Adsorption equilibrium of citric acid from supercritical carbon dioxide/ethanol on cyano column

Supercritical adsorption equilibrium has a significant role in defining supercritical adsorption behavior. In this paper, the adsorption equilibrium of citric acid from supercritical CO2/ethanol on a cyano column was systemat-ical y investigated with the elution by characteristic point method. Equilibrium loading was obtained at 313.15 K and 321.15 K with supercritical CO2/ethanol densities varying from 0.7068 g·cm?3 to 0.8019 g·cm?3. The exper-imental results showed that the adsorption capacity of citric acid decreased with increasing temperature and in-creasing density of the supercritical CO2/ethanol mobile phase. The adsorption equilibrium data were fitted wel by the Quadratic Hill isotherm model and the isotherms showed anti-Langmuir behavior. The monolayer satura-tion adsorption capacity of citric acid is in the range of 44.54 mg·cm?3 to 64.66 mg·cm?3 with an average value of 56.86 mg·cm?3.     

Separation of glycyrrhizic acid from licorice root extract using macroporous resin

Glycyrrhizic acid (GA) is the major active ingredient of licorice which has many pharmacological activities. In the present study, separation of GA from licorice root extract has been carried out by adsorption on five different macroporous resins. Static and dynamic adsorption of GA from crude licorice root extract is studied on ion exchange resins followed by desorption. Indion 810 shows the maximum adsorption as well as desorption capacity. The adsorption experiments indicate that equilibrium can be achieved in 360 min. The adsorption equilibrium data is well fitted in the Langmuir isotherm. The separation process is optimized by investigating the effect of pH on adsorption capacity and effect of concentration of ethanol on desorption capacity. The dynamic adsorption is carried out in a column packed with Indion 810 resin and effect of feed flow rate and initial concentration of GA in extract has been studied. The results showed that increase in feed flow rate as well as initial feed concentration of GA lowers the dynamic binding capacity and mass transfer coefficient while increases the HETP. The purity of GA is increased from 14.3% to 71.5% by the dynamic desorption with 60% ethanol. Indion 810 resin can efficiently separate GA from licorice root extract with the HPLC recovery of 63.6%. This study forms the basis for large scale preparation of GA by resin adsorption.     

Sorption of acid dyes onto GLA and H2SO4 cross-linked chitosan beads

The feasibility of chitosan and cross-linked chitosan beads as efficient adsorbents for the removal of Acid Blue 25 (AB 25) and Acid Red 37 (AR 37) from aqueous solution was studied by using batch adsorption techniques. Glutaraldehyde (GLA) and sulphuric acid were employed as cross-linking reagents. The effect of process parameters like pH, agitation period, agitation rate and concentrations of dyes on the extent of AR 37 and AB 25 adsorption by chitosan and cross-linked chitosan beads was investigated. The best interpretation for the equilibrium data was given by the Langmuir isotherm, while the pseudo-second-order kinetic model could best describe the adsorption of these acid dyes. Thermodynamic parameters such as enthalpy change (ΔH°), free energy change (ΔG°) and entropy change (ΔS°) were estimated and adsorption process was spontaneous and exothermic. The desorbed chitosan, chitosan-GLA and chitosan-H₂SO₄ beads can be reused to adsorb the acid dyes. Results also showed that chitosan, chitosan-GLA and chitosan-H₂SO₄ beads were favourable adsorbers.     

The adsorption of an epoxy acrylate resin on aluminium alloy conversion coatings

A thermodynamic study of the adsorption of an epoxy acrylate resin used for UV-cured coatings on two different anticorrosion pretreatments on aluminium alloys relevant to aerospace industry has been undertaken. Aluminium alloy Al2219 specimens, treated with an inorganic chromate based conversion coating (Alodine 1200S) and an organic titanium based conversion coating (Nabutan STI/310), were immersed in solutions of different concentrations of the resin and adsorption isotherms were determined by assessing the uptake of the adsorbate, as a function of solution concentration, by time-of-flight secondary ion mass spectrometry (ToF-SIMS). The results show different behaviour for the two substrates, which can be attributed to the organic component of the titanium based coating. In the case of the inorganic conversion coating a clear plateau is achieved at relatively low concentrations and at a lower level of adsorption than for the hybrid coating. The data for both the coatings conform well to the Langmuir model, the organic coating, as well as showing a higher level of adsorption of the resin, also presents oscillatory behaviour at low concentration, which is shown to be complementary to the behaviour of the reactive diluent included with the epoxy acrylate to aid processing. A discussion of this competitive adsorption of the epoxy resin and the diluent on the different substrates is presented, based on considerations of the chemistry of the systems under investigation.     

