I am trying to study the adsorption of Alizarin dye on carbon nanoparticles. I have used 0.03 gm of nanoparticles in 20 ml of 7.5x10-5 M Alizarin solution and agitated the system for 60 minutes. After removal of the nanoparticles I found the Alizarin concentration is 1x10-6 M which means alizarin have been adsorbed on the surface of the Carbon nanoparticles. Now for plotting the graph for qe (mg/g) against time, I need to find the value of qe. Can anyone tell me how to do that?
In order to calculate the adsorption capacity, q , it is expressed as q=(amount of adsorbate adsorbed in mg)/(amount of adsorbent used in gm). If the initial concentration of dye is Co ( mg/L )and Ct ( mg/L ) is liquid phase concentrations of dye at any time, the amount of sorption at time t, qt (mg/g), is calculated using the following formula:
qt=[(Co-Ct)*V] / W
where V is the volume of the solution (L) and W is the mass of dry adsorbent (g). Equilibrium concentration,qe, is the concentration that you measured in the final solutions after shaking .If it is found constant ,then the final concentration will be equilibrium concentration and the time after which no change in removal of dye or concentration is observed that will be equilibrium time .You can get equilibrium concentration by plotting qt vs. t of aliquots that collected at 0,15,30,45,60,75,90 min with time of collection. From that graph you can find the time that qt value become constant which represents qe.
Dear Sabry,
Please increase the agitation time by another 30 min or you can increase the time by twenty min and soon you will get the situation that there will be no increase in adsorption and that will be your equilibrium
In order to calculate the adsorption capacity, q , it is expressed as q=(amount of adsorbate adsorbed in mg)/(amount of adsorbent used in gm). If the initial concentration of dye is Co ( mg/L )and Ct ( mg/L ) is liquid phase concentrations of dye at any time, the amount of sorption at time t, qt (mg/g), is calculated using the following formula:
qt=[(Co-Ct)*V] / W
where V is the volume of the solution (L) and W is the mass of dry adsorbent (g). Equilibrium concentration,qe, is the concentration that you measured in the final solutions after shaking .If it is found constant ,then the final concentration will be equilibrium concentration and the time after which no change in removal of dye or concentration is observed that will be equilibrium time .You can get equilibrium concentration by plotting qt vs. t of aliquots that collected at 0,15,30,45,60,75,90 min with time of collection. From that graph you can find the time that qt value become constant which represents qe.
these are qe calculation for batch systems! in fixed-bed continuous systems its unit should be mg/l/g
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)?.
Qe = (Co – Ce) V/W (1)
Where:
Qe: The equilibrium metal ions concentration on adsorbent (mg/g), Co: The initial concentration (mg/L), Ce: the equilibrium concentration (mg/L), V: the volume of aqueous solution (L), W: the weight of adsorbent (g).
qe =(Co-Ce)V/m
where qe is the amount of adsorbate adsorbed(mg) upon adsorbent (g), Co is initial equilibrium concetration(mg/L), Ce is the equilibrium concentration (mg/L), v is the volume (L), m is the mass of absorbent used (g).
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