Study On Preparation And Adsorption For Dye Waste Water Of Activated Carbon From Eggplant Stalk

The activated carbon was prepared from eggplant stalk by activation of Zinc Chloride, meanwhile, the preparation condition and mechanism were discussed. Based on characterization of the activated carbon from eggplant stalk, the adsorption performance, adsoption kinetic and thermodynamics of two dyes (reactive red X-3B and acid blue RL) on the activated carbon from eggplant stalk were studied under different experiment conditions.With orthogonal experiments, based on the iodine value and the methylene blue value, the optimum process condition was obtained:the impregnation ratio of 2; impregnation time of 8 hour; activation temperature of 550℃and activation time of 60 min. On this condition, the iodine value was 1270.06 mg·g-1, the methylene blue value was 17.4 ml·g-1, and the rate of production was 25.7%. The thermogravimetry showed that activator ZnCl2 played up the role of embellish and dehydration to raw materials. While it could prevent occurring tar in the process of pyrolysis, promote the degradation of cellulose, improve the carbon content of the absorbent, and promote the formation of micropore.The surface physical and chemical properties of activated carbon from eggplant stalk under the optimun conditions were characterized by elemental analyzer, nitrogen sdsorption isotherms, SEM, XRD and FI-IR. The carbon content of the prepared activated carbon increased by 42.48% than raw materials, and the BET surface area and Langmuir surface area were 1649.615 and 1851.649 m2/g, respectively. BJH mesopore theoretical analysis showed that the mesopore of the prepared activated carbon were mainly distributed in the range of 2～10nm; the total volume and diameter of micropore characterized by t-diagram method were 0.643cm3/g and 0.926nm, respectively. SEM image showed that the surface of activated carbon from eggplant stalk covered with pores with irrrgular sizes and different shapes. While the XRD analysis showed the diffraction angle of the prepared activated carbon increased, d002 and La decreased. The results of FI-IR were that the surface of activated carbon from eggplant stalk may containd carboxyl groups, alcohol hydroxyl groups, amino groups, ether groups and other groups.The static adsorption showed that the activated carbon from eggplant stalk possessed high capability for reactive red X-3B and acid blue RL by controlling the appropriate dosage, adsorption time, pH value, initial concentration and temperature. Langmuir isotherm equation showed reasonable applicability for the adsorption of two dyes on the activated carbon from eggplant stalk.The adsorption of two dyes on the activated carbon from eggplant stalk was a monolayer adsorption. Moreover, it was endothermic (enthalpy△H>0), spontaneous (free energy△G<0) and accompanied by an increase in entropy (△S>0). The kinetics results showed that the adsorption of each dye by activated carbon followed pseudo second-order kinetic model, and the amount of each dye adsorbed at equilibrium approximated the amount from experiment.The above results indicate that the activated carbon from eggplant stalk can be employed as an effective, safe and economically adsorption material in treatment of waster that contains large molecular pollutant such an dye and that provided an effective way to make the waste eggplant stalk an resources.