甘草中甘草酸的提取及测定方法简述

综述了甘草中有效成分甘草酸的提取、纯化和测定方法的研究概况。稀醇溶液对甘草酸的提取效果较好,添加稀氨水后可提高甘草酸的提取收率;超声波强化或微波辅助提取可提高甘草酸的提取效率并节约提取溶剂和提取时间,CO2超临界流体法无毒、高效且不需加热即可将甘草酸与溶质分离;薄层色谱(TLC)、高效液相色谱(HPLC)、毛细管电泳(CE)方法可实现甘草酸及甘草次酸含量的快速、准确测定。     

Crosslinked polymer embedded Cu/Ag for comparative drug adsorption and kinetics evaluation

Two-dimensional crosslinked polymer (2-DCP) was synthesized for evaluation of drug adsorption and kinetics thereof. Further, polymer properties were evaluated and parameters such as contact time and adsorption isotherm were also studied. Herein, contact time demonstrated 83% and 85% of drug loading in an acidic medium for two-dimensional crosslinked polymer embedded copper and silver (2-DCP-Cu/Ag), respectively in 24 h. Initial 4 h is the exponential drug loading period whereas drug loading was increased gradually after 4 h. Salbutamol loading was well-fitted to Langmuir adsorption isotherm, which indicated a monolayer drug adsorption with respect to 2-DCP-Cu/Ag. Pseudo first- and pseudo second-order kinetics was evaluated to perceive the drug adsorption mechanism and equilibrium adsorption capacity. Monolayer drug adsorption with chemisorption mechanism was observed for 2-DCP-Cu/Ag. In addition to this, decomposition temperature of polymer was 440 and 325°C while glass transition temperature of polymer was 280 and 200°C before and after metal modification, respectively. (A = aqueous phase; B = organic phase; C = drug solution; D = drug loaded polymer; E = enlarged drug loaded polymer.)     

Infrared studies of nitric oxide adsorption on reduced and sulfided P-Ni-Mo/Al2O3 catalysts

A series of P-Ni-Mo/Al₂O₃ catalysts with varying phosphorus content, prepared by co-impregnation, was studied by infrared spectroscopy of nitric oxide adsorption on their reduced and sulfided form. It was found that small concentrations of phosphorus (1 to 3 wt.-% P₂O₅) increased reducibility and sulfidability of nickel and molybdenum. A red shift of the band of nitric oxide adsorbed on molybdenum is observed for sulfided samples with low phosphorus content compared to phosphorus free. In the samples with high phosphorus contents (above 4 wt.-% P₂O₅) reducibility and sulfidability of nickel and molybdenum decreases. A blue shift of the band of nitric oxide adsorbed on molybdenum is observed and three types of nickel species are found with different degree of reduction/sulfidation in the sulfided form of these samples.     

Effect of ultrasound on liquid phase adsorption of azeotropic and non-azeotropic mixture

Relative adsorption experiments of azeotropic and non-azeotropic mixture were separately conducted at constant temperature with and without the presence of ultrasound. The ultrasound wave was applied at a frequency of 21 kHz with 25% amplitude at atmospheric pressure. The adsorption of azeotropic and non-azeotropic mixture was analysed using monolayer adsorption theory and at lower liquid equilibrium concentration it followed a Langmuir type of equation. The adsorptive capacity of azeotropic and non-azeotropic mixtures on activated carbon was found to decrease but the selectivity was increased. The result also showed that the azeotropic point of relative adsorption was noticeably moved due to the ultrasound effect.     

应用Wilson方程和均相溶液理论计算固液吸附平衡

固液吸附平衡计算对于吸附分离设计具有重要意义。采用吸附质固体溶液理论并用Wilson方程描述各组分之间的相互作用,计算了6个烃类二元液体混合物在分子筛NaX和KBaY、硅凝胶和活性炭上的吸附平衡数据,进一步考察了该理论的适用性和计算精度。结果表明,该理论模型可以较好地关联二元液相混合物在固体表面的吸附等温线,关联结果的总平均相对偏差为5.0%,而且该模型可以预测其他温度下的吸附平衡,预测精度也在5%之内。     

氯丙酸改性壳聚糖对Hg~(2+)的吸附性能研究

研究了改性壳聚糖对重金属Hg2+的吸附特性,包括吸附动力学和吸附等温式,且研究了pH、反应时间对其吸附性能的影响.结果表明:羧乙基壳聚糖对Hg2+的吸附在不同温度下符合Freundlich和Langmuir吸附等温式,吸附过程动力学适合二级反应.当pH为4～6,吸附时间为180 min时,羧乙基壳聚糖对Hg2+有较高吸附效果.     

