Aluminum acid precipitation

Magnesium nitrate is prepared by dissolving magnesium oxide, hydroxide, or carbonate in nitric acid, followed by evaporation and crystallization at room temperature. Impurities such as calcium, iron, and aluminum are precipitated by pretreatment of the solution with slight excess of magnesium oxide, followed by filtration. Most magnesium nitrate is manufactured and used on site in other processes. 

The low pH of acid precipitation can destroy forests and kill fish. Some lakes and streams lie in soil that has the natural ability to buffer the increased acidity of acid rain, usually because the soil contains a high amount of lime. Other lakes and streams, however, have no such buffering capacity. The pH of the water is not the main problem—at least not directly. The problem lies in the amount of aluminum compounds that are leached out of the soil surrounding the lake or stream at lower pHs. Aluminum is toxic to many aquatic species. 

Anortal [Anorthosite aluminium] A process for extracting alumina from anorthosite ore (a calcium aluminosilicate) by leaching with hydrochloric acid, precipitating aluminum trichloride hexahydrate, and calcining this. Developed and piloted by I/S Anortal in Norway in the late 1970s but not commercialized. 

Rubidium acid salts are usually prepared from rubidium carbonate or hydroxide and the appropriate acid in aqueous solution, followed by precipitation of the crystals or evaporation to dryness. Rubidium sulfate is also prepared by the addition of a hot solution of barium hydroxide to a boiling solution of rubidium alum until all the aluminum is precipitated. The pH of the solution is 7.6 when the reaction is complete. Aluminum hydroxide and barium sulfate are removed by filtration, and rubidium sulfate is obtained by concentration and crystallization from the filtrate. Rubidium aluminum sulfate dodecahydrate [7488-54-2] (alum), RbA SO 12H20, is formed by sulfuric acid leaching of lepidolite ore. Rubidium alum is more soluble than cesium alum and less soluble than the other alkali alums. Fractional crystallization of Rb alum removes K, Na, and Li values, but concentrates the cesium value. Rubidium hydroxide, RbOH, is prepared by the reaction of rubidium sulfate and barium hydroxide in solution. The insoluble barium sulfate is removed by filtration. The solution of rubidium hydroxide can be evaporated partially in pure nickel or silver containers. Rubidium hydroxide is usually supplied as a 50% aqueous solution. Rubidium carbonate, Rb2C03, is readily formed by bubbling carbon dioxide through a solution of rubidium hydroxide, followed by evaporation to dryness in a fluorocarbon container. Other rubidium compounds can be formed in the laboratory by means of anion-exchange techniques. Table 4 lists some properties of common rubidium compounds. 

The ability of mineralized soil to control the migration of aluminum was observed in another study. Acidic leachate from coal waste containing aluminum was percolated through soil containing varying amounts of calcium carbonate (Wangen and Jones 1984). Soluble aluminum was found to decrease dramatically as the pH of the percolating leachate increased and aluminum oxide precipitates formed at pH 6, no dissolved aluminum was measured. The authors concluded that alkalinized carbonaceous soils provide the best control material for acidic leachates from coal mineral wastes. 

Aluminum levels in groundwater wells at neutral pH generally fall below 0.1 mg/L (100 ppb) (Brusewitz 1984). In areas receiving acid precipitation, aluminum levels in groundwater may be more than 10 times the levels found in areas with neutral pH levels in the water (Brusewitz 1984), possibly due to precipitation of aluminum compounds in the more alkaline medium, or the reaction of aluminum with available silicates. In another study, Miller et al. (1984) reported that the median concentration of aluminum in finished water obtained from groundwater was 0.031 mg/L (ppm) (range,... 

Hemenway DR, Fitzgerald B. 1984. Characterization of aluminum chemistry for acid precipitation. Burlington, Vermont University of Vermont, Vermont Water Resources Research Center. Project Number G873-05. NTISNo. PB85-214542. 

Sparling DW. 1990. Acid precipitation and food quality Inhibition of growth and survival in black ducks and mallards by dietary aluminum, calcium, and phosphorus. Arch Environ Contain Toxicol 19 457-463. 

