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Adsorption Systems (adsorption + system)
Selected AbstractsApplication of solid-phase concentration-dependent HSDM to the acid dye adsorption systemAICHE JOURNAL, Issue 1 2005Vinci K. C. Lee Abstract The fixed-bed adsorption of acid dyes onto granular activated carbon (Chemviron Filtrasorb 400) has been studied using a homogeneous surface diffusion model (HSDM). The model incorporates the external boundary layer mass transport and homogeneous diffusion inside the particle. A new orthogonal collocation method has been developed and used to solve the diffusion equations. This orthogonal collocation gives a faster solution method compared with the numerical Crank,Nicolson method. The surface diffusivity has been determined by an optimization procedure with minimization of sum of the error squared. The equilibrium relationship between the liquid-phase concentration and the solid-phase concentration has been described by the Redlich,Peterson isotherm. A solid-phase concentration-dependent surface diffusivity was introduced. The Darken model with the Redlich,Peterson isotherm was found to be a suitable correlation model for the adsorption of the acid dyes on carbon. The magnitude of the averaged Ds0 of each dye is in the order of AR114 > AB80 > AY117, which implies that, under the same solid-phase concentration gradient, the rate of mass transport diffusion is higher in AR114 than that in AB80 and AY117. This phenomenon may be explained by the different mobilities of the dye molecules present in the solution by the different arrangements of two sulfonic acid groups in the dye structures. © 2004 American Institute of Chemical Engineers AIChE J, 51: 323-332, 2005 [source] Preparation of bioadsorbents for effective adsorption of a reactive dye in aqueous solutionASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2010Shariff Ibrahim Abstract The surface of barley straw, an agricultural waste, was modified chemically using a cationic surfactant hexadecylpyridinium chloride monohydrate (CPC) and used as an adsorbent for removal of Reactive Blue 4 (RB4) from aqueous solution. The raw and surfactant-modified barley straws (SMBS) were characterized by Fourier transform infrared and elemental analysis. The stability of CPC adsorbed on straw surface was evaluated by exposing to water and organic solvents. The adsorption was performed on removing RB4 from wastewater in a batch adsorption system. The effects of contact time, initial concentration of dye and pH of solution on RB4 uptake were investigated and discussed. It was found that the removal percentage of RB4 increased with the increase in contact time. Adsorption was favorable at acidic condition and the maximum removal of 100% was obtained at pH 3. Dye-loaded SMBS was stable and percentage of desorption was less than 7% in water. The kinetic studies revealed that the kinetic data fitted well to the pseudo-second-order model. The isotherm study also indicated that RB4 adsorption on SMBS matched well with the Langmuir model other than the Freundlich model. The maximum adsorption capacity determined from the Langmuir isotherm was 29.2 mg g,1 at 25 °C. Copyright © 2010 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Kinetics and mechanism of Cr(VI) adsorption onto tea-leaves wasteASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2008Md. Salatul Islam Mozumder Abstract Adsorption equilibrium and kinetic experiments have been conducted in batch mode to evaluate Cr(VI)-tea-leaves waste system. The equilibrium data followed the Langmuir adsorption isotherm and the adsorption was viewed as a physicochemical reversible process. A unified approach model was used to describe the adsorption system from both equilibrium and kinetic viewpoints. The model satisfactorily described both kinetic and equilibrium data. The adsorption and desorption rate constants were evaluated from the model fittings and were not dependent on initial concentration and adsorbent doses. pHzpc of the adsorbent was evaluated as 4.2 ± 0.1, and below that pH the adsorbent surface is positively charged. Adsorption of Cr(VI) was found highly pH-dependent, and the removal efficiency dropped sharply from 95 to 10% when pH of the system changed from 2 to 5. The surface functional groups of tea-leaves waste (before and after adsorption) were analyzed by Fourier transform infrared (FTIR) and the amine groups were found to take part in the adsorption of Cr(VI). The experimental result inferred that electrostatic attraction between the surface and the species is one of the major adsorption mechanisms for binding metal ions to the tea-leaves waste. Copyright © 2008 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Interaction of CO and NO with the spinel CuCr2O4 (100) surface: A DFT studyINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 9 2008Xiang-Lan Xu Abstract The characteristics of CO and NO molecules at Cu2+ and Cr3+ ion sites on the CuCr2O4 (100) surface have been studied by first principles calculations based on spin-polarized density functional theory (DFT). The calculated results show that adsorption energies for X-down(C, N) adsorption vary in the order: Cu2+ -CO>Cr3+ -NO,Cr3+ -CO>Cu2+ -NO. CO molecules are preferentially adsorbed at Cu sites, whereas NO molecules adsorb favorably at Cu2+ and Cr3+ ion sites. The C-O and N-O stretching frequencies are red-shifted upon adsorption. Combining the analysis of frontier molecular orbitals and Mulliken charge, for CO and NO X-down adsorption systems, the 5, orbitals donate electrons and the 2,* orbitals obtain back-donated electrons. Although for NO with O-down adsorption systems, the NO-2,* orbitals obtain back-donated electrons from substrates without 5,-donation. Coadsorption calculations show the CO/NO mixture adsorb selectively at the Cu2+ion site but simultaneously at the Cr3+ ion site, respectively. