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Summary Although the binding of pesticides to organic carbon in soil, especially to humic acid (HA), is well recognized, the mechanisms
have not been completely explained. This publication deals with adsorption of atrazine and terbuthylazine by humic acid under
different experimental conditions, including adsorption times longer than those used hitherto. Direct HPLC analysis of HA
suspensions is assessed as an alternative to more complicated techniques for estimation of free triazines, and compared with
combined solid-phase extraction and HPLC. Experimental conditions such as time of exposure, addition of neutral salt, pH of
the suspension, and HA concentration have a significant impact on the extent of triazine adsorption. At alkaline pH, triazines
become partitioned in the HA fraction because of its hydrophobicity, whereas at acidic pH hydrogen-bonding probably occurs
between triazine molecules and humic acid polymers.
Presented at Balaton Symposium on High-Performance Separation Methods, Siófok, Hungary, September 1–3, 1999 相似文献
3.
Kelly M ElkinsDonald J Nelson 《Coordination chemistry reviews》2002,228(2):205-225
Aluminum ion (Al3+) in the ‘free’ (aquo) state is becoming increasingly prevalent in environmental waters, especially fresh waters, as a consequence of acid rain and other environmental processes. As Al3+ ion is known to affect markedly a wide range of biological systems, and since the presence of Al3+ in humans has been linked to a number of human diseases, it is important to understand the speciation of Al3+ ion in natural waters. Since some of the most important complexation agents for Al3+ in both fresh and sea waters are members of the complex humic substances group, it is important to understand the manner in which Al3+ interacts with this class of molecules, especially since binding of Al3+ to these molecules can effectively increase the bioavailability of this toxic metal ion to biological systems. The objective of this review is to present the current state of our understanding of aqueous aluminum complexation with the most acidic members (and therefore the most likely candidates for serving as Al3+ complexing agents) of the humic substances group, the fulvic acids. Much of the current knowledge has been revealed by comprehensive fluorescence titration analyses. Some additional information has come from other experimental approaches, including infrared spectroscopy, nuclear magnetic resonance spectroscopy, and a variety of electrochemical approaches. In this review, we also report on the results of our recent fluorescence and IR spectroscopy survey of the interaction of metals from of all three Nieboer and Richardson categories of environmental metals (Class A, Class B and Intermediate Class) with the fulvic acid sub-group of the humic substances. This has proven helpful in understanding some of the unique spectral behaviors of the Al3+-fulvic acid complex vis-a-vis fulvic acid complexes with many other metal ions. The results of our fluorescence and IR experiments with the model compounds, such as salicylic and phthalic acids, have allowed confirmation of the important roles played by both salicylic acid-like sites and phthalic acid-like sites in the unique complexation of Al3+ to humic substances, and help to explain some of the observed spectroscopic changes associated with Al3+ ion complexation to humic material. From the current work, it seems clear that major sources of the deviation in spectral properties between Al3+ and many other metal ions (across all three Nieboer and Richardson categories) are the unusually high value of its charge density and relatively low propensity for involvement in covalent bonding interactions (i.e. a very high ionic index combined with a relatively low covalent index in the Nieboer and Richardson classification of environmental metals), as well as affinity for certain functional groups. 相似文献
4.
Ultrafiltration fractionation and liquid chromatography (LC) have been applied to the study of the binding and hydrolysis of the polar herbicide atrazine on a stoichiometrically well characterized fulvic acid. Binding requires extensive carboxylate site protonation but the binding sites represent a very small fraction of total carboxylate. The data show that binding of atrazine is not competitive with binding of the hydrolytic product hydroxyatrazine. However, smaller molecular weight fractions of the fulvic acid mixture compete with atrazine for sites on the larger molecular weight fraction. Binding equilibrium is not rapid. A model of binding involving hydrogen bonding and/or charge-transfer complexing to specific sites created dynamically by the conformational equilibria of the higher molecular weight polymeric fulvic acid fractions is proposed as the best accommodation of the variety of observed facts. 相似文献
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Surface-area-exclusion chromatography using Whatman glass microfibre filters modified by adsorption of aluminium ions as
a stationary phase was used to evidence the different interfacial behaviour of aluminium ion complexed (tritium labelled)
humic acids. Histograms with adsorption peaks, plateaux and humps on the stationary phase showed the various adsorption characteristics
of the modified humic acid. The absence of adsorption for those constituents which were recovered in the effluent showed the
very low degrees of complexation by aluminium ions to be responsible for the absence of interaction of the components with
the stationary phase.
Received: 24 July 2000 Accepted: 20 December 2000 相似文献
7.
