Research On The Extraction Of Tea Saponin And Preparation Of Activated Carbon From Camellia Oleifera Shells

In china Camellia oleifera resources is abundant,of which camellia oleifera shell have large production as a by-product,but had not been the use of reasonable and effective.Camellia oleifera shells contains a certain amount of tea saponin and a large number of hemicellulose,cellulose and lignose,which has a larger extract value and could use for preparation of activated carbon as a great raw material.In this paper,the extraction and purification process of tea saponin from the camellia oleifera shells,the preparation of activated carbon from those residue after alcohol extraction and the removal of Cr???in solution by the preparation of activated carbon were studied.The research provides an important basis for the comprehensive utilization of camellia oleifera shells.The main contents are as follows:Tea saponin was extracted from camellia oleifera shells by methanol extraction.The effects of methanol concentration,extraction temperature,time,solid-liquid ratio,extracting times on the extraction yield were investigated by single factor and orthogonal experiments.The results showed that the optimum condition for extraction of tea saponin as follows: temperature of 50? for 4h,methanol concentration of 80%,solid/liquid ratio of 1:4,extraction times of 2,the extraction yield and purity of tea saponin was 10.34% and 36.1%,respectively.The raw product was further purified respectively by NaHSO₃ and water-saturated butanol.The results showed that tea saponin solution of decoloration effect is significant by NaHSO₃.The optimum condition for purification of tea saponin was obtained at addition of NaHSO₃ 1.0 g,water-saturated butanol 50 mL and extraction of 2 times,the yield and purity of product reached 42.77% and 72.47%,respectively.The FT-IR was used to identification the structure of tea saponin,the peak position and structure were basically consistent with tea saponin standards.Activated carbon was prepared from camellia oleifera shells residue after alcohol extraction by phosphoric acid.The influences of liquid-solid ratio,mass fraction of phosphoric acid and activation temperature on the yield of activated carbon and the adsorption capacity were investigated by adsorption iodine and adsorption methylene blue value.The results showed that activated carbon with the optimal adsorption capacity could be prepared at solid/liquid ratio of 3:1,phosphoric acid mass fraction of 70% and activation temperature of 500?.The adsorption iodine value,methylene blue value and yield of activated carbon at optimized parameter were 1043.29 mg/g,148.5 mg/g and 38.77%,respectively.At the same time,nitrogen adsorption isotherms at 77 K of the same activated carbon were measured by physical adsorption instrument.The porous structure was investigated by nitrogen adsorption isotherms on the bases of BET and BJH methods.The specific surface area,average pore size and pore volume were 1626.45 m²/g,4.7 nm and 1.940 cm³/g,respectively.Also some physicochemical characterizations include FT-IR,SEM and XRD were applied to study in surface functional group,morphology and micro-structures of activated carbon.The results showed that has carboxyl,hydroxyl,other oxygen-containing functional group,and aromatic ring structure.Activated carbon has plenty of folds,abundant tiny bumps and turbostratic graphite crystallite structure,belongs to mesoporous activated carbon.Activated carbon which preparation in the above optimum process conditions was used to removal of Cr???in aqueous solution.The influences of adsorption time,solution pH,initial concentration solution,activated carbon dosage on the Cr???adsorption capability.The results showed that activated carbon has the extremely great adsorption effect and was significantly better than the general selling activated carbon on removal effect on Cr?VI?solution,adsorption equilibrium time was 120 min.The removal rate of Cr???could reach 98% when Cr?VI?solution pH at 1.5-5.5,the increase of the solution pH is not conducive to the adsorption of Cr?VI?.Considering removal rate of Cr???and utilization rate of activated carbon factors,the optimum adsorption condition for adsorption of Cr???was obtained as follows: adsorption time of 120 min,solution pH of 5.5,initial concentration of 30 mg/L,activated carbon dosage of 0.10 g,the removal rate and activated carbon adsorption capacity of Cr???could reach 98.71% and 7.403 mg/g,respectively.Adsorption of Cr???solution were simulated by Lagergren first-order,Lagergren second-order and Weber-Morris kinetic equation.The results showed that Lagergren second-order equation can better describe activated carbon adsorption of Cr???kinetic behavior.