The reaction mixture is now transferred to aluminum cooling tanks, and is allowed to cool slowly, over a period of 3 to 4 days, to a terminal temperature of 15-25°C (room temperature). The acetylsalicylic acid precipitates as large, regular crystals. The mother liquor is now filtered or centrifuged from the precipitated acetylsalicylic acid and the filter cake is pressed or centrifuged as free of mother liquor as possible. The crystals are washed with distilled water until completely free of acetic acid, pressed or centrifuged as dry as possible and the filter cake is then dried in a current of warm air at a temperature of 60-70°C. 

To form aspirin, the salicylic acid is refluxed with acetic anhydride in toluene at 88 to 92°C for 20 hours. The reaction mixture is then cooled in aluminum cooling tanks, and the acetylsalicylic acid precipitates as large crystals that are separated by filtration or by centrifugation, washed, and dried. 

Arsenic in soilds has been fractionated by Jackson s T28) procedure for soil phosphorus (15. 27). In this laboratory, a modification of Jackson s procedure is being used on sediment solids. A series of 1 molar solutions of NH4CI, NH4OH, acid ammonium oxalate (29) and HCl are used in sequence. The chloride fraction, or exchangeable fraction, contains weakly adsorbed, coulombically bound arsenic. The hydroxide fraction, contains iron and aluminum arsenate precipitates and surface precipitates (i.e. adsorbed arsenic species having both chemical and coulombic bonding to oxide surfaces). The oxalate, or reductant soluble fraction, contains arsenic occluded in amorphous weathering products. The acid, or calcium, fraction contains arseno-apatites. 

By dissolving aluminum in hydrochloric acid, precipitating Al(OH)3 with base, and heating the collected precipitate to convert it to the oxide, the ratio of aluminum to oxygen in the oxide was found to be 1.124015. Calculate from this experimental value the atomic weight of aluminum. 

A mixture of 10 g. (1.1 mole) of toluene, 40 g. of carbon disulfide (Caution—toxic volatile substance) and 15 g. (1.1 mole) of aluminum chloride is cooled to —10°, and dry hydrogen chloride gas is introduced for 5 minutes. (Hood.) Sulfur dioxide is then introduced for 2 hours, and the mixture is allowed to stand for 12 hours, after which it is poured on ice. Sodium carbonate is added until the mixture is alkaline, and the carbon disulfide is removed by steam distillation. The alumina is removed from the reaction mixture by filtration, and the filtrate is evaporated to a volume of 150 ml. Addition of hydrochloric acid precipitates 16 g. (94%) of p-toluenesulfinic acid melting at 84°. 

Cronan C. S. and Schofield C. L. (1979) Aluminum leaching response to acidic precipitation effects on high-elevation watersheds in the Northeast US. Science 204, 304-306. 

Morphological studies explain the mechanisms of E-glass corrosion. According to these studies, acid corrosion of E-glass is caused by calcium and aluminum depletion which varies depending on the acid type, fiber type, and acid concentration. Oxalic and sulfuric acids are more corrosive than nitric and hydrochloric acids. This difference is due to the fact that, in oxalic acid, precipitated products are formed which decrease the concentration of leachates in solution. In addition to the loss of mineral content, fibers develop axial and spiral cracks. Crack formation depends on the rate of material depletion. 

Acidification of aqueous concentrates and extracts to pH near 1 is the standard procedure to precipitate humic from fulvic acid, and this procedure also has been applied to aquatic humic substances (Thurman and Malcolm, 1981). Aquatic humic substances that interact significantly with metal ions can be precipitated from water by addition of lead(Il) nitrate (Klocking and Mucke, 1969). Co-precipitation of aquatic humic materials with aluminum, copper, iron, and magnesium hydroxides has been used to recover aquatic humic substances from various types of water (Jeffrey and Hood, 1958 Williams and Zirino, 1964 Zeichmann, 1976). Humic acids can also be precipitated from an unconcentrated water sample by adding acetic acid and isoamyl alcohol to a sample contained in a separatory funnel, and after shaking, humic acid precipitates at the alcohol-water interface (Martin and Pierce, 1971). Precipitation methods are among the crudest of fractionation methods... 

