Water sorptivity

The experiment is completed in two phases. In the first phase, the effects of different NC contents on the compressive strength of mortar and concrete are evaluated. The optimum NC content that exhibited the highest compressive strength is selected to be included in HVFA concretes and mortars to evaluate its effects on early age (e.g., at 3 and 7 days) and later age (e.g., up to 90 days) compressive strengths. The mixture proportions of mortars and concretes used in this phase are shown in Tables 11.2 and 11.3, respectively. The second phase was designed to study the effect of optimum NC (i.e., 1 wt%) on water sorptivity, volume of permeable voids (VPV), chloride permeability, porosity, and chloride diffusion of HVFA concretes containing 39 and 59 wt% FA and cured at 28 and 90 days. 

The water sorptivity of ordinary concrete containing 1 wt% CaCOs nanoparticles was approximately 17% and 30% lower at 28 and 90 days, respectively, than the ordinary concrete. In addition, the use of 1 wt% CaCOa nanoparticles in HVFA concrete was found to be significantly effective in reducing the water sorptivity when combined with 39% FA as a partial replacement of cement in concrete. This is an indication that the 1% CaCOa nanoparticle addition in an HVFA system forms a finer pore stmcture than HVFA paste alone. 

The amorphous orientation is considered a very important parameter of the microstructure of the fiber. It has a quantitative and qualitative effect on the fiber de-formability when mechanical forces are involved. It significantly influences the fatigue strength and sorptive properties (water, dyes), as well as transport phenomena inside the fiber (migration of electric charge carriers, diffusion of liquid). The importance of the amorphous phase makes its quantification essential. Indirect and direct methods currently are used for the quantitative assessment of the amorphous phase. 

Fig. 4. Moisture uptakes as a function of water partial pressure for DGEBA-TETA net resin. Influence of previous exposure to 60 °C and 95% relative humidity on the apparent sorptivity. Open circles conditioned samples full circles reference samples. (22)...

Toxaphene. Toxaphene is apparently strongly adsorbed and should not move in the soil profile. Because of its strong sorptive interaction with soils, some material may erode into surface waters during irrigation or precipitation events. There is no evidence for oxidation, hydrolysis, or biodegradation (29). Photolysis probably would not occur. However, volatilization is... 

Rodil R, Moeder M (2008) Development of a method for the determination of UV filters in water samples using stir bar sorptive extraction and thermal desorption-gas chromatography-mass spectrometry. J Chromatogr A 1179(2) 81—88... 

Tan BL, Hawker DW, Muller JF, Tremblay LA, Chapman HF (2008) Stir bar sorptive extraction and trace analysis of selected endocrine disrupters in water, biosolids and sludge samples by thermal desorption with gas chromatography-mass spectrometry. Water Res 42 404 112... 

Such simulations suggest that because of their relatively high water solubility which in combination with low vapor pressure causes low air-water partition coefficients, the phenols tend to remain in water or in soil and show little tendency to evaporate. Their environmental fate tends to be dominated by reaction in soil and water, and for the more sorptive species, in sediments. Their half-lives are relatively short, because of their susceptibility to degradation. 

Dowson and coworkers studied partitioning and sorptive behavior of tributyltin (TBT) and its degradation products, dibutyltin (DBT) and monobutyltin (MBT) in the aquatic environment107. The determination of the sorptive behavior of TBT is necessary in order to understand its fate in freshwater and estuary environments. The results indicate that MBT and TBT in freshwater will be partitioned to a lesser extent towards the particulate phase, whereas DBT exhibits a 50 50 partitioning between the particulate and solution phases. In estuary waters, MBT will almost exclusively be adsorbed on the particulates, while TBT will be predominantly in the solid-phase fractions but 10-30% may remain in solution. DBT, in contrast, is solubilized in estuary waters. The order of adsorption to particulate matter for butyltins is MBT > TBT > DBT107. 

Sorptive reactions of LNAPLs and dissolved organic compounds moving through soil are almost always reversible equilibrium reactions. A concentration equilibrium is established between the concentration of chemical dissolved in water and that which is attached to the soil particles. When concentrations change, the soil may adsorb additional organic molecules or release them to reestablish the equilibrium. 

The sorptive nature of bacterial or algal exterior membranes is well-documented [118-122]. Biological particles can influence the distribution of heavy metals in natural waters because the functional groups on the cell surfaces are able to bind certain metal ions [124]. 

It should be noted that Chiou et al. [77,81,189,190] suggested early that the controlling sorptive mechanism of nonionic organic compounds from water... 

The presence of water-soluble macromolecules in solution at submicel-lar concentrations has been reported to enhance the water solubility of hydro-phobic organic chemicals in several instances [19, 106, 113]. The presence of macromolecules in solution can enhance the apparent solubility of solutes by sorptive interactions in the solution phase. The processes by which macromolecules enhance the solubility of pollutants are probably variable as a function of the particular physical and chemical properties of the system. A macromolecule possessing a substantial nonpolar region can sorb a hydrophobic molecule, thereby minimizing the interfacial tension between the solute and the water. 

The data from a representative study of the disappearance of chlorpyrifos from an EPA-14 sediment/water system (p=0.20, fraction sorbed = 0.94) is illustrated in Figure 3. Comparison with Figure 1 shows that once sorptive equilibrium is achieved (t>14,000 minutes) the disappearance rate is first order for both the water and sediment phases. Also, the aqueous disappearance rate constant calculated from the slope of the linear portion of the natural log aqueous concentration versus time plot is 0.5 0.2 x 10 min, which is similar to the values measured in sediment-free EPA-14 supernatant (Table II). A plot summarizing two experiments using EPA-23 sediment is shown in Figure 4. The value of calculated from the... 

Figure 9.6 Illustration of the retardation of 1,4-dimethylbenzene (DMB) transport in groundwater due to (1) reversible sorptive exchange between water and solids, and (2) limiting transport of DMB to that fraction remaining in the flowing water. As dissolved molecules move ahead, they become sorbed and stopped, while molecules sorbed at the rear return to the water and catch up. Thus, overall transport of DMB is slower than that of the water itself.

So we deduce that only one DMB molecule out of 11 will be in the moving ground-water at any instant (Fig. 9.6). This result has implications for the fate of the DMB in that subsurface environment. If DMB sorptive exchange between the aquifer solids and the water is fast relative to the groundwater flow and if sorption is reversible, we can conclude that the whole population of DMB molecules moves at one-eleventh the rate of the water. The phenomenon of diminished chemical transport speed relative to the water seepage velocity is referred to as retardation. It is commonly discussed using the retardation factor, Rfi, which is simply equal to the reciprocal of the fraction of molecules capable of moving with the flow at any instant, ff (see Chapter 25). 

These results will be used in Section 19.5 when we discuss the kinetics of sorptive exchange of a solute between particles and the water in which they are suspended. 

An isolation-fractionation scheme for the separation of trace organic solutes from natural and drinking waters has been developed. This process involves the separation of a number of organic solutes into several fractions on the basis of their sorptive characteristics onto different adsorbents under varying pH conditions. The specific adsor-... 

---