Prepration of Cu/Fe3O4 nanoparticles using tea leaves extract as a catalyst for reduction of para-nitrophenol

In this paper, we report the green synthesis of the Cu/Fe3O4 nanoparticles using tea leaves extract and their application as magnetically separable nanocatalyst for the reduction of 4-nitrophenol. 50 g of dried leaves powdered of green tea was added to 100 mL double distillated water and 100 mL ethanol in 500 mL flask and well mixed. The preparation of extract was done by using magnetic heating stirrer at 60°C for 1 h. The colorless extract obtained was centrifuged in 7000 rpm then filtered and filtrate was kept at refrigerator to use further. For green synthesis of Cu supported on magnetite nanocatalyst, 0.55 g FeSO4•7H2O, 1.6 g Fe2(SO4)3 and 10 g CuSO4.5H2O were dissolved in 25 mL colorless extract of the leaves of green tea at 60 °C under vigorous stirring. Then, a solution of 0.5 M Na2CO3 was added dropwise to the mixture to obtain alkaline pH which caused to change the color of the mixture to dark and monitoring the product formation using UV–vis at times raining 5–40 min. After being stirred again for 5 min at the same temperature, a suspension was formed which gave precipitate of the Cu/Fe3O4 nanoparticles on centrifugation at 7000 rpm and the obtained nanoparticles were washed with water and ethanol, respectively, and then dried. The nanocomposite was characterized by X-ray diffraction (XRD), Fourier transformed infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), Vibrating sample magnetometer (VSM) and transmission electron microscopy (TEM). The catalytic activity for the reduction of 4-NP to 4-AP in water was also evaluated. The conversion of 4-NP to 4-AP in aqueous medium was monitored by using UV-visible measurements at room temperature. There was a shift of the peak of 4-NP from 317 to 400 nm, observed immediately after the addition of NaBH4. This was due to the formation of 4-nitrophenolate ions under alkaline conditions caused by the addition of NaBH4. After the Cu/Fe3O4 magnetic nanocomposite was added into the reaction system, the reduction process was monitored by measuring the time-dependent adsorption spectra of the reaction mixture solution. The magnetic nanocomposite can be easily separated from the reaction media by means of an external magnet and recycled several times without marked loss of activity.