Adsorption of water vapour on activated alumina. I —- equilibrium behaviour

Equilbrium isotherms are reported for adsorption of water vapour on several different activated alumina adsorbents. The experimentally measured isotherms represent the sum of the contributions from water vapour held in several ways but these contributions can be resolved by detailed analysis. The individual isotherms conform closely to simple idealized models (Langmuir for chemisorption, BET for physisorption), thus providing a rational basis on which to compare different samples and the effects of different regeneration procedures. The apparent complexity in the behaviour of these systems arises from the superposition of the different contributions, the relative importance of which depends upon the nature of the sample and the regeneration conditions. By contrast, the behaviour of the resolved isotherms is relatively straightforward.     

氧化铝上吸附平衡与动力学的分形特性

在实验测定氧化铝吸附氮气的平衡和动力学过程的基础上 ,由平衡数据得到分形维数 ,对动力学结果分别用欧氏几何和分形几何的动力学模型进行处理 ,比较两种方法得到的扩散系数之间的差别。结果表明 :粉状氧化铝的分形维数为 2 .12 ;采用分形动力学模型得到的扩散系数同欧氏几何扩散模型的结果不一样 ,扩散系数不随浓度的变化而改变 ;而欧氏几何扩散模型中的扩散系数随浓度变化发生改变 ,且变化符合Darken关系     

椰壳炭对肌酐吸附性能及动力学研究

采用水蒸气活化法制备得到微孔发达的椰壳活性炭,并研究其对肌酐的吸附性能。以850℃活化所得微孔率最高的活性炭为吸附剂,考察了活性炭投加量、吸附时间、溶液pH值及肌酐初始质量浓度对肌酐吸附性能的影响,并采用准一级、准二级动力学方程对实验数据进行拟合处理。结果表明,制备所得4种椰壳活性炭对肌酐均有较强的吸附能力;微孔率越高,吸附量越大;37℃下,椰壳活性炭对肌酐的吸附平衡时间为6 h,平衡吸附量达到97.88 mg/g;酸性环境更有利于肌酐吸附;平衡吸附量随肌酐初始质量浓度增加而升高;吸附过程符合准二级动力学模型,以化学吸附为主。     

Evaluation of hydrogen permselective separation from “synthesis gas” components based on single gas permeability measurements on anodic alumina membranes

Anodic alumina membranes were prepared by anodizing aluminum followed by chemical and hydrothermal treatments. Anodization was performed on both tube surfaces. External anodization was restricted to selected spots leaving an aluminum mechanically strong frame. Nitrogen sorption data analysed with the CPSM method (Corrugated Pore Structure Model) detected a mesopore structure (i.e. D_mean;15–20) and surface areas of 2–20 m²/g. SEM microscopy images revealed a regular pore structure of independent pores with densities of N_pore ~ 5.6 × 10¹⁴ pores/m². Single gas permeances (Π) for X: H₂, CH₄, CO and CO₂ were measured on a Wicke–Kallenbach apparatus at varying mean transmembrane pressure P_m by the “dead-end” method. The observed slight dependence of Π on Ρ_m is indicative of strong Knudsen diffusion and weak viscous flow contributions. By correlating the experimental data with a linear Π vs Ρ_m relationship, Knudsen contribution evaluation was enabled, and found to vary in the range K_C ≈ 0.7–1.0. The Knudsen number criterion for flow regime discrimination is critically discussed and a realistic dual Knudsen number approach is proposed. Experimental permselectivities α_Η2Χ = Π_H2/Π_X (X ≠ H₂) approach by 70–100% their Knudsen selectivity counterparts. Anodic alumina membranes exhibit pore structure and gas permeability characteristics useful in designing integrated gas separation and catalytic membrane reactor systems.     

改性活性氧化铝除氟性能研究

通过静态实验,研究了改性活性氧化铝(MAA)对F-的吸附性能,考察了吸附时间、改性活性氧化铝的用量对除氟性能的影响,并与新型除氟树脂的除氟性能进行了比较.研究结果表明:活性氧化铝的用量为4 g时,除氟效率最高,为94.57%;活性氧化铝与含氟水的最佳接触时间为3 h;MAA在较低用量(＜4 g)时,除氟效率不如除氟树脂高,但是在较高用量(≥4 g)下,MAA则高于树脂的除氟效率.     

