Preparation And Application Of Lignin-based Activated Carbon

Our country is an agricultural country, A large number of crops straw, contains lots of cellulose, hemicellulose and lignin which can be used as raw materials of fermentation. But lots of by-product lignin produced in cellulosic ethanol production will always be treated with burning, not only reduced the resource utilization, but also do harm to the environment. Therfore how to use the by-product lignin of cellulosic ethanol production become an research hotspot at home and abroad to reduce the cost of cellulosic ethanol production.Activated carbon can be produced by physical activation and chemical activation, the steam activation and carbon dioxide activation were used to produce lignin-based activated carbon in this study. Influence factors in activated carbon preparation such as activation time, activation temperature and dosage of active agent were investigated. by response surface experiments to explore the the best condition of preparation of activated carbon, Response surface methodology(RSM) was used to optimize processing parameters for two methods of activated carbon preparation,the optimum conditions and model parameters have been identified. The optimum conditions of steam activation is: activation temperature of 889℃, activation time of 26 min and the water was amount of 10 g,which resulted in 345.86 mg/g of iodine adsorption capacity. It can be seen that activated carbon has more fluffy surface and pore structure via scanning electron microscopy(SEM).Secondly, the factors affecting the adsorption on PNP and CR as contact time, dosage of adsorbent and initial p H of solution has been studied, The results showed that 60 min and 180 min were the adsorption equilibrium time,best dosage of adsorbent were 0.5g·L-1 and 1.0g·L-1, there is no need to change the initial p H of solution. Several isotherm models like Koble-Corrigan, Freundlich, Langmuir, Redlich-Peterson and Temkin were used to fit with the adsorption data of PNP and CR. The results indicated that the adsorption of PNP onto lignin-based activated carbon follows Langmuir and Temkin isotherm models well, while the adsorption data of CR agreed well with Langmuir, Temkin and Redlich-Peterson models. The maximum adsorption capacity of PNP and CR onto activated carbon were 1.0270mmol·g-1and 0.0907mmol·g-1 at 298 K. Thermodynamic parameterthe shows that adsorption of PNP might be an exothermic and spontaneous process, but the adsorption of CR might be an endothermic and spontaneous process. The kinetic studies showed that the pseudo first-order model fitted the adsorption of PNP well, which means the adsorption of PNP might be physical absorption, and the pseudo seconf-order model described the adsorption date of CR well. Both the two adsorption process were controlled by the boundary layer and intraparticle diffusion.