Colloid calcium carbonates

Pre-liming. Lime slurry, 0.25% lime on juice (0.250 g of CaO/100 g juice), is added to bring the pH of the mixture into the alkaline range. Insoluble calcium salts are precipitated as finely dispersed colloids. Calcium carbonate in the form of recycled first carbonation sludge is added to provide colloid absorption and stabilization. Temperature may be cool (50°C) or hot (80°C) depending on the temperature of the next step, or occasionally on the type of diffusion equipment. Retention time is 15 to 30 min. 

Presence of colloidal calcium carbonate from high concentrations of dissolved lime turns the water of Havasu Falls turquoise. 

Petroleum sulfonates are oil-soluble compounds that find use as emulsifiers in lubricating oil and other functional fluids and in secondary oil recovery. They are usually supplied as sodium salts in mixtures with oil. They may contain unsulfonated oil or be diluted in a light petroleum distillate. Overbased products contain high alkalinity additives, such as colloidal calcium carbonate. 

Alkaline additives are used with petroleum sulfonates in lubricating oils. These can be determined by nonaqueous potentiometric titration with perchloric acid (116). Additives such as colloidal calcium carbonate may also be determined by infrared spectroscopy, based on the carbonate bands (117). 

Tyj)e of dryer Applicable with dry-product recirculation True and colloidal solutions emulsions. Examples inorganic salt solutions, extracts, milk, blood, waste liquors, rubber latex, etc. Pumpable suspensions. Examples pigment slurries, soap and detergents, calcium carbonate, bentonite, clay sbp, lead concentrates, etc. does not dust. Recirculation of product may prevent sticking Examples filter-press cakes, sedimentation sludges, centrifuged sobds, starch, etc. 

Although the terpolymers have the widest possible range of functions, providing not only basic calcium carbonate control, but also high-stress capability and dispersion of colloids, plus iron, phos-... 

Pach L, Duncan S, Roy R, Komameni S (1996) Morphological control of precipitated calcium carbonates and phosphates by colloidal additives. J Mater Sci 31 6565-6569... 

Sheng Y, Zhou B, Zhao J, Tao N, Yu K, Tian Y, Wang Z (2004) Influence of octadecyl dihydrogen phosphate on the formation of active super-fine calcium carbonate. J Colloid Interface Sci 272((2) 326-329... 

In this example, a simple mechanism for breaking a colloid was chosen. The eggshells are made of porous calcium carbonate, their surface covered with innumerable tiny pores. The particles of fat in the broth accumulate in these small pores. Removing the eggshells from the broth (each with oil particles adsorbed on their surfaces) removes the dispersed medium from the broth. One of the two components of the colloid is removed, preventing the colloid from persisting. 

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). 

Bodies of Water and the Chemical Sediments ,— The chemistry of the deposition of salts from sea-water has already been made the subject of special research, and van t Hoff s results in this field are already familiar. The deposition of calcium carbonate awaits a similar thorough study. Allied questions are the formation of dolomite, the deposition of various salts from inclosed bodies of water, the deposition of phosphate rocks, the precipitation of colloidal suspensions of clay and other substances, and the origin of the great deposits of sedimentary iron ore. 

Colloid Chemistry of Sodium Polyacrylate Dispersed Calcium Carbonate Slurries... 

In this section we give a description of the colloidal interactions which govern the state of dispersion and rheology of calcium carbonate slurries. The description is based on a series of fundamental experimental studies that have been described in more detail in previous publications. ... 

To get gold colloids with reproducible size, the given volumes have to be observed exactly. Store the very hygroscopic gold(lll)chloride in a desiccator on anhydrous calcium carbonate powder. 

POWDER. Any solid, dry material of extremely small particle size ranging down to colloidal dimensions, prepared either by comminuting larger units (mechanical grinding), combustion (carbon black, lampblack), or precipitation via a chemical reaction (calcium carbonate, etc ). Powders that are so fine that the particles cannot be detected by rubbing between... 

Calcium carbonate, either powdered limestone or precipitated chalk, is used as an anti-acid in dynamite where it serves as a satisfactory stabilizer. Urea is used in dynamite and in celluloid. It reacts with nitrous acid to produce nitrogen and carbon dioxide, and is unsuitable for use in smokeless powder because the gas bubbles destroy the homogeneity of the colloid and affect the rate of burning. The small gas bubbles however commend it for use in celluloid, for they produce an appearance of whiteness and counteract the yellowing of age. 

