Water Sorbed Onto Solids

1 Water Sorbed Onto Solids. The microdynamics of water and oil on Si02 

Adsorbed palladium leads to the increase of the relaxation times of liquids 

Yamada, T. Tsuda, C. Holst, T. Okuda, H. Ehrenberg, I. Svoboda, H.G. Krane and H. Fuess, 

Duddeck, R. Bradenabl, L. Stefaniak, J. Jazwinski and B. Kamienski, Magn. Reson. Chem., 2001, 39, 709. 

Hiraki, T. Takabasbi, R. Kondo, S. Kagoshima, T. Hasegawa, T. Mochida and Y. Iwasa, 

Molecules Sorbed onto Solids - This section is divided into two subsections Water Sorbed onto Solids and Atoms and other Molecules Sorbed onto Solids . 

2200 j Pietrass, R. Seydoux, R.E. Roth, H. Eckert, and A. Pines, Solid State Nucl. Magn. 

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105A(Progress in Zeolite and Microporous Materials, pt. A), 463 

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In natural waters, arsenic may exist as one or more dissolved species, whose chemistry would depend on the chemistry of the waters. Over time, arsenic species dissolved in water may (1) interact with biological organisms and possibly methylate or demethylate (Chapter 4), (2) undergo abiotic or biotic oxidation, reduction, or other reactions, (3) sorb onto solids, often through ion exchange, (4) precipitate, or (5) coprecipitate. This section discusses the dissolution of solid arsenic compounds in water, the chemistry of dissolved arsenic species in aqueous solutions, and how the chemistry of the dissolved species varies with water chemistry and, in particular, pH, redox conditions, and the presence of dissolved sulfides. Discussions also include introductions to sorption, ion exchange, precipitation, and coprecipitation, which have important applications with arsenic in natural environments (Chapters 3 and 6) and water treatment technologies (Chapter 7). 

Once arsenic dissolves in natural water, it may remain in solution for an extended period of time or participate sooner in abiotic or biotic reactions that remove it from solution. Depending upon the pH, redox conditions, temperature, and other properties of an aqueous solution and its associated solids, dissolved arsenic may precipitate or coprecipitate. Arsenic may also sorb onto solid materials, usually through ion exchange. Due to their importance in understanding the behavior of arsenic in natural environments (Chapter 3) and their applications in water treatment (Chapter 7), the sorption, ion exchange, precipitation, and coprecipitation of arsenic have been the subjects of numerous investigations. 

Although in general water quality at Barton Springs is good, there have been occurrences of contamination across the aquifer. Petroleum hydrocarbons, arsenic, lead, pesticides, and other compounds have been identified from aquifer wells (Hauwert and Vickers, 1994). Many of these compounds sorb onto solid surfaces in much higher concentrations than their concentration in water. 

Metal Ions and Complexes Sorbed Onto Solids. - The Li and Na NMR spectra of clay suspensions in water have been used to show how the smectite structure and the nature of the alkali counterions modulate the quadrupolar interaction. The surface modihcation of Y-AI2O3 by Na+ has been studied by H/ Na double resonance NMR techniques. The organic functionalisation of mesoporous molecular sieves with Grignard reagents has been investigated by C and Si NMR spectroscopy. ... 

Whereas studies have been carried out on the factors (surface coverage, residence time, pH) which influence the desorption of arsenate previously sorbed onto oxides, phyllosilicates and soils (O Reilly et al. 2001 Liu et al. 2001 Arai and Sparks 2002 Violante and Pigna 2002 Pigna et al. 2006), scant information are available on the possible desorption of arsenate coprecipitated with iron or aluminum. In natural environments arsenic may form precipitates or coprecipitates with Al, Fe, Mn and Ca. Coprecipitation of arsenic with iron and aluminum are practical and effective treatment processes for removing arsenic from drinking waters and might be as important as sorption to preformed solids. 

The sorption of water vapor onto nonhydrating crystalline solids below RHq will depend on the polarity of the surface(s) and will be proportional to surface area. For example, water exhibits little tendency to sorb to nonpolar solids like carbon or polytetrafluorethylene (Teflon) [21], but it sorbs to a greater extent to more polar materials such as alkali halides [34-37] and organic salts like sodium salicylate [37]. Since water is only sorbed to the external surface of these substances, relatively small amounts (i.e., typically less than 1 mg/g) of water are sorbed compared with hydrates and amorphous materials that absorb water into their internal structures. 

Tabor and Barber examined the 2800 km reach of the Mississippi river for the occurrence and fate of LAS in waters and bottom sediments [3], Dissolved LAS was concentrated on reversed-phase (RP)-Cis solid-phase extraction (SPE) cartridges, while sediment-bound LAS was extracted with methanol in three 24-h cycles on a rotating mixer. After derivatisation of the extracts to yield the trifluoroethyl esters, analyses were performed by gas chromatography mass spectrometry (GC-MS). Upon enrichment of 900 mL samples, detection limits of 0.1p.gL 1 were achieved. LAS was identified in 21% of the water samples at concentrations ranging from 0.1 to 28 p,g L-1 and was detected at all of the Mississippi river sediment samples at concentrations ranging from 0.01 to 20 mg kg-1 with a mean value of 0.83 mg kg-1. The concentrations of LAS sorbed onto sediment particles generally did not correlate with... 