Adsorption and desorption behaviour of Pb(II) on a natural kaolin: equilibrium,kinetic and thermodynamic studies

BACKGROUND: Pb(II) is common in both waste‐waters and gas emissions. In developing countries, public health problems have been reported concerning Pb(II) pollution, so that stringent measures are required to deal with it. MAJOR RESULTS: The adsorption and desorption behaviour of Pb(II) has been investigated on a natural Chinese kaolin. Several factors, including initial concentration, pH, equilibration time, dosage and temperature correlated positively with Pb(II) adsorption. The Pb(II) adsorption capacity of natural kaolin was 165.117 mg g^?1. A kinetic study shows that Pb(II) adsorption on purified kaolin equilibrates within 35 min. The enthalpy changes of Pb(II) adsorption on purified kaolin were 63.683, 20.488 and 21.371 kJ mol^?1 with entropy changes 262.250, 112.210 and 105.120 J mol^?1 K^?1 for solutions containing 50, 100 and 200 mg L^?1 Pb(II) respectively, indicating an endothermic and spontaneous adsorption process. The desorption of Pb(II) from kaolin was difficult with more than 85% Pb(II) removal. Based on X‐ray diffraction (XRD) analysis, the Pb(II) adsorption on natural and purified kaolin was attributed mainly to the magnesite component and complexation with the mineral surface. CONCLUSIONS: Natural kaolin exhibits a satisfactory performance for adsorption of Pb(II) from aqueous solution. The optimum conditions for adsorption were: ionic strength = 0.01 mol L^?1; pH ≥ 7.2; dosage = 10 g L^?1; temperature = 25 °C; duration ≥ 16 h (C_i = 80 mg L^?1); and the optimum conditions for desorption were ionic strength = 0.1 mol L^?1 and pH ≤ 5.0. Copyright © 2009 Society of Chemical Industry     

水中丙酮在活性炭上吸附平衡与动力学研究

研究了水中丙酮在活性炭上的吸附平衡与动力学曲线,对在20、30、40℃下的吸附等温线用Freundich方程拟合,得出了满意的结果。选择合适的实验条件,在消除了外膜阻力的条件下,表明颗粒内扩散中的表面扩散占主要地位,考察了初始浓度、温度、活性炭粒径等因素对丙酮吸附的影响,并用间歇搅拌槽吸附的表面扩散模型拟合出扩散时间常数。     

氨基改性有序介孔氧化铝吸附二氧化碳性能研究

采用硝酸铝为铝源,碳酸铵为沉淀剂,聚乙二醇（PEG1450）为模板剂,合成廉价的有序介孔氧化铝 （OMA）作为吸附剂载体。以2-氨基-2-甲基-1-丙醇（AMP）为氨基化表面修饰剂,对OMA采用过量浸渍法进行表面氨基化,制备一种高性能低成本的二氧化碳吸附剂OMA-AMP。通过BET法比表面积测定、X射线衍射（XRD）、透射电镜（TEM）、红外光谱（IR）等表征方法对改性前后吸附剂的比表面积、孔结构等特性进行表征,结果表明制备的 OMA-AMP具有比表面积大、孔径分布窄、孔结构有序等特点。利用模拟烟道气,从浸渍时间、吸附床层温度、气体流量以及AMP浓度4个变量考察吸附剂的性能。结果表明,OMA经过质量分数为50%的AMP浸渍12 h,在吸附温度为70 ℃、气体流量为40 mL/min条件下,OMA-AMP对二氧化碳的吸附量高达84.15 mg/g;吸附剂吸附性能较稳定,再生容易且效果良好;吸附剂制备成本低廉,吸附效率高。该吸附剂可以解决在二氧化碳捕集技术中成本居高不下的问题,在工业上具有实际应用价值。     

活性炭纤维对有机废水的吸附研究

以碱性木质素为原料通过静电纺丝法制备得到活性炭纤维。采用比表面积及孔径分析仪对活性炭纤维进行表征分析,同时以该活性炭纤维为吸附剂对甲苯、甲醇和丙酮3种有机废水进行吸附法净化处理,结果表明该活性炭纤维的比表面积达到807.77 m~2/g,孔容为0.484 cm~3/g,中值孔径为2.11 nm;活性炭纤维对3种有机废水具有一定的吸附净化效果,3种有机物中甲苯的吸附最快,吸附量最大;对甲苯、甲醇和丙酮的最大吸附量分别是229.12、156.68和103.34 mg/g。3种有机废水的吸附动力学分析结果表明:活性炭纤维对甲苯、甲醇和丙酮的吸附数据分别与准二阶模型、Werber-Morris模型和准一阶模型具有较好的拟合相关性。     

Adsorption of gold-thiourea complex on activated carbon

The adsorption kinetics of the gold-thiourea complex on activated charcoal was studied. Experimental runs were made in a batch reactor at constant temperatures and stirred by a magnetic system. Samples were taken at different periods of time and were analyzed for gold in a Perkin-Elmer Model 360 atomic absorption spectrophotometer. The samples were prepared with synthetic solution of gold with thiourea, sulfuric acid, and iron sulfate with concentrations similar to the ones in the leaching process. The gold adsorbed on activated charcoal was 99% at 20°C. The adsorption behavior was characterized by the Freundlich model at different temperatures (20°C, 35°C and 50°C).     

