| The pollution of heavy metals in water becomes a big problem. The heavy metals in the environment is greatly concerned due to their toxicity. Many toxic heavy metals have been discharged into the environment as industrial wastes, causing serious soil and water pollution. Chromium is widely used in industry. Chromium pollution of water sources can occur naturally or through contaminated discharges from various industrial processes such as electroplating, leather tanning, and corrosion protection painting. Hexavalent chromium compounds are carcinogenic and corrosive on tissues, and are found to be harmful to bacteria, plants, animals and people. The toxicity of chromium(Ⅵ) to human includes lung cancer, as well as kidney, liver, and gastric damage. Thus, it is necessary to remove Cr(Ⅵ) contaminants from wastewater before being released into the environment. Adsorption is considered as one of the best methods to remove heavy metals from industrial effluents due to its ease of operation and low cost. Common adsorbents such as carbon fiber material, zeolite, clay mineral and resin have the disadvantage of low efficiency. So there is an urgent need to develop new and efficient adsorption materials.Graphene oxide has received world-wide attention due to its exceptional physicochemical properties, but it has the disadvantages of harder solide-liquid separation and low adsorption capacity. Therefore, the solid-liquid separation ability of graphene oxide should be improved by attaching some magnetic materials, and the adsorption ability should be enhanced by grafting new functional groups. In this study, derived materials were synthesized from graphene oxide and were used as adsorbents for removing metal ions from aqueous solution. The adsorption mechanism was investigated. The specific research work and the study results can be summarized as follow:A novel magnetic composite adsorbent was synthesized by grafting 1,2-diaminocyclohexanetetraacetic acid to magnetic graphene oxide(DCTA/E/MGO). The DCTA/E/MGO was employed for removing Cr( VI) from aqueo us solution in this study. The composite was characterized by FESEM, TEM, BET, XRD, FT-IR and XPS. The adsorption behaviors of Cr(Ⅵ) by DCTA/E/MGO in aqueous solution were systematically investigated. Second order kinetic and Freundlich isotherm models validated the experimental data. The adsorption rate was influenced by both film diffusion and intraparticle diffusion. Thermodynamic parameters revealed that the adsorption reaction was an endothermic and spontaneous process. The novel adsorbent exhibited better Cr(Ⅵ) removal efficiency in solutions with low p H. The decontamination of Cr(Ⅵ) by DCTA/E/MGO was influenced by ionic strength. These results are important for estimating and optimizing the removal of metal ions by the DCTA/E/MGO composite. |
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