**Notes**

*Chitin and Chitosan - Physicochemical Properties and Industrial Applications*

*Photograph images of Cts coated perlite beads (a) wet beads (b) dry beads.*

The main purpose of this article was to review some Cts based modified composite adsorbents for the adsorptive removal of Cr (VI). Most adsorbents used for longer in its pristine form, but with few changes carried out. Superior properties of adsorbents can be achieved by functionalizing and converting them into composite forms. The layers are formed by using different levels of polymers. Some of these layers are made up by different adsorbents, eg. Humic acid/graphene oxide, MWCNT/Cts, nanoparticle/Cts and Cts/perlite. Graphene oxide, nanoparticles and silica are known to have high surface areas, while biomass such as black sesame seed pulp and chitosan exhibit low surface area, but contain abundant functional groups. Cross-linking or modification is very effective in functionalization of adsorbents. Features and development history together chromium toxicity, sources, removal mechanism from the aqueous medium, latest trends in composite adsorbent synthesis and preparation were discussed at length. The interpretation of the Cr (VI) removal mechanism summarized in the text. It is possible to reach higher capacities to determine the appropriate conditions in studies with composite adsorbents. The adsorption of Cr (VI) alone electrostatically is not sufficient. If Cr (VI) is considered to be suitable for strong oxidation, it can be removed from the aqueous environment by finding sensitive electrons from the groups in Cts-based adsorbents to transform into Cr (III) form. Heteroatoms such as O and N responsible for

*Adsorption mechanisms involved in adsorption of hexavalent chromium onto Fe3O4@SiO2–Cts (MFSC)* 

**258**

**4. Conclusion**

*biopolymers [21].*

**Figure 14.**

**Figure 13.**

The authors declare no competing financial interest.
