Three-dimensional ZnO–TiO2/graphene aerogel for water remediation: The screening studies of adsorption and photodegradation

Zinc oxide−doped titanium dioxide/graphene aerogel (ZnO−TiO2/GA) nanocomposite was fabricated by the two-step solvothermal method for efficient removal of dyes and toxic metals in aqueous media. Based on the results, ZnO−TiO2/GA material with an optimal ZnO amount of 300 mg has a synergistic effect on exhibiting an excellent photocatalytic-adsorption capacity. The highest degradation efficiency for methylene blue, rhodamine B, and methyl orange was 99.7, 97.3, and 94.9%, respectively, with the optimum conditions: catalyst dose of 0.2 g L−1, 20 ppm dye concentration at 20 min under ultra-visible (UV−11 W) light irradiation. Moreover, the material also showed outstanding reusability with more than 90% dye removal efficiency after 8 cycles of testing. The proposed pathway and intermediate products of dye degradation were also investigated using liquid chromatography−mass spectrometry (LC−MS) analysis. Besides that, the maximum absorption capacity for the toxic metal ions Cd2+ and Co2+ are 380.6 and 230.1 mg g−1, respectively, which followed by the Langmuir isotherm adsorption model. The results exhibited the material's potential for the treatment of water containing toxic metals and waste from textile dyeing.