engleski

γ‐irradiation synthesis of magnetic iron oxide nanoparticles and their ability to decolorize methylene blue organic dye

γ‐irradiation is an attractive and ecologically friendly technique for synthesis of magnetic nanoparticles (NPs) at room temperature. It has the advantage of inducing electrons and other reducing species homogeneously throughout the sample. But unlike radiolytic synthesis of noble metal NPs, the radiolytic synthesis of iron oxide NPs is rarely investigated. One of the reasons is a very complex iron oxide chemistry that produces numerous phases. Also, magnetic NPs have a high tendency for agglomeration and due to these reasons, various polymers are used that act as dispersants and stabilizers of magnetic NPs in suspensions as well as growth and surface modifiers. In this work, we studied the influence of γ‐irradiation dose, dose rate, pH and type of polymers on the magnetic iron oxide NPs synthesized using γ‐ irradiation. In order to achieve reducing conditions upon γ‐ irradiation, iron(III) chloride alkaline aq. solutions were purged with nitrogen in the presence of 2‐ propanol. Since ferrous ions (Fe2+) that form upon γ‐ irradiation of iron(III) precursor are highly susceptible to oxidation, the final product depends not only on the γ‐ irradiation parameters, but also on the process of product isolation. In the presence of DEAE‐dextran, irradiation with the dose of 36 kGy resulted in the formation of very small spherical substoichiometric magnetite NPs, whereas at higher dose (130 kGy) the magnetic delta‐FeOOH nanodiscs were obtained. On the other hand, irradiation with 130 kGy in the presence of dextran sulfate resulted in the formation of mixed phases such as alpha‐FeOOH, delta‐FeOOH and iron(III) hydroxide sulfate. By admixing glycerol in irradiated suspensions, reduced intermediated phases such as Fe(OH)2 and Green Rust were captured thus confirming that γ‐ irradiation generated reducing conditions. In addition, we quantitatively determined the concentration of Fe2+ produced in irradiated suspensions by spectrophotometric technique (using 1, 10‐phenanthroline and ferrozine) as well as by redox titration using potassium permanganate, and compared these results with the amount of Fe(II) in isolated powders. The synthesized magnetic NPs were used for decolorization of methylene blue. Methylene blue (MB) is a cationic organic dye, which is used in color staining of domestic objects and in industry. The removal of MB from industrial wastewater is a major concern and attracts world‐wide attention, because of its health issues and carcinogenic risks. The amino‐ dextran synthesized samples slowly and non‐ completely decolorized MB, however, the magnetic sulfate‐dextran samples rapidly and completely decolorize MB within 180 min. Much higher MB decolorization effect of magnetic sulfate‐dextran samples in comparison to the DEAE‐ dextran samples was explained by the formation of metachromatic complex between the cationic MB dye and anionic sulfate groups adsorbed on the magnetic NPs.

iron oxides ; gamma-irradiation ; dextran sulfate ; DEAE dextran ; methylene blue ; green rust ; feroxyhyte ; magnetite

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