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Table 2

Kinetic parameters obtained in the adsorption study of Cd2+, Pb2+ and Cr3+ on açaí biosorbent (Euterpe oleracea Mart.) for the pseudo-first order, pseudo-second order, Elovich and intraparticle diffusion models

 Pseudo-first order
Pseudo-second order
K1Qeq (cal.)R2K2Qeq (cal.)R2
(min−1)(mg g−1)(g mg−1min−1)(mg g−1)
Cd2+ −0.017 0.159 0.948 0.488 1.170 0.999 
Pb2+ −0.011 0.076 0.876 0.692 0.491 0.998 
Cr3+ −0.012 0.157 0.622 0.926 0.493 0.994 
Elovich
ABR2Qeq (exp.)
(mg g−1h−1)(g mg−1)(mg g−1)
Cd2+ −22.438 23.605 0.957 1.120   
Pb2+ −17.155 45.683 0.933 0.459   
Cr3+ −3.175 15.475 0.927 0.450   
Intraparticle diffusion
Kid (g mg−1 min−1/2)Ci (mg g−1)R2
Line ALine BLine ALine BLine ALine B
Cd2+ 111.524 20.657 22.460 105.952 0.865 0.984 
Pb2+ 40.719 36.000 92.815 109.299 0.789 0.689 
Cr3+ 68.145 8.715 34.005 118.463 0.960 0.784 
 Pseudo-first order
Pseudo-second order
K1Qeq (cal.)R2K2Qeq (cal.)R2
(min−1)(mg g−1)(g mg−1min−1)(mg g−1)
Cd2+ −0.017 0.159 0.948 0.488 1.170 0.999 
Pb2+ −0.011 0.076 0.876 0.692 0.491 0.998 
Cr3+ −0.012 0.157 0.622 0.926 0.493 0.994 
Elovich
ABR2Qeq (exp.)
(mg g−1h−1)(g mg−1)(mg g−1)
Cd2+ −22.438 23.605 0.957 1.120   
Pb2+ −17.155 45.683 0.933 0.459   
Cr3+ −3.175 15.475 0.927 0.450   
Intraparticle diffusion
Kid (g mg−1 min−1/2)Ci (mg g−1)R2
Line ALine BLine ALine BLine ALine B
Cd2+ 111.524 20.657 22.460 105.952 0.865 0.984 
Pb2+ 40.719 36.000 92.815 109.299 0.789 0.689 
Cr3+ 68.145 8.715 34.005 118.463 0.960 0.784 

K1: first order velocity constant; Qeq: amounts of adsorbate retained per gram of adsorbent at equilibrium; K2: rate constant of pseudo-second order; A: constant indicating the initial chemisorption rate; B: number of sites suitable for adsorption, related to the extent of surface coverage and the activation energy of the chemisorption; R2: coefficient of determination; Kid: intraparticle diffusion constant; Ci: suggests the thickness of the boundary layer effect.

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