What should be the unit of Ce (equilibrium concentration) while putting it in the formula of Polanyi potential in Dubinin-Radushkevich Isotherm?
Dear Aditi,
Dubinin-Radushkevich (DR) :
lnq = lnqm - B E2
B is a constant related to the sorption energy
E is Polanyi potential E = RT ln(1+ 1/Cf )
Needless to say, for different sorption systems and mechanisms outside of the scope of these assumptions the application and fit of the model equations is a matter of chance. They become just mathematical relationships which happen to be capable of following the experimental data. The problem with biosorption is that usually not very much specific information is available on the sorption mechanism(s) involved.
· Dubinin–Radushkevich theoretical maximum sorption capacity (mg.g−1);
· q, qt, amount of urea adsorbed at time t (mg.g−1);
· RL, separation factor;
· Ss, outer adsorbent surface per unit volume of particle-free sorbate (cm−1);
· t, adsorption time (min);
· T, absolute temperature (K);
· V,volume of urine (L);
· W, mass of dry adsorbent used (g);
· βL, mass transfer coefficient (cm.sec−1);
· ε, Polanyi potential;
· θ, Degree of surface coverage
ubinin–Radushkevich isotherm constant (mol2.kJ−1);
kid, intra-particle diffusion rate constant (mg.g−1.min−1/2);
k1, first order rate constant (min−1);
k2, second order rate constant (g.mg−1.min−1);
KF,Freundlich isotherm constant (mg.g−1.(L.mg−1)1/n);
KL, Langmuir isotherm constant (L.mg−1);
n, adsorption intensity;
qe, equilibrium urea uptake or sorption capacity (mg.g−1);
qm, maximum monolayer urea sorption (mg.g−1);
qs,
Dubinin–Radushkevich isotherm was 132.36 mg.g−1 and both agree closely with the experimental results.
Dubinin–Radushkevich isotherm was 132.36 mg.g−1 and both agree closely with the experimental results. Further, the mean free energy for urea sorption was calculated using the Dubinin–Radushkevich isotherm constant (Kad; mol2.kJ−1) through following equation Equation
E=1/√2Kad
Regards,
Prem Baboo
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