German specialty chemicals company Lanxess has expanded its Lewatit line of ion-exchange resins to include a new generation of finely dispersed grades.
Monodisperse, macroporous chelating resins of this kind significantly enhance the efficiency of brine treatment for chloralkali electrolysis based on membrane technology. Furthermore, they effectively help to prevent damage to the increasingly sensitive, latest-generation membranes.
The critical difference between the new resin grades and those sold previously is the bead diameter. In the monodisperse small (MDS) grades, such as Lewatit MDS TP 208, the diameter is only 390 μm, or 40% smaller than that of the monodisperse grade Lewatit MonoPlus TP 208. This size difference translates into roughly twice the bead surface per unit of volume.
As a result of this difference, says Lanxess, the MDS grades display improved kinetics, a higher degree of regeneration and a significantly increased total and operating capacity specifically for alkaline earth cations. At the same time, they have optimal mechanical and osmotic stability.
Barium and strontium ions are removed from the brine with particular efficiency. This is a remarkable characteristic in view of the low selectivity of many other resins and their slow exchange kinetics. The chelating resins also bind the lighter elements in the alkaline earth group, such as calcium and magnesium.
Their improved leakage is an important advantage, because the reduced leakage helps to increase the service life of the electrolysis membranes. In this respect, says Lanxess, the MDS resins have anticipated the continuous advancements in membrane development, because the concentration tolerances for alkaline earth ions will likely decrease further in the future.
Resins in the MDS line give electrolysis operators a number of economic advantages, most of which are based on the following effects:
· Longer life for the membranes and the resin
· Lower operating costs as a result of lower regenerating agent requirements and less wastewater
· Longer cycle times for the resin
· Higher throughput in brine production.
The new resin grades have already been used successfully on an industrial scale in Germany.