Synthesis of spinel ferrite and its role in the removal of free fatty acids from deteriorated vegetable oil

Abstract

Deterioration and loss of quality of vegetable oil is a big challenge in the food industry. This study investigated the synthesis of nickel ferrite (NiFe 2 O 4 ) via co-precipitation method and its use for the removal of free fatty acids (FFAs) in deteriorated vegetable oil. NiFe 2 O 4 was characterized using Fourier transformed infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric (TG) analysis, Brunauer–Emmett–Teller (BET) surface area, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). Synthesis of NiFe 2 O 4 was confirmed by characterization, which revealed a BET surface area of 16.30 m 2 ·g −1 and crystallite size of 29 nm. NiFe 2 O 4 exhibited an adsorption capacity of 145.20 L·kg −1 towards FFAs with an 80.69% removal in a process, which obeys Langmuir isotherm and can be described by the pseudo-second-order kinetic model. The process has enthalpy (Δ H ) of 11.251 kJ·mol −1 and entropy (Δ S ) of 0.038 kJ·mol −1 ·K −1 with negative free energy change (Δ G ), which suggests the process to be spontaneous and endothermic. The quantum chemical computation analysis via density functional theory further revealed the sorption mechanism of FFAs by NiFe 2 O 4 occurred via donor–acceptor interaction, which may be described by the lowest unoccupied molecular orbital (LUMO) and the highest occupied molecular orbital (HOMO). The study showed NiFe 2 O 4 to be a potential means that can remove FFAs from deteriorated vegetable oil.