Results and discussion
Effect of pH
pH has a direct influence on the biosorption mechanism and uptake of metal by the adsorbent. To understand the effect of pH, the adsorption of Fe(II) as a function of pH in the range of 2.5 to 7.5 was measured, and the re- sult was shown in Figure 1. There was an increase in the biosorption capacity of the biomass with the increase in pH from 2.5 to 5.0 and was maximum in the pH range of 5.0 to 6.0. Then, it decreased when pH reached 7.5. This fact can be explained by the competition between the surface charge and solution chemistry as two im- portant factors. In highly acidic pH, adsorbent surface is protonated and act as a positive charge. Deprotonation occurs when pH increases and causes negative charges