Title: Separations Technology

Title: Separations Technology

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JCR Abbreviated Title: Separ Technol

ISSN: 0956-9618

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Batabyal, D., Sahu, A. and Chaudhuri, S.K. (1995), Kinetics and mechanism of removal of 2,4-dimethyl phenol from aqueous solutions with coal fly ash. Separations Technology, 5 (4), 179-186.

Full Text: S\Sep Tec5, 179.pdf

Abstract: Coal fly ash, a solid waste from thermal power stations was used to successfully remove 2,4-dimethyl phenol by adsorption from aqueous solutions. The rate of adsorption follows first order kinetics before attaining equilibrium. Both diffusional and kinetic resistances affect the rate of adsorption and their relative effects vary with operating temperatures. Equilibrium adsorption data satisfied both Langmuir and Freundlich isotherms.

Keywords: Fly Ash, 2,4-dimethyl Phenol, Diffusion and Kinetics Resistances, Physical Adsorption, Equilibrium Isotherms

Lim, B.G., Ching, C.B. and Tan, R.B.H. (1996), Determination of competitive adsorption isotherms of enantiomers on a dual-site adsorbent. Separations Technology, 5 (4), 213-228.

Full Text: S\Sep Tec5, 213.pdf

Abstract: The competitive adsorption isotherms of praziquantel enantiomers on microcrystalline cellulose triacetate were determined by concentration pulse chromatography. A model comprising a non-selective linear term and a selective first order improved Langmuir term was found to fit the data excellently. It is postulated that this chiral stationary phase consists of two types of binding sites: one responsible for the chiral, selective interactions and one responsible for the achiral, non-selective interactions of the enantiomers with the stationary phase. The selective sites are easily saturated compared to the non-selective sites, accounting for the experimental observation of lower separation efficiency at higher enantiomer concentrations.

Keywords: Praziquantel, Adsorption Isotherm, Microcrystalline Cellulose Triacetate, Concentration Pulse Chromatography

Liang, L.Y., Gu, B.H. and Yin, X.P. (1996), Removal of technetium-99 from contaminated groundwater with sorbents and reductive materials. Separations Technology, 6 (2), 111-122.

Full Text: S\Sep Tec6, 111.pdf

Abstract: Pertechnetate oxyanion (TcO₄^-), which is highly soluble in water and readily mobile in the environment, can be immobilized through an ion exchange/adsorption process and chemical reduction followed by adsorption and/or precipitation. Previous studies have focused on the separation and removal of ⁹⁹TcO₄^- from high-level waste streams, however, little information is available for ⁹⁹TcO₄^- removal from only slightly contaminated groundwater. This paper describes treatment of ⁹⁹TcO₄^- contaminated groundwater with both batch and column flowthrough experiments. Synthetic resins and sponges, and zero-valence iron filings were used to evaluate their capacities and the rates of ⁹⁹TcO₄^- removal. The toxicity characteristic leaching procedure (TCLP) was applied to evaluate the leachability of ⁹⁹Tc adsorbed or co-precipitated on iron. Results suggest that both iron and synthetic resins remove ⁹⁹TcO₄^- from groundwater and that at a high flow rate (with residence time of less than 1 min), ⁹⁹TcO₄^- removal capacity is greater for iron filings than for the synthetic resins on a volume basis. Additionally, the rate of (TcO₄^-)-Tc-99 sorption on the sponge is slow (approximately 3 days), and the capacity is relatively low. No appreciable amount of ⁹⁹Tc can be leached out from the spent iron filings by the TCLP test. Overall, zero-valence iron filings provide fast reaction and high removal capacity for ⁹⁹TcO₄^- in groundwater. The high removal efficiency, low cost, and the small waste production of zero-valence iron are attractive for remediation of ⁹⁹TcO₄^- contaminated groundwater.

Keywords: Technetium, Synthetic Resins, Zero-Valence Iron, Reductive Precipitation, ⁹⁹Tc, Chemistry, Sorption

Chen, J.P., Yiacoumi, S. and Blaydes, T.G. (1996), Equilibrium and kinetic studies of copper adsorption by activated carbon. Separations Technology, 6 (2), 133-146.

Full Text: S\Sep Tec6, 133.pdf

Abstract: Copper adsorption by granular activated carbon is reported in this paper. The experimental section includes titrations of activated carbon, as well as equilibrium and kinetic studies of copper adsorption. The potentiometric titration results show that the point of zero charge is 9.5, and that the surface charge increases with decreasing pH. The adsorption of copper strongly depends on solution pH and increases from 10 to 95% at pH ranging from 2.3 to 8. A dramatic increase in pH and emission of small gas bubbles are observed during the experiments, which may result from adsorption of hydrogen ion and/or reduction-oxidation reactions. The two-pK triple-layer model is employed to describe copper adsorption. KINEQL, an adsorption kinetics algorithm, is used to represent the experimental data, and it is found that the model can describe reasonably well the experimental measurements of surface charge, adsorption equilibrium, and adsorption kinetics. Calculations show that formation of the surface-metal complexes SO-Cu²⁺ and SO-CuOH⁺ (a hydrolysis product of SO-Cu²⁺) in the outer layer around the surface of carbon results in removal of copper ion. It is also found that mass transfer controls the adsorption rate, and that adsorption occurs in the micropore region where both external mass transfer and diffusion are important.

Keywords: Granular Activated Carbon, Copper Adsorption, Two-Pk Triple-Layer Model, Kineql, Adsorption Equilibrium, Adsorption Kinetics, Oxide-Water Interface, Surface-Ionization, Complexation, Sorption, Model