Kinetic models |
|
Equation |
Nomenclature |
Reference |
Pseudo-first-order |
|
qe1
and qt: biosorption capacity [mg g-1] at equilibrium and at any time t [h], respectively; k1: rate constant of the model [h-1] |
[33] |
Pseudo-second-order |
|
qe2
and qt: biosorption capacity [mg g-1] at equilibrium and at any time t [h], respectively; k2: rate constant of the model [h-1] |
[34] |
Intraparticle diffusion |
qt = kidt0.5 + c
|
qt: biosorption capacity [mg g-1] at any time t [h]; kid: intraparticle diffusion rate constant [mg g-1 h-0.5]; c: model intercept |
[35] |
Elovich |
|
AE: initial biosorption rate [mg g-1 h -1]; BE: desorption constant of the model [g mg-1] |
[16] |
Fractional power |
qt = kfptv
|
v: fractional power rate constant [h-1]; kfp: fractional power model constant [mg g-1] |
[16] |
Isotherm models |
Two-parameter models |
Langmuir |
|
qe
and qm: biosorption capacity at equilibrium and maximum biosorption capacity [mg g-1], respectively; Ce: liquid phase concentration of dye at equilibrium [mg L-1]; KL: Langmuir constant [L mg-1] |
[30] |
Freundlich |
|
KF: constant of the Freundlich model [(mg g-1)(mg L-1)-1/nF]; nF: heterogeneity factor. |
[16] |
Temkin |
|
T: absolute temperature [K]; R: ideal gas constant [8.314 J mol-1 K-1]; BT: constant related to heat of biosorption [J mol-1]; AT: Temkin isotherm constant [L mg-1] |
[35] |
Halsey |
|
KH: Halsey isotherm model constant [L g-1]-1/nH; nH: Halsey model exponent |
[16] |
Dubinin-Radushkevich |
|
BDR: biosorption energy constant [mol2 J-2]; EDR: Polanyi potential [kJ mol-1] |
[36] |
Three-parameter models |
Sips |
|
Ks: Sips constant; 1/ns: Sips model exponent |
[30] |
Toth |
|
bT: Toth model constant [L mg-1]-1/nT; nT: Toth model exponent |
[36] |
Redlich-Peterson |
|
KRP: Redlich-Peterson model isotherm constant [L g-1]; ARP: Redlich-Peterson model constant [L mg-1]BRP; BRP: Redlich-Peterson model exponent |
[36] |
Radke-Prausnitz |
|
AR: [L g-1] and RR [L mg-1]: Radke-Prausnitz model constants; BR: Radke-Prausnitz model exponent |
[16] |
Thermodynamic models |
Gibbs free energy change |
Δ G° = −R T ln Kc
|
T: absolute temperature [K]; R: ideal gas constant [8.314 J mol-1 K-1]; Kc: equilibrium constant [L g-1]; Δ G°: Gibbs free energy change [J mol-1] |
[37] |
Entropy change |
∂ΔG° = ∂T ∂ΔS° |
T: absolute temperature [K]; Δ S°: entropy change [J mol-1 K-1] |
[37] |
Enthalpy change |
Δ H° = ΔG° − T ΔS° |
Δ H°: enthalpy change [J mol-1] |
[16] |