Interaction of Eu(III)/Cm(III) with alumina-bound poly(acrylic acid): sorption, desorption, and spectroscopic studies

This paper contributes to the comprehension of kinetic and equilibrium phenomena governing trace metal ion sorption on organic matter coated mineral particles. Sorption and desorption experiments were carried out with trivalent metal ions M(III) (M = Eu, Cm) and poly(acrylic acid) (PAA)-coated alumina colloids at pH 5 in 0.1 M NaClO4. Under these conditions, M(III) interaction with the solid is governed by sorbed PAA. The results were compared with spectroscopic data obtained by time-resolved laser-induced fluorescence spectroscopy (TRLFS). Within less than 30 s, a state of local equilibrium is reached between M(III) and adsorbed poly(acrylic acid). M(II) bound to the organic-mineral surface and to dissolved PAA keeps five water molecules in its first hydration sphere. Interaction of M(III) with alumina-bound PAA appears to be strongerthan with dissolved PAA. With increasing contact time, a change of the metal ion speciation occurs at the organic-mineral surface. This change is explained quantitatively by kinetically controlled reactions, which succeed a rapid local equilibrium. The experimental findings suggest, in agreement with model calculations, that a part of the initially sorbed M(III) is slowly converted to a kinetically stabilized species, thereby losing water molecules from the first coordination sphere as indicated by TRLFS. This species might be assigned as a ternary Al2O3-M(III)-PAA complex. The second part of the initially bound M(II) appears to experience as well kinetically controlled reactions, however, without showing changes in the first coordination sphere. We assume that the kinetic stabilization is the consequence of rearrangement processes of the PAA at the alumina surface.     

Incorporation of Eu(III) into hydrotalcite: a TRLFS and EXAFS study

The behavior of radionuclides in the environment (geo-, hydro-, and biosphere) is determined by interface reactions like adsorption, ion exchange, and incorporation processes. Presently, operational gross parameters for the distribution between solution and minerals are available. For predictive modeling of the radionuclide mobility in such systems, however, individual reactions and processes need to be localized, characterized, and quantified. A prerequisite for localization and clarification of the concerned processes is the use of modern advanced analytical and speciation methods, especially spectroscopy. In this study, Eu(III) was chosen as an analogue for trivalent actinides to identify the different species that occur by the Ln(III)/hydrotalcite interaction. Therefore, Eu(III) doped Mg-Al-Cl-hydrotalcite was synthesized and investigated by TRLFS, EXAFS, and XRD measurements. Two different Eu/hydrotalcite species were obtained. The minor part of the lanthanide is found to be inner-sphere sorbed onto the mineral surface, while the dominating Eu/hydrotalcite species consists of Eu(III) that is incorporated into the hydrotalcite lattice. Both Eu/hydrotalcite species have been characterized by their fluorescence emission spectra and lifetimes. Structural parameters of the incorporated Eu(III) species determined by EXAFS indicate a coordination number of 6.6 +/- 1.3 and distances of 2.41 +/- 0.02 A for the first Eu-OH shell.     

Uptake of Cm(III) and Eu(III) by calcium silicate hydrates: a solution chemistry and time-resolved laser fluorescence spectroscopy study

The interaction of the two chemical homologues [Cm(III) and Eu(III)] with calcium silicate hydrates (CSH phases) at pH 13.3 has been investigated in batch-type sorption studies using Eu(III) and complemented with time-resolved laser fluorescence spectroscopy (TRLFS) using Cm(III). The sorption data for Eu(III) reveal fast sorption kinetics and a strong uptake by CSH phases with distribution ratios of (6 +/- 3) x 10(5) L kg(-1). Three different Cm(III) species have been identified: A nonfluorescing species, which was identified as a curium hydroxide (surface) precipitate, and two fluorescing Cm(III)/CSH-sorbed species. The fluorescing sorbed species have characteristic emission spectra with main peak maxima at 618.9 and 620.9 nm and fluorescence emission lifetimes of 289 +/- 11 and 1482 +/- 200 micros, respectively. From the fluorescence lifetimes, it was calculated that the two fluorescing Cm(III) species have one or two and no water molecules left in their first coordination sphere, suggesting that these species are incorporated into the CSH structure. A structural model for Cm(III) and Eu(III) incorporation into CSH phases is proposed based on the substitution for Ca at two different types of sites in the CSH structure.     

