Making Calcium Chloride 37%

[bushywalrus]

Hi All,

 

I'm reacting various types of limestone with 38% HCL to make Calcium Chloride Brine. Some older, hard grey limestones produce a very colorless CaCl2 solution. I'm currently using a very pourous, soft, oceanic limestone but I get a yellow CaCl2 product. How can I remove the yellow color?

 

My method for making the CaCl2 is to react the acid with the limestone in a bucket to completion. I then raise the pH to 8.3 and filter with a buchner filter apparatus. Fe is 1 ppm, Mg is 75 ppm and Mn is 0.1 ppm. EMF is +375 at pH 8.3. However, the solution is yellow. I suspect its a residual organic from the limestone but how would I remove it. I tried a 0.2 g/liter addition of Ca(OCl)2 Calcium Hypochlorite then added some Ditomaceous Earth, followed by still another filtration. EMF is +600 at this point as I'm creating a oxidizing enviornment. I thought this would oxidize the organic (if its an organic) but the yellow color still remains. I tried adding 30% H2O2 also, it didn't work.

 

Anybody have any ideas on how to remove the yellow color?

[John Cuthber]

You seem to have tried most of the things I would have though of.

Have you tried activated charcoal?

 

The only other idea I had would be to roast the lime before you begin which might oxidise off the organics but that would take a lot of energy and would also give you the problem of handling quicklime.

 

Blowing ozonised air through the solution might work. Ozone generators are available on eBay and such for use with aquaria.

 

The other thing to note is that a lot of organic oxidations are quite slow. You might need to leave the stuff to stand for a while for the oxidation to take place.

[ercdndrs]

Iron chloride solution is yellow; I don't know if the little bit of iron in your solution could cause that drastic a colour change though.