**2.6. Batch sorption experiments**

Sorption studies were carried out on a mechanical reciprocating shaker (SKZ-1 NO. 1007827, India) using plastic screw cap bottles. Batch experiments were conducted to investigate the effects of pH, adsorbent dosage, adsorbate concentration and contact time on the adsorption of Pb2+, Cd2+ and Cu2+ on the modified and unmodified algae. The pH of the model test solutions containing a known concentration of the metal ion was adjusted to values between 3 and 7. A known weight of the sorbent (0.03 g) was added to each of the solutions and then allowed to equilibrate giving sufficient time for sorption. The resulting mixture was filtered through Whatman No. 42 filter paper, and the metal ions in the filtrate were determined by atomic adsorption spectrophotometry (UNICAM 919).