Complexation of copper(ll) in organic soils and in dissolved organic matter--EXAFS evidence for chelate ring structures

Associations with functional groups of natural organic matter (NOM) are of great importance for bioavailability, toxicity, and mobility of trace metals in soils and waters. In this study, the coordination chemistry of copper, Cu(ll), in organic soils and dissolved organic matter (DOM) from soils and streams was investigated by extended X-ray absorption fine structure (EXAFS) spectroscopy. In both soil organic matter (SOM) and DOM (990-11 000 microg Cu g(-1) dryweight, pH 2.8-6.3), Cu(ll) was coordinated by 4 oxygen/ nitrogen (O/N) atoms at a distance of 1.92-1.95 angstroms in the first coordination shell. These four atoms are positioned in the equatorial plane of a Jahn-Teller distorted octahedron. In samples with a pH of 4.8-6.3, a second coordination shell with 2.0-3.8 C atoms was located at a distance of 2.76-2.86 angstroms. A significant improvement (19-39%) of the fit was obtained by including a third coordination shell with 2.0-3.8 O/C atoms involved in single scattering at an average distance of 3.69 angstroms and multiple scattering at an average distance of 4.19 angstroms. Our results provide evidence for inner-sphere complexation of Cu(ll) in NOM and suggest that Cu(ll) is complexed by either one or two five-membered chelate rings involving possible combinations of amino, carboxyl, or carbonyl functional groups. Ion activity measurements showed that less than 0.2% of total Cu was in the form of free Cu2+ in our samples at pH 4.8-6.3.     

Complexation of mercury(II) in soil organic matter: EXAFS evidence for linear two-coordination with reduced sulfur groups

The chemical speciation of inorganic mercury (Hg) is to a great extent controlling biologically mediated processes, such as mercury methylation, in soils, sediments, and surface waters. Of utmost importance are complexation reactions with functional groups of natural organic matter (NOM), indirectly determining concentrations of bioavailable, inorganic Hg species. Two previous extended X-ray absorption fine structure (EXAFS) spectroscopic studies have revealed that reduced organic sulfur (S) and oxygen/ nitrogen (O/N) groups are involved in the complexation of Hg(II) to humic substances extracted from organic soils. In this work, covering intact organic soils and extending to much lower concentrations of Hg than before, we show that Hg is complexed by two reduced organic S groups (likely thiols) at a distance of 2.33 A in a linear configuration. Furthermore, a third reduced S (likely an organic sulfide) was indicated to contribute with a weaker second shell attraction at a distance of 2.92-3.08 A. When all high-affinity S sites, corresponding to 20-30% of total reduced organic S, were saturated, a structure involving one carbonyl-O or amino-N at 2.07 A and one carboxyl-O at 2.84 A in the first shell, and two second shell C atoms at an average distance of 3.14 A, gave the best fit to data. Similar results were obtained for humic acid extracted from an organic wetland soil. We conclude that models that are in current use to describe the biogeochemistry of mercury and to calculate thermodynamic processes need to include a two-coordinated complexation of Hg(II) to reduced organic sulfur groups in NOM in soils and waters.     

