大孔吸附树脂纯化黑穗醋栗花色苷研究

文章选择了八种大孔吸附树脂,分别测定它们对黑穗醋栗花色苷粗提液的吸附率及解吸率,确定了AB-8为最佳树脂。通过Langmuir及Freundlich吸附等温方程对20℃条件下的试验数据进行拟合分析,结果表明,平衡浓度范围在0.056~1.00mg·100mL-1,遵循Freundlich吸附等温方程;平衡浓度范围在1.00~7.05mg·100mL-1,遵循Langmuir吸附等温方程,由Langmuir吸附等温式拟合结果得到AB-8大孔吸附树脂在给定试验条件下的单层饱和吸附量是15.92mg·g-1。根据AB-8大孔吸附树脂吸附特性的研究,得出最佳纯化条件为:选择pH1.0~2.0、浓度19.15mg·100mL-1的黑穗醋栗花色苷粗提液,以1.0mL·min-1的流速上样,经0.1%盐酸溶液洗涤后,用pH2.5的60%乙醇作为洗脱剂,在洗脱流速为0.5BV·h-1的情况下,得到的花色苷产品,纯度约为91.76%。     

土壤粘粒吸附脲酶特征的研究

研究了 8种土壤粘粒对脲酶的吸附情况 ,结果显示 ,土壤粘粒对脲酶吸附 12 0 min可达平衡。土壤粘粒对脲酶的吸附等温线为 L型 ,可用双表面 L angm uir方程较好描述。初步认为土壤粘粒对脲酶吸附为化学吸附和物理吸附 ,且以化学吸附为主     

Geochemical Fractionation and Adsorption Characteristics of Zinc in Thai Major Calcareous Soils

Zinc (Zn) is a vital plant nutrient that is widely deficient in Thai cultivated calcareous soils. The chemical fractionation and adsorption of Zn are among the most important solid- and liquid-phase interactions that determine the retention of Zn in the soils. This study aimed to investigate the fractionation and adsorption isotherms of Zn in cultivated Thai calcareous soils. The results of sequential extractions showed that Zn is mainly distributed in residual fractions followed by organic-bound, iron and manganese oxides-bound, carbonate-bound, and exchangeable Zn, respectively. Zinc adsorption was well fitted by the Langmuir and Freundlich isotherms. Thai calcareous soils had high Zn adsorption capacity. Soil pH, organic carbon, calcium carbonate, cation exchange capacity, and extractable calcium were the major soil properties that affected the Zn adsorption isotherms in these soils. Zinc hydroxide was the solid precipitate and the Zn hydroxide ion (ZnOH⁺) was the dominant Zn ion in alkaline equilibrium solution.     

Contributions of Extractives and Lignin to the Fractal Geometry of Internal Wood Surfaces

Internal wood surfaces can be treated as fractals, which are between Euclidean geometry and complete randomness. The fractal dimension Dfs is very informative in investigating the roughness of the internal surfaces of wood. In this study, the water sorption isotherms, including adsorption and desorption isotherm, of untreated, benzene-alcohol extracted and delignified (after benzene-alcohol extracted) spruce (Cuninghamia lanceolata) were measured at 30℃. On the basis of these isotherms, the Dfs values were calculated by FHH equation, which is based on multimolecular sorption. The results showed that both groups of Dfs values (respectively calculated from adsorption and desorption isotherms) of untreated, benzene-alcohol extracted and delignified wood have same order, that is, untreated > benzene-alcohol extracted - delignified. Therefore, the conclusion can be made that the benzene-alcohol extractives have significant contribution to the fractal geometry of internal wood surfaces. Lignin also has influ     

Sorption of Cr(VI) on the wood of Japanese larch treated with concentrated sulfuric acid

A carbonaceous sorbent was prepared from the wood of Japanese larch (Larix leptolepis) by dehydration with concentrated sulfuric acid in a 69% yield. The abilities of the sorbent to remove Cr(VI) from aqueous solutions were investigated. Research parameters included the initial solution pH, temperature, and initial concentration of Cr(VI) in solution. The removal of Cr(VI) was highly solution pH dependent and was mainly governed by physicochemical sorption under weak acidic conditions. The equilibrium data fit well in the Langmuir isotherm model. The Langmuir constants were calculated at different temperatures, and the sorption capacity increased with rising temperature, indicating the endothermic nature of the Cr(VI) sorption onto the sorbent. The desorption experiments suggest that the Cr(VI) sorption is generally irreversible, owing to strong interaction of HCrO ₄ ⁻ with the active sites of the sorbent.     

Titanium dioxide photoinduced degradation of some pesticide/fungicide precursors

Five-membered nitrogen heterocycles (pyrrole, imidazole and 1,2,4-triazole) have been degraded using titanium dioxide and simulated solar radiation at pH = 8. The degradations followed a simple Langmuir-Hinshelwood mechanism. Accordingly, the adsorption equilibrium constants K of the heterocycles on the titanium dioxide surface and the rate constants k of degradation of the heterocycle-catalyst adduct have been obtained experimentally. While the K values decrease with heterocycle pKa, the k values increase with increasing pKa. Therefore, apparently, the rate constant depends on the availability of the electron pair on nitrogen, but at the same time the electron pair repulsion induced by the negatively charged titanium dioxide surface at pH = 8 causes a reverse effect in the adsorption equilibrium constant. Only in the case of imidazole, where the adsorption equilibrium constant is low enough (K = 0.013 M(-1)), can the rate constant be approximated to a pseudo-first-order rate expression: k(obs) = Kk. In all other cases, k(obs) = Kk/(1 + K(heterocycle)).     

Flowability,moisture sorption and thermal properties of tef [Eragrostis tef (Zucc.) Trotter] grain flours

Recently tef is attracting the attention of the modern food industry since it is a gluten-free grain encompassing highly appreciated nutritional advaxntages. As a relatively new raw material, little information on its handling and processing properties is available. Flowability, water sorption characteristics and thermal properties of flours from three Ethiopian tef varieties were studied. Wheat (whole and refined) and rice flours were included as references. Tef flours were less flowable than the reference flours and their flow properties were more sensitive to water activity changes. Tef flours led to sigmoidal sorption isotherms with estimated monolayer water content of 0.053 (BET model) and 0.057 (GAB model) g water/g dry solids. No significant differences among the three tef varieties were observed on their gelatinization enthalpies that were higher than that of wheat and similar to rice. The amylopectin recrystallization extent after 7 days of storage at 4 °C was significantly higher in tef than in wheat flour.     

活性炭C40/4吸附甲苯和丙酮吸附性能研究

为探讨活性炭吸附C40／4有机蒸汽的性能曲线规律，在不同温度288．15K，293．15K和298．15K下实验测试了活性炭C40／4吸附有机气体甲苯和丙酮的吸附性能，基于langmuir等温吸附理论，从吸附动态平衡的角度，理论分析了吸附性能曲线中参数与温度之间的关系，提出一个经验的langmuir等温吸附曲线模型，它能很好地描述不同温度下的有机蒸汽在活性炭上的吸附性能曲线，模型计算值与实验测试值之间的误差小于6％，为确定活性炭吸附有机蒸汽的吸附量提供了有效的计算模式，从而为有机蒸汽吸附过程的设计、预测和优化提供有益的支持。