Removal of Heavy Metal Ions from Polluted Waters by Using of Hydrogel-based Absorbetnts

The growth of industry fulfills our necessity and promotes economic development. However, pollutants from such industries pollute water bodies which pose a high risk for living organisms. Thus, researchers have been urged to develop an efficient method to remove toxic heavy metal ions from water bodies. The adsorption method shows promising results for the removal of heavy metal ions and is easy to operate on a large scale, thus can be applied to practical applications. Numerous adsorbents were developed and reported, among them hydrogels, which attract great attention because of the reusability, ease of preparation, and handling. Hydrogels are macromolecular networks that swell, but do not dissolve, in water. The ability of hydrogels to absorb water arises from hydrophilic functional groups such as -NH2, -COOH, -OH, -CONH2, - CONH -, and -SO3H attached to the polymeric backbone, while their resistance to dissolution arises from crosslinks between network chains. Thus, this review provides various methods of hydrogel adsorbents preparation and summarizes recent progress in the use of hydrogel adsorbents for the removal of heavy metal ions. Further, the mechanism involved in the removal of heavy metal ions is briefly discussed. The most recent studies about the adsorption method for the treatment of heavy metal ions contaminated water are presented.