水热法制备Mn_3O_4及其对水中刚果红的吸附研究

用水热法制备Mn3O4材料,通过调整反应中Mn（NO3）2与H2O2溶液的体积比,研究H2O2对反应产物的种类和形貌的影响。结果发现,适量H2O2有助于Mn3O4的生成,但是过量的H2O2会导致产物向纳米线状MnO2的生成。用粉末X射线衍射（XRD）、场发射扫描电镜（FE-SEM）、氮气吸附脱附技术对样品进行了表征,并考察了Mn3O4对水中刚果红的吸附性能。结果表明,水热法制备Mn3O4材料,其比表面积（BET）可达119.31 m2/g;Mn3O4对刚果红的吸附符合准二级动力学方程,平衡吸附数据符合Langmuir吸附等温模型;当Mn（NO3）2与H2O2的体积比为2∶1时,在140℃下水热反应15 h合成的Mn3O4对刚果红的吸附效果最佳,最大吸附量可达81.63 mg/g。     

甘草酸及甘草黄酮类物质的提取、精制和应用的研究进展

随着甘草酸和甘草黄酮类物质在药理研究中的新发现,尤其在治疗SARS方面的可能应用,使其提取和精制具有重要的意义。对甘草酸和黄酮类物质的各种提取、精制方法进行了归纳和总结,指出优缺点,并对有效物质的应用现状及发展前景进行了简述。     

乙炔气变压吸附深度干燥工艺研究与实践

介绍了乙炔气（C2H2）变压吸附干燥机理,考察了专用干燥剂吸附量与吸附力对C2H2原料气干燥效果的影响,提出了干燥单元内干燥剂组合填装使用方案,优化了C2H2变压吸附5塔（5-2-1）干燥工艺流程与操作条件,工程化实践取得较好的效果。     

Ethylene physisorption on C60 fullerene

Monte Carlo computer simulation results on the adsorption of ethylene on C₆₀ fullerene are employed to locate the adsorption sites observed for the adsorption of other simple gases. The distributions of molecules according to the gas-solid interaction energy obtained from the simulations are in agreement with experimental results reported in the literature. We focused our attention on the isotherm obtained at 150 K. At this temperature, the molecules with a certain gas-solid energy have been identified and their location employed to find out the adsorption sites. This sort of distribution has been averaged over all the equilibrated configurations generated during the simulation. The results obtained confirm the assignment of adsorption sites previously reported for the adsorption of N₂, Ar, and CO₂. The distribution of molecules over the gas-gas interaction energy is also analyzed and the obtained results suggest that the adsorbed molecules prefer a T-shaped stacking. This conclusion is obtained through the analysis of the distributions with the aid of the gas-gas interaction potential. This observation agrees with recently published results by other authors. The information obtained from the microdensity profiles has also been employed to locate the adsorption sites.     

Effects on lutein adsorption of adding polar solvents to silicic acid or to soy oil/hexane miscellas

Polar solvents limit adsorption of lutein from a soy oil miscella on silicic acid by competitive adsorption. Water and selected alcohols were added to miscella and adsorbent to observe if the mode of adding solvent affected lutein adsorption. No differences were produced by the method of addition. However, different mechanisms of limiting lutein adsorption were observed. Isopropanol limited lutein adsorption by competitive adsorption. Water was less competitive because it was less soluble in the miscella and was more thermodynamically stable as free water. Propanediol, a polyol, totally inhibited lutein adsorption by binding silica particles together. This study may have implications for silicic acid adsorption of oil components from hydrolyzed oils in which glycerides and free glycerol are present.     

