Sorption dynamics and isotherms at different pH values in a batch systemIn order to determine the minimum contact time for the equilibrium experiments, the sorption dynamics was examined
first. Figure 3 shows the profiles of dimensionless copper concentration against time.
The copper biosorption rate was strongly influenced by the sorption system pH value, the copper solution concentration
in the solution decreased with contact time faster at higher pH values. At various pH values, approximately 60-70% of
the copper present originally in the solution was sorbed onto biomass in about 25 minutes after the start of biosorption
and the equilibrium could be reached within 3 hours. This provided a guide for the biosorption contact time to be used
in the equilibrium experiments. Same conditions were also applied to determine the contact time at pH 4 and it was
observed that 3 hours is sufficient for the system to reach equilibrium as represented in figure 3. Best adsorption was
observed at pH 4 as illustrated in figure 4 by approximately 75% adsorption rate.