Comparative study for separation of aquatic humic-type organic constituents by DAX-8, PVP and DEAE sorbing solids and tangential ultrafiltration: elemental composition, size-exclusion chromatography, UV-vis and FT-IR

Aquatic humic-type solutes were separated in parallel from the same fresh water source by four different procedures: non-ionic polymethyl methacrylate (DAX-8) and functional cross-linked polyvinylpyrrolidone (PVP) resins, functional diethylaminoethyl cellulose (DEAE) and tangential ultrafiltration completed with a weakly basic anion exchange resin (IRA-67). The similarity-dissimilarity between the quantities and qualities of the different humic samples is discussed, especially in the light of the original dissolved organic matter (DOM). During the past two decades, a significant progress has occurred in the aquatic humic research due to the so-called hydrophobic-hydrophilic properties possessed by certain non-ionic sorbing solids. As a result of many coincidences, it may be justifiable to examine critically the prevailing isolation techniques of aquatic humic solutes and to try to update their complicated definitions. For that reason, it is reasonable to summarize the leading principles of different isolation techniques in Section 1 of this article. The results of the present study strongly support the applicability of the PVP resin, alone or completed in sequence with a suitable non-ionic sorbing solid, for isolation of aquatic humic-type solutes from both quantitative and qualitative points of view. In certain cases, the DEAE cellulose gives a useful alternative for conventional sorbing solids in the isolation of the bulk of aquatic humic solutes. The base-catalyzed ester hydrolysis of the HM during the chromatographic isolation of the DOM seems to be relative minor.     

Separation of humic acid with XAD resins

Summary Separation of humic acid with different XAD resins has been studied. The effect of pH on the adsorption of humic acid by XAD resins and effect of pH on the distribution coefficient constant in a system of XAD resin and humic acid solution are reported. The XAD-12 was found to be the most efficient resin to remove humic acid from a solution at pH 5.0.

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Zusammenfassung Die Abtrennung von Huminsäure mit verschiedenen XAD-Harzen (Amberliten) wurde untersucht. Über den Einfluß des pH auf die Adsorption der Huminsäure an XAD-Harzen und auf den Verteilungskoeffizienten in einem System aus XAD-Harz und Huminsäure-Lösung wurde berichtet. XAD-12 erwies sich als das am besten wirksame Harz, um Huminsäure bei pH 5 aus einer Lösung zu entfernen.

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This study was supported by Office of Water Research and Technology, U. S. Department of Interior.     

Structural Characterisation of the Coloured Organic Matter from an Eucalyptus Bleached Kraft Pulp Mill Effluent

Abstract

XAD-8 and XAD-4 resins in tandem were used to isolate and fractionate the coloured organic matter from an eucalyptus bleached Kraft pulp mill effluent which is discharged into river Vouga (Portugal) near the lagoon that exists in its terminal part. The composition of the isolated organic matter was investigated by FTIR and CPMAS-¹³C-NMR and compared to that of humic matter isolated before from the same river at a non-polluted site and a site very contaminated with the effluent of a sulphite pulp mill. The results put into evidence that the organic matter from both kinds of effluent is more aromatic and contains more lignin derived structural units than the humic matter from the unpolluted site. However, the organic matter from the sulphite pulp mill effluent is more soluble due to its content of sulphonic functional groups.     

Comparison between DAX-8 and C-18 solid phase extraction of rainwater dissolved organic matter

Rainwater is a very low concentrated matrix and, for dissolved organic matter (DOM) characterization, an efficient extraction procedure is essential. Isolation procedures based on the adsorption onto XAD-8 and C-18 sorbents have been used in the literature for rainwater DOM isolation, but a comparison between these procedures is lacking. In this work, UV-visible and molecular fluorescence spectroscopies highlighted differences between rainwater DOM isolated by DAX-8 (replacement for XAD-8) and by C-18. It was possible to recover higher rainwater DOM percentage by the C-18 based procedure than by the DAX-8 one. Rainwater protein-like compounds were better concentrated by the C-18 procedure than by the DAX-8 one, while humic-like compounds were similarly concentrated by both procedures. Furthermore, rainwater DOM extracted by the C-18 procedure was more representative of the global matrix, while DAX-8 preferentially extracted humic-like compounds.     