Binding of organic ligands with Al(III) in dissolved organic matter from soil: implications for soil organic carbon storage

The binding characteristics of organic ligands with Al(III) in soil dissolved organic matter (DOM) is essential to understand soil organic carbon (SOC) storage. In this study, two-dimensional (2D) FTIR correlation spectroscopy was developed as a novel tool to explore the binding of organic ligands with Al(III) in DOM present in soils as part of a long-term (21-year) fertilization experiment. The results showed that while it is a popular method for characterizing the binding of organic ligands and metals, fluorescence excitation-emission matrix-parallel factor analysis can only characterize the binding characteristics of fluorescent substances (i.e., protein-, humic-, and fulvic-like substances) with Al(III). However, 2D FTIR correlation spectroscopy can characterize the binding characteristics of both fluorescent and nonfluorescent (i.e., polysaccharides, lipids, and lignin) substances with Al(III). Meanwhile, 2D FTIR correlation spectroscopy demonstrated that the sequencing/ordering of organics binding with Al(III) could be modified by the use of long-term fertilization strategies. Furthermore, 2D FTIR correlation spectroscopy revealed that the high SOC content in the chemical plus manure (NPKM) treatment in the long term fertilization experiment can be attributed to the formation of noncrystalline microparticles (i.e., allophane and imogolite). In summary, 2D FTIR correlation spectroscopy is a promising approach for the characterization of metal-organic complexes.     

Chromium(III)–docosahexaenoic acid complex: Synthesis and characterization

Supplements containing chromium in its trivalent oxidation state [Cr(III)] are used by diabetic patients to improve their glucose and insulin levels and omega-3 fatty acids are also beneficial for people with insulin resistance or diabetes. It seemed very useful to combine chromium(III) and omega-3 functional entities into single molecules. Here we synthesized and characterized a chromium cis-4,7,10,13,16,19-docosahexaenoic acid (DHA) complex, one of the two main components of the heterogeneous chromium(III) fish oil omega-3 concentrate products. Ethyl cis-4,7,10,13,16,19-docosahexaenoate was hydrolyzed with sodium hydroxide, and the generated salt was reacted in situ with chromium(III) chloride hexahydrate and converted into an oxo-centred trinuclear chromium(III) complex. A study of the DHA–chromium(III) complex by liquid chromatography/tandem mass spectrometry/(LC/MS/MS) is reported in this work. The data suggest a triaqua-μ3-oxohexakis-μ-docosahexaenoatotrichromium(1+), [Cr₃O(C₂₂H₃₁O₂)₆(H₂O)₃]⁺, core structure.     

Sorption of Eu(III) on humic acid or fulvic acid bound to hydrous alumina studied by SEM-EDS, XPS, TRLFS, and batch techniques

To identify the effect of humic acid (HA) and fulvic acid (FA) on the sorption mechanism of Eu(III) on organic--inorganic colloids in the environment at a molecular level, surface adsorbed/ complexed Eu(III) on hydrous alumina, HA-, and FA-hydrous alumina hybrids were characterized by using X-ray photoelectron spectroscopy (XPS) and time-resolved laser fluorescence spectroscopy (TRLFS). The experiments were performed in 0.1 mol/L KNO3 or 0.1 mol/L NaClO4 under ambient conditions. The pH values were varied between 2 and 11 at a fixed Eu(III) concentration of 6.0 x 10(-7) mol/L and 4.3 x 10(-5) mol/L. The different Eu(III)/FA(HA)/hydrous alumina complexes were characterized by their fluorescence emission spectra ((5D0-F1)/ (5D0 --> 7F2)) and binding energy of Eu(III). Inner-sphere surface complexation may contribute mainly to Eu(III) sorption on hydrous alumina, and a ternary surface complex is formed at the HA/ FA-hydrous alumina hybrid surfaces. The sorption and species of Eu(III) in ternary Eu-HA/FA-hydrous alumina systems are not dominated by either HA/FA or hydrous alumina, but are dominated by both HA/FA and hydrous alumina. The results are important for understanding the sorption mechanisms and the nature of surface adsorbed Eu(III) species and trivalent chemical homologues of Eu(III) in the natural environment.     

