Solid Partition

There are a number of reagents which precipitate classes of surfactants. Many anionics are at least partially precipitated as the salts of divalent cations like barium and calcium. The precipitation of ethoxylated nonionics with molybdophosphoric acid in the presence of divalent cations may be used as the basis of a preparative separation from other surfactants (21). Similar reactions are covered in Chapter 17 with gravimetric techniques. 

Dodecylsulfate may be separated from aqueous solution by treating the sample with concentrated calcium chloride to precipitate the calcium salt. The solubility of calcium dodecylsulfate is only 0.0003 molal (22). Separation of LAS from water was demonstrated by addition of sodium chloride about 95% of LAS initially present at concentrations over 0.01% can be removed by making the solution 5% in NaCl (23). The presence of nonionic surfactants will inhibit the precipitation of salts of anionic surfactants due to the formation of mixed micelles (24,25). 

Many methods for isolation of surfactants are based upon the solubility of the materials. For example, the sodium salts of most anionic surfactants are soluble in acetone, while soap is not (26). It is difficult to make general statements in this field because of the many exceptions. For example, the sodium salt of the most common anionic surfactant, LAS, is only partially soluble in acetone. Surfactants which would be insoluble by themselves may become soluble in mixtures with other surfactants. Govindram and BGishnan report for a number of common surfactants that all are soluble in ethanol, but that only nonionics and free fatty acids are soluble in petroleum ether or ethyl acetate, with cocomonoethanola-mide being only partially soluble in petroleum ether (26). The solubility of anionics differs depending upon whether they are present as free acids or sodium salts. 

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Separation Phase 1 Phase 2 In phase 1 In phase 2 Notes Ref.  

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The diffusion coefficient in these phases D,j is usually considerably smaller than that in fluid-filled pores however, the adsorbate concentration is often much larger. Thus, the diffusion rate can be smaller or larger than can be expected for pore diffusion, depending on the magnitude of the flmd/solid partition coefficient. 

Class I Locations. Table 515-2 shall be applied where Class I liquids are stored, handled, or dispensed and shall be used to delineate and classify bulk storage plants. The Class I location shall not extend beyond a floor, wall, roof, or other solid partition that has no communicating openings. 

Prior to the development of modern SPE formats, liquid-solid partitioning with charcoal, silica, Florisil, and/or alumina was common to aid in the removal of lipids in the determination of nonpolar pesticides, but these sorbents are less useful in the cleanup of semi-polar and polar pesticides owing to the large elution volumes needed. Applications of modern SPE are discussed in Section 3.2. 

Sediment may be added by bulk mixing via imbricate thnisting (Bebout and Barton 2002), dehydration (Class et al. 2000), or melting (Johnson and Plank 1999). The latter two may differ in their P-T conditions and, therefore, residual mineralogy as well as relevant partition coefficients. In general, fluids are less effective transport agents than melts (i.e., trace elements are more soluble in melt than in pure water or even brine), but fluid/solid partitioning can fractionate some elements, notably Ba-Th and U-Th, more than melt/solid. However, as pressure increases, the distinction between fluid and melt decreases as their mutual solubility increases and they approach a critical end-point. 

Voice, T.C., Weber Jr., W.J. (1985) Sorbent concentration effects in liquid/solid partitioning. Environ. Sci. Technol. 19(9), 789-796. 

Storey, J. M. E., W. Luo, L. M. Isabelle, and J. F. Pankow, Gas Solid Partitioning of Semivolatile Organic Compounds to Model Atmospheric Solid Surfaces as a Function of Relative Humidity. 1. Clean Quartz, Environ. Sci. Technoi, 29, 2420-2428 (1995). 

Simple extraction (e.g., liquid-liquid or liquid-solid partition) Specific extraction (e.g., pH adjustment and/or ion-pair extraction) Solid-phase extraction... 

Hence, A asurf is expressed in m I. Furthermore, we assume that ATiasurf is not dependent on the concentration of the compound at the surface that is, we assume that we are far from saturating the surface with compound /. This then corresponds to a linear adsorption isotherm for a homogeneous mineral surface, since the sorbate molecules do not feel each other in the gas phase or at the solid surface. Finally, we should point out that in the literature, contrary to the notation used here, gas/solid partition coefficients are often expressed in a reciprocal way that is, the reported... 

Waste solids Waste or complex mixtures consisting of <502 water and having relative firmness and coherence of particles or persistence of form as matter that is not liquid or gaseous at 25 °C. This category includes tarry material that is sticky or viscous, such as coal tar, adhesive waste, sludge, airborne particulates (e.g., re-entrained particles blown from a waste site), and solids partitioned from waste water. 

Waste solids are defined as heterogeneous materials that range from sticky, viscous, or tarry material to dry solid particulates. Special techniques for the treatment of oily, gummy, and adhesive materials (e.g., addition of anhydrous sodium sulfate or silica gel) are specified in the protocol. The gravity phase-separation procedure (24 h at 4 °C) developed by the Environmental Waters and Waste Water Work Group is incorporated by reference to address the removal of liquids from waste solids samples. The waste solids protocol can also be applied to solids partitioned from aqueous or nonaqueous liquids or from gaseous media. 

Voice, T. C., and W. J. Weber. 1985. Solids effect in liquid/solid partitioning. Environmental Science and Technology 19 789. 

As shown in Figure 6.7, partitioning between the aqueous and solid phases may result from absorption, adsorption/desorption, and sedimentation processes. The contaminant may be taken up into the interior of a solid by means of diffusion in a process known as absorption. As previously described in air-solid partitioning, the contaminant may also be taken up by the surface of the solid, known as adsorption, and its release from the surface of the solid is known as desorption. Adsorption of a chemical to soil or sediment particles may be a result of electrostatic or hydrophobic attraction between the contaminant and the solid surface.23 Once associated with solid particles, the contaminant may also settle to the sediment surface. This process, known as sedimentation, typically occurs in water bodies with laminar flow, such as a wetland. The increase in contaminant concentration in the solid phases as a result of any of these partitioning processes is known as accumulation.14... 

The contaminant s aqueous solubility and density greatly influence its final disposition in water-solid systems. Dense nonaqueous phase liquids (DNAPLs) are chemicals with densities greater than water and typically low aqueous solubilities. DNAPLs naturally partition away from the aqueous phase and towards the solid phase, often pooling on top of an impermeable solid layer. On the other hand, light nonaqueous phase liquids (LNAPLs) possess densities less than water and have a tendency to pool on the water s surface where they may be prone to volatilization and photolysis reactions. Various liquid-solid partition coefficients have been... 

A. T. James and A. J. P. Martin, Gas-solid partition chromatography. The separation and micro-estimation of volatile fatty acids from formic acid to dodecanoic acid,/. Biochem. 50 (1952), 679-690. 

Permeation of antimicrobial agents into rubber stoppers and other closures is another example of partitioning. Although mbber is an amorphous solid, partitioning between the aqueous phase and mbber depends, as in liquid systems, on the relative affinities of the solute for each phase. 

Size exclusion Liquid in interstices of a polymeric solid Partition/sieving... 

Abraham et al. [64] characterized fullerene as adsorbent in gas-solid chromatography experiment. From the adsorption isotherms, gas-solid partition coefficients defined by Eq.(35), were calculated ... 

Now, assume this gas isothermally fills an enclosure made of gray surfaces. The resulting enclosure problems can be treated by replacing the gas with a transparent solid partition with negligible reflectivity. 

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