Kinetic, isotherm and thermodynamic investigations on adsorption of trace elements and pigments from soybean oil using high voltage electric field-assisted bleaching: A comparative study

Abstract

In this study, the amounts of trace elements (Fe (II) and Cu (II)) and pigments (chlorophyll and carotenoid) in soybean oil were evaluated under high voltage electric field (HVEF) bleaching method at different voltage (10 and 20 kV), temperature (35–65 °C), time (0−30 min) and clay percentage (0.5–2 %) and then were compared to the industrial bleaching method (IBM). The kinetic data of ions and pigments adsorbed on activated bentonite clay under IBM and HVEF at two voltages of 10 and 20 kV followed the mechanism of the pseudo-first-order model (PFOM). The carotenoid and chlorophyll equilibrium data followed a Freundlich isotherm type model, which demonstrated multilayer adsorption under HVEF. The thermodynamic parameters (ΔG°, ΔH°, and ΔS°) displayed that the adsorption of trace metal ions and pigments on bentonite clay under IBM and HVEF were feasible, endothermic and spontaneous between 35 and 65 °C. The results indicated that the HVEF, especially at higher voltage, has a high remarkable capability to remove metal ions and pigments from soybean oil than the IBM. The highest removal capacity for metal and pigments of soybean oil bleaching were obtained in the order of HVEF-20 kV > HVEF-10 kV > IBM.