Improvement of adsorption performance and selectivity of GO-COOH towards MB dye through effective carboxylation approach: Combined experimental and DFT studies

In this work, the impact of carboxylation of graphene oxide (GO) on the adsorption performance and selective adsorption towards methylene blue (MB) dye was explored by both experimental and density functional theory (DFT) approaches. The GO was first synthesized and then functionalized with ClCH2COOH to produce carboxylated GO (GO-COOH). The COOH content and zeta potential at pH 6 for GO-COOH were 6.644% and -37.2 eV, and for GO were 3.132% and -29.1 eV, respectively. Results revealed that the adsorption behavior of MB absorbed on the GO and GO-COOH surfaces was best described by the pseudo-second-order model and Langmuir isotherm. The GO-COOH exhibited a maximum adsorption capacity (q(m)) of 1731 mg/g and was a more active adsorbent compared to the GO (916 mg/g). According to the DFT calculations, the more stable MB/GO-COOH complex and stronger CH center dot center dot center dot O interaction between OCOOH and H of -CH3 of MB were mainly responsible for the enhanced q(m) and greater selective adsorption of GO-COOH, whereas other interactions like S center dot center dot center dot O, CH center dot center dot center dot N interactions and other CH center dot center dot center dot O interactions were almost identical to MB/GO. These results demonstrate that carboxylation could be a fruitful way to boost the adsorption performance of GO-based adsorbents and eliminate the MB dye pollutants.

Automated summary

This study explores the impact of carboxylation of graphene oxide (GO) on the adsorption performance and selective adsorption towards methylene blue (MB) dye. The results show that carboxylated GO (GO-COOH) has higher adsorption capacity and better selective adsorption compared to GO. Carboxylation presents a promising approach to enhance the adsorption performance of GO-based adsorbents and eliminate MB dye pollutants.