Binding of iron(III) to organic soils: EXAFS spectroscopy and chemical equilibrium modeling

The complexation of iron(III) to soil organic matter is important for the binding of trace metals in natural environments because of competition effects. In this study, we used extended X-ray absorption fine structure (EXAFS) spectroscopy to characterize the binding mode for iron(III) in two soil samples from organic mor layers, one of which was also treated with iron(III). In most cases the EXAFS spectra had three significant contributions, inner-core Fe-O/N interactions at about 2.02(2) A, Fe-C interactions in the second scattering shell at 3.00(4) A, and a mean Fe-Fe distance at 3.37(3) A. One untreated sample showed features typical for iron (hydr)oxides; however, after treatment of iron(III) the EXAFS spectrum was dominated by organically complexed iron. The presence of a Fe-Fe distance in all samples showed that the major part of the organically complexed iron was hydrolyzed, most likely in a mixture of complexes with an inner core of (O5Fe)2O and (O5Fe)3O. These results were used to constrain a model for metal-humic complexation, the Stockholm Humic Model (SHM). The model was able to describe iron(III) binding verywell at low pH considering only one dimeric iron(III)-humic complex. The competition effect on trace metals was also well described.     

金属离子及pH对谷氨酰胺发酵的影响

试验了金属离子及pH对谷氨酰胺发酵的影响。结果表明,在下述条件下谷氨酰胺产量最高:Zn2+为1.0mg,Fe2+为1.0mg,Mn2+为2.0mg（每100g培养基）;初始pH为7.0。      

Alkaline earth metal cation exchange: effect of mobile counterion and dissolved organic matter

The goal of this research was to provide an improved understanding of the interactions between alkaline earth metals and DOM under conditions that are encountered during drinking water treatment with particular focus on cation exchange. Both magnetically enhanced and nonmagnetic cation exchange resins were converted to Na, Mg, Ca, Sr, and Ba mobile counterion forms as a novel approach to investigate the exchange behavior between the cations and the interactions between the cations and DOM. The results show that cation exchange is a robust process for removal of Ca(2+) and Mg(2+) considering competition with cations on the resin surface and presence of DOM. DOM was actively involved during the cation exchange process through complexation, adsorption, and coprecipitation reactions. In addition to advancing the understanding of ion exchange processes for water treatment, the results of this work are applicable to membrane pretreatment to minimize fouling, treatment of membrane concentrate, and precipitative softening.     

离子色谱法测定诺丽果粉中常见有机酸和阴离子含量

采用戴安ICS-5000离子色谱建立了诺丽果粉中14种有机酸和阴离子的分离测定方法。实验利用电导检测器对诺丽果粉中常见有机酸和阴离子进行测定。采用Ion Pac AS11-HC分析柱（带Ion Pac AG11-HC保护柱）为色谱柱,以ASRS 300（4 mm）自循环电抑制模式,KOH作为淋洗液作梯度淋洗,流速为1.0 m L/min,柱温30℃为色谱条件实现诺丽果粉中有机酸和阴离子理想分离。方法拥有良好的线性（r≥0.9988）、检出限（≤0.508 mg/L）、回收率（91.50%¹07.22%）和重复性（RSD 0.18%⁵.2%,n=8）。诺丽果粉中含有的有机酸和阴离子主要是乳酸、苹果酸、草酸、柠檬酸、氯离子、硫酸根和磷酸根。其中乳酸含量为5.893 mg/g,苹果酸含量为74.631 mg/g,草酸含量为9.631 mg/g,柠檬酸含量为10.826 mg/g,氯离子含量为27.930 mg/g,硫酸根含量为4.226 mg/g,磷酸根含量为7.747 mg/g,丙酮酸含量为3.965 mg/g,其余几种分析组分未检出。该方法准确可靠,可用于诺丽果粉中有机酸和无机阴离子的定性、定量分析。      

Adsorption of Pb(ll) and Eu(III) by oxide minerals in the presence of natural and synthetic hydroxamate siderophores

