**5.3 Effect of temperature on removal of heavy metal ions**

Zendehdel et al. [44] reported about the synthesis of SAH of poly acrylamideco-acrylic acid (p(AAm-co-AA/Na zeolite)) for the successive removal of heavy metal ions (Pb2+ and Cd2+) and studied the effect of temperature (ranging from 285 to 323 K) on the removal of these heavy metal ions from the aqueous solution. They reported that raising temperature from 285 to 303 K, the adsorption of heavy metal ions increased, which indicates that the process is endothermic. However, further increase in temperature up to 323 K, the adsorption of heavy metal ions was decreased, which is due to the desorption of heavy metal ions from the hydrogel network.
