3.2. Effect of pH
It is well-known that pH can affect protonation of functional
groups (i.e. carboxyl, phosphate and amino groups) in the biomass, as
well as the chemistry of the metal (i.e. its solubility).
As shown in Fig. 2, the metal uptake increased with the increasing
pH in the range of 2 to 5. At pH values of about 5, sorption capacities
achieved maximum values. When the pH decreased, concentrations of
protons increased and competition in binding the active sites on the