SINTESIS NANOKOMPOSIT Fe3O4/ZnO-Ni DAN UJI AKTIVITASNYA SEBAGAI FOTOKATALIS PADA DEGRADASI METIL JINGGA

ANES OCTAVIANI, Dra. Eko Sri Kunarti, M.Si., Ph.D./Prof. Drs. Sri Juari Santosa, M.Eng., Ph.D.

2021 | Tesis | MAGISTER KIMIA

Sintesis material nanokomposit Fe3O4/ZnO-Ni sebagai fotokatalis pada degradasi metil jingga telah dilakukan. Penelitian diawali dengan sintesis material magnetit (Fe3O4) dengan metode kopresipitasi dan sonikasi, kemudian dilakukan proses pelapisan material magnetit menggunakan seng oksida (ZnO) melalui metode sol-gel dengan memvariasikan massa ZnO. Selanjutnya dilakukan doping menggunakan logam Ni yang bervariasi secara in situ. Material hasil sintesis dikarakterisasi dengan Spektrofotometer Inframerah (FT-IR), Difraktometer sinar-X (XRD), Scanning Electron Microscope-Energy Dispersive X-ray (SEM-EDX), Diffuse Reflectance UV-Visible Spectrophotometer (SR-UV), Vibrating Sample Magnetometer (VSM), dan Transmission Electron Microscope (TEM). Uji aktivitas fotokatalis dilakukan dengan sistem batch dalam reaktor tertutup yang dilengkapi dengan sumber sinar UV dan sinar tampak. Hasil penelitian menunjukkan bahwa nanokomposit Fe3O4/ZnO-Ni telah berhasil disintesis dan responsif terhadap sinar tampak dibuktikan oleh spektra SR UV-visibel. Sifat magnet terbaik diperoleh pada rasio massa Fe3O4/ZnO 1:5 dengan nilai momen magnet masing-masing sebesar 5,21 dan 9,33 emu/g untuk Fe3O4/ZnO dan Fe3O4/ZnO-Ni 3% (m/m). Energi celah pita mengalami penurunan dengan penambahan dopan Ni. Penurunan terjadi hingga 2,94 Ev setelah penambahan logam Ni sebanyak 3%. Material Fe3O4/ZnO-Ni 3% menunjukkan aktivitas fotokatalitik optimum pada paparan sinar tampak dan sinar UV terhadap degradasi metil jingga (30 ppm), masing-masing sebesar 86,93 dan 82,87% pada pH 2 dengan massa fotokatalitis 20 mg selama 45 menit. Material nanokomposit Fe3O4/ZnO-Ni menunjukkan aktivitas fotokatalitik yang masih sangat baik pada 3 kali penggunaan ulang. Studi kinetika degradasi metil jingga menunjukkan bahwa proses degradasi metil jingga secara fotokatalitik mengikuti model kinetika orde kedua semu dengan nilai konstanta laju degradasi sebesar 0.0095 g mg-1 menit-1 pada paparan sinar UV dan 0.0176 g mg-1 menit-1 pada paparan sinar tampak.

The synthesis of Fe3O4/ZnO-Ni nanocomposite material as a photocatalyst for methyl orange degradation has been conducted. The study was initiated with the synthesis of the magnetite material (Fe3O4) using the co-precipitation and sonication methods, then the magnetite material coating was carried out using zinc oxide (ZnO) by the sol-gel method with varying amount mass of ZnO. The doping of Fe3O4/ZnO was then conducted in-situ using various concentrations of Ni. The synthesized material was characterized by Fourier-transform Infrared Spectrometer (FTIR), X-ray Diffractometer (XRD), Scanning Electron Microscope-Energy Dispersive X-ray (SEM-EDX), Diffuse Reflectance UV-Visible Spectrophotometer (SR-UV), Vibrating Sample Magnetometer (VSM), and Transmission Electron Microscope (TEM). The photocatalytic activity test of the photocatalyst was carried out in a batch system, in a closed reactor equipped with UV and visible light sources. The result of the study indicated that Fe3O4/ZnO-Ni nanocomposites have been successfully synthesized and responsive to visible light as evidenced by the SR UV-Vis spectra. The best magnetic property was obtained at Fe3O4/ZnO with a ratio mass of 1:5 with the magnetic moments of 5.21 and 9.33 emu/g for Fe3O4/ZnO and Fe3O4/ZnO-Ni 3% (m/m) materials, respectively. The bandgap energy decreases with increasing concentration of Ni and reached up to 2.94 Ev after the addition of 3% of Ni dopant. The Fe3O4/ZnO-Ni 3% material showed the optimum photocatalytic activity toward methyl orange (30 ppm) degradation under visible light and UV irradiation which are 86.93 and 82.87%, respectively, at pH 2 with 20 mg of photocatalyst materials for 45 min irradiation. The Fe3O4/ZnO-Ni nanocomposite still showed a good photocatalytic activity toward methyl orange degradation after three times of reuse. The kinetic study showed that the photocatalytic degradation of methyl orange followed the pseudo-second-order kinetic model with a rate constant value were 0.0095 and 0.0176 g mg-1 minute-1 on the UV and visible light exposure, respectively.

Kata Kunci : fotokatalis, Fe3O4/ZnO-Ni, degradasi, metil jingga