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008 [source] Improved design and optimization models for the fixed bed adsorption of acid dye and zinc ions from effluentsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 12 2002Danny C Abstract The bed depth service time (BDST) design model, which accounts for the change of bed adsorption capacity with service time, has been modified to expand its application and overcome the limiting assumptions of the original BDST analysis. Column experiments were undertaken to test the new model for two adsorption systems, namely zinc ion,bone char and Acid Blue 80 dye-activated carbon. It was found that the percentage of saturation capacity could be correlated using a square-root dependence on the service time and this correlation was incorporated into the original BDST analysis to replace the total sorption capacity term, giving the model a much wider application to real systems. The empty bed residence time optimization approach was modified using the same time-dependent capacity expression and was successfully applied to the metal ion,bone char and the dye-activated carbon system with the use of equilibrium saturated bed capacity. These modifications to the BDST design model and the EBRT optimization model will give more accurate scale-up data for the design of large-scale column adsorption systems. © 2002 Society of Chemical Industry [source] ADSORPTION CHARACTERISTICS OF CROCIN IN THE EXTRACT OF GARDENIA FRUITS (GARDENIA JASMINOIDES ELLIS) ON MACROPOROUS RESINSJOURNAL OF FOOD PROCESS ENGINEERING, Issue 1 2009BIN YANG ABSTRACT To study resin adsorptions and investigate the differences between processes in crude extracts and microfiltrates, the adsorption characteristics of crocin in the extract of Gardenia jasminoides Ellis on 10 macroporous styrene-divinylbenzene (SDVB) resins were investigated. Ground gardenia fruit was extracted with water and the crude extract was partially purified by microfiltration. The crude extract and microfiltrate were mixed with the 10 resins until the adsorption of crocin reached equilibrium on resins. The adsorption followed the pseudo-second-order kinetics closely, but the data also fitted the first-order and intraparticle diffusion models. Furthermore, the Freundlich isotherm was found suitable for describing the equilibrate adsorption data. XAD-1180, HP20, HPD-100A and AB-8 stood out as the best performing resins in terms of their adsorptive capacities and selectivities for crocin. The thermodynamics of the adsorption process was shown to be spontaneous and exothermal in nature, and controlled by physical rather than chemical mechanisms. Adsorption with SDVB resins in conjunction with microfiltration was found to be an efficient process for the purification of crocin in gardenia extract. PRACTICAL APPLICATIONS Macroporous resins have been industrially applied in the recovery and purification of some products from plant extracts. However, there is a lack of understanding of the adsorption process and many of the applications are based on empirical data rather than on predicable models. Therefore, the development of reliable mathematical models that can accurately describe and predicate experimental data of adsorption would be extremely helpful in understanding the adsorption process as well as optimizing the design of adsorption systems. [source] Simulation and optimal design of multiple-bed pressure swing adsorption systemsAICHE JOURNAL, Issue 11 2004Ling Jiang Abstract Pressure swing adsorption (PSA) is a very versatile technology for gas separation and purification. The widespread industrial application of PSA has called for an efficient set of simulation, design, and optimization methodologies. In previous work by Jiang and co-workers, we used a Newton-based approach to quickly converge the cyclic steady state and design constraints, and a simultaneous tailored approach with the state-of-art nonlinear optimization strategy to design optimal PSA processes. In this work we extend the simulation and optimization strategies to multiple bed systems. Both unibed and multibed frameworks are adopted to describe bed behaviors. The unibed framework models only one bed over a cycle and uses storage buffers to mimic the bed interactions. The multibed framework simultaneously solves all beds but only for a portion of the cycle. Challenges and implementation details of both frameworks are discussed. A five-bed, 11-step hydrocarbon separation process, which separates H2 from a mixture of H2, N2, CO2, CO, and CH4, is used for illustration. By manipulating valve constants, step times, flow rates, and bed geometry, the optimizer successfully maximizes H2 recovery, while meeting product purity and pressure specifications. © 2004 American Institute of Chemical Engineers AIChE J, 50: 2904,2917, 2004 [source] | ||||||||||