Hypothesis: Oxides, hydrous oxides and hydroxides of aluminium and iron are important in determining the availability of trace and heavy metals in soil systems. The presence of complexing anions is also known to affect the binding of these metals in soils. Since organophosphates, such as inositol hexaphosphate (IP6), are present in most soil systems they are expected to affect the nature of the interaction between metal ions and metal (hyr)oxides.
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February 2015
The sorption of Inositol hexaphosphate (IP6) onto gibbsite was investigated using a combination of adsorption experiments, (31)P solid-state MAS NMR spectroscopy, and surface complexation modeling. Adsorption experiments conducted at four temperatures showed that IP6 sorption decreased with increasing pH. At pH 6, IP6 sorption increased with increasing temperature, while at pH 10 sorption decreased as the temperature was raised.
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February 2012
Adsorption of inositol hexaphosphate (IP(6)) on goethite has been studied as a function of pH and concentration, and by use of Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR). While adsorption was highest at low pH, a significant amount remained adsorbed above pH 10 where, in the absence of IP(6), the surface is expected to have a net negative charge. The adsorption isotherm at pH 5.
View Article and Find Full Text PDFColloids Surf B Biointerfaces
September 2009
Attempts to measure the hydrophobicity of the cell surfaces of Gordonia amarae and Rhodococcus erythropolis, filamentous bacteria found in wastewater treatment plants, by several methods--microbial adhesion to hydrocarbons (MATH) or bacterial adhesion to hydrocarbons (BATH), contact angle, and micro-sphere adhesion to cells (MAC)--were unsuccessful. The results were erratic and inconsistent. This was in part because of the filamentous growth habit of G.
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May 2008
Bacteria have been implicated in the formation of viscous brown foams that can appear suddenly on wastewater treatment plants. Three strains of the filamentous bacterium Gordonia amarae, isolated from wastewater treatment plants, were investigated to determine their effect on foam formation and stabilisation. During the exponential phase of the bacterial growth a biosurfactant was formed, causing a significant drop in the surface tension of the filtered medium and the formation of persistent foam.
View Article and Find Full Text PDFJ Agric Food Chem
September 2007
Sorption of chlorpyrifos (CPF) from 2.85 microM (1 mg/L) aqueous solutions in 0.01 M NaCl to montmorillonite, kaolinite, and gibbsite was investigated at 25 degrees C.
View Article and Find Full Text PDFSorption of phosphate onto gibbsite (gamma-Al(OH)3) and kaolinite has been studied by both macroscopic and 31P solid-state NMR measurements. Together these measurements indicate that phosphate is sorbed by a combination of surface complexation and surface precipitation with the relative amounts of these phases depending on pH and phosphate concentration. At low pH and high phosphate concentrations sorption is dominated by the presence of both amorphous and crystalline precipitate phases.
View Article and Find Full Text PDFThe adsorption of mellitic acid (benzene-1,2,3,4,5,6-hexacarboxylic acid) onto kaolinite was investigated at five temperatures between 10 and 70 degrees C. Mellitic acid adsorption increased with increasing temperature at low pH (below pH 5.5), but at higher pH, the effect of increasing temperature was to reduce the amount adsorbed.
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May 2006
Sorption of the endocrine disrupting chemicals (EDCs) bisphenol A (BPA), 17alpha-ethynylestradiol (EE2) and estrone (E1) from 3 microM aqueous solutions in 10 mM KNO3 to goethite, kaolinite and montmorillonite was investigated at 25 degrees C. Uptake of the EDCs by goethite and kaolinite suspensions was <20%, and little affected by pH. Sorption by montmorillonite was greater, ranging from 20 to 60%, and steadily increased from about pH 7.
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April 2006
The adsorption of mellitic acid (benzene-1,2,3,4,5,6-hexacarboxylic acid) onto goethite was investigated at five temperatures between 10 and 70 degrees C. Mellitic acid adsorption increased with increasing temperature below pH 7.5, but at higher pH the effect of increasing temperature was to reduce the amount adsorbed.
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January 2003
The adsorption of Cd(II) onto goethite, kaolinite, and illite was measured as a function of pH (adsorption edges) and concentration (adsorption isotherms) at 25 degrees C. As the pH was increased, adsorption onto goethite occurred mainly in the pH range 5.5-8, whereas adsorption onto kaolinite occurred in two stages, separated by a plateau in the pH region 5.
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April 2005
Data from acid-base titrations at 25 degrees C of Zn(NO(3))(2) and 2-, 3-, or 4-aminopyridine in 10 mM KNO(3) as background electrolyte suggested that soluble complexes ZnL(2+) and Zn(OH)L(+) form, where L represents aminopyridine. Zinc-hydroxyaminopyridine complexes have not been reported previously. The cosorption of Zn(II) with each of the aminopyridines to K-saturated Wyoming (SWy-K) and Texas (STx-K), and Ca-enriched Texas (STx-Ca) montmorillonites was measured at 25 degrees C, with 10 mM KNO(3) or 3.
