I have conducted an experiment on heavy metal biosorption from industrial effluents by using green biomass and its kinetic study; had run the experiment upto 120 min and investigated the qt but I am confused for how to do calculation of qe as many references have given the equation qe= Co-Ce*V/w. how to derive ce and qe please explain.
thank you in advance.
Equilibrium adsorption capacity (qe) is calculated by
qe = [(Co –Ce) / W] * V
Where, Co and Ce are the initial and final concentrations of the solute in mg/L, in each adsorption experiment. V is the volume of the solution in litres, W is the weight of adsorbent in grams in each trial and qe is in mg/g.
I've attached one of my articles for easy understanding.
Dear Krishna,Herewith i hhave enclosed some articles related to kinetic adsorption study.
The quantity of metal adsorbed is calculated according to the following equation :
Qe = V(Co –Ce) / m
Where Qe is the sorption capacity (mg/g) , m is the weight of adsorbent (g), Co initial concentration (mg/L), Ce is the equilibrium concentration (mg/ L) and V is the volume of solution (L).
Contact time
The removal of heavy metal by green biomass must be examined at different time intervals and plotting the relationship between heavy metal % removal and time until maximum value of heavy metal % removal is reached and no significant change of removal is observed. Depending on these results, it can be concluded that the adsorption equilibrium is reached at this time Ce
Kinetics and Mechanisms Study of Congo red, Eosin B and Neutral red Adsorption from Aqueous Solutions on Kaolin
Hi Krishna,
When you make a kinetic study of adsorption or biosorption of a pollutant on an adsorbent or biosorbent, you know the initial concentration of this pollutant in the liquid phase, for example, 50 mg/L. You start your kinetic study and at different times (i.e., 5, 10, 15, 30, 45, 60, 90 and 120 min) you take a sample from the reactor, and you quantify the residual concentration of your pollutant in the liquid phase with the most convenient analytical technique depending on the nature of your contaminant. So, let see the equation to calculate the instantaneous adsorption capacity, qt:
qt= [(Ci-Ct)/m]·V
You know the value of Ci, which is the initial concentration of the pollutant (50 mg/L). Also, you know the values of Ct (mg/L) for each contact time t, the mass m (g) of the adsorbent or biosorbent that you use in the experiment, and the volume V (L) of the liquid phase for each contact time. So, you can calculate qt with the previous equation. In this way, you have couples of values (qt, t), and you can make a graphic representation of qt Vs t.
When you prepare this representation, you should obtain a curve that grows quickly initially and then stabilizes by describing a plateau. This plateau indicates that equilibrium state has been reached for the conditions of your experiment. If you extrapolate the plateu to the ordinate axis (qt), you can determine the experimental value of qe.
You can apply different kinetic adsorption models to your experimental data, as pseudo-first order model or pseudo-second order model, to obtain the values of the kinetic constants and predicted equilibrium adsorption capacities. In this case, the non-linear forms of these models are more appropriate than linear forms.
The expression qe=[(Ci-Ce)/m]·V is used in the equilibrium studies, for the extraction of the adsorption isotherms.
I hope this information helps you in your work.
Thank you very much everyone here, your answers are helpful to me.
Hello,
First of all, I want to inform you that, for calculating the equilibrium adsorption capacity (AC), i.e. qe, the experiment time should be as long as the residual UV-Vis absorption, i.e. the residual dye concentration change becomes almost negligible with the increase in time. It can not be 120 minutes. The data you obtained after 120 minutes can be utilized to obtain the AC after 120 minutes. Continue your experiment, until the adsorption becomes constant (maximum). Then, the residual concentration of the supaernatant solution, i.e. Ct, can be replaced by Ce. In fact, there is no different formula to calculate qe. The formula is for qt. It is:
qt=((C0-Ct)*V)/ms, [C0: initial concentration, V: volume of solution taken in Lt and ms: mass of adsorbent in g].
At equilibrium condition, when Ct=Ce, then qt=qe.
I am having a challenge on the difference between qt and Ct as well as Ce and Ct. If Ct = Ce and qt = qe, does it mean that for Pseudo-first order kinetics Log(qe-qt) = Log (0)?.
Usually, we measure changes in concentration in the adsorbate solution and on their basis we determine the adsorbed mass related to the mass of the adsorbent, i.e. the so-called adsorption capacity denoted by q. The value of Ce and qe can be determined by extrapolation of Ce vs t and qe vs t, respectively. Approximation by means of increasing functions with an upper limit, eg exponential or hyperbolic, may also help.
How to calculate Ce and qe how to find out which isotherm vil fit and kinetics please help me my work is also on removal of heavy metals by adsoption studies facing problem in calculation part.
These videos can answer your question: https://www.youtube.com/watch?v=NUM11s1X-68&list=PLxbTf96DhNSTS0j5d-LengkeEQS1qjrOC
This video shows how to calculate Ce and qe in adsorption isotherm study easily.https://youtu.be/rdj058lMyHU
Hello,
Could I ask you please, if we want to do calculations for one element that is assumed to be adsorbed on the adsorbent, like Zn metal present as salts (Zn(NO₃)₂·6H₂O) dissolved in water. We need to measure the amount of adsorbed Zn on the adsorbent material, so will we calculate the Co, Ce, and Qe for the Zn or Zn salt molecule (Zn(NO₃)₂·6H₂O)? Another question: does the adsorbent desorb the adsorbent material to the liquid again after a long time of immersion or maybe by washing it with distilled water?