Potential of the main magnetic iron oxides synthesized over graphene oxide in integrated adsorption and photocatalysis of inorganic and organic emergent contaminants

• Published in: Colloids and surfaces. A, Physicochemical and engineering aspects Physicochemical and engineering aspects, 2023-08, Vol.671, p.131647, Article 131647
• Main Authors: Nascimento Júnior, Welenilton José do, de Aguiar, Giovane Henrique, Landers, Richard, Vieira, Melissa Gurgel Adeodato, Motta Sobrinho, Mauricio Alves da
• Format: Article
• Language: English
• Subjects: Advanced oxidation; Heavy metal cations; Integrated photocatalytic adsorption; Multi-component adsorption; Synthetic organic dyes
• ISSN: 0927-7757; 1873-4359
• DOI: 10.1016/j.colsurfa.2023.131647

There is significant recent research into the development of iron-oxide/graphene-oxide materials for the removal of contaminants from water. However, studies are limited to simple synthetic samples and single-treatment operations. This work aimed to evaluate the efficiency of Graphene Oxide (GO), magnetite-(FeO.Fe2O3), and hematite-(α-Fe2O3) decorated GO as Integrated Photocatalyst Adsorbents (IPCAs) in the uptake of toxic metal cations and oxidation of organic dyes by simultaneous adsorption and photocatalysis for the first time. Higher adsorption affinities for Ni2+ were observed in single-cation adsorption, however, competition for active sites was observed in multi-metal systems by displacing Ni2+ ions to increase Cu2+ and Pb2+ uptakes. GO-αFe2O3 presented the highest removal rates of metal cations. The cationic organic dyes exhibited maximum color removal while anionic dye only exhibited considerable removal rates with iron-decorated nanomaterials (GO-αFe2O3 > GO-Fe3O4 > GO). In cycle experiments, the treatment of equimolar Pb2+/Methyl Blue samples was investigated and CaCl2 displayed the best performance to recover Pb2+ with minor Fe leaching. All nanomaterials were able to keep their photocatalytic activity for five cycles with TOC removal ranging between 86% and 95%. Despite GO and GO-αFe2O3 achieved appreciable metal removal rates, GO-Fe3O4 was not able to adsorb metal cation from the third cycle. Characterization analyzes (XPS, FTIR, XRD, UV-Vis, and DRS) corroborated the success of the syntheses and pointed out the iron-oxygen interaction in the materials. The structure of the nanomaterials after five cycles was observed to change by XPS and XRD. [Display omitted] •Original investigation on simultaneous adsorption and photocatalytic activity of GO, GO-Magnetite, and GO-Hematite.•Three metal cations and three organic dyes were used as contaminants in single and ternary samples.•One model metal cation and one organic dye were chosen for integrated adsorption-photocatalysis.•Material efficiency was evaluated by TOC removal, metal uptake, and Fe leaching for 5 cycles.•XRD, FTIR, DRS, and XPS analyses were performed before and after the treatment process.