Batch adsorption of trichlorotrifluoroethane (freon-113) onto activated carbon — surface diffusivity and pore diffusivity

Activated carbon was found more active than molécular sieve 13X and silica gel in adsorbing 1,1,2 trichloro-1,2,2 trifluoroethane (CFE). Batch adsorption experiments were carried out with activated carbon to adsorb CFE at 15, 25 and 30°C. The adsorption isotherms of CFE on activated carbon were of the Langmuir type: q(C) = q_m KC / (1 + KC) where q^m and K were evaluated for the three temperatures. The measured bulk concentration-time data were interpreted equally well with the surface diffusion model and the pore diffusion model; for the former model the surface diffusivity increased with increasing initial CFE concentration, and for the latter the pore diffusivity was independent upon the initial CFE concentration.     

活性碳纤维对水中喹啉的吸附性能

采用活性碳纤维（activated carbon fiber,ACF）静态吸附模拟废水中的喹啉,考察了吸附时间、喹啉初始浓度、温度、pH值、有机物等对吸附速率与吸附行为的影响。结果表明,ACF对喹啉的吸附速率快,30 min内基本达到平衡,初始浓度较高时,最终吸附容量较大,达210 mg/g,低温和pH值小于7时,吸附效果较好,苯酚与喹啉产生竞争吸附,配水中的吸附行为能较好的符合Langmuir等温方程,吸附动力学符合准二级动力学模型,热力学参数ΔH0、ΔG0为负值,表明该吸附是一个自发的放热过程。本研究为环境功能材料ACF应用于工业化生产提供了理论依据,有必要在此基础上进行动态吸附实验以及实际焦化废水的吸附处理实验,同时ACF成本高及脱附再生等方面问题还有待进一步深入研究。     

热改性活性炭吸附有机气体的性能

根据热重分析结果,确定了活性炭热改性的温度条件;采用Boehm滴定、傅式转换红外光谱仪（FTIR）、比表面积分析仪对活性炭表面物化性质进行了测试;以甲苯、丙酮、二氯乙烷、甲醇为吸附质,在283K下进行了固定床吸附实验,探讨了改性前后活性炭表面结构变化与吸附量之间的关系,同时计算了相应的动力学参数和吸附能。实验结果表明,热改性可以改善活性炭的孔径分布和改变表面官能团的分布,吸附量与有效孔容呈明显的线性关系;一阶动力学方程和二阶动力学方程均可描述四种吸附质在活性炭上的吸附过程;孔内扩散模型表明改性活性炭对有机气体的吸附速率均大于未改性活性炭;四种吸附质在活性炭上的吸附能均小于20kJ?mol-1,表明活性炭对四种有机气体以物理吸附为主。     

Research on crack mechanism and kinetic model of alumina ceramic in the degreasing stage based on stereolithography

Given that the kinetics of the thermal degreasing process of alumina ceramics based on stereolithography apparatus (SLA) has not been investigated, the mechanism of crack generation is still not fully revealed. This paper aims to elucidate the mechanism of crack generation in the degreasing process of alumina ceramics and to establish a kinetic model for alumina ceramics. Two sintering atmospheres, air, and argon, were selected for the degreasing tests at 100°C–700°C. The reaction products and mass changes of alumina ceramics were analyzed by TG-FTIR and TG-DSC (heating rates of 5, 10, and 15°C/min, respectively). Meanwhile, Boswell, Friedman, Ozawa, and DAEM model was used to describe the nonisothermal kinetics of the SLA alumina ceramic degreasing process. The results showed that setting the holding time to 400°C–425°C could promote the slow release of heat from the alumina ceramics. The thermal degreasing stage of the ceramic generated fewer cracks in the argon atmosphere than in the air atmosphere. The corresponding average activation energy values were 105.40 kJ/mol (Boswell model), 112.48 kJ/mol (Friedman model), 108.14 kJ/mol (Ozawa model), and 101.36 kJ/mol (DAEM model). The results of the study could provide an invaluable reference for the fabrication of defect-free SLA alumina ceramics.     

扩展球形溶液表面上decanoyl-N-methylglucamine的吸附动力学

A general expression of the dynamic surface adsorption [Г（t）] on the expanding spherical surface was derived by solving the corresponding diffusion equation under different initial and boundary conditions. Different from the result of the still spherical surface, two factors （smaller than 1） appeared in the equation for the short time adsorption. Using the derived results, the adsorption kinetics of aqueous decanoyl-N-methylglucamine （Mega-10） solution was studied. In the short time region （t→0）, a good agreement of experimental results with the theory was reached and the adsorption was controlled by diffusion.     

