Based on this result, the sorption process was more suitably described by pseudo-second order model and suggests that the sorption rate of Pb, Cu and Cd ions onto CMSS-acid hydrogel are probably controlled by chemical process that involves the valence of sorbent and sorbate by sharing or exchanging the electron (Al-qudah, Mahmoud, & Khalek, 2014). In this experiment,the carboxylic group of CMSS takes the major responsibility in the interaction between the hydrogel and metal ions.