The adsorption isotherms of 4-tert.-butyl phenol were measured on four different monolithic columns, using three different techniques, classical frontal analysis (FA), the perturbation on a plateau method (PP) and the recently introduced numerical procedure known as the inverse numerical method (IN). This last approach requires only the recording of a few overloaded profiles and has the potential advantage of affording a dramatic decrease of the amounts of compounds, solvent, and time needed to determine accurate estimates of the coefficients of the isotherm. The reproducibility of the adsorption data measured on the four columns is discussed with reference to the specific techniques used for obtaining these data and to the most suitable equation used for modeling them. The data obtained for the different columns were highly consistent. The inverse numerical approach was confirmed to provide a powerful, accurate, and economic method for measuring single component adsorption data. 相似文献
The suitability of recycled paperboard packaging materials for direct food contact applications is a major area of investigation. Chemical contaminants (surrogates) partitioning between recycled paper packaging and foods may affect the safety and health of the consumer. The partition behavior of all possible organic compounds between cardboards and individual foodstuffs is difficult and too time consuming for being fully investigated. Therefore it may be more efficient to determine these partition coefficients indirectly through experimental determination of the partitioning behavior between cardboard samples and air. In this work, the behavior of organic pollutants present in a set of two paper and board samples intended to be in contact with foods was studied. Adsorption isotherms have been plotted and partition coefficients between paper and air have been calculated as a basis for the estimation of their migration potential into food. Values of partition coefficients (Kpaper/air) from 47 to 1207 were obtained at different temperatures. For the less volatile surrogates such as dibutyl phthalate and methyl stearate higher Kpaper/air values were obtained. The adsorption curves showed that the more volatile substances are partitioning mainly in air phase and increasing the temperature from 70 to 100 degrees C their concentrations in air (Cair) have almost doubled. The analysis of surrogates was performed with a method based on solvent extraction and gas chromatographic-flame ionization detection (GC-FID) quantification. 相似文献
Antifouling coatings are the most reliable way to prevent biofouling of immersed surfaces. As concerning the high toxicity of organotin paints, the tendency is the development of coatings, which do not present environmental risks. In this work, we prepare binders from modification of acrylic copolymers containing free carboxylic acid groups. Biocides chosen are tertiary ammonium salts; alkyl chain substituents with different length are considered. The chemical modifications of resins are carried out via a single step reaction. Modification extents are monitored through proton nuclear magnetic resonance and thermogravimetric analysis and the modified resins are characterised by Fourier transform infrared spectroscopy. The glass transition temperature of the acrylate systems is assessed by dynamical mechanical analysis (pin point method) and compared with data obtained by differential scanning calorimetry. The erosion and antifouling properties of the binders are followed during an exposure to marine environment by a visual observation. 相似文献
A chitosan resin functionalized with 3-nitro-4-amino benzoic acid moiety (CCTS-NABA resin) was newly synthesized for the collection/concentration of trace molybdenum by using cross-linked chitosan (CCTS) as base material. The carboxyl group of the moiety was chemically attached to amino group of cross-linked chitosan through amide bond formation. The adsorption behavior of molybdenum as well as other 60 elements on the resin was examined by passing the sample solutions through a mini-column packed with the resin. After the elution of the elements collected on the resin with 1 M HNO3, the eluates were analyzed by inductively coupled plasma-mass spectrometry (ICP-MS) and atomic emission spectrometry (ICP-AES).
The CCTS-NABA resin can adsorb several metal ions, such as vanadium, gallium, arsenic, selenium, silver, bismuth, thorium, tungsten, tin, tellurium, copper, and molybdenum at appropriate pHs. Among these metal ions, only molybdenum could be adsorbed almost completely on the resin at acidic regions. An excellent selectivity toward molybdenum could be obtained at pH 3–4. The adsorption capacity of CCTS-NABA resin for Mo(VI) was 380 mg g−1 resin. Through the column pretreatment, alkali and alkaline earth metals in river water and seawater samples were successfully removed.
The CCTS-NABA resin was applied to the adsorption/collection of molybdenum in river water and seawater samples. The concentrations of molybdenum in river water samples were found in the range of 0.84 and 0.95 ppb (ng g−1), whereas molybdenum in seawater was about 9 ppb. The validation of the proposed method was carried out by determining molybdenum in the certified reference materials of SLRS-4, CASS-4, and NASS-5 after passing through the CCTS-NABA resin; the results showed good agreement with the certified values. 相似文献
X-ray powder diffraction studies were performed of the polyhydrates, formed at positive temperature in swelled grains of carboxylic cation-exchange resins in the form of tetraisoamylammonium (cross-linked tetraisoamylammonium polyacrylates, differing in the degree of cross-linking: 1, 2 and 3%). It was shown that the polyhydrates exist as the crystalline phase under specific conditions, determined earlier by DTA technique. Diffraction patterns of the samples, recorded at the temperature +3 ± 1 °C, indicate that the polyhydrates crystallize in hexagonal symmetry, the unit cell parameters are close to a=12.25 Å, c=12.72 Å and do not depend significantly upon the degree of cross-linking. The suppositions were made concerning the size of hydrate crystallites, formed in the swelled grains of the studied resins.This revised version was published online in July 2005 with a corrected issue number. 相似文献