活性碳纤维对硝基酚的吸附行为和应用研究

研究了粘胶基活性碳纤维(ACF)在水溶液中对硝基酚的吸附行为,包括ACF对硝基酚的吸附等温线、吸附容量、再生方法、吸附和再生速率、对硝基酚的吸附选择性等。结果表明:ACF对硝基酚的吸附容量达到664mg g,该吸附是一个可逆过程,吸附和解吸速率快;采用质量分数10%的NaOH作再生剂,可以恢复吸附能力,重复进行吸附-再生过程,ACF的吸附容量不变,对硝基酚的回收率均>90%。对进水硝基酚质量浓度为9790mg L的废水,吸附处理后出水浓度达到一级排放标准,同时可以回收硝基酚。     

Adsorption of Cr(VI) ions onto poly(ethylene glycol dimethacrylate‐1‐vinyl‐1,2,4‐triazole)

Poly(ethylene glycol dimethacrylate‐1‐vinyl‐1,2,4‐triazole) [poly(EGDMA‐VTAZ)] beads (average diameter = 150–200 μm) were prepared by copolymerizing ethylene glycol dimethacrylate (EGDMA) with 1‐vinyl‐1,2,4‐triazole (VTAZ). Poly(EGDMA‐VTAZ) beads were characterized by swelling studies and scanning electron microscope (SEM). The adsorption of Cr(VI) from solutions was carried at different contact times, Cr(VI) concentrations, pH, and temperatures. High adsorption rates were achieved in about 240 min. The amount of Cr(VI) adsorbed increased with increasing concentration and decreasing pH and temperature. The intraparticle diffusion rate constants at various temperatures were calculated. Adsorption isotherms of Cr(VI) onto poly(EGDMA‐VTAZ) have been determined and correlated with common isotherm equations such as Langmuir and Freundlich isotherm models. The Langmuir isotherm model appeared to fit the isotherm data better than the Freundlich isotherm model. The pseudo first‐order kinetic model was used to describe the kinetic data. The study of temperature effect was quantified by calculating various thermodynamic parameters such as Gibbs free energy, enthalpy, and entropy changes. The dimensionless separation factor (R_L) showed that the adsorption of metal ions onto poly(EGDMA‐VTAZ) was favorable. It was seen that values of distribution coefficient (K_D) decreasing with Cr(VI) concentration in solution at equilibrium (C_e) indicated that the occupation of activate surface sites of adsorbent increased with Cr(VI). © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Removal of 3—(3,4—dichlorophenyl)—1, 1 dimethylurea from aqueous solution by natural and activated bentonite

The adsorption of 3-(3,4-dichlorophenyl)-1,1 dimethylurea (diuron) on bentonite desiccated at 110°C untreated, and acid treated with H₂SO₄ solutions over a concentration range between 0.25 M and 5.00 M, from aqueous solution at 30°C has been studied. In addition, adsorption of diuron on combined acid/heat treated samples (0.50 M and 2.50 M H₂SO₄/200°C and 400°C) has also been studied. The experimental data points have been fitted to the Freundlich equation in order to calculate the adsorption capacities (K) of the samples; K values range from 0.92 μg g^?1 for the untreated bentonite up to 974.42 μg g^?1 for the 0.50 M H₂SO₄/400°C acid/heat treated bentonite. The removal efficiency (R) has also been calculated; R values ranging from 2.02% for the untreated bentonite up to 97.17% for the 0.50 M H₂SO₄/400°C acid/heat treated bentonite. The adsorption experiments show that bentonite heat treatment is more effective than bentonite acid treatment in relation to adsorption of diuron.     

Removal of phosphate by adsorption onto oyster shell powder—kinetic studies

Kinetic studies on the removal of phosphate by adsorption onto oyster shell powder have been investigated at 24 °C. The results showed that the equilibrium occurred in 10 min and the equilibrium data followed the Freundlich isotherm. Freundlich constants were found to be k_f, 1.4 × 10^?2, and n, 0.71. The phosphate removal was not influenced by pH over the range 5.0–10.5. Continuous agitation studies at 24 °C and 530 rpm reached equilibrium after 7.7 days, when 24 g dm^?3 of oyster shell powder reduced the phosphate concentration from 50 to 7.0 mg dm^?3. The Lagergren rate constant for the slow adsorption process was observed to be 3.81 × 10^?4 dm³ min^?1. Comparison with calcium carbonate, GR grade, showed that oyster shell powder and CaCO₃ behave more or less in the same way. Copyright © 2004 Society of Chemical Industry