Similar result has been reported by Singanan and Peters (2013) suggesting that the saturation of a system occurred at certain amount of sorbent applied where the metal bonded to sorbent and free metal ions in aqueous solution remain constant. The predominant sorption mechanism is ion exchange as well as surface absorption on the hydrogel. The optimum amount of CMSS-acid hydrogel for Pb ions was 0.050 g, while for Cu and Cd ions were 0.150 g and 0.200 g with the amount of metal uptake was 94.0%, 87.8% and 84.4%, respectively.