Acid tailings solutions

Phospholipids are the most important of these liposomal constituents. Being the major component of cell membranes, phospholipids are composed of a hydrophobic, fatty acid tail, and a hydrophilic head group. The amphipathic nature of these molecules is the primary force that drives the spontaneous formation of bilayers in aqueous solution and holds the vesicles together. 

PANI is usually produced by the anodic oxidation of aniline in acidic aqueous solution [5, 139], but can also be produced by chemical oxidation [138b, 140]. Hence, it is not surprising that the oxidation of PANI is pH-dependent and that, therefore, in addition to electron-transfer processes, proton-transfer reactions occur during charging. Although it is usually assumed that PANI has a chain structure (emeraldine) with head-tail connections... 

Some authors based their approach to selective binding of the more lipophilic a-amino acids in water on hydrophobic effects using water-soluble, cavity-containing cyclophanes for the inclusion of only the apolar tail under renouncement of any attractive interaction of the hosts with the zwitterionic head . Kaifer and coworkers made use of the strong affinity of Stoddart s cyclobis(paraquat-p-phenylene) tetracation 33 for electron-rich aromatic substrates to achieve exclusive binding of some aromatic a-amino acids (Trp, Tyr) in acidic aqueous solution [48]. Aoyama et al. reported on selectivities of the calix[4]pyrogallolarene 34 with respect to chain length and t-basicity of aliphatic and aromatic amino acids, respectively [49]. Cyclodextrins are likewise water-soluble and provide a lipophilic interior. Tabushi modified )S-cyclodextrin with a 1-pyrrolidinyl and a carboxyphenyl substituent to counterbalance the... 

Liposomes are artificial structures composed of phospholipid bilayers exhibiting amphiphilic properties (chapter 12). In complex liposome morphologies, concentric spheres or sheets of lipid bilayers are usually separated by aqueous regions that are sequestered or compartmentalized from the surrounding solution. The phospholipid constituents of liposomes consist of hydrophobic lipid tails connected to a head constructed of various glycerylphosphate derivatives. The hydrophobic interaction between the fatty acid tails is the primary driving force for creating liposomal bilayers in aqueous solutions. 

Absorption Abatement or extended absorption refers to modifications that involve the addition of increased absorption capacity or optimization of the existing absorption system to oxidize and react the nitrogen oxides with water to form acid.. Tail gases are passed through an absorber containing either water or an aqueous solution of ammonia, urea or sodium hydroxide. When water is used as the absorbent, the resultant weak acid is recycled. This increases nitric acid yields by 1% to 3%. When other absorbents are used, the recovered NOx is typically consumed in the production of nitrogen solutions for fertilizer use. If sodium hydroxide is the absorbent, pure sodium nitrite and sodium nitrate may be recovered91,104. 

Membrane lipids spontaneously form extensive bimolecular sheets in aqueous solutions. The driving force for membrane formation is the hydrophobic interactions among the fatty acid tails of membrane lipids. The hydrophilic head groups interact with the aqueous medium. Lipid bilayers are cooperative structures, held together by many weak bonds. These lipid bilayers are highly impermeable to ions and most polar molecules, yet they are quite fluid, which enables them to act as a solvent for membrane proteins. 

The formation of -aminodiphenylamine is supposed to be the key intermediate in the formation of a dark green precipitate at the electrode surface during continued electrolysis of acidic aniline solutions. This has been characterized as an oligomer of aniline, for example, as the octamer emeraldine formed by a cascade of head-to-tail condensations [38,39]. Nelson, however, explained it as a mixture of mainly quinhydrone with a small amount of benzidine salt [37]. Today the electropolymerization of aniline under strongly acidic conditions is intensively studied as an important way to form the conducting polymer polyaniline [40] (see Chapters 31 and 32). 

Chemical absorption in scrubbers, which employ any of water, nitric acid, alkaline solutions, or solutions of urea in water can reduce tail gas NOx concentrations to below 200 ppm [55]. Physical adsorption on molecular sieves is also a feasible control method. Activated carbon cannot be used because of oxidation hazards. Chemical and physical adsorption were improved if both nitric oxide and nitrogen dioxide were present in the tail gas rather than just nitric oxide, perhaps from the formation of dinitrogen trioxide (N2O3). An advantage of any absorption or adsorption system is that the NOx collected is recovered in some form. 