Sutlovic D Gamulin S Definis-Gojanovic M Gugic D Andjelinovic S 《Electrophoresis》2008,29(7):1467-1472
Human DNA quantification by quantitative real-time PCR (QRT-PCR) has gained great importance in forensic DNA and ancient DNA studies. However, in such samples, DNA quantification is impaired by the frequently present humic acid (HA). We have previously shown that the addition of synthetic HA inhibits QRT-PCR. In this study we investigated the possible mechanisms of HA interaction with human DNA, and kinetics of QRT-PCR inhibition. In QRT-PCR with pure human DNA and no HA added, VMAX was 40. With DNA sample containing 4 microg/mL of HA, VMAX was 30.30 while the addition of extra Taq polymerase to the same sample changed VMAX into 38.91, amplifying between 80 and 90% of input DNA. The KM/VMAX ratio in all the samples remained constant, indicating that the mechanism of HA inhibition of QRT-PCR is uncompetitive by nature. Moreover, HA shifts the human DNA melting temperature point (Tm) from 75 to 87 degrees C and inhibits DNase I-mediated DNA cleavage, most probably affecting the enzyme's activity. 相似文献
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The phenolic-group capacities of five humic substances, such as, the Aldrich humic acid, the humic and fulvic acids extracted from a soil, the humic and fulvic acids extracted from a peat have been precisely determined by the non-aqueous potentiometric titration technique. The titration by KOH in the mixed solvent of DMSO:2-propanol:water = 80:19.3:0.7 at [K+] = 0.02 M enabled to measure the potential change in a wide range of pOH (=−log [OH−]), and thus to determine the capacities of phenolic groups which could not be precisely determined in the aqueous titration. The results of the titration revealed that the mean protonation constants of the phenolic groups were nearly the same for all humic substances and close to that of phenol in the same medium, indicating that each phenolic-group in the humic substances is rather isolated and is not electronically affected by other affecting groups in the humic macromolecule. 相似文献
9.
Julien Brevet Francis Claret Pascal E. Reiller 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2009,74(2):446-453
Although a high heterogeneity of composition is awaited for humic substances, their complexation properties do not seem to greatly depend on their origins. The information on the difference in the structure of these complexes is scarce. To participate in the filling of this lack, a study of the spectral and temporal evolution of the Eu(III) luminescence implied in humic substance (HS) complexes is presented. Seven different extracts, namely Suwannee River fulvic acid (SRFA) and humic acid (SRHA), and Leonardite HA (LHA) from the International Humic Substances Society (USA), humic acid from Gorleben (GohyHA), and from the Kleiner Kranichsee bog (KFA, KHA) from Germany, and purified commercial Aldrich HA (PAHA), were made to contact with Eu(III). Eu(III)-HS time-resolved luminescence properties were compared with aqueous Eu3+ at pH 5. Using an excitation wavelength of 394 nm, the typical bi-exponential luminescence decay for Eu(III)-HS complexes is common to all the samples. The components τ1 and τ2 are in the same order of magnitude for all the samples, i.e., 40 ≤ τ1 (μs) ≤ 60, and 145 ≤ τ2 (μs) ≤ 190, but significantly different. It is shown that different spectra are obtained from the different groups of samples. Terrestrial extract on the one hand, i.e. LHA/GohyHA, plus PAHA, and purely aquatic extracts on the other hand, i.e., SRFA/SRHA/KFA/KHA, induce inner coherent luminescent properties of Eu(III) within each group. The 5D0 → 7F2 transition exhibits the most striking differences. A slight blue shift is observed compared to aqueous Eu3+ (λmax = 615.4 nm), and the humic samples share almost the same λmax ≈ 614.5 nm. The main differences between the samples reside in a shoulder around λ ≈ 612.5 nm, modelled by a mixed Gaussian–Lorentzian band around λ ≈ 612 nm. SRFA shows the most intense shoulder with an intensity ratio of I612.5/I614.7 = 1.1, KFA/KHA/SRHA share almost the same ratio I612.5/I614.7 = 1.2–1.3, whilst the LHA/GohyHA/PAHA group has a I612.5/I614.5 = 1.5–1.6. This shows that for the two groups of complexes, despite comparable complexing properties, slightly different symmetries are awaited. 相似文献
10.
van Zomeren A van der Weij-Zuiver E Comans RN 《Analytical and bioanalytical chemistry》2008,391(6):2365-2370
Characterization of humic substances (HS) in environmental samples generally involves labor-intensive and time-consuming isolation
and purification procedures. In this paper, the development of an automated system for HS isolation and purification is described.
The novelty of the developed system lies in the way the multiple liquids and columns used in the isolation/purification procedure
are handled in both forward and back-elution mode by solenoid valves. The automated procedure significantly reduces the total
throughput time needed, from 6–7 days to 48 h, and the amount of labor to obtain purified HS for further characterization.
