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Open AccessArticle

The Role of Surface Chemistry and Polyethylenimine Grafting in the Removal of Cr (VI) by Activated Carbons from Cashew Nut Shells

1
Department of Chemistry, Biochemistry and Physics, Becton College of Arts and Sciences, Fairleigh Dickinson University, Madison, NJ 07940, USA
2
Departamento de Química Inorgánica, Facultad de Ciencias Universidad de Málaga, Campus de Teatinos, 29071 Málaga, Spain
*
Author to whom correspondence should be addressed.
Received: 12 February 2021 / Revised: 23 February 2021 / Accepted: 24 February 2021 / Published: 27 February 2021
Activated carbons prepared from cashew nut shells and modified by grafting polyethylenimine onto the surface were tested for removal of Cr (VI). The removal efficiency of carbons without and with polyethylenimine decreased with an increase in pH, with maximum efficiency found at pH 2. The average maximum adsorption capacities of carbons were calculated to be 340 ± 20 mg/g and 320 ± 20 mg/g for unmodified and modified carbons, respectively. Surface characterization of carbons revealed that C–O functionalities are actively involved in both polyethylenimine grafting and Cr (VI) removal. Moreover, lactone groups and amides, formed by polyethylenimine grafting, seemingly undergo acid hydrolysis with formation of phenol and carboxylic groups. Considering that Cr (III) is the only form of chromium found on the surface of both carbons, the reduction mechanism is deduced as the predominant one. Here Cr (VI), majorly present as HCrO4¯, is attracted to the positively charged carbon surface, reduced to Cr (III) by phenol groups, and adsorbed inside the pores. The mechanism of Cr (VI) removal appears to be similar for unmodified and modified carbons, where the smaller adsorption capacity of the latter one can be related to steric hindrance and pore inaccessibility. View Full-Text
Keywords: activated carbon; adsorption capacity; cashew nut shells; chromium (VI) removal; polyethylenimine; surface chemistry activated carbon; adsorption capacity; cashew nut shells; chromium (VI) removal; polyethylenimine; surface chemistry
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MDPI and ACS Style

Smith, V.A.; Rivera, J.F.A.; Bello, R.; Rodríguez-Aguado, E.; Elshaer, M.R.; Wodzinski, R.L.; Bashkova, S. The Role of Surface Chemistry and Polyethylenimine Grafting in the Removal of Cr (VI) by Activated Carbons from Cashew Nut Shells. C 2021, 7, 27. https://0-doi-org.brum.beds.ac.uk/10.3390/c7010027

AMA Style

Smith VA, Rivera JFA, Bello R, Rodríguez-Aguado E, Elshaer MR, Wodzinski RL, Bashkova S. The Role of Surface Chemistry and Polyethylenimine Grafting in the Removal of Cr (VI) by Activated Carbons from Cashew Nut Shells. C. 2021; 7(1):27. https://0-doi-org.brum.beds.ac.uk/10.3390/c7010027

Chicago/Turabian Style

Smith, Victoria A.; Rivera, Juster F.A.; Bello, Ruby; Rodríguez-Aguado, Elena; Elshaer, Mohammed R.; Wodzinski, Rebecca L.; Bashkova, Svetlana. 2021. "The Role of Surface Chemistry and Polyethylenimine Grafting in the Removal of Cr (VI) by Activated Carbons from Cashew Nut Shells" C 7, no. 1: 27. https://0-doi-org.brum.beds.ac.uk/10.3390/c7010027

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