Modeling of Adsorption and Regeneration of Volatile Organic Compounds on Activated Carbon Fiber Cloth

A mathematical model is developed to predict continuous adsorption-regeneration cycling of volatile organic compounds (VOCs) on activated carbon fiber cloth (ACFC) at the indoor VOC concentration levels. The adsorption-regeneration model incorporates both the adsorption equilibrium and mass transfer fundamentals. It assumes local equilibrium between the gas-phase and the solid-phase, and axially dispersed-flow, film transfer, and intraparticle transport by surface and pore diffusion. Successful agreement between model simulations and experimental data was obtained and the kinetic properties of the adsorption/regeneration cycling on the ACFC were characterized. For the adsorption process, the film transfer is the dominant factor for mass transfer at low flow rates (45–184 L/min), and the intraparticle mass transfer rate controls over the gas-phase rate as the flow rates increase. The regeneration concentration profiles are most sensitive to the adsorption isotherms at the temperatures of interest, especially as desorption is initiated. The surface diffusivity also contributes to the shape of the regeneration profile: the tailing of desorption profile shifts up with the increase of surface diffusivity.     

Adsorption of erbium(III) on D113-III resin from aqueous solutions: batch and column studies

The adsorption and desorption behaviors of Er(III) ion on D113-III resin were investigated. Batch adsorption studies were carried out with various Er(III) ion concentrations, pH, contact time and temperature, indicating that D113-III resin could adsorb Er(III) ion effectively from aqueous solution. The loading of Er(III) ion onto D113-III resin increased with increasing the initial concentration. The adsorption was strongly dependent on pH of the medium with enhanced adsorption as the pH turned from 3.45 to 6.75. In the batch system, the D113-III resin exhibited the highest Er(III) ion uptake as 250 mg/g at 298 K, at an initial pH value of 6.04, calculated from the Langmuir isotherm model. The adsorption kinetics was in agreement with Lagergren-first-order kinetics among the Lagergren-first-order model, pseudo-second-order model, liquid film diffusion model and intraparticle diffusion model. The adsorption data gave good fits with Langmuir isotherms. The thermodynamic parameters such as ΔG, which were all negative, indicated that the adsorption of Er(III) ion onto D113-III resin was spontaneous and the positive value of ΔH showed that the adsorption was endothermic in nature. Thomas model was applied to experimental column data to determine the characteristic parameters of column useful for process design. Er(III) ion could be eluted by using the 4.0 mol/L HCl solution. The characterization of both before and after adsorption of Er(III) ion on D113-III resin was undertaken with IR spectroscopic technique. Moreover, the surface characterization of D113-III resin was described by scanning electron micrographs (SEM).     

Oxidation of zinc sulfide in a fluidized bed

Kinetics of oxidation of ZnS particles in a batch-type fluidized bed were studied at temperatures between 800 and 910°C. A two-phase model was employed for the fluidized bed, and the partial pressure of oxygen and the gas-film mass transfer coefficient on the particle surface were separately evaluated in gas bubbles and in the emulsion phase. The calculated fractional reaction coincided well with the experimental results. The difference in O₂ partial pressure between gas bubbles and emulsion phase was found to be fairly large especially under the vigorous fluidizing condition. Furthermore, it was shown from the mathematical model that the reaction of ZnS particles in the gas bubbles is negligible because of the extremely low solid concentration and that the overall rate of reaction in the emulsion phase is virtually controlled by the rate of gas-film mass transfer at higher temperature. The resistance of interfacial reaction within the particle also becomes significant when the temperature is lowered. Y. Fukunaka and T. Monta are both former Graduate Students, Kyoto University, Kyoto, Japan.     

Some aspects of ion exchange in copper hydrometallurgy

Ion exchange systems of chelating ion exchange resins, bead and foam impregnates have been evaluated for the possible applications to copper winning processes. Whereas the bulk properties and capacities of the chelating resins are far superior to the impregnates, the latter class of exchanger exhibits far better selectivity and kinetic properties to the resins. However, only chelating resin systems are likely to find application in copper hydrometallurgy, the copper selective resin XF-4196 finding application in dump leach processes. Improvements in the uptake rates of XF-4196 are suggested as being necessary for the incorporation of an ion exchange process into existing copper winning plant utilising spent acid liquors from electrolysis procedures as the eluting medium.     

