Abstract
Industrial and agricultural discharges have been shown as important sources for a wide range of contaminants like heavy metals. This study focused on the assessment of the toxic effect of heavy metals and illustrates some methods of eliminating or avoiding these contaminants. In certain methods, heavy metals (Cu, Zn, Cr, Ni, Pb, Hg, and Cd) are recovered, and range of absorbents are tested. A number of studies have reported the complex interaction of polymers with metal ions with the polymers for eliminating heavy metals (e.g. cellulose, chitosan, and chitin. Metal ions are absorbed by these polymers by the amine and hydroxyl groups. They have unique features that incorporate polyxysalt arrangement, capacity to frame films, optical underlying qualities, and chelates metal particles. Chemical bonds, pH, crystallinity, and deacetylation are controlling the mechanism and performance of the absorption. Some methods increase the efficiency, selectivity, and quality of chitosan: the first is through chemical modification employing grafting and crosslinking, and the second by physical modification, such as manufacturing gel granules and reducing crystallization. This study aims to investigate the removal of heavy metals from water by the sorption method and to study and analyze literature dealing with this topic using chitosan hydrogel.
Highlights
The increased exploitation of heavy metals, colloids, and smaller organic substances, for more than 20 toxic metals, has caused an increase in the level of harmful minerals flowing into the water [1]
Mercury, lead, cadmium, and chromium) and is very harmful if it flows into the water or is discharged into nature induced by humans even at low concentrations, such contaminants have five times the gravity of water [2]
Various techniques were applied, which inspired researchers to develop new and bio-absorbent materials and others derived from biopolymers such as chitosan due to their effectiveness in absorbing ions and being green, environmentally friendly materials with low cost
Summary
The increased exploitation of heavy metals, colloids, and smaller organic substances, for more than 20 toxic metals, has caused an increase in the level of harmful minerals flowing into the water [1]. There are classic techniques used to remove heavy metals from solutions and reduce environmental pollution They are as follows: Solvent extraction, chemical and biological absorption [4], coprecipitation and precipitation [5], ion exchange [6], and electrochemical reduction [7]. Among these techniques, the adsorption method is used by using adsorbents to absorb organic materials and remove their ions because of the possibility of applying them on a large scale at reduced costs and replacing carbon with them because its cost is high compared to other types of adsorbents [8]. This study aims to investigate the removal of heavy metals from wastewater by adsorption method and to study and analyze all kinds of literature dealing with this topic using chitosan hydrogel
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