Solid-phase calcium concentration

Fig. 8 shows an example of comparison of the analysis results and actually measured results of solid-phase calcium concentration after leaching. The actually measured results are for concrete of age 30-100 years in various kinds of environments such as distribution reservoir in a water supply facility, building foundation structure in contact with groundwater, dam, and so on, similar to Fig. 3. Variation exists in actually measured results also, and although calculated accuracy cannot be discussed unconditionally, satisfactory predictions can be made depending on various conditions.

Fig. 7. Equilibrium model of solid-phase calcium concentration and liquid-phase calcium ion concentration.

Figure 9. Computer-calculated percentage of the total Ca in a simulated urine present as solid-phase calcium hydrogen phosphate as a function of NTA concentration and urine pH...

These solid phases are connected to the components in Fig. 4, with which they are in reversible equilibrium. For example, if magnesium ion were added to a complex solution containing solid calcium oxalate monohydrate (COM), the magnesium would compete with calcium for an increased share of the oxalate this would reduce the amount of the calcium oxalate complex, and finally a small amount of calcium oxalate sohd would dissolve to restore the complex concentration to its equilibrium value. In urine, this picture must be extended to account for the molecular substances that coat crystals and reduce access of the solution to the surface coated crystals do not redissolve readily. 

The level of impurity uptake can be considered to depend on the thermodynamics of the system as well as on the kinetics of crystal growth and incorporation of units in the growing crystal. The kinetics are mainly affected by the residence time which determines the supersaturation, by the stoichiometry (calcium over sulfate concentration ratio) and by growth retarding impurities. The thermodynamics are related to activity coefficients in the solution and the solid phase, complexation constants, solubility products and dimensions of the foreign ions compared to those of the ions of the host lattice [2,3,4]. 

For both cesium and barium sorption, there is reasonable agreement between the total concentrations of desorbed species and the ion-exchange capacities determined by isotopic redistribution. The small differences which exist could easily be due to the precision in the elemental analyses. (Also, the experimental technique would not have detected desorption of hydrogen ions.) The solid-phase concentrations of sodium, potassium, magnesium, calcium. 

When a reaction involves two different phases, that is. when the system is nut homogeneous but heterogeneous, as in reactions lielwccn a solid phase, such us zinc or calcium carbonate, and a liquid phase, such as hydrochloric acid solution, the rate of reaction involves consideration of tl I the area of the surface of contact of the solid with the solution, and 121 the rale of diffusion from the surface of the solid, as well as (31 the concentration of hydrogen ion of the acid solution. 

The System Lime and Phosphoric Acid —Solubility of Calcium Phosphates— Conditions of Formation of Basic and Acid Calcium Phosphates—Composition of Solutions Saturated with Calcium Hydrogen Phosphates—Equilibria between Solid Phases and Solutions at Various Temperatures—Changes during Neutralisation—The Acid Phosphates—Manufacture of Superphosphate—Retrogression—Treatment of Special Ores—Phosphoric Acid— Commercial Preparation and Extraction from Rook—The History and Technology of Superphosphate Manufacture—Mixed and Concentrated Phosphorio Fertilisers—Potassium Phosphates—Ammonium Phosphates. 

Inclined plate clarification is a traditional separation technology that has been used for decades to remove suspended solids from a liquid stream in various types of systems including traditional precipitation [12]. In the semiconductor industry, the clarifier is commonly used in fluoride waste treatment systems where calcium fluoride precipitate is concentrated prior to dewatering in a press, or in assembly/test operations to separate silicon fines from backgrind operations. The clarifier will concentrate the solid phase of slurry like a UF, but unlike the UF or MF, the clarifier may require the addition of a chemical polymer to facilitate the agglomeration of the suspended solids so that they settle and concentrate. Polymer addition adds another level of complexity to the waste treatment system. The clarifier does not provide a physical barrier to prevent the transport of solids to downstream equipment, so it may be necessary to install a UF or MF downstream of the clarifier to capture extraneous particles or to protect the downstream equipment from clarifier upsets. 

