Acid deposition organic acids

The gas/particulate/aqueous forms of sulfuric and nitric acid are the major contributors in polluted areas. Smaller contributions in these areas are made by hydrochloric acid and organic acids (mainly formic and acetic). These latter contributions have usually been neglected in most acid deposition studies, with the exception of remote areas. However, atmospheric bases, mainly NH3 and Ca", and other crustal elements play as important a role as the acids, neutralizing to various extents the atmospheric acidity. The net acidity is... 

Oxidation first produces soluble oxygenated compounds of molecular weights between 500 and 3000 that increase the viscosity of oil then they polymerize, precipitate, and form deposits. Oxidation also causes formation of low molecular weight organic acids which are very corrosive to metals. 

In appHcations as hard surface cleaners of stainless steel boilers and process equipment, glycoHc acid and formic acid mixtures are particularly advantageous because of effective removal of operational and preoperational deposits, absence of chlorides, low corrosion, freedom from organic Hon precipitations, economy, and volatile decomposition products. Ammoniated glycoHc acid Hi mixture with citric acid shows exceUent dissolution of the oxides and salts and the corrosion rates are low. 

Three different types of chemical mechanisms have evolved as attempts to simplify organic atmospheric chemistry surrogate (58,59), lumped (60—63), and carbon bond (64—66). These mechanisms were developed primarily to study the formation of and NO2 in photochemical smog, but can be extended to compute the concentrations of other pollutants, such as those leading to acid deposition (40,42). 

Deposits contained organic acids formed by oxidation of rolling oils. Up to 40% by weight of the lumps shown in Fig. 4.27A and B was iron oxides, hydroxides, and organic-acid iron salts. Acidic species concentrated in the deposits. 

Clostridia are anaerobic bacteria that can produce organic acids. Short-chain organic acids can be quite aggressive to steel. Clostridia are frequently found deep beneath deposit and corrosion-product accumulations near corroding surfaces and within tubercles. Increased acidity directly contributes to wastage. 

Organic acids concentrated in deposits and caused most attack. 

F. ferro-oxidants is capable of accelerating the oxidation of pyritic (FeSj) deposits at acid pH values. It is usually found in association with Thio-bacillus and was known as Thiobacillus ferroxidans before the distinction between the two organisms was appreciated. It is responsible for pollution problems arising from acid waters in gold and bituminous coal mines such waters are corrosive to pumping machinery and mining installations (see Fig. 2.20). 

Preceding and subsequent homogeneous chemical reactions that occur in the bulk solution are very common. Examples include dehydration (when only a nonhydrated form of the substance is involved in the electrochemical reaction), protonation (e.g., of the anions of organic acids), and decay of complexes (in metal deposition from solutions of complex salts). 

Hydrochloric acid in combination with chlorine dioxide can be used as a treatment fluid in water-injection wells that get impaired by the deposition of solid residues [332,333]. The treatment seems to be more effective than the conventional acidizing system when the plugging material contains iron sulfide and bacterial agents because of the strongly oxidative power of chlorine dioxide. Mixtures of chlorine dioxide, lactic acid, and other organic acids [1172,1173] also have been described. 

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