Effective precipitation

The iodate is a poison potassium iodide, however, is used in foodstuffs. Thus the iodate must be completely removed frequently by a final reduction with carbon. After re-solution in water, further purification is carried out before recrystallization. Iron, barium, carbonate, and hydrogen sulfide are used to effect precipitation of sulfates and heavy metals. 

Sodium alumiaate is an effective precipitant for soluble phosphate ia sewage and is especially useful ia wastewater having low alkaliaity (20,21). Sodium alumiaate hydrolyzes ia water to Al(OH)2 and Al" which precipitate soluble phosphate as aluminum phosphate [7784-30-7], AlPO. Sodium alumiaate has also been described as an effective aid for the removal of fluorides from some iadustrial waste waters (22). Combiaations of sodium alumiaate and other chemicals are being used to improve the detackification of paint particles ia water from spray-painting operations (23). 

Some hemicelluloses are partiaUy extractable with water, but they are usuaUy extracted with alkaline solutions foUowing removal of Upids and lignin. DeUgnifted plant material is termed, holoceUulose. Neutralization of the alkaline extract effects precipitation of the more linear and less acidic hemicelluloses, termed the hemiceUulose A [63100-39-0] fraction. The more acidic and more branched material, termed hemiceUulose B [63100-40-3], is precipitated with ethanol (70%). HemiceUulose B types type are usuaUy water-soluble after extraction. 

Bromo-2-pyridyla2o)-5-diethylamiQophenol (5-Br-PADAP) is a very sensitive reagent for certain metals and methods for cobalt have been developed (23). Nitroso-naphthol is an effective precipitant for cobalt(III) and is used in its gravimetric determination (24,25). Atomic absorption spectroscopy (26,27), x-ray fluorescence, polarography, and atomic emission spectroscopy are specific and sensitive methods for trace level cobalt analysis (see... 

Effective precipitators are relatively weak acids, such as Co2+, Ni2+, Cu2+, Zn2+ etc. Such precipitators were ranked by Pirson to form a contiguous group of cations [65]. However, in order to synthesize compounds of either Mn(TaF6)2 or Mn(NbF6)2 type, it is necessary either to use cations with a higher acidity or anhydrous hydrogen fluoride, HF [64]. 

It may be noted that enhancement of the concentration of ammonia gives rise to two opposing effects. Precipitation is encouraged on account of destruction of the liberated acid, but at the same time, precipitation is retarded on account of the reduction of the availability of reducible metal ions, Cu2+, due to the prevalent complexing action by ammonia. It is for this reason that an optimum [NH3]/[Cu2+] ratio must be maintained so that the opposing effects are at balance. 

The precipitation of arsenic with H2S gas in the normal condition could occur only in strongly acidic medium whereas another cation of the second group Cd(II), precipitates only in faintly acidic medium, therefore, the precipitation of both cadmium and arsenic with H2S gas in the same solution was not easily possible. To precipitate both in the same solution, the H2S gas is conventionally first passed into the strongly acidic original solution of basic radicals followed by its bubbling into the diluted solution. To examine the role of ultrasound on the precipitation of arsenic in faintly acidic or neutral medium, few experiments were carried out. The results obtained showed effective precipitation of arsenic even in mild reaction solutions, with their pH ranging from 5.1 to 8.8. under ultrasonic field. Hence Cd2+ and As3+/5+ both could be precipitated in the same solution at low pH under the... 

If S moles of CaCC>3 dissolve in a liter of water, then S moles each of calcium ion and carbonate ion form. With these ion concentrations equal to S, the solubility of CaCC>3 is calculated as 9.3 x 10 5 M. The higher solubility of magnesium carbonate in water, 6.3 x 10 3 M, results from the larger solubility product constant. Nevertheless, both of these carbonate salts are rather insoluble, and the excess carbonate anions provided by the sodium carbonate effectively precipitate the calcium and magnesium ions from solution. 

Within a similar series of reagents, complexing tendency toward the different cycloamyloses can be qualitatively correlated with the size of the reagent. All three cycloamyloses, for example, are effectively precipitated from aqueous solution by benzene, but only cyclooctaamylose is precipitated by anthracene. Similarly, for cycloheptaamylose, bromobenzene is a more effective precipitant than benzene, whereas the reverse is true for cyclohexaamylose. Discriminating precipitants such as these have been incorporated by French and associates (1949) and by Cramer and Henglein (1958) into schemes for the separation of cyclohexa-, cyclohepta-, and cyclooctaamylose. 

The removal of inorganic salts from reaction mixtures afforded by polymeric materials may be simply and effectively accomplished by dialysis,166 178 after decomposition of remaining periodate with ethylene glycol130 131 or butylene glycol. 161 170 Alternatively, the iodate and periodate ions may be removed as such, or after reduction to free iodine. The iodate and periodate ions have been effectively precipitated by means of sodium carbonate plus manganous sulfate,6 or by lead dithionate,191 barium chloride,24 192 193 strontium hydroxide194 202 or barium hydroxide,203 204 lead... 

