Hydrogels reaction with sodium alginate over pollutant degradation

Sodium alginate is a naturally occurring polysaccharide, obtained from brown algae. It is converted into hydrogel and modified through cross linking and surface grafting and addition of several natural and synthetic polymers and nanoparticles to impart required characteristics in the adsorbent to elucidate a wide variety of heavy metals ions from wastewater released into the environment through industrial wastes. The SA adsorbents are biodegradable, regenerable, reusable and do not generate secondary pollutants unlike other adsorbents i.e., activated carbon, coal ash, natural zeolite, clay mineral and cationic exchange resin. However, SA adsorbents have few downsides hat are discussed in this article. So, the areas to strengthen SA adsorbents are also suggested. A number of adsorbents with the highest and lowest adsorption capacity for heavy metal ions i.e., Au, Ag, Pd, Pb, Cu, Cr, Hg, Sb, U and Zn are also listed. The objective of this article is to summarize modifications in sodium alginate hydrogel to remove heavy metal ions from wastewater using adsorption mechanism. These adsorbents have capacity to bind heavy metals to open surfaces of sodium alginate. Each modified adsorbent has adsorption sites for specific heavy metal with specific adsorption capacity. Some of these adsorbents have capacity to undergo 3 or 4 adsorption–desorption cycles at least and eight adsorption–desorption cycles at most in some cases.