The Selective Adsolrption Performance Of Modlified Bamboo-based Activated Carbon For Seperation Of Bio-ethanol From Aqueous Solution

Bio-ethanol is one of clean,renewable energies.In particular,the application of bio-ethanol not only can relieves the problem of energy shortage,but also solves the environmental pollution,to some extend.Unfortunately,the low biomass conversion rate,high energy consumption,as well as high equipment damage in the process of bioethanol purification limit the application of bio-ethanol in industry.In this paper,the ethanol-water separation device designed and fabricated by our research group was employed to simulate the separation of ethanol from an ethanol fermentation solution via adsorption technology.And the parameters of the process was discussed.The experimental results show that,the bamboo-based activated carbon indicates higher adsorption capacity at 5 ? than those at 15 ? and 24 ?,suggesting that the process of ethanol adsorption onto the bamboo-based activated carbon is an exothermic process.Low temperature is in favor of the process.However,lower temperature condition needs more energy consumption.Accordingly,24 was chose as the adsorption temperature in our experimental.the liquid flow rate also impacts on the ethanol adsorption capacity.The maximal ethanol adsorption capacity value,and the minimum adsorption equilibrium time are obtained at the same time under the power of 40 r/min with a liquid flow rate of 18.4 mL/min.It is also found that at low concentration,the concentration of ethanol in aqueous solution give low effect on the adsorption properties of the materials.Increase the ethanol concentration from 500 ug/mL to 600 ug/mL leads to only 1 mg/g increment in the ethanol adsorption capacity.The selective adsorption of activated carbon on ethanol and water is relatively low,which is not conducive to the adsorption and separation of ethanol and water.In order to improve ethanol/water separation performance,the chemical vapor deposition(CVD),Hydrogen and urea modification technologies were employed to tailor the pores and surface of the bamboo-based activated carbon.N2,CO2 adsorption-desorption test,elemental analyzer and FTIR were employed to investigate the pore structure and surface chemical feature of the modified activated carbon.It is clear that,in the CVD process,the bamboo-based carbon molecular sieve with a specific surface area of 634.5 m2/g and pore size distribution of 0.5 nm-1.2 nm can be obtained under the conditions of methane flow rate of 30 mL/min,reaction temperature of 800 ? and deposition time of 23 min.In hydrogen modification process,the parameters have been optimized as hydrogen flow rate of 100 mL/min,calcination temperature of 700 ? and calcination time of 1 h.The resultant hydrogen-modified bamboo-based carbon molecular sieve shows a good ethanol selective adsorption property,the ethanol solution adsorbed in the column give a concentration of 3.69%,which is as 182 times as the initial ethanol concentration.In urea modification process,the optimal conditions was obtained as urea dosage of 1 mol/L,reaction temperature of 700 ? and reaction time of 1 h.The resultant N-doped bamboo-based carbon molecular sieve gives an excellent condensation ability.The concentration of ethanol adsorbed in the column raises from 0.62%to 29.66%,increasing by 533.2 times.The results suggest that,modified activated carbon possesses higher ethanol adsorption selectivity.The materials is candidate for application in separation of ethanol and water from the ethanol fermentation broth.