Intensification of delignification and subsequent hydrolysis of sustainable waste as banana peels for the HMF production using ultrasonic irradiation

Abstract

The present work deals with the intensification of delignification of banana peels and subsequent acid hydrolysis and HMF production using ultrasound assisted approach. The delignification by conventional method was only 45.78% which increased to 92% for ultrasound clearly demonstrating intensification. The study into effect of operating parameters in the ultrasound-assisted acid hydrolysis on the yields of reducing sugars established optimum conditions as 4% acid concentration (v/v%), solid to solvent ratio of 0.0143, temperature of 80°C, power of 110 W, duty cycle of 70% and time as 3 h. Comparison of sugar yields using conventional approach, ultrasonic horn, and ultrasonic bath indicated that the yield of reducing sugars were 4 times more in ultrasonic horn and 2 times more in ultrasonic bath than conventional method. The studies for conversion of sugars to 5-hydroxymethylfurfural using acid catalyzed hydrothermal treatment revealed the best yield as 50 g/L after 1 h of treatment with 5% sulphuric acid for the approach of ultrasound assisted delignification and acid hydrolysis followed by hydrothermal treatment whereas the conventional approach resulted in much lesser yield of 6.1 g/L. The obtained results demonstrated that there was significant intensification in HMF yield based on using ultrasound for both alkaline pretreatment and acid hydrolysis.