[WillS]

Hi there,
I was just wondering if there is a known relationship between the number of moles of a specific cation removed from a solution, namely Calcium,  and the time it is in contact with the resin. I was planning on treating 25ml of 0.01M CaCl₂ through 5g of a sodium based resin, adjusting the rate of flow using a stopcock and timing it with a stopwatch. This will be a prelimanry experiment and I would like to know the relationship that exists so I can plan time periods etc.

[jwesterway]

There would be a relationship seeing as it is a surface reaction (calcium in solution has to be in contact with the resin in order to react) so there definatly would be a relationship however it would depend on the exact type of the resin, flow rate, size and shape of resin reaction surface(s) etc... you could prepare a standard concentration of calcium and run the standard through the same type of resin cartridge at varying flow rates and titrate the effluent with EDTA or use a spectrometric technique to determine the remaining calcium in solution. This would allow you to see the relationship and determine the best possible flow rate for that particular resin cartridge.

-Josh

[WillS]

Is it likely to be a linear relationship or something more complex?

[ozonoyo]

The relations is up to each resin. Usually, each supplier has some graphics or data. Perhaps the data is not exactly the same for each ion but will be a good aproach for your experiments.