Recent Developments in Chitosan-Based Adsorbents for the Removal of Pollutants from Aqueous Environments

Abstract

The quality of water is continuously under threat as increasing concentrations of pollutants escape into the aquatic environment. However, these issues can be alleviated by adsorbing pollutants onto adsorbents. Chitosan and its composites are attracting considerable interest as environmentally acceptable adsorbents and have the potential to remove many of these contaminants. In this review the development of chitosan-based adsorbents is described and discussed. Following a short introduction to the extraction of chitin from seafood wastes, followed by its conversion to chitosan, the properties of chitosan are described. Then, the emerging chitosan/carbon-based materials, including magnetic chitosan and chitosan combined with graphene oxide, carbon nanotubes, biochar, and activated carbon and also chitosan-silica composites are introduced. The applications of these materials in the removal of various heavy metal ions, including Cr(VI), Pb(II), Cd(II), Cu(II), and different cationic and anionic dyes, phenol and other organic molecules, such as antibiotics, are reviewed, compared and discussed. Adsorption isotherms and adsorption kinetics are then highlighted and followed by details on the mechanisms of adsorption and the role of the chitosan and the carbon or silica supports. Based on the reviewed papers, it is clear, that while some challenges remain, chitosan-based materials are emerging as promising adsorbents.

Chitosan-Based Nanocomposite Polymeric Membranes for Water Purification—A Review

“…Carbon nanotubes were considered valuable materials in combining them with chitosan for developing adsorbent membranes for heavy metals removal [ 321 , 322 ]. Special attention is brought to the chitosan/biochar (BS) composite which was used to give higher performing adsorbent capacity to the obtained polymeric membrane.…”

“…Special attention is brought to the chitosan/biochar (BS) composite which was used to give higher performing adsorbent capacity to the obtained polymeric membrane. Due to the porous structure of biochar, it has been studied in adsorbent membranes with important applications, such as removal of heavy metals, phosphates, and various antibiotics and pharmaceuticals from waters [ 321 , 322 ].…”

Polysaccharide-Based Nanocomposites for Food Packaging Applications

“… Antimicrobial action of chitosan against ( A ) Gram +ve bacteria, ( B ) Gram -ve bacteria, and ( C ) Fungi. (Reproduced from [ 37 ]). …”

Highly Porous Hydroxyapatite/Graphene Oxide/Chitosan Beads as an Efficient Adsorbent for Dyes and Heavy Metal Ions Removal

“…The amine groups are protonated partially or entirely at pH ≤ 6.5 (pKa of NH 2 groups), forming -NH 3 + cations, whereas the hydroxyl groups' protonation occurs at pH ≤ 4.7 (pKa of -COOH groups). The CTS cationic form with positive charges easily attracts anionic compounds [29,30]. However, at a high pH medium, these amine groups begin to lose their charges due to an increase in OH − groups, resulting in more negative on the surface of chitosan-based materials.…”