In my experiments, using an adsorbent i have found that the removal percent is increasing with the temperature for chromium, However for copper, removal percent is decreasing with increase in temperature. How to explain this phenomena because in the previous reported work on copper removal, removal percent is increasing with temperature for copper for the same adsorbent.
Please suggest
Dear Ms.Renu Bisht, generally the increase of adsorption with temperature is due to the generation of new active sites on the adsorbent surface and also due to the increased rate of pore diffusion.
The decrease of adsorption due to increase in temperature may be because of the nature of adsorption which is exothermic and physical which involves weak forces of attraction between the sorbate and sorbent molecules.
The decrease of adsorption due to increase in temperature may be because of at higher temperature pore texture of adsorbent may shrink
THILAGAN JAGANNATHAN, sir..is it possible that the same adsorbent is behaving differently for different metal ion?
Detailing of the conditions of experiment including concentration of the solute employed is required to give an appropriate answer. Endothermic reaction leads to the increase of adsorption amount while exothermic reaction will opposite behaviour.
For removal of copper from waste water and how temperature effect on this process. This is a interesting research problem and require series of observation before getting any conclusion.
Yes, of course, same adsorbent can show different sorption behaviour for different metal ions. I hope that you have already analysed the effect of adsorbent dosage, effect of pH, effect of contact time and effect of initial metal ion concentration and determined the optimum values. If you have analysed the effect of temperature with those optimum values, you should have obtained accurate result and no need to worry.
When I was observing the adsorptive removal of Copper (II) ions by Chitosan, the adsorptive removal of metal ions was slightly increasing up to certain temperature and then it was decreasing for further raise in temperature. Hence I found that the initial slight increase was due to the generation of new active sites and also pore diffusion; the decrease in adsorption beyond certain temperature showed that the adsorption process was exothermic & physical and desorption started beyond certain temperature.
Your results depend on the accuracy of your optimum values and the experimental conditions you have followed.
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