Figure 12.25 (a) Plot of log 1AP versus pH for 64 samples from a drainage basin affected by acid mine waters from the Leviathan mine, Cali-fornia-Nevada. Points shown as open squares have pH <4.6, plus symbols are those with pH >4.9. The solid lines are theoretical solubilities of amorphous AI(0H)3 and microcrystalline gibbsite. (b) Plot similar to (a) for acid mine drainage from Appalachia (solid circles) and Adirondack lake waters affected by acid precipitation (open circles). From Science 232 54-56, D. K. Nordstrom and J. W. Ball, The geochemical behavior of aluminum in acidified surface waters. Copyright 1986 by Science-AAAS. Used by permission. 

Blush and bloom are caused by the etching of the anodized oxide which changes the surface reflectivity of the trim material. Problems of a milky white appearance (blush and bloom) on the surface of anodized aluminum trim have frequently been reported. However, this effect has been more pronounced in recent years in the Northeast USA and Canada. Although in previous years the problem has been related to quality variations, recent data indicates that acid precipitation enhances this effect. 

The combination of acid precipitation with road salt spray produced the worst effects on anodized aluminum. As the MIST test pH became more acidic and the amount of salt increased the time to achieve an equivalent milky white appearance was reduced significantly (Table I). At more neutral high chloride concentrations severe pitting occurred while at more acid high chloride concentrations blush and bloom predominated. The latter environment is similar to that existing in the Northeast USA and Canada and, therefore, the results can explain the problems of blush and bloom in these areas. Corrosion surveys by automotive companies and trim producers in these areas have shown that blush and bloom and pitting have become increasingly more severe over the last ten years.5 These problems have led to a shift away from anodized aluminum as an automotive trim material in recent years. 

An accelerated MIST test procedure has been developed which duplicates the mechanisms of corrosion of anodized aluminum trim in automotive environments. Blush and bloom of anodized aluminum automotive trim is more severe in environments with acid precipitation and this effect can be duplicated in an acidified MIST test procedure. Pitting of anodized aluminum is more prevelant in automotive environments with high chloride concentrations and this effect can be duplicated in a neutral chloride MIST test procedure. A change in the mechanism of corrosion of anodized aluminum trim from pitting to blush and bloom in chloride containing environments occurs in the pH range of 2 to 4. These results indicate that blush and bloom of anodized aluminum will become more severe as the acidity of precipitation increases. Thus more expensive trim materials such as bimetal are being used by the automotive industry. 

Driscoll, C. T., J. P. Baker, J. J. Bisogni, and C. L. Schofield (1984), Aluminum Speciation and Equilibria in Dilute Acidic Surface Waters of the Adirondack Region of New York State, in O. R. Bricker, Ed., Acid Precipitation Geological Aspects, Butterworth, Boston. 

The formation of hydroxyaluminosilicate species at near-neutral pH is unique. No interactions occur between silicic acid and Ca2+ or Mg2+ at less than pH 10, so that the transport and binding of these cations is unhindered. The interactions of Fe3+ with silicic acid at near-neutral pH are very different from those of aluminum. Acidic solutions containing Fe3+ (10-4 M) with a threefold molar excess of silicic acid remain clear on neutralization no visible precipitate forms. Instead, Fe-O polymers are formed as spherical hydrated ferric oxide particles 10-15 nm in diameter,... 

It seems likely that there are some natural aqueous systems, especially those impacted by acidic precipitation or discharges of acid mine drainage, in which polymeric Al species like those studied in this work will be formed. Most of these systems will contain solid surfaces, and a tendency for aluminum polymeric species to nucleate and precipitate on certain types of mineral surfaces was documented by Brown and Hem (21). Conclusions relevant to the probable course of the aluminum hydroxide polymerization process in natural water may be summarized as follows ... 

A commonly observed effect of acidic precipitation is an increased concentration of aluminum in water of streams and lakes. Water of lakes that received acidic runoff may increase in transparency (26) owing to coagulation and settling of suspended organic and inorganic particulates. This effect is probably related to aluminum hydrolysis, as it is the same as the coagulation step in water-supply treatment cited earlier. 

A study of the chemistry of a small California stream that receives acid mine water (27) showed that above pH 4.9 the dissolved aluminum concentration appeared to be controlled by aluminum hydroxide solubility equilibria, but below pH 4.6 aluminum hydroxy-sulfates apparently predominated. This study also cited data for acid mine drainage in the Appalachian region and lakes affected by acid precipitation that showed a similar pattern of aluminum behavior. 

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