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Desorption Experiments (desorption + experiment)
Selected AbstractsAssociation of europium(III), americium(III), and curium(III) with cellulose, chitin, and chitosanENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 8 2006Takuo Ozaki Abstract The association of trivalent f-elements,Eu(III), Am(III), and Cm(III),with cellulose, chitin, and chitosan was determined by batch experiments and time-resolved, laser-induced fluorescence spectroscopy (TRLFS). The properties of these biopolymers as an adsorbent were characterized based on speciation calculation of Eu(III). The adsorption study showed that an increase of the ionic strength by NaCl did not affect the adsorption kinetics of Eu(III), Am(III), and Cm(III) for all the biopolymers, but the addition of Na2CO3 significantly delayed the kinetics because of their trivalent f-element complexation with carbonate ions. It also was suggested from the speciation calculation study that all the biopolymers were degraded under alkaline conditions, leading to their masking of the adsorption of Eu(III), Am(III), and Cm(III) on the nondegraded biopolymers. The masking effect was higher for cellulose than for chitin and chitosan, indicating that of the three, cellulose was degraded most significantly in alkaline solutions. Desorption experiments suggested that some portion of the adsorbed Eu(III) penetrated deep into the matrix, being isolated in a cavity-like site. The TRLFS study showed that the coordination environment of Eu(III) is stabilized mainly by the inner spherical coordination in chitin and by the outer spherical coordination in chitosan, with less association in cellulose in comparison to chitin and chitosan. These results suggest that the association of these biopolymers with Eu(III), Am(III), and Cm(III) is governed not only by the affinity of the functional groups alone but also by other factors, such as the macromolecular steric effect. The association of degraded materials of the biopolymers also should be taken into consideration for an accurate prediction of the influence of biopolymers on the migration behavior of trivalent f-elements. [source] Mercury removal: a physicochemical study of metal interaction with natural materialsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 11 2009Leticia Carro Abstract BACKGROUND: Mercury is considered one of the most harmful heavy metals to the environment and human health, so recently remediation processes have been developed to eliminate this metal from wastewaters. Metal retention by natural polymers is a good alternative technique to remove heavy metals from solution. RESULTS: A screening of 25 potential mercury sorbents was carried out at three different pH values in order to find appropriate biomass to remove this metal from polluted waters. High sorption capacities were found for many of the materials studied. Four of these materials were selected for further detailed study. Kinetic studies showed short times to reach equilibrium. For S. muticum, sorption isotherms were obtained at several temperatures and a sorption enthalpy value was obtained. Desorption experiments were performed to determine the possibility for recycling of this brown alga. CONCLUSIONS: Different materials have been found to be potentially good adsorbents of mercury. A detailed study showed that S. muticum is an excellent material with a mercury uptake about 200 mg g,1. This brown alga has a fast kinetic process (80% of metal is removed from solution in 30 min), and very high metal uptake over a wide pH range, up to 92% elimination for pH values above 3,4. Copyright © 2009 Society of Chemical Industry [source] An investigation of the mechanisms of ultrasonically enhanced desorptionAICHE JOURNAL, Issue 2 2007Oualid Hamdaoui Abstract In this work, the mechanisms underlying ultrasonic desorption of 4-chlorophenol from granular activated carbon have been explored. Desorption experiments are investigated in the absence and presence of 516 kHz ultrasound of different intensities. Using three regenerating solutions and two temperatures, it has been shown that ultrasonic irradiation considerably improves both the amount and the rate of desorption. Desorption increases with increasing temperature and ultrasound intensity. The addition of sodium hydroxide or a mixture of sodium hydroxide and ethanol to the regenerating medium leads to an enhancement of the desorption, especially in the presence of ultrasound. The mechanisms of ultrasonically enhanced desorption is due both to the thermal and non-thermal (hydrodynamical) effects of ultrasound. Hydrodynamical phenomena are principally produced by the acoustic vortex microstreaming within porous solids as well as at the solid-liquid interface and by the high-speed micro-jets and high-pressure shock waves produced by acoustic cavitation. The thermal effects are evaluated as localized hot spots formed when bubbles cavitated as well as by global heating of the medium and piezoelectric transducer heating-up. Additionally, the non-thermal effect of ultrasound is greater than the thermal effect, and it is more noticeable when the ultrasonic irradiation is carried out in a high temperature