It is important to note that addition of iron salts keeps the sulfide as a precipitate in the wastewater and hinders the emission to the sewer atmosphere and the following negative effects. Precipitation of sulfide normally has no effect on the formation of sulfide. 

In the precipitation reaction involving chloride and silver nitrate, the addition of even a small quantity of the latter shall effect precipitation of AgCl provided that Ksp has been exceeded significantly. At this juncture, the concentrations of both Ag+ and Cl are related by the solubility-product equilibrium constant thus, we have ... 

In the former case the sodion is the precipitating ion, in the latter the chloride, it is evident however that the hydroxyl ion is more readily adsorded by the platinum than the chloride necessitating a greatly increased concentration of the sodium hydroxide to effect precipitation. 

Other agents besides ammonium sulfate or other salts can be employed to effect precipitation. As an example, for add-stable enzymes such as are often encountered in proteins from Lactobacilli, responsible for spoiling milk, low pH conditions often lead to precipitation of unwanted proteins while the target protein survives (for an example, see Riebel, 2002). Likewise, heat (typically 1 h at 50-60°C) can be employed to separate heat-labile proteins from more stable ones. 

Saponins appear to lower plasma LDL cholesterol concentration by interfering with cholesterol absorption. Studies in rats and monkeys fed naturally occurring saponins exhibited significant reductions in cholesterol absorption efficiency and an increase in fecal cholesterol excretion (Malinow et al., 1981 Nakamura et al., 1999 Sidhu et al., 1987). Decreased bile acid absorption and increased excretion has also been reported in animals fed saponins (Malinow et al., 1981 Nakamura et al., 1999 Stark and Madar, 1993). One possible mechanism of action for decreased cholesterol absorption is the ability of saponins to form insoluble complexes with cholesterol (Gestetner et al., 1972 Malinow et al., 1977). In an effort to isolate the specific properties of saponins, Malinow (1985) prepared a variety of synthetic saponins in which the complex carbohydrate moieties of native plant saponins were replaced with simplified carbohydrates such as glucose or cellobiose. One of these synthetic saponins, tiqueside (Pfizer, Inc.), can effectively precipitate cholesterol from micelle solutions in vitro and inhibit cholesterol absorption in a variety of animals (Harwood et al., 1993) and in humans (Harris et al., 1997). But despite ample data showing the formation of a saponin/cholesterol complex in vitro, there is essentially no definitive evidence that complexation occurs in the intestinal lumen (Morehouse et al., 1999). 

A number of other precipitating agents have been used in the purification of proteins. In some instances, the use of sodium sulfate can result in a purer antibody preparation, but generally it does not offer advantages over ammonium sulphate. Caprylic (octanoic) acid, however, offers a different approach and also has a long history of use (5). Conditions can be created where this short chain fatty acid will effectively precipitate the majority of serum proteins with the exception of the immunoglobulins. 

Fig. 9.10 Monthly mean <5lsO values in precipitation and monthly mean air temperatures from 1971-1978 for Swiss stations. The value of January (1) is shown twice to complete the cycle. The d180 values are seen to covary with the temperature, reflecting a pronounced temperature effect of 0.35-0.5%o d180/°C. The measurements, carried out at three stations of different altitudes, revealed an altitude effect, precipitation at higher altitudes having isotopically lighter compositions. (From Siegenthaler and Oeschger, 1980.)...

Barium is seen in Fig. 16.12 to drop faster than chlorine in wells TW 11 and TW 20, indicating effective precipitation en route. 

Moreover, intermacromolecular complex formation is applied to selective recovery of organic and metallic ions. For example, as shown in Table 27, Cu2+ ion is much more effectively precipitated by the polyelectrolyte complex than by one of its components520. Furthermore, polyelectrolyte complexes including some metal ions have been studied in recent years (see Sect. 3.2.). Crown ethers can bind certain cations they especially exhibit high affinity to K+. Smid et al.S21) synthesized poly(vinylbenzo-[18]-crown-6). Such polymers containing crown ether with K+ behave like polycations in solution and can interact with polyanions such as poly(carboxyHc acid) to generate a kind of polyelectrolyte complexes. Moreover, PAA may interact with the ether oxy-... 

Double carbonate, double sulfate or double acetate has been used to separate and recover actinide so far (7, 8). However,high concentrations of carbonate, sulfate or acetate are necessary for their effective precipitation. On the other hand, relatively low concentrations of sulfate or carbonate are sufficient for the precipitation of actinide in the present method. Therefore, it is favorable for treatment of waste solution after separation and recovery of actinide. 

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