The batch experiment was carried out by contacting 0.1 g of alga with 100 ml of 50 mg/L of metal solution in 250 ml stopper conical flask at different pH value, ranging from 2 to 6 (below 2, the high proton concentration minimizes the metal sorption and above 6 the metal precipitation is favored). The pH of the solutions was adjusted either by hydrochloric acid or sodium hydroxide. The mixture was shaken for 2 h at room temperature, filtered, and the final pH for each sample was determined.