regenerating medium. © 2007 American Institute of Chemical Engineers AIChE J 2007 [source] Slow desorption behavior of one highly resistant aromatic amine in Lake Macatawa, Michigan, USA, sedimentENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 12 2005Shihua Chen Abstract The desorption behavior of benzidine from Lake Macatawa (Holland, MI, USA) sediment was investigated in this study using batch solvent extraction method. Seven solvents were tested as the extracting reagents: Deionized water (DI), calcium chloride in DI (CaCl2), sodium hydroxide in DI (NaOH), acetonitrile (ACN), a mixture of acetonitrile and ammonium acetate in DI (ACNNH4OAc), methanol (MeOH), and hydrochloric acid in DI (HCl). These solvents are proposed to react with sediment-associated benzidine by different mechanisms (e.g., cation exchange, hydrophobic partitioning, and covalent binding). Three sets of sorption isotherm experiments were conducted separately in these seven solvents with a 7-d, three-week, and two-month contact time. The results demonstrated nonlinear isotherms with Freundlich 1/n values varying from 0.25 to 0.52. The desorption behavior of benzidine in the solvents was evaluated after the sorption of benzidine onto the sediment with same contact times of 7 d, three weeks, and two months. A two-stage model subsequently was applied to simulate the experimental data. The rapidly desorbing rate constants were on the order of one to two per day for ACN, ACN-NH4OAc, and NaOH solvents, and the slowly desorbing rate constants were on the order of 10,5 to 10,4/d. Sequential desorption experiment demonstrated low total extraction efficiency of less than 40%. Both the observed sorption and desorption phenomena suggested that hysteresis and/or mass-transfer limited diffusion may result in the slow desorption behavior observed in this study. [source] Synthesis of the hydrophobic,hydrophilic macroporous poly divinylbenzene/poly(sodium acrylate) IPN resin and adsorption performance for berberinePOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 12 2009Guqing Xiao Abstract The macroporous polydivinylbenzene/poly(methyl acrylate) interpenetrating polymer network (PDVB/PMA IPN) was prepared by the sequential suspension polymerization method, and was modified to be hydrophobic,hydrophilic macroporous polydivinylbenzene/poly (sodium acrylate) IPN (PDVB/PNaA IPN) by converting the PMA to PNaA under the condition of base. The effects of different mass ratio of the two networks and different cross-linking degree of the second network on the pore structure and adsorption capacity of PDVB/PNaA IPN resin were studied. The PDVB/PNaA IPN resin whose adsorption quantity is the biggest was chosen to study further. The pore structure, the weak acid exchange capacity, the water retention capacity, and the swelling ability of PDVB/PNaA IPN resin were measured. The study focused on the adsorption isotherms of berberine at different temperatures. Isosteric adsorption enthalpy, adsorption Gibbs free energies can be calculated according to thermodynamic functions. The results show that the saturated adsorption quantity of berberine is up to 109.4,mg,ml,1 (wet resin) by the way of dynamic adsorption and desorption experiment. The resin could be reused by the mixture with 0.5% sodium chloride and 80% ethanol. On the one hand the hydrophobic PDVB in the PDVB/PNaA IPN resin has the ability of adsorption using ,,, interaction, and on the other hand the hydrophilic PNaA in the PDVB/PNaA IPN resin has the ability of adsorption using ion exchange interaction. An important conclusion can be drawn that the PDVB/PNaA IPN resin has a promising application prospect in extracting and separating quaternary ammonium type alkaloids such as berberine. Copyright © 2009 John Wiley & Sons, Ltd. [source] Complex biopolymeric systems at stalk/epicuticular wax plant interfaces: A near infrared spectroscopy study of the sugarcane exampleBIOPOLYMERS, Issue 8 2009Deborah E. Purcell Abstract Naturally occurring macromolecules present at the epicuticular wax/stalk tissue interface of sugarcane were investigated using near infrared spectroscopy (NIRS). Investigations of water, cellulose, and wax-cellulose interrelationships were possible using NIRS methods, where in the past many different techniques have been required. The sugarcane complex interface was used as an example of typical phenomena found at plant leaf/stalk interfaces. This detailed study showed that sugarcane cultivars exhibit spectral differences in the CHn, water OH, and cellulose OH regions, reflecting the presence of epicuticular wax, epidermis, and ground tissue. Spectrally complex water bands (5276 cm,1 and 7500,6000 cm,1) were investigated via freeze-drying experiments which revealed sequentially a complex band substructure (7500,6000 cm,1), a developing weak H-bonding system (,7301 cm,1), and strong H-bonding (,7062 cm,1) assigned to water,cellulose interactions. Principal component analysis techniques clarified complex band trends that developed during the desorption experiment. Bands from wax-free stalk were minimized in the 4327,4080 cm,1 region (CHn vibrational modes associated with long chain fatty compounds), while bands from the stalk tissue (particularly lignin and moisture) became more pronounced. This work is a comprehensive guide to similar studies by scientists involved in a variety of plant and fiber research fields. © 2009 Wiley Periodicals, Inc. Biopolymers 91: 642,651, 2009. This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source] Experimentelle Bestimmung der hygrischen Sorptionsisotherme und des Feuchtetransportes unter instationären BedingungenBAUPHYSIK, Issue 2 2006Assistent und Laborleiter Rudolf Plagge Dr.