Structural, optical and magnetic properties of Zn1-xMnxFe2O4 (0 ≤ x ≤ 0.5) spinel nano particles for transesterification of used cooking oil

Abstract

Pure and manganese doped zinc ferrite nanoparticles were prepared via sonication assisted microwave irradiation method and it's employed for biodiesel production from used cooking oil (UCO). The nanoparticles were characterized by XRD, FTIR, DRS, HR-SEM, EDX and VSM techniques. The X-ray diffraction (XRD) results confirmed the formation of cubic spinel structure with Fd-3m space group without any impurities. The average crystalline size of manganese doped and undoped zinc ferrites were in the range from 7.49 nm to 9.65 nm as calculated from Scherer's formula. Fourier transformed infrared spectroscopy (FTIR) studies show the characteristic bands at 550 cm−1 and 419 cm−1 which confirming the presence of Fe-O and Zn-O vibrational stretching frequencies related to octahedral and tetrahedral positions of the zinc ferrite spinel's. UV–vis diffuse reflectance spectroscopy (DRS) revealed the optical energy band gap values in the range 1.90 eV–1.99 eV. The magnetic parameter such as coercivity (Hc), remanence magnetization (Mr) and saturation magnetization (Ms) were determined from hysteresis curves recorded at room temperature. The prepared ferrite nanoparticles were employed for the production of biodiesel from used cooking oil by transesterification process. The maximum yield of biodiesel 98.3% was achieved with 4 wt% of Mn2+ doped ZnFe2O4 nanocatalyst (ZnMnF5), reaction time 50 min, reaction temperature about 65 °C and methanol to oil molar ratio of 21:1. The ZnMnF5 sample was reused atleast 10 times with less reduction in activity. The standard values of biodiesel was measured using ASTM D-6751 method. The formation and composition of fatty acid methyl esters (FAME) were conformed using Gas chromatography-Mass spectroscopy. Mechanism for the biodiesel production using the doped zinc ferrite nanoparticle was proposed.