Chemical characterization of purified HS showed that results were in good agreement with previously published values for HS
from a variety of sources, including the IHSS standard HS collection. It was also shown that the general properties of HS
were consistent among the different source materials (soil, waste, aquatic) used in this study. The developed system greatly
facilitates isolation and characterization of HS and reduces the risk of potential (time-dependent) alteration of HS properties
in the manual procedure.
Figure Photograph of the rear (left) and front (right) of the automated system for the isolation and purification of humic substances
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
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Rapid determination of atrazine in environmental water samples by a novel liquid phase microextraction 总被引:2,自引:0,他引:2
Qing Xiang Zhou Guo Hong Xie Long Pang 《中国化学快报》2008,19(1):89-91
A novel method was described for the rapid determination of atrazine using dispersive liquid phase microextraction in combination with high performance liquid chromatography (HPLC). Possible impact parameters such as sample pH, extraction and disperser solvents, salting-out effect, and extraction time were investigated. The experimental results indicated that proposed method possessed an excellent analytical performance, The linear range, detection limit, and precision (R.S.D.) were 0.1- 50 ng mL- 1 (R2 = 0.9955), 0.601 ng mL- 1 and 6,4%, respectively. The proposed method was validated with the real water samples, and the spiked recoveries were in the range of 69.9-89.8%, respectively. These results indicated that the established method with high enrichment factor, short extraction time was an excellent alternative for the routine analysis of atrazine in environmental samples. 2007 Qing Xiang Zhou. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved. 相似文献
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The aim of this study was to improve the flocculation of wastewater from gravel pits, especially the separation of the finely dispersed inorganic particles and the removing of humic acid. Clay was used as a model to investigate the influence of humic acid on the flocculation with two different types of polycation. The dependence of the sedimentation behaviour on time was investigated as well as the turbidity of the supernatant and the light absorption as a measure for humic acid removal. Bridging of particles remained the dominant mechanism of particle destabilisation by treating the clay in water with cationic polyacrylamides of very high molecular mass (CPAM). Poly(diallyldimethylammonium chloride) (PDADMAC) of lower molar mass (35 000 g/mol) was found to act by charge neutralisation. In this case the so-called flocculation window was very small. This behaviour is the same for systems containing humic acid. However, the need for cationic flocculant increases because humic acid as a weak polyanion can interact with the polycation. By using CPAMs with low charge this interaction does not play a significant role. The optimum flocculation concentration is relatively high. The flocs are larger and the velocity of sedimentation is higher than for the short-chain and highly charged polycation PDADMAC. However, because the latter is more effective in removal of humic acid at the point of optimum flocculation it is more advantageous to combine the highly charged polycation with a high molecular weight polyanion (dual system). 相似文献
15.
The adsorption of humic acid (HA) on kaolin particles was studied at various conditions of initial solution pH, ionic strength and solid-to-liquid ratio. The resulting affinity of interactions between humic acid and kaolin was attributed to the surface coordination of HA in ambient suspensions of mineral particles and the strong electrostatic force at low pH. Addition of inorganic salt can also influence the adsorption behavior by affecting the HA molecular structure, the clay particle zeta potential and so on. Equilibrium data were well fitted by the Freundlich model and implied the occurrence of multilayer adsorption in the process. In addition, the enthalpy dependent of system temperature was 79.17 kJ/mol, which proved that the mechanism of HA adsorption onto kaolin was comprehensive, including electrostatic attraction, ligand complexation and hydrogen bonding. 相似文献
16.
Soil samples were collected from an antimony smelting site in Guangxi Zhuang Autonomous Region, China, at four locations characterized by different land usage, including two cultivated sites: one formerly cultivated and one uncultivated. Surface soils from all four sites were heavily polluted by toxic metals including antimony (Sb), lead (Pb) and arsenic (As), and their concentrations were 410-3330 mg·kg−1, 410-3690 mg·kg−1 and 200-460 mg·kg−1, respectively. In the uncultivated area metal levels were 1.4-6.2 times higher as compared to the formerly and currently agriculture land. Lower levels at the cultivated sites may have resulted from an accumulation of airborne particles by vegetation and lower contents in the surface soil. However, the elevated mercury (Hg) content may reflect both natural and anthropogenic origins in this smelting site. Soil-derived humic acid (HA) from the smelting site reacted directly with Sb (III) aqueous solutions with concentrations of 12, 71 and 143 mg·g−1. The maximum Sb (III) binding to the soil-derived HA was 253 μmol·g−1 (added concentration of 71 mg·g−1) and showed more binding (up to 50%) at lower Sb content. 相似文献
17.