Numerous kinetic studies have been made of the spontaneous precipitation of calcium phosphates from solutions containing concentrations of lattice ions considerably in excess of the solubility values (33, 34). Although attempts, are usually made to control the mixing of reagent solutions, it is difficult to obtain reproducible results from such experiments since chance nucleation of solid phases may take place on foreign particles in the solution. Many of these difficulties can be avoided by studying the crystal growth of well-characterized seed crystals in metastable supersaturated solutions of calcium phos.phate. 

Dissolved metals other than calcium have a minor effect on the distribution of phosphorus between the water column and sediment in this fluvial system. The two principal metals of potential interest, iron and aluminum, are present in Genesee River water almost entirely in the particulate phase ( ). Dissolved concentrations of these metals are below the detection limit (less than 50 ug/1). Iron and aluminum minimum detectable dissolved concentrations were used to estimate the saturation levels of the corresponding phosphate minerals. These calculations suggest that both iron and aluminum phosphate minerals are substantially below saturation levels. The solid surfaces exhibited by iron and aluminum hydrous oxides (as particulate material in the water column) undoubtedly serve as sites for phosphorus adsorption and incorporation in the fluvial system. Data presented for the oxalate extraction procedure in Table III demonstrate the importance of phosphorus binding by hydrous metal oxides. 

Figure 1 presents the dependence of the catalytic activity and isobutane selectivity of samples precipitated at pH = 9 on the CaO concentration. This study made it possible to evaluate the role of the cubic solid solution in their catalytic properties. One can see an obvious maximum on the dependence of the activity on the alkaline earth metal concentration in the structure of Zrj.xCaxOz-x solid solution. Without calcium the catalytic activity is low. This agrees with the literature data that sulfation of a calcined monoclinic phase without any special treatment does not yield an active catalyst [9]. The maximum activity is observed for the samples with the CaO concentration of 5-10 mol.%. The material with the calcium concentration of 50 mol.% does not show any catalytic activity at all. This sample is mostly composed of perovskite crystalline phase CaZrOs. A comparison of the catalytic activity of the samples with their surface areas clearly indicates that the activity growth is mostly caused by the formation of the cubic phase rather than just by an increased surface area. 

Gladkii(16) at the State Scientific Research Institute of Industrial and Sanitary Gas Cleaning at Moscow did work on the three-phase calcium sulfite slurry oxidation system, finding that the liquid phase oxidation (pH 3.6-6) is first order with respect to the sulfite species. He pointed out, on the basis of pH versus time data from his semi-batch reaction, that the slurry oxidation had different periods in which either reaction kinetics or solid-liquid mass transfer controlled the oxidation rate. He also presented an omnibus empirical correlation between pH, temperature, and the liquid phase saturation concentration of calcium sulfite solution for predicting the slurry oxidation rate. The catalytic effect of manganese... 

The batch precipitation tests show dramatic effects of adipic acid slurry concentration and solid phase oxidation fraction on coprecipitation of adipic acid in scrubber solids. Real world scrubbers would probably never operate at adipic acid concentrations as high as those tested and would also not likely ever produce pure phase calcium sulfite hemihydrate. Therefore, the magnitude of the results observed is somewhat a product of the laboratory test conditions. The results do, however, establish the potential importance of adipic acid coprecipitation and, hence, the need for analysis of scrubber solids for adipic acid when determining adipic acid chemical degradation rates by a mass balance calculation approach. 

Many anionic species appearing in the solubility products may also be involved in protonation equilibria in solution, such as those of phosphoric acid H2P04 H+ + HPO42 HPO42 P04 -I- H + etc. When the prospects for the formation of a solid phase under certain solution conditions are investigated, the activity, or concentration, of the particular anionic species specified in the solubility product must be known, not only total phosphate or total calcium, etc. The data in Table 3.3 show that, at pH > 5, the most stable (i.e., insoluble) solid calcium phosphate is hydroxyapatite. 

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