Evaluation of the use of adsorbents based on graphene oxide and cellulose for Cr(VI) adsorption

Water contamination is an environmental problem caused by the growth of the manufacturing industry. Among these contaminants, Cr ions, especially in their hexavalent form, can be highlighted. The objective of this study is to evaluate the capacity of graphene oxide (GO), cellulose aerogels, and GO-containing cellulose aerogels to remove hexavalent chromium (Cr(VI)) by adsorption. The aerogels were manufactured using a freeze-drying process, GO was synthesized using a modified Hummers' method, and a batch adsorption system was used to verify the influence of the experimental factors. To interpret experimental data, Langmuir, Freundlich, Sips, Redlich-Peterson, Temkin isotherm, pseudo-first-order, pseudo-second-order, and Elovich kinetic models were used to interpret experimental data. The adsorbed amounts obtained were 274.52 mg.g(-1) (GO), 199.89 mg.g(-1) (cellulose aerogel), 237.42 mg.g(-1) (0.5% GO aerogel), and 235.85 mg.g(-1) (1% GO aerogel) at 25 degrees C. The data fit best to Langmuir and pseudo-second-order, indicating monolayer adsorption controlled by external and intraparticle diffusion. Additionally, thermodynamic parameters reflected spontaneous and exothermic adsorption. Furthermore, the adsorbents could be reused in more than 1 removal cycle, demonstrating the potential of using materials from renewable sources for Cr(VI) adsorption.