In the wastewater, an average ethoxylate chain length of 10 was found, with total A9PEOn concentrations of 500 pgL-1 [5]. Of these A9PEOn, 6-60% was sorbed onto suspended solids. One likely removal process of A9PEOn from the estuarine water column is therefore sedimentation of suspended matter. However, no sediments were analysed to test this hypothesis. 

Uptake is the process by which chemicals (either dissolved in water or sorbed onto sediment and/or suspended solids) are transferred into and onto an organism. For surfactants, this generally occurs in a series of steps a rapid initial step controlled by sorption, where the surface phenomenon is especially relevant then a diffusion step, when the chemical crosses biological barriers, and later steps when it is transported and distributed among the tissues and organs. 

Application of pollutant chemodynamic models, which neglect the DHS phase, may result in inaccurate estimations of apparent solubility and transport parameters. The impact of a DHS solubility enhancement is most pronounced for the least water-soluble solutes. The affinity of a solute for a DHS is a function of the same properties, which drive a complex organic mixture(s) to sorb onto the stationary solid phase, namely bonding interactions and hydrophobicity. 

Hence, DHS will manifest the greatest solubility enhancement for those pollutants which are the least soluble in water or the most attracted to the solid phase. Organic pollutants, which are soluble in water, are less likely to be sorbed onto the solid or colloidal phase in the absence of specific bonding interactions. 

The target substance must be physically accessible to the degrading organism. (Inaccessibility may result if the substance is present in a different microenvironment, dissolved in a solvent that is not miscible with water, or sorbed onto a solid surface). 

Surface analytical techniques. A variety of spectroscopic methods have been used to characterize the nature of adsorbed species at the solid-water interface in natural and experimental systems (Brown et al, 1999). Surface spectroscopy techniques such as extended X-ray absorption fine structure spectroscopy (EXAFS) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) have been used to characterize complexes of fission products, thorium, uranium, plutonium, and uranium sorbed onto silicates, goethite, clays, and microbes (Chisholm-Brause et al, 1992, 1994 Dent et al, 1992 Combes et al, 1992 Bargar et al, 2000 Brown and Sturchio, 2002). A recent overview of the theory and applications of synchrotron radiation to the analysis of the surfaces of soils, amorphous materials, rocks, and organic matter in low-temperature geochemistry and environmental science can be found in Fenter et al (2002). 

The sorption of water vapor onto non-hydrating crystalline solids below RHq will depend on the polarity of the surface(s) and will be proportional to surface area. For example, water exhibits little tendency to sorb to non-polar solids like carbon or polytetrafluoroethylene... 

Reaction Blank of 0 NH2 and Peroxidase. Twenty five mg peroxidase, 100 pi of 0 NH2, and 3 ml of H2O2 were added sequentially to 100 ml of pH 6 phosphate buffer, and stirred for 6.5 hours. The reaction was then quenched by acidifying to pH 2 with acetic acid. The colored reaction products were sorbed onto a C18 solid phase extraction cartridge, rinsed with distilled deionized water, and then eluted with methanol. The methanol was removed using rotary evaporation and the reaction products redissolved in 2 ml of DMSO-d for NMR analysis. Reaction of Humic Acid with 0 nH2 in Presence of Bimessite. Four hundred mg of the soil humic acid was added to 200 ml of H2O and adjusted to pH 6 with IN NaOH. Two hundred pi of 0 NH2 and 50 mg of bimessite were added and the reaction mixture stirred for 6 days. The reaction solution was then dialyzed, filtered through a sintered glass funnel, H" - saturated on the cation exchange resin,... 

The important chemical transformation process in surface water is the oxidation or reduction of plutonium. In waters with low suspended solids, plutonium is generally found in oxidized forms, dissolved in the water. In waters with high suspended solids, plutonium is generally reduced and sorbed onto either suspended solids or sediments (Choppin and Morse 1987 Higgo and Rees 1986 Nelson etal. 1987). 

Effluents from wastewater treatment plants will contain low levels of PDMS (<5 ag/L) sorbed onto effluent solids. These solids will eventually deposit into bottom sediments. The potential for PDMS biodegradation in sediments was examined by Christianson [21] in sediment/water columns amended with 500 ppm of 350-Cst C-labeled PDMS. The cores were aerated and the overlying water and off-gas were monitored for the formation of soluble or volatile materials. Results showed no evidence of biodegradation or biotransformation, indicated by the lack of formation of volatile or solubilized materials, over a 56-day period. 

Due to their stror g lipophilic properties and poor solubility, the PCDDs and PCDFs dissolved in water were generally measured at levels lower than 1 pg/L- If particulate matter is present, most PCDDs and PCDFs are sorbed onto suspended solid material. In this case, the determination should be performed on the aqueous phase and particulate matter as well. In general, the analysis of PCDDs and PCDFs dissolved in water requires large sample volumes, possibly up to hundreds of liters. The use of systems to collect and concentrate the analytes is also recommended [20]. To this aim, solid hydrophobic adsorbents or nonpolar organic solvents are used. 

SPME is a solvent-free extraction technique that utilizes short thin solid rod of fused silica coated with absorbent stationery phase. This extraction procedure involves the immersion of the fiber for a certain amount of time while it is being stirred in a water sample from which PAHs are to be extracted. During this period, analytes are sorbed onto the stationary phase of the fiber. Afterwards the fiber is subjected to desorption in the gas chromatography (GC) injector [43]. 

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