Direct contact membrane distillation of humic acid solutions 总被引:3,自引:0,他引:3
Direct contact membrane distillation process has been conducted for the treatment of humic acid solutions using microporous polytetrafluoroethylene and polyvinylidene fluoride membranes. The membranes were characterized in terms of their non-wettability, pore size and porosity. Water advancing and receding contact angles on the top membrane surfaces were measured. Experiments were also carried out employing pure water as feed at different mean temperatures and the water vapor permeance of each membrane was determined. Different humic acid concentrations in the feed solution, pH values and transmembrane temperature difference were tested. The direct contact membrane distillation technique is more adequate for the treatment of humic acid solutions than the applied pressure-driven separation processes, as lower membrane fouling was detected. 相似文献
18.
Aishwarya Jain Kartikey Yadav Manoj Mohapatra S.V. Godbole B.S. Tomar 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2009,72(5):1122-1126
Time resolved fluorescence spectroscopy (TRFS) of Eu(III) (an analogue of trivalent actinides) complexation with humic acid (HA) and its model compounds, namely phthalic acid (PA), mandelic acid (MA) and succinic acid (SA) has been carried out at varying concentration ratios of ligand to metal ion. The emission spectra were recorded in the range of 550–650 nm by exciting at an appropriate wavelength. The intensity of the 616 nm peak of Eu(III) was found to be sensitive to complexation. The ratio of the intensities of 616 and 592 nm peaks was used to determine the stability constants of Eu-phthalate, Eu-mandelate and Eu-succinate complexes. In the case of model compounds, the life-time was found to increase with increasing ligand to metal ratio (L/M) indicating the decrease in quenching of the fluorescence by coordinated water molecules with increasing complexation. On the other hand in the case of HA, the life-time was found to be constant at least up to L/M of 5, indicating the formation of outer sphere complex. Beyond L/M = 5 the life-time value was found to increase which can be attributed to the binding of the metal ion to the higher affinity sites in the HA macromolecule. 相似文献
19.
《Journal of Coordination Chemistry》2012,65(19):3492-3501
Four MnIII-porphyrin complexes, chloro(tetraphenylporphinato)MnIII(1,6-diaminohexane), bromo(tetraphenylporphinato)MnIII(1,6-diaminohexane), azido(tetraphenylporphinato)MnIII(1,6-diaminohexane), and thiocyanato(tetraphenylporphinato)MnIII(1,6-diaminohexane), have been synthesized. These complexes have been characterized using UV-Vis, IR, ESI-mass spectra, elemental analyses, magnetic susceptibility measurements, and conductivity measurement. The molar conductance values of these complexes in ethanol indicate non-electrolytes. The utility of these complexes in de-polymerization of coal using humic acid as the coal model has been tested by the optical density method. 相似文献
20.
Effect of pH and ionic strength on the interaction of humic acid with aluminium oxide 总被引:4,自引:0,他引:4
E. Tombácz Á. Dobos M. Szekeres H. D. Narres E. Klumpp I. Dékány 《Colloid and polymer science》2000,278(4):337-345
The effect of pH and neutral electrolyte on the interaction between humic acid/humate and γ-AlOOH (boehmite) was investigated.
The quantitative characterization of surface charging for both partners was performed by means of potentiometric acid–base
titration. The intrinsic equilibrium constants for surface charge formation were logK
a,1
int=6.7±0.2 and logK
a,2
int = 10.6±0.2 and the point of zero charge was 8.7±0.1 for aluminium oxide. The pH-dependent solubility and the speciation of
dissolved aluminium was calculated (MINTEQA2). The fitted (FITEQL) pK values for dissociation of acidic groups of humic acid were pK
1 = 3.7±0.1 and pK
2 = 6.6±0.1 and the total acidity was 4.56 mmol g−1. The pH range for the adsorption study was limited to between pH 5 and 10, where the amount of the aluminium species in the
aqueous phase is negligible (less than 10−5 mol dm−3) and the complicating side equilibria can be neglected. Adsorption isotherms were determined at pH ∼ 5.5, ∼8.5 and ∼9.5,
where the surface of adsorbent is positive, neutral and negative, respectively, and at 0.001, 0.1, 0.25 and 0.50 mol dm−3 NaNO3. The isotherms are of the Langmuir type, except that measured at pH ∼ 5.5 in the presence of 0.25 and 0.5 mol dm−3 salt. The interaction between humic acid/humate and aluminium oxide is mainly a ligand-exchange reaction with humic macroions
with changing conformation under the influence of the charged interface. With increasing ionic strength the surface complexation
takes place with more and more compressed humic macroions. The contribution of Coulombic interaction of oppositely charged
partners is significant at acidic pH. We suppose heterocoagulation of humic acid and aluminium oxide particles at pH ∼ 5.5
and higher salt content to explain the unusual increase in the apparent amount of humic acid adsorbed.
Received: 20 July 1999 /Accepted in revised form: 20 October 1999 相似文献