**4. Conclusion**

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

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**Author details**

Şerife Parlayıcı and Erol Pehlivan\*

provided the original work is properly cited.

Sciences, Konya Technical University, Konya, Turkey

\*Address all correspondence to: erolpehlivan@gmail.com

Department of Chemical Engineering, Faculty of Engineering and Natural

© 2021 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

*Modified Chitosan Forms for Cr (VI) Removal DOI: http://dx.doi.org/10.5772/intechopen.96737*

**Conflict of interest**

**Notes**

**Abbreviations**

Cts Chitosan

CNT Carbon Nanotubes GO Graphene Oxide HA Humic Acids RS Rosehip Seed Shell

vided to remove Cr (VI) for water treatment applications.

The authors declare no competing financial interest.

BSSP Black sesame (*Sesamum indicum* L.) seed pulp

The authors declare no conflict of interest.

MWCNT Multiwalled Carbon Nanotubes

MFSC Magnetic Fe3O4@SiO2–Cts

donating electrons are found in almost every Cts-based adsorbent structure. The removal mechanism of adsorbents is also affected by surface chemistry and physical properties in the Cr (VI) elimination process. Their high surface area properties, usability, porosity and cost effectiveness play an important role in increasing the capacity of the Cts-based adsorbent for Cr (VI) removal in wastewater. The modified adsorbents together with Cts for Cr (VI) removal have been shown to possess high capacities and they can be economically used in wastewater treatment units. By using Cts modified adsorbent, a faster and more efficient process will be pro*Modified Chitosan Forms for Cr (VI) Removal DOI: http://dx.doi.org/10.5772/intechopen.96737*

donating electrons are found in almost every Cts-based adsorbent structure. The removal mechanism of adsorbents is also affected by surface chemistry and physical properties in the Cr (VI) elimination process. Their high surface area properties, usability, porosity and cost effectiveness play an important role in increasing the capacity of the Cts-based adsorbent for Cr (VI) removal in wastewater. The modified adsorbents together with Cts for Cr (VI) removal have been shown to possess high capacities and they can be economically used in wastewater treatment units. By using Cts modified adsorbent, a faster and more efficient process will be provided to remove Cr (VI) for water treatment applications.