逆向法测定氨氯地平在色谱柱Chiralpak OD-H上的竞争吸附等温线

使用逆向法测定氨氯地平在色谱柱Chiralpak OD-H上的竞争吸附等温线,先用泵进样的方式在高效液相色谱上测定氨氯地平的过载流出曲线,再选用5参数Bi-langmuir吸附等温线模型对过载流出曲线进行拟合,确定吸附等温线模型及模型参数,并验证参数准确性。     

New polyanhydrides derived from C12,C13,C14,C15 dibasic acid: synthesis and characterization

Poly(dodecanedioic acid-tetradecandioic acid) (P(DDDA-TA)) copolymers and poly(brassylic acid-pentadecandioic acid) (P(BA-PA)) copolymers have been prepared by melt polycondensation of the corresponding mixed anhydride prepolymers derived from dodecanedioic acid, brassylic acid, tetradecandioic acid and pentadecandioic acid. The copolymers were characterized by FT-IR, gel permeation chromatography (GPC), differential scanning calorimetry (DSC), wide angle X-ray powder-diffraction, and thermal gravimetric analysis (TGA). In vitro studies showed that all the copolymers are degradable in phosphate buffer at 37 °C. The release profiles of hydrophilic model drug, ciprofloxcin hydrochloride, from the copolymers, follows first order release kinetics. All the preliminary results suggested that the copolymer might be potentially used as drug delivery devices.     

Kinetics and equilibrium of dissolved oxygen adsorption on activated carbon

The macroscopic adsorption behavior of dissolved oxygen on a coconut shell-derived granular activated carbon has been studied in batch mode at 301 and 313 K for initial dissolved oxygen concentrations of 10-30 mg/l and oxygen/carbon ratios of 2-180 mg/g. BET (Brunauer, Emmett, and Teller) surface area, micropore volume, and pore size distribution were determined from N₂ isotherm data for fresh and used samples of carbon. The surface groups were characterized using Boehm titrations, potentiometric titrations, and FTIR study. The material is characterized by its high specific surface area , microporocity (micropore volume ), its basic character ( total basic groups) and its high iron content (15,480 ppm Fe). BET n-layer isotherm describes adsorption equilibrium suggesting cooperative adsorption and important adsorbate-adsorbate interactions. Kinetic data suggest a process dependent on surface coverage. At low coverage a Fickian, intraparticle diffusion rate model assuming a local equilibrium isotherm (oxygen dissociation reaction) adequately describes the process. The calculated diffusion coefficients (D) vary between and for initial oxygen concentration of 10 and 20 mg/l, respectively. Sensitivity analysis shows that the oxygen dissociation equilibrium constant determines the equilibrium concentration, whereas the diffusion coefficient controls the kinetic rate of the adsorption process having no effect at the final equilibrium concentration. A combined kinetic mass transfer model with concentration-dependent diffusion (parabolic form) has been developed and successfully applied on the dissolved oxygen adsorption system at high surface coverage. For equilibrium uptake of the estimated mean mass transfer coefficient and adsorption rate constant are and , respectively.     

Saturated fatty acid adsorption by acidified rice hull ash

Rice hull ash (RHA) was treated with 1.0 M HNO₃ (RHA-A1) and another batch was treated with 14.0 M HNO₃ (RHA-A14). RHA-A1 and RHA-A14 had a pH of 6.58 and 6.13, respectively. Adsorption of saturated fatty acids (C₈, C₁₀, C₁₂, C₁₄, C₁₆, and C₁₈) was carried out on RHA-A1 and RHA-A14 at 32±1°C. The adsorption data conformed to the Langmuir isotherm. The specific surface area of RHA-A1 was 183.84 m² g⁻¹ while that of RHA-A14 was 174.67 m² g⁻¹. The specific pore volume of RHA-A1 was 0.216 cm³ g⁻¹ while that of RHA-A14 was 0.234 cm³ g⁻¹. The acid-treated ash, RHA-A14 (q _m =0.43±0.03 mmol g⁻¹ where q _m is the amount of adsorbate adsorbed to form a monolayer coverage on the ash particles) showed a twofold increase in the adsorption of fatty acid per gram ash compared to RHA-A1 (q _m =0.25±0.03 mmol g⁻¹). The free energy of adsorption, ΔG° _ads, was determined to be −7.06±0.10 and −6.75±0.11 kcal mol⁻¹ for RHA-A1 and RHA-A14, respectively. The reduced ΔG° _ads values observed for RHA-A14 were attributed to the electrostatic repulsion of the hydrophobic chain of the fatty acid adsorbed on adjacent sites and brought into close proximity of each other. The ΔG° _ads values showed that the process of adsorption took place through physisorption on both RHA.