent of about 10 %.
• In acidic conditions, ß-alanine and starch were completely removed up to the breakthrough point of the sulfate ions. Those elute the organics. Humic acid will be removed owing to precipitation.
• The last mechanism allows the removal of humic acid by the copolymers too. These are inefficient in regard to the uptake of ß-alanine and starch.
• The variation in the concentration of the organics as well as that in the loading temperature have only a subordinate influence on the uptake.