Trihydroxamate siderophores have been proposed for use as mediators of actinide and heavy metal mobility in contaminated subsurface zones. These microbially produced ligands, common in terrestrial and marine environments, recently have been derivatized synthetically to enhance their affinity for transuranic metal cations. However, the interactions between these synthetic derivative and adsorbed trace metals have not been characterized. In this paper we compare a natural siderophore, desferrioxamine-B (DFO-B), with its actinide-specific catecholate derivative, N-(2,3-dihydroxy-4-(methylamido)benzoyl)desferrioxamine-B (DFOMTA), as to their effect on the adsorption of Pb(II) and Eu(III) by goethite and boehmite. In the presence of 240 microM DFO-B, a strongly depleting effect on Eu(III) adsorption by goethite and boehmite occurred above pH 6. By contrast, almost total removal of Eu(III) from solution in the neutral to slightly acidic pH range was observed in the presence of either 10 or 100 microM DFOMTA, due primarilyto the formation of metal-DFOMTA precipitates. Addition of DFOMTA caused an increase in Pb(II) adsorption by goethite below pH 5, but a decrease above pH 5, such that the Pb(II) adsorption edge in the presence of DFOMTA strongly resembled the DFOMTA adsorption envelope, which showed a maximum near pH 5 and decreasing adsorption toward lower and higher pH.     

The effect of supplementing red deer (Cervus elaphus) with different forms of ascorbic acid upon the concentration of ascorbic acid in rumen fluid and blood plasma

Two indoor experiments were conducted at the Massey University Deer Research Unit to study whether the blood plasma ascorbic acid (AA) concentration in farmed red deer (Cervus elaphus) could be raised, using a single large intraruminal administration of AA (2.7 g kg^?1 live weight) prior to a simulated slaughter situation. Deer fistulated in the rumen were individually fed chaffed lucerne hay ad libitum at 30 min intervals; feed was then withdrawn 8 h before AA was administered, and fasting continued during the period of rumen fluid and blood sampling (30 h of fasting in total). Blood (jugular vein) and rumen fluid samples were taken 15 min before and at various intervals after dosing with AA. Rumen fluid pH values were also recorded. In Experiment 1 the effects of administration of pure ascorbic acid (AA), ethyl cellulose‐coated ascorbic acid (EC) and silicone‐coated ascorbic acid (SC) were compared. All three types increased rumen fluid and blood plasma AA concentrations to a desirable level (500 µg ml^?1 blood plasma or greater), with the maximum concentrations in both sites occurring 1 h after administration. The area under the concentration versus time curve (AUC), the area under the curve corrected for baseline concentration (AUCB) and the maximum concentration (MAX) of AA in both rumen fluid and blood plasma were not significantly different among the three formulations of AA, indicating that all three were degraded at similar rates in the rumen and that their bioavailabilities were similar. Rumen pH decreased from approximately 7.0 to 5.0 within 1 h of administering each compound, increased to 6.0 after 4 h and then progressively increased to approximately 7.0 after 22 h. Experiment 2 was conducted to investigate the rumen‐buffering effect after dosing with AA with and without added sodium bicarbonate. Including NaHCO₃ increased rumen pH by approximately 1 unit during the first hour after dosing and by 0.7–0.4 units thereafter. AUC and AUCB for rumen fluid were significantly lower for the AA + NaHCO₃ group of deer than for the AA group (p < 0.05), indicating that increasing rumen pH increased the rate of ruminal destruction of AA. AUC, AUCB and MAX of AA in blood plasma were not statistically different between the two treatments (p > 0.05). It was concluded that the single large intraruminal AA dose technique could be used to consistently increase AUC, AUCB and MAX of AA in both rumen fluid and blood plasma. Methods for improving the efficiency of the technique are discussed. © 2002 Society of Chemical Industry     

Effects of the rootstock Ramsey (Vitis champini) on ion and organic acid composition of grapes and wine, and on wine spectral characteristics

