I am studying the adsorption of lincomycin on activated carbons. I have determined the equilibrium time and now I would like to begin with the isotherms construction. Therefore, I have read several papers where the concentration of adsorbate is changed (e.g 10, 20, 30, 40 ppm) and the concentration of adsorbent is constant (e.g. 100 ppm). However, I have seen that, sometimes, instead of changing the adsorbate concentration (it keeps constant for all the essays) the concentration of adsorbent is changed. Could anyone tell me what is the difference between both methods? Besides, what are the consequences of selecting one of them?
No prefrable consequences of selecting one of them first, it can be start with adsorbent or adsorbate concentration with giving the same results.
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Yes it is not the amount of adsorbent or adsorbate used that is important. In most cases researchers are more concerned about the amount adsorbed per g of adsorbent used. i.e. mg/g or g/g. So once you look at it in that angle, it is not the absolute amount of adsorbent or adsorbate used that is important.
Hi, one case where the adsorbate/adsorbent ratio could be important is when a species released by the surface is involved in the equilibrium. See for example the explanation for isotherm presenting adsorption maximum.
Ananthapadmanabhan K.P., Somasundaran P. (1983) - Mechanism for adsorption maximum and hysteresis in a sodium dodecylbenzenesulfonate/kaolinite system. Colloids Surf., 77, pp 105-114
Regards
Adsorption isotherm is about the equilibrium relationship representing distribution of solute or adsorbate between two phases ,one is obviously adsorbent.As the adsorption isotherms/ relationship is function of concentration of adsorabate also, it becomes necessary to take care of it while experimenting.Hence different combinations of two phases are more acceptable for developing realistic adsorption correlations.
At the end what matters in adsorption isotherms is the equilibrium concentration. Variation of adsorbat and adsorbent concentration gives you higher flexibility.
I think that the two parameters are important to evaluate the adsorptive properties of a given adsorbent toward a definite adsorbate. Adsorbent content should be chosen such that achieving best removal. Also, studying the effect initial adsorbate concentration is very critical for adsorption isotherm investigation.
Yes. Concentration of adsorbent is important as the adsorption sites are proportional to the adsorbent dose.
Adsorption isotherm study is performed by 1. changing the adsorbent quantity (keeping adsorbate quantity constant); 2. changing the the adsorbate quantity (keeping the the adsorbate quantity constant). Both processes can be employed and the result(isotherm) would be the same. Choice of the process may depend on experimental set up, convenience in measurement of dose etc.
I think varying the concentration of metal ion (adsorbate) gives the concentration at which the adsorption capacity is maximum for constant weight of adsorbent. while varying the adsorbent doses, maximum adsorption capacity at constant concentration of adsorbate is obtained. so, it will be the same whether you take constant adsorbate or adsorbent. But be sure, the variation of each of adsorbent or adsorbate should be enough, so calculation could be reliable. Make sure which point gives you maximum adsorption capacity, that point is helpful to maintain the rest of your other study (e.g kinetic study), pH variation study adsorption.@ Milan Babu Poudel
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