1.) We are conducting adsorption experiments with methylen blue onto powdered acitvated carbon (liquid batch).
2.) To ensure constant pH conditions we have worked with potassium phosphate buffer (pH=6-7) but it seems that this one intereferes with the adsorption by e.g. adsorption oh phophate onto the activated carbon.
--> Can someone recommend a pH buffer System that does not interfere with adsorption under these circumstances?
Christian von Heynitz
Activated carbon adsorbs molecules through van der Waals interactions. Therefore, all components of any buffer will be adsorbed on the surface of this adsorbent.
I agree with Yuri Mirgorod . Using a strongly ionic, small-molecule buffer like potassium phosphate is in principle a good choice.
What I would try is to reduce the buffer concentration to the minimum necessary and see if you still get the interference. If the concentration of the buffer has an effect, you can try a series of decreasing concentrations and extrapolate to what would happen in the absence of the buffer.
after washing with deionized water, you may try without buffer and check if there is a remarkable shift in pH or not.
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