Antioxidant and anticorrosive properties of oil palm frond lignins extracted with different techniques

Oil palm (Elaeis guineensis Jacq.) fronds are produced as waste during the harvest of oil palm fruits. It mainly consists of cellulose, lignin, and hemicelluloses. Lignins like other polyphenols are potent free radical scavengers and are considered to be a valuable source of antioxidant phenolic compounds. The aim was to quantify the antioxidant properties of lignins extracted from oil palm biomass using Kraft, soda, and organosolv pulping. The potential of the extracted lignins as inhibitors of mild steel corrosion was also assessed. Ground and dried 1-3-mm-mesh-size oil palm fronds were submitted to Kraft, soda, and organosolv pulping in rotary digesters. The extracted lignin was characterized and oxygen uptake was measured. Anticorrosion properties of extracted lignins were monitored via electrochemical measurements and surface analysis. Soda-extracted lignins displayed the highest antioxidant activities as compared to Kraft and ethanol organosolv lignins. The highest inhibition of corrosion of mild steel was reached in the presence of soda-extracted lignins. Oil palm fronds are potential sources of lignins usable as green antioxidant for corrosion inhibition of mild steel.