The purpose of these experiments was to determine the contact time required to reach the equilibrium between
dissolved and solid-bound sorbate. Equilibrium time is a function of many factors, such as type of biomass (number and
kind of biosorption sites), size and form of biomass, physiological state of biomass (active or inactive, free or
immobilized), as well as the metal involved in the biosorption system. Reported values for equilibrium time are in the
range from 15 minutes (Aksu et al., 1991).
Figure 5 presents the results at two different initial concentrations of 92 and 162 mg/l of copper with a contact time of 3
hours was enough for the system to reach equilibrium. So, this time was used to obtain the isotherms in all experiments.
Figure 5 clearly indicates that sorption can be divided into two stages: one in which the sorption rate is very high (60%
of biomass saturation capacity in a contact time of 25 minutes), followed by a second stage with a much lower sorption
rate. This behaviour has often been reported by other researches (Crist et al., 1994), the proton uptake by algal cells
consists of two processes, a fast surface reaction and a slow diffusion of protons into the cells. The fast biosorption
kinetics observed is typical for biosorption of metals involving no energy-mediated reactions, where metal removal
from solution is due to purely physico-chemical interactions between biomass and metal solution (Aksu and Kutsal,
2001).
The purpose of these experiments was to determine the contact time required to reach the equilibrium betweendissolved and solid-bound sorbate. Equilibrium time is a function of many factors, such as type of biomass (number andkind of biosorption sites), size and form of biomass, physiological state of biomass (active or inactive, free orimmobilized), as well as the metal involved in the biosorption system. Reported values for equilibrium time are in therange from 15 minutes (Aksu et al., 1991).Figure 5 presents the results at two different initial concentrations of 92 and 162 mg/l of copper with a contact time of 3hours was enough for the system to reach equilibrium. So, this time was used to obtain the isotherms in all experiments.Figure 5 clearly indicates that sorption can be divided into two stages: one in which the sorption rate is very high (60%of biomass saturation capacity in a contact time of 25 minutes), followed by a second stage with a much lower sorptionrate. This behaviour has often been reported by other researches (Crist et al., 1994), the proton uptake by algal cellsconsists of two processes, a fast surface reaction and a slow diffusion of protons into the cells. The fast biosorptionkinetics observed is typical for biosorption of metals involving no energy-mediated reactions, where metal removalfrom solution is due to purely physico-chemical interactions between biomass and metal solution (Aksu and Kutsal,2001).
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