Rapid Degradation of Tartrazine Yellow Dye by Photo-Fenton Action at the Interface of Magnetite and Silica Nanoparticles

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Chinese explanation / 中文解读

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Original abstract

This study reports the synthesis of magnetic nanoparticles (Fe<sub>3</sub>O<sub>4</sub>) supported on silica (SiO<sub>2</sub>), obtained from the chemical and thermal treatment of coconut mesocarp. The spectroscopic and morphological properties of this nanocomposite composed of magnetite and silica (Np-Fe<sub>3</sub>O<sub>4</sub>/SiO<sub>2</sub>) were investigated using Infrared (FTIR), Ultraviolet and Visible (UV-Vis), X-ray Diffraction (XDR), Field Emission Scanning Electron Microscopy (FEG-SEM), and Energy Dispersive X-ray Spectroscopy (EDS) techniques. The synthesized material was applied in heterogeneous catalytic reactions to photodegrade the tartrazine yellow dye in the presence of hydrogen peroxide (Fenton reaction). FTIR spectra showed that treatment in a basic medium (NaOH) promotes the rupture of lignocellulosic fiber units, thereby decreasing the intensity of the chemical bonds. Heat treatment at 800°C generates silica, confirmed by the presence of the Si–O–Si band stretching vibration. Morphologically, the generated silica presented a random geometry, with particles larger than 10 µm filled with pores. The magnetite synthesized by basic co-precipitation on the silica presented an average diameter of 10 nm, as confirmed by FEG-SEM images and the Scherrer equation. The photocatalytic performance of the Np-Fe<sub>3</sub>O<sub>4</sub>/SiO<sub>2</sub> was analyzed, achieving nearly 100% degradation of the tartrazine dye in 75 minutes of reaction in the presence of H<sub>2</sub>O<sub>2</sub>. In the absence of H<sub>2</sub>O<sub>2</sub>, the dye concentration decreases by only 18% over the same reaction time, probably due to saturation of the dye molecules at the nanocatalyst interface. The adsorption equilibrium parameters were investigated using the Langmuir adsorption isotherm model, which revealed that the adsorption capacity of the Np-Fe<sub>3</sub>O<sub>4</sub>/SiO<sub>2</sub> system is approximately twice that of the SiO<sub>2</sub> system: the maximum amount of dye adsorbed on the nanomaterial’s (<em>q<sub>m</sub></em>) surface was 0.35 mg/g for SiO<sub>2</sub> and 0.79 mg/g for Fe<sub>3</sub>O<sub>4</sub>/SiO<sub>2</sub>. This photodegradation efficiency is associated with an increase in the nanoparticle’s surface area, which enhances the adsorption capacity for dye molecules. Furthermore, the excess radicals generated by the Fenton reaction also catalyze the degradation of the dye.

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