Valorization of rice straw through FeCl3 pretreatment: experiments-modelling and optimization

Abstract Lignocellulosic biomass has an enormous potential to produce liquid biofuels and platform chemicals. The present investigation evaluated the effect of pretreatment time (5–15 min) and temperature (150–190 °C) on the cellulose and xylan hydrolysis of rice straw (RS) using 0.2 M ferric chloride (FeCl 3 ) solution. A 2-factor (temperature and time) with a central composite statistical design in response surface methodology (RSM) was used to optimize the degradation of xylan and cellulose, and the yield of glucose, xylose, and furfural. Combining the effects of time and temperature of pretreatment and the pH of the FeCl 3 solution, the combined severity (CS) for hydrolysis of components (such as hemicellulose, cellulose) has also been evaluated. The optimum yields of glucose, xylose and furfural were obtained as 70.82, 43.34 and 70.21 g/kg of RS, respectively, whereas the optimum degradation of xylan and cellulose were 97.34% and 43.81%, respectively. The pretreated RS has been characterized by using thermo-gravimetric analysis (TGA), Fourier Transform Infra-red (FTIR), X-ray diffractive (XRD), Field emission scanning electron microscopy (FESEM) and Energy-dispersive X-ray spectroscopy (EDS) analysis. The optimum yield of glucose, obtained through the pretreatment, followed by enzymatic hydrolysis (using cellulase enzyme) was 80.34%, and the yield of ethanol obtained through fermentation of glucose (using Saccharomyces cerevisiae ), was 82.4%. A mathematical model for the FeCl 3 pretreatment of Indian RS has been developed and validated for the first time. It is expected that the results of our study will open a new arena in their application in the bioenergy sector of India and abroad.