Effect of the degree of oxidation of graphene oxide on As(III) adsorption

TL;DR

This study investigates how the degree of oxidation of graphene oxide influences its ability to adsorb arsenic (As(III)), revealing that higher oxidation levels significantly enhance adsorption capacity and elucidating the interaction mechanisms via DFT models.

Contribution

It demonstrates the impact of oxidation degree on graphene oxide's arsenic adsorption capacity and provides molecular insights through DFT modeling, including the highest reported adsorption capacity.

Findings

Higher oxidation increases As(III) adsorption capacity.

DFT shows hydrogen bonds as primary interaction mechanism.

Graphene oxide exhibits 57% cell viability at 50 μg/ml.

Abstract

The study of the interaction between graphene oxide and arsenic is of great relevance towards the development of adsorbent materials and as a way to understand how these two materials interact in the environment. In this work we show that As(III) adsorption, primarily H3AsO3, by graphene oxide is dependent on its degree of oxidation. Variations in the concentration of potassium permanganate resulted in an increase on the C/O ratio from 1.98 to 1.35 with C-OH and C-O-C concentrations of 18 and 32%, respectively. Three oxidation degrees were studied, the less oxidized material reached a maximum As(III) adsorption capacity of 124 mg/g, whereas the graphene with the highest degree of oxidation reached a value of 288 mg/g at pH 7, to the authors knowledge, the highest reported in the literature. The interaction between graphene oxide and As(III) was also studied by Density Functional Theory (DFT) computer models showing that graphene oxide interacts with As(III) primarily through hydrogen bonds, having interaction energies with the hydroxyl and epoxide groups of 378 and 361 kcal/mol, respectively. Finally, cytotoxicity tests showed that the graphene oxide had a cellular viability of 57% with 50 {\mu}g/ml, regardless of its degree of oxidation.