Thermal decomposition of limestone in a fluidized bed

Particles of limestone of 16 to 28 and 60 to 100 mesh sizes were decomposed in a fluidized bed. A mathematical model for the thermal decomposition was proposed comprising the thermal decomposition at the interface within particles and the related heat and mass transfer steps. It was assumed in this model that the particles are completely mixed within the fluidized bed and that gas is in upward plug flow. Fractional decomposition of limestone particles and the bed temperature during thermal decomposition calculated from this model coincide very well with the experimental results. It was further revealed that the overall reaction rate of 60 to 100 mesh size particles is virtually determined by the rate of heat transfer from the reactor wall to the fluidized bed, and that both rates of interfacial reaction and heat transfer from the wall to the bed contribute to the overall decomposition rate of 16 to 28 mesh size particles. Former Graduate Student at Kyoto University, is now with the Railway Technical Research Center, JNR, Tokyo, Japan.     

D261大孔树脂吸附氰化物的性能及机理研究

研究了D261大孔树脂对氰化物的吸附性能及机理,考察了酸度、温度、溶液中氰化物质量浓度、时间及树脂用量对氰化物吸附的影响。试验结果表明,D261大孔树脂能有效地吸附简单氰化物和金、银、铜、锌、铁的氰络合物。热力学试验表明,吸附等温线符合Freundlich方程,吸附过程属于优惠吸附。动力学研究表明,吸附在室温下是瞬时反应,静态吸附过程主控步骤为Boyd液膜扩散,吸附的本质为物理吸附。同时,确定D261树脂的静态饱和吸附量为25.28mg/mL湿树脂。     

Modeling of fluidized bed chlorination of rutile

A model has been developed for fluidized bed chlorination of rutile in the presence of coke to produce titanium tetrachloride. At various reaction conditions, the model can predict the conversion of chlorine, particle size distribution in the bed, composition of the product gas, and reaction temperature. The bubble assemblage model is used to calculate the reactant gas mass transfer rate from the bubble phase to the emulsion phase. The population balance is employed to determine the size distribution of particles in the bed. The reaction in the freeboard zone is neglected. The model predictions have been compared with the results from a pilot-scale experiment, and the model gives good agreement between computed and experimental results. The effects of various reaction parameters on the reaction rate are discussed using the model.     

无溢流管多层流化床换热器的热态模型研究

本文对无溢流管多层流化床换热器进行了热态模型实验研究，得出了气－固两相间的界膜换热系数曲线，所得结论可供参考。     

Control of Incinerator Organics by Fluidized Bed Activated Carbon Adsorber

Adsorption on activated carbon of organic compounds from a particle-free and low temperature gas stream has been investigated previously. However, the adsorption processes in a fluidized bed adsorber of particles interfacing with high temperature flue gas has rarely been studied. The major objective of the work was to demonstrate the performance of a fluidized activated carbon adsorber for removal of organic compounds [polycyclic aromatic hydrocarbons (PAHs) and benzene, toluene, ethylbenzene, and xylene (BTEX)] and particulate from flue gas of an incinerator at selected fluidized velocities, fixed bed heights, and bed temperatures. The particle-size distribution of particulate prior to and after flowing through the fluidized adsorption bed were also analyzed. The results indicate that the fluidized bed activated carbon adsorber has a high removal efficiency of PAHs and BTEX. Three evaluated parameters show different effects on PAHs, BTEX, and particles. That the fluidized bed activated carbon adsorber has the ability to filter coarse particles due to the inertia collision is also identified.     

Investigating highly crosslinked macroporous resins for solid-phase synthesis

The washing efficiencies of a chromophore and the reaction rates of a classical esterification reaction are improved with macroporous resins (MRs) relative to a classical Merrifield resin. Furthermore, Wacker-oxidation of a MR bound alkene yielded the expected methylketone product whereas an alkene bound to a low-crosslinked Merrifield resin gave no product, a function of the relative permeability of each of these resins to the aqueous solvent conditions employed.     

