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Table 3

Parameters of Langmuir's, Freundlich's and Dubinin–Radushkevich's models for biosorbent açaí (Euterpe oleracea Mart.) endocarp in the adsorption of Cd2+, Pb2+ and Cr3+ ions

ParametersAçaí endocarp
Activated coal
Cd2+Pb2+Cr3+Cd2+Pb2+Cr3+
Langmuir 
 Qm (mg g−18.130 16.173 1.211 45.998 −18.979 15.047 
 b or KL (L mg−10.226 0.055 8.274 0.001 −0.009 0.006 
 RL 0.022 0.084 0.001 0.822 0.222 0.478 
 R2 0.990 0.825 0.981 0.830 0.329 0.985 
Freundlich 
 Kf (mg g−11.181 0.682 0.231 13.352 31.714 6.152 
 n 2.418 1.918 2.951 1.296 1.620 3.256 
 R2 0.984 0.981 0.979 0.982 0.979 0.964 
Dubinin–Radushkevich 
 Qd (mol g−10.000 0.000 0.000 0.001 0.008 0.000 
 Bd −0.003 −0.005 −0.002 −0.004 −0.005 −0.002 
 E (KJ mol−112.328 9.704 16.440 10.976 9.960 17.623 
 R2 0.798 0.841 0.838 0.728 0.759 0.702 
ParametersAçaí endocarp
Activated coal
Cd2+Pb2+Cr3+Cd2+Pb2+Cr3+
Langmuir 
 Qm (mg g−18.130 16.173 1.211 45.998 −18.979 15.047 
 b or KL (L mg−10.226 0.055 8.274 0.001 −0.009 0.006 
 RL 0.022 0.084 0.001 0.822 0.222 0.478 
 R2 0.990 0.825 0.981 0.830 0.329 0.985 
Freundlich 
 Kf (mg g−11.181 0.682 0.231 13.352 31.714 6.152 
 n 2.418 1.918 2.951 1.296 1.620 3.256 
 R2 0.984 0.981 0.979 0.982 0.979 0.964 
Dubinin–Radushkevich 
 Qd (mol g−10.000 0.000 0.000 0.001 0.008 0.000 
 Bd −0.003 −0.005 −0.002 −0.004 −0.005 −0.002 
 E (KJ mol−112.328 9.704 16.440 10.976 9.960 17.623 
 R2 0.798 0.841 0.838 0.728 0.759 0.702 

Qm (mg g−1): maximum adsorption capacity; KL or b (L mg−1): constant related to adsorbent/adsorbed interaction forces; RL: Langmuir's constant; R2: coefficient of determination; Kf (mg−1g): related to adsorption capacity; n: related to the solid's heterogeneity; Qd (mol g−1): maximum adsorption capacity; E (kJ mol−1): average sorption energy.

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