Production of green energy – ethanol dehydration using rice straw, rice husk and castor oil

Dehydration of 96.4 vol% ethanol was carried out using three biomaterials: rice straw, paddy husk and castor oil to identify a cheap biomaterial for ethanol dehydration. Dehydration using rice straw and paddy husk was separately carried out by circulating 96.4-vol% ethanol through a glass tube filled with the biomaterial. The concentration of the collected ethanol was analysed using a Gas chromatography and verified by dichromate regent method. Kinetic and equilibrium adsorption were also carried out to identify the best model to describe water adsorption in rice straw and paddy husk and to calculate the selected kinetic and equilibrium modelling parameters. Pseudo-second-order kinetic model and Langmuir and Freundlich isotherm explained well the water adsorption in rice straw and paddy husk. From the solid biomaterial experiment, maximum ethanol concentrations of 92.86 vol% and 96.71 vol% were obtained for the rice straw and paddy husk, respectively. Since ethanol dehydration using castor oil by differential solubility method for ethanol dehydration was successfully carried out, optimization of the ethanol yield of the dehydrated ethanol was carried out by response surface methodology considering three factors: ethanol to castor oil ratio, mixing time, and settling time. The predicted maximum ethanol concentration is observed about 99.29 vol% by mixing ethanol with castor oil at a ratio of 1.5:1 for 2 min at 250 rev/min with an adjusting settling time for water about 1 h. A confirmation run was carried out, and the average concentration of the dehydrated ethanol was found to be 99.15 vol%. Regeneration of castor oil was successfully carried and hence castor oil was identified as a low-cost liquid biomaterial for ethanol dehydration.