A Pearls are a type of colloid, a mixture of large particles consisting primarily of calcium carbonate. 

The nature of silicate scaling is often complex and can involve the nucle-ation of calcium carbonate crystals (which tends to provide seeding points for silicate precipitation) and magnesium hydroxide (which can form at the heat-transfer surfaces, especially at cathodic sites where localized pH levels may exceed 10.0, then reacting with colloidal silica from the bulk water to form silicate scale). 

Adsorption This method is the simplest way to immobilize enzymes. Enzymes can be adsorbed physically on a surface-active adsorbent by contacting an aqueous solution of enzyme with an adsorbent. Commonly employed adsorbents are (Zaborsky, 1973) alumina, amon-exchange resins, calcium carbonate, carbon, cation-exchange resins, celluloses, clays, collagen, colloid-ion, conditioned metal, glass plates, diatomaceous earth, and hydroxyapatite. The advantages of adsorption techniques are as follows ... 

Like sediments, colloids are often important in sorbing and transporting arsenic in soils (Sadiq, 1997 Waychunas, Kim and Banheld, 2005). Colloids may consist of clay minerals, organic matter, calcium carbonate, and various aluminum, manganese, and iron (oxy)(hydr)oxides (Sadiq, 1997). Important iron (oxy)(hydr)oxides include goethite, akaganeite (/J-FeO(OH)), hematite, ferrihydrites, and schwertman-... 

The initial rate of nucleation depends on the degree of supersaturation which can be reached before phase separation occurs, so that colloidal sols are most easily prepared when the substance in question has a very low solubility. With material as soluble as, for example, calcium carbonate, there is a tendency for the smaller particles to redissolve (see page 68) and recrystallise on the larger particles as the precipitate is allowed to age. 

The term hard-core RMs is used to describe dispersions containing an excess of colloidal carbonate over that required to neutralize the sulfonic acid. The excess is found in calcium carbonate trapped in a micellar structure. The total base number (TBN) of the additive so obtained is 368 mg KOH/g of oil. The crude additive consisted of 33 wt% CaC03 (Delfort et al., 1995 Giasson et al., 1992). Some typical results of the core particle with the overall diameter and the detergent layer thickness are shown in Table 3.6 (Marsh, 1987). 

Fig. 3.6. Partial (10%) neutralization of colloidal CaC03with dithiodiglycolic acid leading to comicellized calcium carbonate and calcium dithiodiglycolic carboxylate...

Modified hard-core RMs by phosphosulfurized compound. Improved extreme-pressure and antiwear properties have also been obtained with the introduction of some chemical species, such as sulfur, phosphorus or boron derivatives, into the colloidal core (Delfort et al., 1998 Inoue, 1993 Inoue and Nose, 1987). Welding loads, load wear index and wear scar diameter at 5 wt% of a CaC03 core surrounded by a calcium alkylaryl-sulfonate surfactant shell, and modified by phosphosulfurized calcium carbonate core were evaluated for calcium dialkyl dithiophosphate (CaDTP) and calcium trithiophosphate (CaTTP) with the four-ball extreme-pressure test (ASTM D2783 standard method). Both modified products exhibit improved extreme-pressure performances (welding load and load wear index), while their antiwear properties (wear scar diameter) compared to those of the original micellar substrate remain at least at the same level. 

Synthesis of oil soluble micellar calcium thiophosphate was performed in a one-step process involving the reaction of calcium oxide, tetraphosphorus decasulfide and water in the presence of an alkylaryl sulfonic acid. This product could be defined as a calcium thiophosphate hard-core surrounded by a calcium alkylarylsulphonate shell in accordance with a reverse micelle type association in oil. Three micellar products with the same chemical nature core were prepared, each with different core/shell ratio of 0.44, 0.92 and 1.54. Better performances are expected with products of higher core/shell ratios. The antiwear performance of micellar calcium carbonates is directly linked to the size of the mineral CaC03 colloidal particles. At a concentration of 2 % micellar cores, no antiwear effect is observed whatever the micellar size. At an intermediate concentration of 4 % of micellar cores, the wear scar diameter is clearly dependent on the micellar size, slipping from 1.70 mm to 1.10 mm, then to 0.79 mm when the core diameter moves from 4.37 nm to 6.07 nm, then to 6.78 nm. Size dependence is increased at a concentration of 5 % in colloidal cores. This clearly confirms the size dependence of the micellar cores on their antiwear performance (Delfort et al.,... 

---