Calcium carbonate precipitation potential

Precipitation potential of the calcium ion Precipitation potential of CaCOs Carbonate complex of calcium ion Bicarbonate complex of calcium ion Hydroxide complex of calcium ion... 

A composite pigment-biopolymer structure with potential use in biocomposites can be formed by different techniques, such as precipitation, mixing, self-assembly, or hierarchical methods. There are many open questions about the production, use, and potential benefits of these filler-fibre complexes. In this chapter, we present some targeted work, which investigated biopolymer composites produced by in situ calcium carbonate precipitation and mixing techniques. 

Due to the complexity of the precipitation process, the saturation index (SI) is calculated to estimate the calcium carbonate precipitation in water, and is used to describe the saturation state (from a thermodynamic point of view) of the aqueous phase composition versus different solids. It is widely used to estimate the potential precipitation of different solids from an equilibrated aqueous phase speciation. 

To increase the solubility of calcium carbonate and reduce its potential for precipitation and hence membrane fouling, the pH of the feed water is lowered through the addition of acid (Greenlee et al. 2009). Sulphuric acid and hydrochloric acid are most commonly used. Acid treatment can also help to improve the coagulation of colloids and slightly increase the solubility of silica (Bergman 2007). 

Hoi-Lime Zeolite Softening. In this process hydrated lime is employed to react with the bicarbonate alkalinity of the raw water. The precipitate is calcium carbonate and is filtered from the solution. To reduce silica, the natural magnesium of the raw supply can be precipitated as magnesium hydroxide, which acts as a natural absorbent fur silica. These reactions are carried out in a vat or tank that is located just head of the zeolite softener tank. The effluent from this tank is filtered and then introduced into the zeolite softener. There is always some residual hardness leakage from the hot-process softener to be removed in the final zeolite process. The hot lime process operates at about 220T (I04°C). At this temperature the potential for the exchange of sodium for hardness ions is greater than at ambient temperature, and the result is a lower hardness effluent than is achieved at ambient temperatures. This system is shown schematically in Fig. 2. 

Inhibition of the precipitation of calcium carbonate is one potential commercial application for 0-(carboxymethyl flnulin. The formation of calcium carbonate crystals is a major problem in boilers, heat exchangers, saltwater desalination, gas and oil production, laundry, and other fields. As the water temperature increases, the solubility of calcium carbonates decreases, resulting in crystalli-zation/scale formation/incrustation, decreasing the efficiency of the operation and increasing costs. 

The primary particle size of Winnofil stearate coated precipitated calcium carbonate from Zeneca Resins is in the region of 0.075 micron. When compounded into natural and synthetic elastomers, the hydrophobic surface coating assists wetting and aids dispersion. When compounded into plasticised PVC for cable sheathing, the PCC allows for formulations with minimal potential for acid gas release in combustion conditions. In rigid PVC, stearate coated PCC has been used in compounding as an alternative to conventional acrylic processing aids and as a means to reduce impact modifier levels. 

In conclusion, such a model is convenient to get an idea of the calcium oxalate concentration, CO2 pressure and conditions for potential precipitation of secondary calcium carbonate through oxalotrophic bacterial activity. It demonstrates that as long as calcium is available and oxalotrophic bacteria are present, transformation of oxalate into carbonate can occur under normal conditions found in soils and surficial sediments. Therefore, an oxalate-carbonate cycle, or at least pathway, must exist at the surface of continents (Verrecchia Dumont, 1996), explaining the absence of calcium oxalate accumulation in soils and the fossil record. 

CaCOspp,] is the precipitation potential of calcium carbonate. C pp in turn, can be obtained from the original calcium, minus the calcium at equilibrium, Ca r-... 

Solution The saturation pH is given as pHj = 10. The actual pH is 8.7, so the system is not saturated with calcium carbonate and no carbonate will precipitate the precipitation potential is therefore zero. At equilibrium at the Langelier saturation pH, the calcium ion concentration will remain the same at [Ca ] = 10 gmol/L. Ans... 

Precipitation potential—The amount of calcium carbonate that will precipitate when the solution is left by itself from its supersaturating condition. 

Attention must be paid here to changes caused by access or escape of gases. For example, oxidation of dissolved bivalent iron can occur through access of oxygen. The water will become turbid and the oxidation reduction potential will be shifted. The same applies to the measurement of electrical conductivity, when precipitation of e.g. calcium carbonate, iron hydroxide or silicic acid occurs through release of gas. The sampling procedure in question must be matched to the intended measurement procedures so that secondary changes in the water before measurement can be avoided, or can if necessary be reversed or taken into account in the calculations in the laboratory. 

Calcium in the form of calcium carbonate contained in limestone is added in the neutralization processes after nickel laterite leaching. Calcium sulfate solids in the form of gypsum (and possibly hemihydrate and anhydrite) precipitate and have the potential to form scale on equipment and piping surfaces. 

On May 25, 2008, the mission landed and began to investigate samples. The mass spectrometer obtained spectra of atmospheric constituents, and measured the evolved gas from multiple samples collected directly in front of the lander [82,83]. It was critical in the potential discovery of calcium carbonate in surface material when it was used in peak mode to identify when CO2 was evolved. A significant increase in the concentration of CO2 was detected from a sample named Wicked Witch when the oven temperature approached 1200°C [82]. In the discovery of perchlorate in the Martian regolith, TEGA identified the evolved mass from O2 in a sample named Baby Bear. The onset of evolved O2 at 325°C and a peak at 465°C, which is consistent with the thermal decomposition of perchlorate [84]. These two discoveries, along with the measurement of the Ph and identification of precipitation from water ice clouds were highlights of the Phoenix mission [85]. 

HARDNESS of the water. The compounds are potentially damaging because they can accumulate in pipes and boilers. They also react with, and therefore waste, soap. Temporary hardness can be removed by boiling the water. Permanent hardness can be removed in a number of ways by distillation by the addition of sodium carbonate (which causes dissolved calcium, for example, to precipitate out as calcium carbonate) and by the use of ion-exchange products such as Permutit (utilizes zeolites) and Calgon (utilizes polyphosphates). 

An example of the use of this method follows, and also shows the potential for combining ultrasonics with adsorption techniques in studies related to the use of coated fillers in composites. Dye adsorption curves for congo red (Cl 22120) on various precipitated calcium carbonates are presented in Figure 4.2. 

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