Sintering and ferrite formation during high temperature roasting of sulfide concentrates

The newly developed toroidal fluidized bed reactor has potential for improving sulfide roasting efficiency due to its unique and good mass/heat transfer characteristics. To achieve effective roasting at high temperature using the toroidal fluidized bed reactor, engineering issues associated with sintering and ferrite formation are investigated in this study by roasting industrial sulfide concentrates of zinc and copper. Laboratory tests are conducted at 800–1100°C by using an electric tube furnace under controlled roasting conditions. The test program is based on statistical design, and the products are characterized by XRD, SEM and EDX. It is revealed that the oxygen concentration plays an important role in promoting roasting. Roasting temperatures higher than 950°C do not favor roasting conversion due to the sintering of sulfide particles which inhibits oxygen diffusion into the particle core. Close contact of the oxidized particles favors the atomic interdiffusion between particles, leading to the formation of undesired zinc ferrite. Roasting in toroidal fluidized bed reactor results in zinc calcines with increased surface area and reduced zinc ferrite formation, thus improving zinc recovery.     

几种螯合树脂在模拟的钴电解液中吸附铜的性能研究

对比研究了三种亚胺二乙酸螯合树脂D850、D463、D751、一种氨膦酸基螯合树脂D860及一种氨甲基吡啶树脂CuWRAM在模拟的钴电解液的硫酸盐体系、氯盐体系及硫酸盐-氯盐混合体系中吸附铜的性能.结果表明:五种树脂均在料液pH较高的条件下对铜的吸附容量最大,其中以D860的对铜的交换容量最大,以CuWRAM对铜的交换...     

Dowex50W-X树脂吸附硫酸溶液中的锶

In this study, strontium adsorption from sulfuric acid solution by different Dowex 50W-X ion exchange resins was investigated. Among these resins, Dowex 50W-X8 resin showed the maximum sorption of strontium from the aqueous solutions. The effect of pH, contact time, mass of resin, temperature, and concentration of interfeting ions on strontium adsorption were evaluated to determine the optimum conditions of strontium sorption process. The kinetic models of sorption were analyzed using pseudo-first and pseudo-second order models. The results indicated that the pseudo-second order kinetic model was more appropriate than the other one. Moreover, the data obtained in this study were fitted into several sorption isotherm models and it was found that the Langmuir sorption isotherm shows the best fitting to the experimental data.     

Monomethacrylate co-monomers for dental resins

Polymerisation shrinkage is widely recognised as a major drawback of resin based dental restoratives. Bis-GMA is often employed as the principal dimethacrylate monomer. Due to its high viscosity, Bis-GMA is normally mixed with large proportions of low viscosity glycol dimethacrylates. The purpose of this study was to determine whether the polymerisation shrinkage of Bis-GMA-based resins would be lower if alternative monomethacrylate co-monomers were used in place of conventional dimethacrylate co-monomers as viscosity modifiers. Conventional resins used were ethyleneglycol dimethacrylate and triethyleneglycol dimethacrylate; the alternative monofunctional co-monomers were tetrahydrofurfuryl methacrylate, hydroxypropyl methacrylate and isobornyl methacrylate. Model resins containing 54% mol/mol of co-monomer in Bis-GMA and 1% w/w of benzoyl peroxide as initiator were heat-cured at 70 degrees C for 8 h. Polymerisation shrinkage, degree of conversion and concentration of remaining methacrylate groups were calculated from density changes obtained gravimetrically. Other properties evaluated were Young's modulus, water uptake and viscosity of the monomer mixtures. The Bis-GMA-based resins exhibited lower shrinkage when mixed using the monomethacrylates rather than with conventional glycol dimethacrylates. Among the alternative co-monomers, tetrahydrofurfuryl methacrylate conferred the best balance of all measured properties.     

Dynamic Mathematical Modeling of an Isothermal Three-Phase Reactor: Model Development and Validation