The influence of Ramsey, used as rootstock of the scion cvs Muscat Gordo Blanco (syn. Muscat of Alexandria), Shiraz (syn. Syrah), Riesling, Cabernet Sauvignon and Chardonnay, on the characteristics of the grape berries and of wine made from them was investigated, comparing ‘own-rooted’ and ‘grafted’, and comparing wine fermented as juice (without skins) and must (juice and skins). The study involved the partitioning of K+ within berries, changes in juice K+, malic and tartaric acid through fermentation, wine inorganic ion and organic acid composition, and wine spectral characteristics. K+ concentration was higher in berries from grafted than from own-rooted for all varieties except Chardonnay, and highest for grafted Shiraz. It was higher in skin than in pulp and seeds. In the pulp, it was highest for grafted Shiraz. K+ concentrations in all ferments using must (i.e. juice plus skins) increased during the initial two days after crushing, with the increase reflecting extraction from skins, being greatest for Shiraz and Muscat Gordo Blanco. Tartaric acid concentration in must also increased during the initial two days after crushing and then decreased. Malic acid concentration was higher in juice of Ramsey-grafted than own-rooted vines, especially for Shiraz; concentrations did not change markedly during the initial 12 days of fermentation, except where malo-lactic fermentation occurred. Wine made from grapes of grafted contained significantly less tartaric and more malic acid than that made from own-rooted for all varieties and for both fermentation types, with the exception of tartaric acid in wine of Muscat Gordo Blanco fermented as must. Wine made from juice had significantly higher tartaric acid and lower malic acid than that made from must for all varieties except for tartaric acid in wine from grafted Shiraz and malic acid in own-rooted Chardonnay. Wine had a smaller tartaric acid/malic acid ratio when made from must. Wine pH was positively correlated with K+ but negatively with tartaric acid and with the tartaric acid to malic acid ratio. Overall, Shiraz wine contained highest Cl?, Na+ and K+ concentrations. Red wines obtained from grafted had higher colour hue, especially those from Shiraz. Wines made from fruit borne on own-rooted Cabernet Sauvignon had the highest concentration of total anthocyanins, ionised anthocyanins and total phenolics.     

Photodegradation of a ternary iron(III)-uranium(VI)-citric acid complex

The mechanisms of photodegradation of binary iron- and uranium-citrate and ternary iron-uranium-citrate complexes were elucidated. Citric acid degradation products were identified by HPLC and GC, and the metal precipitates were identified by XRD and EXAFS. Photodegradation of a binuclear iron-citrate complex occurred as a result of two one-electron oxidations of citric acid with the formation of 3-oxoglutarate and two ferrous ions. The ferrous ions were reoxidized by a photo-Fenton reaction, resulting in the precipitation of iron as two-line ferrihydrite Fe(OH)3. The citric acid in the uranium-citrate complex underwent a two-electron oxidation to acetoacetate with the concomitant reduction of U(VI) to U(IV). The U(IV) was subsequently photooxidized in the presence of dioxygen with precipitation of uranium as the mineral schoepite (UO3 x 2H2O). A two-step electron reduction of two ferric ions to two ferrous ions wasthe primary mechanism for photodegradation of the ternary iron-uranium-citrate complex with oxidation of citric acid to 3-oxoglutarate; reduction of uranium was not observed. The iron precipitated as ferrihydrite and the uranyl ion as a uranyl hydroxide species. These results show the potential application of photochemical treatment of wastewater and decontamination solutions containing binary and ternary iron- and uranium-citrate complexes.     