Figure 5.7 Titration of an acid uranium mill-tailings solution with a standard NaOH solution. The tailings solution had a pH of 0.9 and TDS =112 g/L. A solution analysis showed that in addition to the important acid species present were HSO4, Fe, and AF. Data and plot from Langmuir and Nordstrom (1995). See Problem 8 at the end of this chapter.

TABLE A12.4 Chemical analyses of some acid mine waters, tailings waters, and a wastewater (tailings solution)... 

Note Values are in mg/kg except as indicated. All samples except the Bluewater Mill sample acquired their initial acidities and solutes because of pyrite oxidation. The Bluewater Mill tailings solution is derived from sulfuric acid leaching of uraniferous sandstone ore. Although listed as Fe(III), iron concentrations in the Bluewater Mill solution and Coal A leachate are total iron values. Except for Bluewater Mill and Coal A laboratory studies. Eh and pH values were measured in the field. All samples were filtered through 0A5foa filters prior to acidification, except for Well 201. 

Felmy, a, R S. a, Peterson, and R. J. Serne. 1987. Interactions of acidic uranium mill tailings solution with sediments Predictive modeling of precipitation/dissolution reactions. Uranium 4 25-41. 

A series of oc- and j -axial diaquo and aquocyano positional isomer complexes of cobinamide, cobyric acid, and cobinic acids-1, -2 and -3 were separated using a C,g colimm (A = 365nm) and a 30/4/64 acetonitrile/THF/water (80 mM pyridine acetate at pH 3.6) mobile phase [1265]. Retention times varied from 5.4 to 13.6min and resolution times between isomers was always >0.5min. The diaquo-cobinamide and diaquocobinic acid-2 solutes generated tailed peaks. 

Given the structural similarity between the carbon side-chains of the pyrone molecules and the fatty acid tails of membrane phospholipids, it was considered plausible that peroxidation of the pyrone molecules might occur in a similar fashion to lipid peroxidation (Sect. 1.2.2.3, Scheme 14), resulting in end products derived from 44, 43 and 9, which would themselves form adducts with thiobarbi-turic acid (124), potentially skewing the results of the assay. In order to rule this out a set of negative control experiments were conducted. This involved irradiation of aqueous solutions of the pyrone molecules, at the concentrations used in the liposomal studies, but in the absence of the liposomes themselves. The samples were then tested for TEARS using the same assay method as above. The results are depicted in Fig. 4.3. 

To a tail-form beaker is added a solution of 3.0 ml (0.014 mole) of sebacoyl chloride dissolved in 100 ml of distilled tetrachloroeth-ylene. Over this acid chloride solution is carefully poured a solution of 4.4 gm (0.038 mole) of hexamethylenediamine (see Note) dissolved in 50 ml of water. The polyamide film which begins to form at the interface of these two solutions is grasped with tweezers or a glass rod and slowly pulled out of the beaker in a continuous fashion. The process stops when one of the reactants becomes depleted. The resulting rope -like polymer is washed with 50% aqueous ethanol or acetone, dried, and weighed to afford 3.16-3.56 gm (80-90%) yields of polyamide, 7i h = 0.4 to 1.8 (w-cresol, 0.5% cone, at 25°C), m.p. 215°C (soluble in formic acid). 

Figure 10.10 shows the PSDs of a natural clay with 79% kaolinite content before and after thermal activation at 700°C. Two optical models (model A, n = 1.55, k = 0.01, and model B, w = 1.529, k = 0.01) were used after dispersion in 0.01 wt.% polyacrylic acid aqueous solutions (pH around 10, adjusted with NH4OH). Further information on the powder chemical composition and thermal treatment can be found in Souri et al. (2015). It can be seen that the two models give comparable results, albeit with the slightly lower refractive index of 1.529 a finer tail is observed before thermal activation (D io = 1 00 pm and [n = 1.529] = 0.33 pm), again... 

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