A catalytic reactor model (CatReac) that describes the transport and series reactions of compounds in a three-phase fixed-bed catalytic reactor is developed for the purpose of describing the volatile assembly reactor system within the potable water processor on-board the International Space Station. CatReac includes these mechanisms: advective flow, axial dispersion, gas-to-liquid and liquid-to-solid mass transport, intraparticle mass transport with pore and surface diffusion, and series reactions of multiple compounds. A dimensional analysis of CatReac revealed the following seven dimensionless groups may be used to determine the controlling transport and/or reaction mechanisms: (1) the Peclet number is the ratio of the advective to the dispersive transport; (2) the Stanton number is the ratio of the external mass transfer rate to the advective rate; (3) the Damk?hler number compares the reaction rate to the advective transport rate; (4) the surface diffusion ratio equals the rate of transport by surface diffusion divided by the rate of transport by advection; (5) the pore diffusion modulus is the ratio of the rate of transport by pore diffusion to the rate of transport by advection; (6) the ratio of the gas to liquid advective rates; and, (7) the Biot numbers for surface and pore diffusion compare the external mass transfer rate to the intraparticle mass transfer rate. These dimensionless numbers are used to evaluate the impacts of the different mechanisms on the overall performance of the reactor. The numerical solution using orthogonal collocation was validated for a wide range of controlling mechanisms by comparing model simulations with several analytical solutions: (1) Gas-to-Liquid mass transfer controlling the overall mass transfer-reaction mechanisms, for a wide range of Pe number values; (2) Liquid-phase dispersion controlling the overall process; (3) Liquid-to-solid mass transfer resistance controlling the overall mass transfer-reaction process; (4) Reactions in series with two possibilities (4a): No intraparticle mass transfer resistance, and (4b): Significant intraparticle mass transfer resistance; (5) Langmuir isotherm (5a): single compound, no mass transfer resistance, and (5b): multicomponent competitive adsorption without mass transfer resistance; (6) Unsteady state operation: Plug flow with mass transfer and no reaction. These validations systematically examine all the mechanisms that are included in the general model and examine the model limitations based on the controlling mechanisms.     

Comparative study of chelating ion exchange resins for the recovery of nickel and cobalt from laterite leach tailings

Commercially available chelating resins with the iminodiacetate functional group have been evaluated for their suitability for the adsorption of nickel and other metal ions by a resin-in-pulp process from the tailings of a pressure acid leach process for nickel laterites. The Amberlite IRC 748 and TP 207 MonoPlus resins were found to be the most suitable in terms of loading capacity for nickel and kinetics of adsorption. The resin with the highest nominal capacity was observed to adsorb less nickel as a result of the adsorption of greater amounts of the impurity ions. The equilibrium loading for nickel on the preferred resin was found to be similar from the ammonium and protonated form of the resin although the kinetics of adsorption is greater when the resin is initially in the ammonium form. A study of the kinetics of the loading of nickel and cobalt from pulp has shown that the rate can be described in terms of a first-order approach to equilibrium. The optimum pH for adsorption was found to be in the range 4 to 5 as this pH is high enough to maximize the adsorption of nickel and cobalt while preventing precipitation of nickel and cobalt as hydroxides from the pulp. A method for minimizing the competition from more strongly loaded ions such as iron(III) and chromium(III) which are present in the pulp was also developed in the initial laboratory phase of the study.     

Modelling the adsorption kinetics of erythromycin onto neutral and anionic resins

In this study the selective adsorption method was chosen to enable the recovery of erythromycin. The following sorbents were tested: neutral resins (XAD-4, XAD-7 and XAD-16) and an anionic resin (IRA-410). A mathematical kinetic model for the adsorption of erythromycin against time, on XAD-4, XAD-7 and XAD-16 resins, is proposed. Both Freundlich and Langmuir models showed a good fit for the sorbents XAD-7 and IRA-410 resins. The highest adsorption efficiency was observed when synthetic neutral resin, XAD-7 and XAD-16, were used. The estimated affinity and concentration factors show that the neutral resins tested are adequate for the selective adsorption of erythromycin. The estimated values of enthalpy and free energy of adsorption, lower than 12 kJ mol(-1) and -2 kJ mol(-1), respectively, indicate that a physiosorption process occurred.     

D-290大孔阴离子交换树脂吸附金的机理和应用

本文报道了D—290大孔强碱性阴离子交换树脂吸附金的机理、酸度曲线、吸附速率、平衡时吸附的容量及吸附反应活化能。通过柱色谱试验,拟定了用D—290树脂分离、原子吸收法测定阳极泥中微量金的方法,取得较好结果。     

Positive transfer from successive reversal training to learning set in blue jays ( Cyanocitta cristata ).

Five blue jays received 160 successive reversal training (SRT) problems and were then tested on 96 learning set (LS) problems. During LS testing, SRT birds performed at higher levels than did 5 jays that had received an equivalent amount of experience on a single problem (SP), but they performed at lower levels than did 5 jays that had received 160 previous LS problems. In addition, the SP birds performed better than did naive birds that were given LS testing directly after pretraining. Analyses of the effects of the Trial 1 outcome indicated that win-stay strategy learning may have produced the SP transfer and that lose-shift learning definitely contributed to SRT transfer. Results strongly support the conclusion that the learning of a win-stay, lose-shift response strategy underlies LS performance in blue jays. (19 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)