Artefacts in XAD-8 NOM fractionation

The XAD-8 resin has been widely used during the last decades to characterize and isolate natural organic matter (NOM) in water. The present work focuses on the performance and limitations of the XAD-8 method. A number of different NOM samples (mostly RO-isolates) have been XAD-8 fractionated with the purpose to study (1) the impact of DOC concentration of the samples on the quality of the resulting fractions and (2) the stability of NOM in the different fractions during the XAD-8 fractionation procedure and storage. Focus is placed on the method's independence of NOM concentration, the stability (quantity and quality) of the hydrophilic fraction during the fractionation, the relationship between hydrophilic and hydrophobic fractions, and the stability of the obtained fractions after the fractionation is completed.

The main conclusions are that the division into hydrophobic and hydrophilic fractions are not independent of the NOM concentration and not constant during the procedure, furthermore that the XAD-8 fractions may undergo irreversible alteration of structure due to the procedure or storage that will influence on the interpretation of the data. The possible consequences for the interpretation of results and further analysis or use of the XAD-8 based fractions are discussed.     

Flow microcalorimetry and competitive liquid sorption II. Liquid sorption and wetting on macroreticular hydrophilic/hydrophobic networks

Three different types of polymer networks (polymer resins) were investigated by flow microcalorimetry and selective liquid sorption from 1-propanol(1)-water(2) mixtures. Type 1 network structure is formed by non-polar, non-swelling, macroporous resins (Amberlite XAD-2, Amberlite XAD-4). The composite isotherms for alcohol sorption were S-shaped. 1-Propanol is preferentially sorbed up to x₁≈0.5. Macroreticular non-ionic resins, Amberlite XAD-7 and XAD-8, represent the second type of polymer structure. These particles have a considerable extent of swelling in the binary liquid mixture and 1-propanol was preferentially sorbed by the polymer. The composite isotherms were U-shaped and exhibit maxima and minima. The third type of network structure is attached to macroreticular polar, hydrophilic ion-exchange resins (Chelite-S, Amberlyste A-21). Depending on the composition range of the binary liquid mixture, the resins may swell to a different extent and water is preferentially embeded in the porous polymer network. The swelling of the polymer networks was monitored by the gravimetric technique in separate experiments. The sorption capacity determined from the liquid uptake of the resins was related to the sorption capacity derived from the reduced surface excess. The enthalpy effect accompanying the sorption process was determined by flow and immersion microcalorimetry. The enthalpy of displacement isotherms reveals differences in polarity and swelling ability of the polymer network fairly well. Structural changes in the adsorption layers and formation of alcohol-water clusters on the surfaces play an important role.     

Extraction of Organic Compounds from Aqueous Media by Amberlite XAD Resins

Abstract

Three Amberlite polymeric resins, XAD-2, XAD-4 and XAD-7, were evaluated for extraction efficiency from aqueous media of several organic compounds representing pesticides, polyaromatic hydrocarbons, phenols and phthalate esters. The three resins exhibited different extraction characteristics. The extraction efficiency of the resins was found to be dependent on pH conditions and, on the average, was best at pH7. At this pH the XAD-2 and XAD-4 resins yielded quantitative recoveries in the 90–100% range for most compounds at the 20–200ppb level. Recoveries by XAD-7 resins were lower for several compounds. The recovery of aldrin and o, p DDT under all conditions was relatively low (>68%) and showed a higher degree of variability than that obtained for the other compounds. Alkaline pH conditions were generally unfavourable for the extraction of phenolic compounds but acidification to pH2 was not found to be a necessary step for the quantitative extraction of the phenolic compounds. Acidification to pH2 further led to a decrease in the recovery of most compounds for XAD-4 resins. A combined resin column yielded extraction efficiencies comparable to the XAD-2 column at pH 7, but since the three resins possess different extraction characteristics, a mixture comprising all three is recommended for the preconcentration of organic compounds from environmental water samples containing a wide range of compounds.     

