Forgot your password?
New user?
New Window Opens on the Secret Life of Microbes: Scientists Develop First Microbial Profiles of Ecosystems
CAS announces the release of SciFinder Scholar for Mac OS X
Press Releases
Press Releases
| Check out our New Publishers' Select for Free Articles |
Adsorption: Journal of the International Adsorption Society (v.8, #3)
A Branched Pore Model Analysis for the Adsorption of Acid Dyes on Activated Carbon by Danny C.K. Ko; John F. Porter; Gordon McKay (pp. 171-188).
A new branched-pore adsorption model has been developed using an external mass transfer coefficient, K f, an effective diffusivity, D eff, a lumped micropore diffusion rate parameter, K b, and the fraction of macropores, f, to describe sorption kinetic data from initial adsorbent-adsorbate contact to the long-term adsorption phase. This model has been applied to an environmental pollution problem—the removal of two dyes, Acid Blue 80 (AB80) and Acid Red 114 (AR114), by sorption on activated carbon. A computer program has been used to generate theoretical concentration-time curves and the four mass transfer kinetic parameters adjusted so that the model achieves a close fit to the experimental data. The best fit values of the parameters have been determined for different initial dye concentrations and carbon masses. Since the model is specifically applicable to fixed constant values of these four parameters, a further and key application of this project is to see if single constant values of these parameters can be used to describe all the experimental concentration-time decay curves for one dye-carbon system.The error analysis and best fit approach to modeling the decay curves for both dye systems show that the correlation between experimental and theoretical data is good for the fixed values of the four fitted parameters. A significantly better fit of the model predictions is obtained when K f, K b and f are maintained constant but D eff is varied. This indicates that the surface diffusivity may vary as a function of surface coverage.
Keywords: adsorption model; acid dye; activated carbon; macropore; micropore; variable surface diffusivity
Effects of Adsorption Mechanisms on the Efficiency of ASC Whetlerite Carbon Reactor by Jong Sun Lim; Chulsung Kim; Yongwoo Lee; Wha-Seung Ahn (pp. 189-195).
Dynamic adsorption equation was evaluated for its validity to characterize two different initial adsorption mechanisms with dimethyl methylphosphonate (DMMP) and cyanogen chloride (CNCl) onto ASC whetlerite carbon. Experimental results show that a linear relation between breakthrough time and the amount of carbon was occurred with high values of coefficient of correlation (0.9790–0.9993 for DMMP, 0.9979–0.9998 for CNCl) satisfying the pre-requirement for application of the adsorption equation. With initial adsorption data, as superficial flow rate increases, the dynamic adsorption capacity for DMMP increases and that for CNCl decreases which are not consistent with the earlier observation of less-relationship between dynamic adsorption and superficial flow rate. An effort was conducted to obtain numerical formulas for the dynamic adsorption capacity as a function of superficial flow rate and the calculated maximum adsorption capacities for DMMP and CNCl were 0.4291 (g/g) and 0.2500 (g/g), respectively.For DMMP, $$W_e = 0.3328{ 1 - exp ( - 0.0626V_f )} + 0.0936$$ For CNCl $$W_e = 0.1154exp ( - 0.1387V_f )} + 0.1346{ ext{ exp( - 2}}{ ext{.32}}^{{ ext{ - 10}}} V_f { ext{)}}$$ The rate constant for both DMMP and CNCl adsorption, has linear relation to superficial flow rate within our experimental range from 4 to 50 cm/sec. Critical bed weight which is the minimum amount of carbon to satisfy the arbitrary chosen effluent concentration, was affected by not only superficial flow rate but also rate constant.
Keywords: dynamic adsorption; ASC whetlerite carbon; dimethyl methylphosphonate (DMMP); cyanogen chloride (CNCl)
Adsorption of Binary Liquid Crystals onto Cellulose Membrane for Thermo-Responsive Drug Delivery by Shan-Yang Lin; Hsiu-Li Lin; Mei-Jane Li (pp. 197-202).
A thermo-responsive membrane was developed by adsorbing the binary liquid crystals (LC) onto the cellulose nitrate membrane. The binary LC mixture is consisted of 36% cholesteric oleyl carbonate (COC) and 64% cholesteryl nonanoate (CN). The physico-chemical and the thermo-responsive properties of this binary LC adsorbed-membrane were examined. The results indicate that the adsorption behavior of binary LC mixture on the cellulose membrane was quick and reached to the equilibrium about 10 min, and linearly correlated with the increase of LC concentration used. The hydrophilic membrane was hydrophobicized after adsorption of binary LC mixture. The focal conic fan textures of binary LC mixture were observed from the surface of cellulose membrane. Due to the obedience and reproducibility of the binary LC used, the binary LC mixture-adsorbed membrane continuously exhibited an on-off thermo-responsive sensitivity to control the drug penetration.
Keywords: adsorption; liquid crystal; membrane; thermo-responsive; penetration; drug delivery
Adsorption Equilibrium and Kinetics of Egg-White Proteins on Immobilized Metal Ion Affinity Gels for Designing Fractionation by Sadhana Sharma; Gopal P. Agarwal (pp. 203-213).
