Microwave-assisted production of pyroligneous acid from palm kernel shell

Oil palm plantation is one of the biggest contributors to Malaysian economy. However, the processing of oil palm fruit into palm oil resulted in the generation of huge volumes of biomass. Traditionally, oil palm biomass such as oil palm frond, oil palm trunk, palm kernel shell and empty fruit bunch was left at the plantation to decompose naturally, which with time, would ultimately lead to soil and water pollutions. Amongst the various solutions available to manage the abundance of oil palm biomass, pyrolysis offers an interesting solution where oil palm biomass can be converted into bio-oil, pyroligneous acid (PA) and biochar. The objectives of this study were to determine the optimum pyrolysis condition to produce PA with the highest total phenolic contents, to evaluate the potential of optimized microwave-assisted PA as antioxidant and antifungal agents and to investigate the adsorptive properties of the biochar produced from pyrolysis of palm kernel shell to remove dye from wastewater. The dye removal capability was evaluated using methylene blue (MB) based on three parameters namely initial concentration of MB, amount of adsorbent dosage and batch equilibrium studies. The adsorption equilibrium data was best fitted with the Freundlich isotherm model with R2 of 0.95 and qmax of 27.23 mg/g. PA containing highest total phenolic contents (optimized PA) was produced at the following condition: final temperature of 480°C, microwave power of 580 W and nitrogen flow rate of 2.4 LPM (liter per minute). The ethyl-acetate extracted optimized PA showed an antifungal capacity with inhibition zone between 12.3 to 56.1 mm. Microwave-assisted concentrated pyroligneous acid (CPA) showed 2,2-Diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity of 83 ± 2.11 µg/mL and trolox equivalent antioxidant activity (TEAC) of 35.75 ± 0.63 µg/mL while for industrial CPA, the value was 1096.24 ± 3.56 µg/mg (DPPH) and 1287.82 ± 2.89 µg/mg (TEAC). From the findings of this study, it can be concluded that biochar and PA produced from the pyrolysis of palm kernel shell showed good potential to be used as dye removal, antifungal and antioxidative agents