Some ion-exchange resins for anion-chromatography

The quaternary ammonium salts, n-butyltrimethylammonium iodide, 1,1,3,3-tetramethylbutyltrimethylammonium iodide, n-octadecyltrimethylammonium iodide and tri-n-dodecylmethylammonium iodide were synthesized from commercially available amines and together with n-hexadecyltrimethylammonium bromide tested for retention by a series of macroreticular resins (XAD-2, XAD-4, XAD-7, XAD-8 and XAD-11) for use as "surface" ion-exchangers in the chromatography of anions. Exchange-capacity studies of the coated resins showed that the non-polar XAD-2 and XAD-4 resins had retention characteristics superior to those of the polar resins and that pore size in the resin was more important than surface area per unit weight of resin. Tri-n-dodecylmethylammonium salts in XAD-2 gave the highest exchange capacity, with best retention under elution conditions. Columns prepared from this anion-exchanger were used to separate and analyse simple mixtures of anions (chloride, nitrate and sulphate) each within the 1-30 ppm range, by single-column operation with indirect photometric detection and also by conductivity detection with background-ion suppression. Though of use for the determination of anions in simple mixtures, the resolution and performance were generally poorer than those displayed by a commercial (Dionex) column. This is at least partly attributable to the inferior column-packing properties of the granular XAD-resin.     

Purification of soluble fulvic acid low concentrations by a diafiltration technique

The purification of soluble fulvic acids (FA) based on a diafiltration technique is carried out on antarctic water and snow samples, characterised by low humic compound content (0.1-0.8 mg/l). Results are compared with those of FA purified with the dialysis technique that, together with ion-exchange resins, performs an often used purification process. With the adopted procedure it is possible to minimise the high content of inorganic salts deriving in part from the isolation method XAD-8 adopted, as shown by FTIR, elemental and thermogravimetric analysis.     

Preparation of Amberlite XAD resins coated with dithiosemicarbazone compounds and preconcentration of some metal ions

The Amberlite XAD resins coated with dithiosemicarbazones were prepared and their collection behavior of metal ions from aqueous solution was investigated. Among the resins used, the reagent-loaded Amberlite XAD-7 was found to be superior for the collection of metal ions to other reagent-loaded resins used. The quantitative collection of mercury(II), palladium(II) and copper(II) was obtained from acidic medium, while cadmium(II) and lead(II) was obtained from neutral medium by the Amberlite XAD-7 resin coated with dimethylglyoxal bis(4-phenyl-3-thiosemicarbazone) (DMBS). These metal ions collected on the resin were easily eluted with a small volume of N,N-dimethylformamide as their DMBS chelates. This collection-elution method was applied to the determination of their metal ions by reversed-phase high performance liquid chromatography with a spectrophotometric detection.     

Preconcentration and determination of Ce, La and Pr by X-ray fluorescence analysis, using Amberlite XAD resins loaded with 8-Quinolinol and 2-(2-(5 chloropyridylazo)-5-dimethylamino)-phenol

8-Quinolinol (oxine) and 2-(2-(5 chloropyridylazo)-5-dimethylamino)-phenol (5ClDMPAP) were immobilized on the non ionic sorbents Amberlite XAD-4 and XAD-7. These loaded resins were used for the preconcentration of Ce, La and Pr. High preconcentration factors were obtained in each case. After the retention of these rare earths, the resins were measured as thin films by x-ray fluorescence spectrometry. Up to 50 ppm of REEs can be retained on these thin films.     

Isolation of organic water pollutants by xad resins and carbon

The recovery efficiencies of XAD resins −2, −4, −7, and −8 and of resin mixtures were measured using distilled water samples containing 13 organic pollutants. An equal-weight mixture of XAD-4 and XAD-8 was most efficient. XAD-2 and XAD-4/8 were further terted and found effective using tapwater. Carbon was tested as a sorbent for materials not well retained by the resins. In-column solvent washing before sample sorption was found to be as effective as Soxhlet extraction for removing background impurities. Some compounds can be desorbed from carbon by in-column solvent elution; others require Soxhlet extraction. An XAD-4/8 column in series with a carbon column was used to sample 1000 1 of tapwater. Halomethanes, n-hydrocarbons, polynuclear aromatic compounds and dibenzofuran in the order of ng/l were identified using a gas chromatograph-mass spectrometer-computer system.     

