Kinetic, Thermodynamic and Optimization Studies of Dilute Acid Hydrolysis of Manihot esculenta Peels for Glucose Production

Abstract

Hydrolysis of various cellulosic and lignocellulosic materials has been a focus of many researches, with sole aim of large scale conversion of these materials to the benefit of mankind. However, there are few reports on the hydrolysis of materials from agricultural wastes compared with commercially available products. This study therefore investigates the hydrolysis of cellulosic materials from the peels of Manihot esculenta (cassava) using dilute hydrochloric acid. The effects of initial substrate and acid concentrations as well as temperature were investigated. The morphological changes upon hydrolysis were also studied using Fourier-transform infrared spectroscopy, scanning electron microscope and X-ray diffraction analysis. Optimization study was carried out by using 3-levels full factorial experimental design to test the combine effect of acid concentration, temperature and time on glucose yield. The kinetics study showed that the reaction is substrate, acid concentration and temperature dependence with maximum yield of 20.24 g/L for a liquid/substrate ratio of 5 L/g. Morphological characterization shows that the hydrolysis impacted greatly on the structure of the substrate. Optimization study showed that mild acid concentration of 0.3 mol/dm3, as the temperature approaches 120 °C and reaction time of 60 min produced 18.4 g/L of glucose. The results obtained positioned M. esculenta peel as a source of glucose for alcohol production in bio-fuel production.