Vereinfachte Auslegung der simulierten Gegenstromchromatographie mittels des Hodographenraums

A simplified and explicit shortcut method for the design of simulated moving bed processes is derived on the basis of equilibrium theory. The applicability of this approach is discussed using the hodograph plane for competitive adsorption equilibria with nonconstant selectivity, namely modified Langmuir‐, Bi‐Langmuir, and Jovanovic isotherms. The approach shows excellent accuracy when validated against literature data. Furthermore, it is demonstrated that systems described by modified or Bi‐Langmuir isotherms may comprise complex nonlinear phenomena.     

New adsorbent material based on nitrothiophene-functionalized silica particles for aqueous heavy metals removal

Research of efficient materials is a well-established technology. In this work, a novel and excellent host, with sulfur donor atom, for heavy metals adsorption was synthesized by chemical immobilization of nitrothiophene receptor onto silica particles. The new adsorbent was well characterized by Brunauer–Emmett–Teller, Barrett-Joyner-Halenda, scanning electron microscopy, elemental analysis, FT-IR, and solid-state ¹³C nuclear magnetic resonance. The new surface exhibits good thermal stability determined by thermogravimetric analysis, and a good chemical stability as investigated in various acidic and buffer solutions. The adsorption properties were investigated using Cu(II), Pb(II), Cd(II), and Zn(II) metals by varying all relevant parameters including pH, contact time, concentration, temperature, kinetics, and Langmuir isotherms. The adsorption efficiency increases with increasing pH and follows pseudo-second-order kinetics. The maximum equilibrium time was found to be 30?min for all metal ions. The thermodynamic analysis (ΔH°, ΔS°, and ΔG°) revealed that the adsorption was endothermic and spontaneous.     

Synthesis and Applications of Functional Polymers from Natural Okra Fibers for Removal of Cu(II) Ions from Aqueous Solution

Functional groups (?COOCH₃ and ?NH₂) in natural okra fiber had been introduced by free radical graft polymerization of methyl methacrylate (MMA) and acrylamide (AAm) from their binary solution using ascorbic acid/H₂O₂ as a redox initiator at a temperature of 45°C for 90 min. Factors affecting the grafting of lignocellulosic fiber such as feed molarity and comonomer composition were investigated. The grafted copolymers were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM-EDX), and thermogravimetric analysis (TGA). Functional groups were tested for their potential application in the removal of copper ions from aqueous solutions. Batch experiments were performed to evaluate the adsorption capacity of the maximum grafted cellulosic fibers toward the Cu (II) ions. Pseudo-first-order and pseudo-second-order kinetic models were studied to analyze the Cu²⁺ adsorption process and results showed that the pseudo-second-order model was more suitable than the pseudo-first-order model. Further, Langmuir, Freundlich, and Tempkin models were also applied to describe the adsorption isotherm of Cu²⁺ by different fiber adsorbents. The results indicate that the Langmuir model fitted the adsorption equilibrium data better than other two models. The maximum monolayer capacity q_m calculated using the Langmuir isotherm for raw and MMA+AAm grafted fiber were 4.89 and 33.05 mg/g, respectively.     

一类可降解的生物表面活性剂(Ⅰ)-芦丁脂肪酸酯在弱碱性水溶液中表面活性的研究

研究了3种可降解的生物表面活性剂-芦丁脂肪酸酯,在弱碱性水溶液中的表面吸附性质。芦丁硬脂酸酯(RS)、芦丁月桂酸酯(RL)和芦丁正己酸酯(RC)弱碱性水溶液的表面饱和吸附量分别为:1·71×10-11、1·35×10-11和1·41×10-11mol/cm2,它们的临界胶束浓度(CMC)分别是3×10-3、1·65×10-3和1·3×10-3mg/mL。其吸附等温线都属于Langmuir型。3种芦丁脂肪酸酯弱碱性水溶液的表面吸附,在标准状态下均能自发进行。     

基于吸附等温线及玻璃化转变的夹心海苔贮藏稳定性研究

为了解夹心海苔在贮藏期间水分活度、含水率、玻璃化转变温度与贮藏温度之间的关系,该研究探讨了夹心海苔吸附等温线和玻璃化转变曲线并用数学模型进行拟合,分析夹心海苔绝对安全含水率和临界含水量,并探讨热力学性质。结果表明：GAB模型能较好地反映出夹心海苔水分吸附特性,并得出在20、30、40 ℃条件下夹心海苔的绝对安全含水率分别为5.19%、4.69%、3.72%,作为预测夹心海苔加工及贮藏过程中最佳含水率的依据;同理可得20、30、40 ℃的临界含水量分别为0.98、0.84、0.71 g/g,作为判断贮藏稳定性的依据。当夹心海苔的平衡含水率高于0.08%时,水同物质的结合能较小,易失水。夹心海苔水分吸附过程中等温速率为0.62 K,吉布斯自由能为2.61 kJ/mol,为一种熵驱动的自发的吸热过程。综合分析,随着温度降低夹心海苔安全含水率升高,不易使玻璃化结构发生崩塌,对其加工工艺及干制品贮藏等方面具一定的参考意义,该研究结果可为夹心海苔产业提供科学依据。     

Effect of soybean substitution for cowpea on physical,compositional, sensory and sorption properties of<Emphasis Type="Italic"> akara</Emphasis> Ogbomoso