树脂基球状活性炭的制备及对二氧化碳吸附性能的研究

以四种离子交换树脂（两种强碱性树脂D201和D280、两种弱碱性树脂D301G和D301R）为原料,经过磺化、炭化、活化处理制备了树脂基球状活性炭。采用TG、SEM、N₂吸附等对球状活性炭的收率、表面形貌、比表面积进行了表征,研究了所制球状活性炭对CO₂的吸附性能。结果表明,磺化处理有助提高树脂球的炭化收率;得到的四种球状活性炭对CO₂吸附性能良好,强碱性树脂球原料比弱碱性树脂球更具有优势,其中,由强碱性树脂球D201制得的树脂球状活性炭在30 ℃下对CO₂的吸附量可达2.57 mmol/g;十次循环吸附之后,树脂球仍能保持很好的CO₂吸附性能。     

Separation and determination of traces of heavy metals complexed with humic substances in river waters by sorption on indium-treated amberlite xad-2 resin

A nonionic macroreticular styrene/divnylbenzene copolymer, Amberlite XAD-2 resin is pulverized to 1–10 μm and treated with indium ions to saturate traced of cation exchange sites for the quantitative separation of humic complexes from cations. A 100-ml filtered sample is passed through an indium-treated XAD-2 column (16 diameter, 5 mm tall) at pH 5 at a flow rate of 2 ml min^? to sorb heavy metals complexed with humic and fulvic acids. Inorganic cations and anions, EDTA complexes and colloidal hydrated iron(III) oxide are not retained on the column at all. The heavy metals sorbed on the column are then ultrasonically desorbed with 0.5 M nitric acid and determined by graphite-furnace atomic absorption spectrometry. The results fo two river water samples obtained are in good agreement with those obtained when the macroreticular weak-base anion-exchanger DEAE-Sephadex A-25 is used.     

Isolation and seasonal effects on characteristics of fulvic acid isolated from an Australian floodplain river and billabong

Fulvic acids from an Australian floodplain river and billabong were isolated using DEAE and DAX-8 resins, and characterised with the use of size exclusion chromatography and solid-state CP-MAS (13)C NMR spectroscopy. Differences between the two resin isolates were evident. Fulvic acids isolated using DEAE-cellulose had higher apparent M(n) and M(w) values, while the DAX-8 resin showed a slight preference for aliphatic components. Fulvic acids from the river and billabong had the same functional groups present, however, the river fulvic acids had higher apparent M(n) (number average molecular weight) and M(w) values (weight average molecular weight), and were more polydisperse than the billabong fulvic acid. There were no significant changes in the characteristics of the fulvic acid isolated from the river at four sampling times: summer, autumn, winter and spring. In contrast, fulvic acids isolated from a billabong displayed seasonal variation in molecular weights. This work emphasizes the importance in ecological studies of isolation procedure for the operationally defined fulvic acids.     

The use of solid-phase extraction and direct injection of a copolymer sorbent as slurry into the graphite furnace prior to determination of cadmium by ETAAS

Abstract

Several aquatic heterogeneous humic-solute fractions with known molecular-size ranges were fractionated further by coupled size-exclusion chromatography (SEC) and polyacrylamide gel electrophoresis (PAGE). The results of SEC-PAGE, obtained for several humic-solute fractions, corresponded reasonably well to the known molecular-size distributions of the dissolved organic matter (DOM). Despite the limited resolving power PAGE appears to offer an alternative coarse method, beside SEC, for fractionation of the heterogeneous humic matter (HM).     