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April 2005
The sorption of 2-, 3-, and 4-aminopyridine on K-saturated Wyoming (SWy-K) and Texas (STx-K) and Ca-enriched Texas (STx-Ca) montmorillonite was measured at 25 degrees C with 10 mM KNO(3) or 3.3 mM Ca(NO(3))(2) as the background electrolyte. The aminopyridines adsorbed to montmorillonite at low pH, but not at high pH.
View Article and Find Full Text PDFThe nature of the interaction between mellitic acid (benzene hexacarboxylic acid) and the common soil mineral goethite (alpha-FeOOH) has been investigated as a function of pH and ionic strength by use of attenuated total reflection Fourier transform infrared spectroscopy. Molecular orbital calculations of the theoretical vibrational frequencies of the mellitate ion (L6-) and dihydrogen mellitate (H2L4-) have allowed the measured absorption frequencies to be accurately assigned. At pH values above 6, adsorption involves outer-sphere complexation of the deprotonated L6- ion.
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May 2004
The effect of aspartic acid on the adsorption of Pb(II), Cu(II), Zn(II), Co(II), and Mn(II) on kaolinite at 25 degrees C in the presence of 5 mM KNO3 was investigated by means of potentiometric titrations and adsorption measurements over a range of pH and concentration. Data were modeled by extended constant capacitance models. Aspartic acid slightly enhanced the adsorption of Pb(II), Zn(II), and Co(II) at low pH, but inhibited the adsorption of all the metal ions at higher pH.
View Article and Find Full Text PDFThe interaction of aspartic acid with kaolinite was studied by potentiometric titrations and by adsorption measurements both at constant aspartate concentration (but varying pH) and at a constant pH of 5.5. The temperature was 25 degrees C, and the ionic medium 5 mM KNO3.
View Article and Find Full Text PDFThis paper describes apreviously unreported problem with the use of N,O-bis-(trimethylsilyl)trifluoroacetamide (BSTFA) and N-(tert-butyldimethylsilyl)-N-methyltrifluoroacetamide (MTBSTFA) to derivatise the natural hormone estrone (E1) and the synthetic estrogen 17alpha-ethinylestradiol (EE2). The resulting trimethylsilyl (TMS) and t-butyldimethylsilyl (TBS) derivatives of EE2 were partially converted to their respective El derivatives. Therefore, these reagents may not be suitable for simultaneous determination of estrogens in environmental samples, which raises questions about the reliability of results from some earlier studies.
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February 2004
The adsorption of cadmium onto kaolinite and Muloorina illite in the presence of citric acid has been measured as a function of pH and cadmium concentration at 25 degrees C. When citric acid is present in the systems cadmium adsorption is slightly enhanced below pH 5, but significantly suppressed between pH 5 and 8, for both substrates. At higher citric acid concentrations very little cadmium adsorbs onto kaolinite from pH 5 to 8.
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January 2004
The adsorption of cadmium onto goethite in the presence of citric acid was measured as a function of pH and cadmium concentration at 25 degrees C. Potentiometric titrations were also performed on the system. Cadmium adsorption onto goethite was enhanced above pH 4 in the presence of 50 microM, 100 microM and 1 mM citric acid.
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November 2003
The adsorption of citric acid onto goethite, kaolinite, and illite was measured as a function of pH (adsorption edges) and concentration (adsorption isotherms) at 25 degrees C. The greatest adsorption was onto goethite and the least onto illite. Adsorption onto goethite was at a maximum below pH 5 and decreased as the pH was increased to pH 9.
View Article and Find Full Text PDFSorption of the endocrine-disrupting chemical 17beta-estradiol (E(2)) from aqueous solutions to goethite, an iron oxide, and the clay minerals kaolinite, illite, and montmorillonite (K and Ca forms) was measured at 25 degrees C. The clay minerals sorbed more E(2) than the oxide, with sorption capacity increasing in the order goethite
Scanning electron microscopy, surface area determination, elemental analysis, organic matter extraction and solid-state cross polarization/magic angle spinning and Bloch decay/magic angle spinning 13C nuclear magnetic resonance (NMR) spectroscopy were used to investigate distinctive features among carbonaceous combustion residues. Black carbon (BC) samples included diesel soot, urban dust, carbon black, chimney soot, vegetation fire residues, wood and straw charcoals. Particles varied from small spheres (<50 nm) in fossil BC (>100 m(2)/g), to large layered structures in plant-derived BC (generally <8 m(2)/g).
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