Designing an Immobilized Metal ion Affinity (IMA) chromatographic process on large scale demands a thorough understanding to be developed regarding the adsorption behaviour of proteins on metal loaded IMA (IMA-M(II)) gels and the characteristic adsorption parameters to be evaluated. This research investigation illustrates the significance of these aspects for the proposed fractionation of chicken egg-white proteins on these gels. Consequently, a systematic investigation of the adsorption characteristics of three chicken egg-white proteins viz., ovalbumin, conalbumin and lysozyme on Cu(II) and Ni(II) loaded IMA gels, iminodiacetate (IDA) and tris(2-aminoethyl)amine (TREN), has been undertaken. These gels differ in their selectivity towards the proteins of interest under the identical sets of experimental conditions. While TREN-Ni(II) was selective only for lysozyme, IDA-Cu(II), IDA-Ni(II) and TREN-Cu(II) showed varying affinities for all the three proteins. The equilibrium and kinetic data were analysed using various theoretical models and adsorption parameters were quantified. On the basis of these investigations, various strategies have been proposed for the efficient large-scale fractionation of chicken egg-white proteins on these gels.
Keywords: adsorption; immobilized metal affinity; IMAC; iminodiacetic acid; tris(2-aminoethyl)amine; protein fractionation
Comparison of Adsorption Capacity of p-Cresol & p-Nitrophenol by Activated Carbon in Single and Double Solute by Sirous Nouri; Fouad Haghseresht; G.Q. Max Lu (pp. 215-223).
Adsorption of p-Cresol and p-Nitrophenol by untreated activated carbon in single and multisolute solutions was carried out at 301 K and at controlled pH conditions. In acidic conditions, well below the pK a of both solutes, it was observed that the adsorbate solubility and the electron density of aromatic rings influenced the extent of adsorption by affecting the extent of London dispersion forces. The fitted parameters obtained from single-solute Langmuir equation show that Q max and the adsorption affinity of carbon for the compound with low pK a decrease more significantly. In higher solution pH conditions, on the other hand, it was found that electrostatic forces played a significant role on the extent of adsorption. The presence of another compound decreases Q max and the adsorption affinity of carbon for the principal compound. The effect of pH, on the carbon surface and on the solute molecules, must be considered. Adsorption of the solute at higher pH values was found to be dependent on the concentration of anionic form of the solute. The isotherm data were fitted to the Langmuir isotherm equation for both single and double solute solutions.
Keywords: effects of pH; point of zero charge (PZC); adsorption capacity; activated carbon; Langmuir; spectrophotometer
Synthesis and Sorption Behaviour of Some Radioactive Nuclides on Sodium Titanate as Cation Exchanger by I.M. El-Naggar; E.A. Mowafy; I.M. Ali; H.F. Aly (pp. 225-234).
Crystalline (Na4TiO4·0.32H2O) and amorphous (Na2TiO3·1.45H2O) forms of sodium titanate were prepared by fusion reaction of TiO2 and Na2CO3 at 1100°C in molar ratios of 2:1 and 1:2, respectively. The prepared products were characterized using IR, DTA-TG, X-ray and elemental analyses. Kinetic studies of the order of reaction (n) and activation energy (E a) for crystallization transformation step (for crystalline sodium titanate only) have been determined from DTA thermogram and their values were found to be 0.87 (univalent order) and 3.97 kJ mol−1, respectively. Ion exchange capacities and some distribution studies were carried out at different conditions in the presence of some complexing agents (EDTA, boric and citric acids) and the results showed that the capacities of the crystalline form are always less than the amorphous one.
Keywords: sodium titanate; cation exchanger; sorption; radioactive nuclides
Ethanol-Water Separation in the PSA Process by M.J. Carmo; J.C. Gubulin (pp. 235-248).
An investigation was carried out on ethanol-water separation employing a PSA adsorption cycle with zeolite 3A as the adsorbent. The cycle was operated under the following operating variables: feed flow (2, 4, 6 and 8 L/h), adsorption temperature (200°C) and adsorption pressures (2, 4 and 6 bar). All experimental runs were performed under vacuum of 0.2 bar in the desorption step. The effect of these variables on the enrichment and recovery percentage of the product, on the productivity and on the total cycle time was studied, using the adsorption pressure as a parameter. The results showed that these variables significantly affect the responses of interest. We also studied the influence of such variables as: adsorption pressures, desorption pressures, flow rates and adsorption temperatures (T), on the enrichment, recovery, productivity and on the total cycle time. The data were obtained from operational cycles in a Kahle's system. The experiments were organized by a three level factorial design. The results obtained were compared with from the fitted empirical equations as well as with the corresponding surface responses and all variables showed to be influential. Last, by an optimal combination of the variables was obtained by means of the ridge analysis method and the optimized multi-response method.
Keywords: adsorption; zeolite; ethanol