-Ing. Mit der vorgestellten Augenblicksprofil-Methode (APM) werden sowohl die relative Luftfeuchte und die Temperatur, als auch der volumetrische Wassergehalt in bestimmten Positionen in einem porösen Material bestimmt. Die Messungen werden kontinuierlich unter instationären Bedingungen durchgeführt. Damit erlaubt die APM eine dynamische und gleichzeitige Messung der hygroskopischen Sorptionsisotherme und der hygrischen Feuchteleitfähigkeit für einzelne Kompartimente innerhalb der Materialprobe. Die Feuchteleitfähigkeit wird aus den sich zeitlich ändernden Potentialgradienten und den dazugehörigen Feuchteverteilungen für die jeweiligen Kompartimente berechnet. Die Anwendung nicht konstanter Randbedingungen in der APM erlaubt die Untersuchung des hygrodynamischen Verhaltes von porösen Materialien. In der vorliegenden Studie werden die zeit- und prozeßabhängige Feuchtespeicherung und der Feuchtetransport bestimmt. Die vorgestellten Adsorptions- und Desorptionsexperimente wurden an dem kapillar- aktiven Wärmedämmstoff Calciumsilikat durchgeführt. Die Ergebnisse geben das Hystereseverhalten und den Einfluß der Dynamik der Prozesse wider. In Positionen mit schnellen Feuchteänderungen wird die Feuchtespeicherfunktion im Vergleich mit Regionen langsamer Feuchteänderung nach oben verschoben. Die Feuchteleitfähigkeit als Funktion der relativen Luftfeuchte zeigt eine bedeutende Hysterese. Hingegen ist die Feuchteleitfähigkeit in Relation zum Wassergehalt nicht hysteretisch. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) Experimental determination of the hygroscopie sorption isotherm and the moisture conductvity under transient conditions. By means of the proposed Instantaneous Profile Method (IPM) the relative humidity or the capillary pressure as well as the volumetric water content at specific locations inside a porous medium can be determined. The measurements are carried out under transient conditions and continuously in time. Thus, the IPM allows dynamic measurements of the hygroscopic sorption isotherm and the hygroscopic moisture conductivity. In addition, the moisture conductivity can be obtained via calculation of the moisture flow distribution from the temporal change of moisture contents in the compartments of the sample. The application of non-constant boundary conditions in the IPM allows investigation of the hygrodynamic behaviour of porous materials. In the presented study, the time and process dependent moisture retention characteristic and moisture conductivity are determined. The adsorption and successive desorption experiments presented here have been performed on the capillary active insulation material Calcium Silicate. The results show a hysteretic behaviour with a pregnant influence of the process dynamics. At locations with a rapid moisture increase, the moisture retention characteristic is shifted up in comparison to regions with slow moisture change. The moisture conductivity as function of relative humidity shows a remarkable hysteresis. However, the moisture conductivity in relation to the water content turned out to be non-hysteretic. [source] Adsorption of SO2 on Activated Carbon for Low Gas ConcentrationsCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 5 2007P. Zhang Abstract Adsorption experiments of SO2 on activated carbon has been carried out for low concentrations (about 100,ppm) at room temperature (15 to 33,°C) with varying humidity in the air. The breakthrough curves show that at high relative humidity or relative higher SO2 concentration, the load capacity increases with respect to temperature. The humidity of the air is also of benefit to the load capacity of SO2. When an adsorption process is interrupted and the activated carbon is kept closed for a while, the SO2 concentration at the exit of a fixed-bed adsorber is similar to that of the fresh activated carbon and begins at a very low value. It appears that the sorption potential has been refreshed after the storage period. Analysis of desorption experiments by simultaneous thermal analysis combined with mass spectrometry (MS) after loading, shows that the physisorbed SO2 and H2O are desorbed at low temperatures. At higher temperatures, the MS peak of SO2 and H2O occur at the same time. Compared with desorption immediately after loading, after one day, the desorption peak due to the physisorbed SO2 disappears. From this, it can be concluded that the refreshment of the loading capacity of the activated carbon after storage is mainly due to a change in the nature of the SO2 from a physisorbed state to a chemisorbed form. The same mechanism leads to a continuous refreshment of the sorption potential by means of a chemical reaction during the adsorption process. [source] | ||||||||||