Akara Ogbomoso was prepared from cowpea:soybean flour mixture ratios of 100:0, 80:20, 60:40 and 40:60. Physical, compositional, sensory and sorption characteristics of the akara were evaluated. Protein and fat content increased, while carbohydrate content decreased as the soy content of the flour mixture of akara Ogbomoso increased. There were no significant differences (P<0.01) in the colour, taste, aroma and overall acceptability for either the freshly prepared akara Ogbomoso or the akara Ogbomoso stored for 10 weeks. There were significant differences (P<0.01) in crunchiness, increasing as the soy substitution increased both in the freshly prepared and stored akara Ogbomoso. The adsorption isotherms of akara Ogbomoso varied with varying levels of soy substitution and at 20, 30 and 40 °C, had sigmoid shaped, type II isotherms according to Brunauer-Emmet-Teller (BET) classification, and were affected by temperature and composition. Increased levels of soy substitution and temperature depressed the isotherms. Calculated monolayer moisture contents using BET and Guggenhein Anderson deBoer models decreased with increasing soy substitution and temperature.     

氢在碳纳米材料中吸附的实验研究

按照容积法的原理建立了用于氢气吸附储存研究的吸附等温线测量的实验装置，从实验和理论的角度分析了本实验装置的精度和误差，用实验的方法验证了理想气体状态方程、RK状态方程以及MBWR方程描述实际气体的适用性。本文还测量了经三种不同后处理方式所得到的碳纳米纤维在298K下的吸附等温线，实验结果低于Rzepka的分子模拟计算结果。实验证明，利用MBWR方程描述实际气体和实验结果符合最好，本实验装置适合用于准确确定氢在碳纳米材料中的吸附储存量。     

Adsorption of surfactant during chemical enhanced oil recovery

Surfactant is extensively used as chemicals during chemical enhanced oil recovery (CEOR) process. Effectiveness of surfactant CEOR process depends on several parameters like formation of micro emulsion, ultra-low interfacial tension (IFT) and adsorption of surfactant. First two parameters enhance the effectiveness while the last parameter reduces the effectiveness. Micro emulsions are highly desirable for CEOR due to its low interfacial tension (IFT) value and higher viscosity. In this research the size of the emulsions were studied with particle size analyzer to study the liquid–liquid absorption process and the entrapment of oil drops inside surfactant drop. Initially, the average surfactant drop size was found to be 100 nm, after mixing the surfactant slug with reservoir crude, the size was increase up to 10 times. It signifies the formation of micro emulsion between surfactant and oil. Another attempt was done in this research to study the adsorption mechanism of surfactant on reservoir rock. The process of adsorption was studied by Langmuir and Freundlich isotherm to understand the adsorption phenomena. In this study, it was found that the adsorption follows Freundlich isotherm and the adsorption phenomena was chemical for surfactant flooding process. In chemical adsorption phenomena, the rate of adsorption is high because, surfactant molecules are adsorbed layer after layer by the rock surface. Use of alkali along with surfactant reduces adsorption of surfactant since, alkali blocked the active clay sites before interacting with surfactant and hence the adsorption isotherm was found to be Langmuir and phenomena was physical adsorption.     

Molecular simulation of copper based metal-organic framework (Cu-MOF) for hydrogen adsorption

Metal organic framework (MOF) are widely used in adsorption and separation due to their porous nature, high surface area, structural diversity and lower crystal density. Due to their exceptional thermal and chemical stability, Cu-based MOF are considered excellent hydrogen storage materials in the world of MOFs. Efforts to assess the effectiveness of hydrogen storage in MOFs with molecular simulation and theoretical modeling are crucial in identifying the most promising materials before extensive experiments are undertaken. In the current work, hydrogen adsorption in four copper MOFs namely, MOF-199, MOF 399, PCN-6′, and PCN-20 has been analyzed. These MOFs have a similar secondary building unit (SBU) structure, i.e., twisted boracite (tbo) topology. The Grand Canonical Monte Carlo (GCMC) simulation was carried at room temperature (298 K) as well as at cryogenic temperature (77 K) and pressures ranging from 0 to 1 bar and 0–50 bar. These temperatures and pressure were selected to comply with the conditions set by department of energy (DOE) and to perform a comparative study on hydrogen adsorption at two different temperatures. The adsorption isotherm, isosteric heat, and the adsorption sites were analyzed in all the MOFs. The findings revealed that isosteric heat influenced hydrogen uptake at low pressures, while at high pressures, porosity and surface area affected hydrogen storage capacity. PCN-6′ is considered viable material at 298 K and 77 K due to its high hydrogen uptake.     

色谱固定相吸附性质的测定方法

吸附等温线是描述色谱分离中 ,组分在固定相、流动相两相之间平衡状态的物化参数 ,是色谱分离工艺设计和过程模拟研究中最基本的热力学信息 .准确测定吸附等温线 ,拟合出它的数学模型 ,进而模拟组分在固定相上的吸附和脱附情况 ,可大大减少实验次数 ,迅速找到最佳色谱操作条件 .采用静态法和吸附脱附法 ,测定木糖、木糖醇单、双组分在固定相上的吸附等温线 ,比较测定结果 ,确定吸附脱附法是准确测定等温线的简便方法 .