Protonated active sites were incapable of binding the bind metal
ions, leading to free ions remaining in the solution. When the initial
pH of the solution was adjusted to a value higher than 5.5, Cr(III) and
Cu(II) ions precipitated because of the higher concentration of
hydroxyl anions in the solution. For this reason, the experiments
were not conducted at pH values higher than 5.5.
3.3. Effect of contact time
Typical biosorption kinetics exhibits a rapid initial uptake,
followed by a slower process. It has been observed that maximum
removal took place within the first 20 min (Figs. 3–6). After this
period, the amount of bound metal ions did not change during the
course of the process.
In order to analyze the biosorption kinetics of Cr(III) and Cu(II)
ions, kinetic models can be applied to fit the experimental data
(Figs. 3–6). Four kinetic models with different reaction orders were
used and nonlinear fitting was performed to determine the model
parameters.
The experimental results pertaining to the biosorption kinetics
were compared to four kinetic models, allowing determining the
parameters of these models (Table 1). Correlation coefficients and
ERRSQ values allow for the assessment of the correlation of the model
with the experimental data. The pseudo-first order model is poor in
Protonated active sites were incapable of binding the bind metalions, leading to free ions remaining in the solution. When the initialpH of the solution was adjusted to a value higher than 5.5, Cr(III) andCu(II) ions precipitated because of the higher concentration ofhydroxyl anions in the solution. For this reason, the experimentswere not conducted at pH values higher than 5.5.3.3. Effect of contact timeTypical biosorption kinetics exhibits a rapid initial uptake,followed by a slower process. It has been observed that maximumremoval took place within the first 20 min (Figs. 3–6). After thisperiod, the amount of bound metal ions did not change during thecourse of the process.In order to analyze the biosorption kinetics of Cr(III) and Cu(II)ions, kinetic models can be applied to fit the experimental data(Figs. 3–6). Four kinetic models with different reaction orders wereused and nonlinear fitting was performed to determine the modelparameters.The experimental results pertaining to the biosorption kineticswere compared to four kinetic models, allowing determining theparameters of these models (Table 1). Correlation coefficients andERRSQ values allow for the assessment of the correlation of the modelwith the experimental data. The pseudo-first order model is poor in
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