Effects of increasing acidity on metal(loid) bioprecipitation in groundwater: column studies

Large-scale column experiments were carried out over a period of 545 days to assess the effect of increasing acidity on bacterial denitrification, sulfate reduction, and metal(loid) bioprecipitation in groundwater affected by acid mine drainage. At a groundwater pH of 5.5, denitrification and Cu2+ removal, probably via malachite (Cu2(OH)2CO3) precipitation, were observed in the ethanol-amended column. Sulfate reduction, sulfide production, and Zn2+ removal were also observed, with Zn2+ removal observed in the zone of sulfate reduction, indicating likely precipitation as sphalerite (ZnS). Se6+ removal was also observed in the sulfate reducing zone, probably as direct bioreduction to elemental selenium via ethanol/acetate oxidation or sulfide oxidation precipitating elemental sulfur. A step decrease in groundwater pH from 5.5 to 4.25 resulted in increased denitrification and sulfate reduction half-lives, migration of both these redox zones along the ethanol-amended column, and the formation of an elevated Cu2+ plume. Additionally, an elevated Zn2+ plume formed in the previous sulfate reducing zone of the ethanol-amended column, suggesting dissolution of precipitated sphalerite as a result of the reduction in groundwater pH. As Cu2+ passed through the zone of sphalerite dissolution, SEM imaging and EDS detection suggested that Cu2+ removal had occurred via chalcocite (Cu2S) or covellite (CuS) precipitation.     

Fatty acid composition of mixed-rumen bacteria: effect of concentration and type of forage

The effects of concentration and type of forage in the diet on lipid content and fatty acid (FA) composition of rumen bacteria were studied in 14 goats fitted with duodenal cannulas. The goats were fed a complete maintenance diet containing 40, 70, or 100% chopped forage (dry matter basis) in two equal meals. Forage was either corn stover or alfalfa hay. Microbial cell matter (MCM) was isolated by differential centrifugation of duodenal contents. The FA content of the MCM varied from 5 to 11% of DM and decreased with forage level in the diet. Main FA in MCM were C18:0 and C16:0: together they accounted for 70% of total FA in MCM. The mono-unsaturated FA and branched-chain FA (iso-FA and anteiso-FA) each represented about 10% of FA by weight. The proportion of even-chain saturated FA decreased and those of odd- and branched-chain FA increased with increasing forage. With the corn stover-based diet even-chain saturated FA were lower than with the alfalfa hay-based diet, whereas the unsaturated FA, odd-chain FA, and branched-chain FA were higher. The neutral detergent fiber content of the diet seemed to explain most of the variation associated with even-chain saturated FA, and odd- and branched-chain FA. Our results suggest that, for diets not supplemented with fat, mixed rumen bacteria accumulated energy reserves, by increasing synthesis of either even-chain saturated FA, or saturated odd-chain FA and saturated branched-chain FA.     

有机酸蒙囿铝(Ⅲ)配合物与皮胶原反应性的研究

研究了有机酸蒙囿铝 (Ⅲ )配合物溶液各段 GFC分离流份中的配合物与皮胶原的反应性 ;同时考察了不同鞣制工艺条件下有机酸蒙囿铝 (Ⅲ )配合物与胶原的反应性。     

Antimony(III) binding to humic substances: influence of pH and type of humic acid

Conditional distribution coefficients (Dom) for Sb(III) binding to three commercial humic acids (terrestrial, coal, and aquatic) were measured at environmentally relevant Sb(III)/DOC ratios and as a function of pH using an equilibrium dialysis method. Maximum binding of Sb(III) was observed around pH 6 for two of the humic acids. The third humic acid showed constant Dom values up to pH 6 and decreasing Dom values for pH > 6. Sb(III)/DOC ratio was found to be important for Dom (20 times higher Dom for 60 times lower Sb(III)/DOC ratio). Moreover, Dom depends on the individual humic acid, suggesting that different functional groups are involved and/or different degrees of stabilization by chelation or H-bridges. Chemical modeling of Sb(III)-humics binding at different pH values is consistent with two binding sites involving (i) a phenolic entity forming a neutral complex and (ii) a carboxylic entity forming a negatively charged complex. Under environmentally relevant conditions, over 30% of total Sb(III) may be bound to natural organic matter.