Redox effects on resin extraction of herbicides from soil

Relative soil aeration affects the surfaces upon which pesticides adsorb and non-ionic resins offer a means of observing and evaluating this factor. A non-ionic resin extractor, developed for pesticide extraction under reducing conditions, was used to adsorb a fraction of the reversibly adsorbed (active portion) herbicides. The extractor consists of cleaned XAD-2 resin encased in a dialysis membrane composed of regenerated cellulose. Anaerobiosis was achieved by incubating soil suspensions with glucose under a 95% N(2)-5% H(2) environment until the redox potential reached -150 mV. Nine soils with a range of physical and chemical characteristics were examined for atrazine, metribuzin, and alachlor content. Amounts of atrazine, metribuzin, and alachlor extracted from soil ranged to 100, 140, and 75 ng g(-1), respectively. Resin extractions (RE) conducted under aerobic conditions recovered about 25-50% of the pesticide extractable with conventional solid phase solvent extraction at 60 degrees C (SPE(60)). Under anaerobic conditions, equal amounts of atrazine were extracted with RE and SPE(60). Slightly less metribuzin was recovered under anaerobic extraction with the exception of those soils lacking detectable amounts by SPE(60). Larger amounts of alachlor were extracted with resins under anaerobic conditions than under aerobic conditions but the amounts were not correlated with those determined by SPE(60). Large amounts of soil organic matter were solublized under anaerobiosis and smaller molecular weight material was extracted with the herbicides. The nature and amounts of co-extracted organic matter varied among soils. RE directly from soil suspensions enabled simultaneous determination of all three herbicides.     

Detoxification of lignocellulose hydrolysates with ion-exchange resins

Lignocellulose hydrolysates contain fermentation inhibitors causing decreased ethanol production. The inhibitors include phenolic compounds, furan aldehydes, and aliphatic acids. One of the most efficient methods for removing inhibiting compounds prior to fermentation is treatment of the hydrolysate with ion-exchange resins. The performance and detoxification mechanism of three different resins were examined: an anion exchanger, a cation exchanger, and a resin without charged groups (XAD8). A dilute acid hydrolysate of spruce was treated with the resins at pH 5.5 and 10.0 prior to ethanolic fermentation with Saccharomyces cerevisiae. In addition to the experiments with hydrolysate, the effect of the resins on selected model compounds, three phenolics (vanillin, guaiacol, and coniferyl aldehyde) and two furan aldehydes (furfural and hydroxymethyl furfural), was determined. The cation exchanger increased ethanol production, but to a lesser extent than XAD-8, which in turn was less effective than the an ion exchanger. Treatment at pH 10.0 was more effective than at pH 5.5. At pH 10.0, the anion exchanger efficiently removed both anionic and uncharged inhibitors, the latter by hydrophobic interactions. The importance of hydrophobic interactions was further indicated by a substantial decrease in the concentration of model compounds, such as guaiacol and furfural, after treatment with XAD-8.     

Chemical composition of natural colophony from Pinus brutia and comparison with synthetic colophony

The compositions of colophony resins obtained from Pinus brutia Ten trees by three different methods (acid paste, carved hole and scraping) from Ayvacik, G?kova and Kemalpa?a in Turkey were analyzed by capillary GC-MS. The main components were the monoterpenes alpha-pinene, beta-pinene, and delta3-carene, and the diterpenic resin acids palustric, abietic, kaur-9(11)-16-en-18-oic and neoabietic acid. The synthetic colophony resins exhibited similar contents to those of the natural resins obtained from the G?kova and Kemalpa?a regions of Turkey. However, colophony resins from Ayvacik exhibited only half the diterpenic acid content as those of the G?kova and Kemalpa?a resins. Out of the three techniques, the carved hole method caused rather different percentages in the constituents of the essential oils.     

Sorption of humic substances on a weakly basic anion-exchange resin: Relationship with the adsorbate structure

Adsorption of a broad range of humic substances (HS) of different origins and fractional compositions on a macroporous weakly basic anion-exchange resin is studied. It is found that the nature of the HS has a substantial effect on both the efficiency of sorption and the mechanism of interaction with the adsorbent. The dependence of the determined thermodynamic parameters of sorption on the HS origin, composition, and structure is shown for a broad range of HS. It is concluded that the results can be used to predict the sorption properties of weakly basic anion-exchange resins with respect to HS of known origin and structural group composition.