Thermal degradation and kinetics stability studies of oil palm (Elaeis Guineensis) biomass-derived lignin nanoparticle and its application as an emulsifying agent

Abstract

In this paper, lignin was extracted from oil palm empty fruit branch fibers by using a soda pulping process. The homogenizing method was used to reduce the size of lignin into nanoparticles. Four different homogenization shear speeds i.e. 6400, 8400, 10,400, and 12,400 rpm were explored to control the particle size of lignin. Lignin nanoparticles (LNPs) were characterized using FT-IR, UV, TEM, SEM, zeta potential, kinetic thermal degradation, and toxicological analyses. The stability of water-in-oil (W/O) emulsions was characterized by visual observation and cross-polarized microscopy (CPM). The FT-IR results showed similar spectra of all the samples while the particle distribution from TEM demonstrated up to 98% of the samples are in the nano range. The zeta potential of LNP12* (emulsifying agent produced from LNP12 at 12,400 rpm) was observed at |−32.0| mV and found to be the best among all samples to stabilize W/O emulsion at a ratio of 30:70 (water to oil) as a result from creaming index percentage and CPM. Therefore, LNP12 was further analyzed for shelf-life prediction using a kinetic thermal degradation study. Flynn-Wall-Ozawa and Kissinger methods were used in kinetic thermal degradation to determine the activation energy (Ea) of LNP12. It was found that both methods are in good agreement. The Ea value of LNP12 demonstrated better stability and longer shelf-life (around 20 months) at a temperature below 35 °C. LNP12 showed to be safe both, in vitro and in vivo toxicological methods at a concentration below 2000 mg/kg.