Adsorption of hydrochloric acid

Isotherms are presented for adsorption of hydrochloric acid on coconut carbon in the presence of different concentrations of NaCl. The solid lines represent the corresponding calculated Freundlich isotherms, respective values for the parameters of which are given in Table II... 

It has been established for Pt(100) and Pt(l 11) that when the specific adsorption of hydrochloric acid is strong enough, anions are partially displaced from the surface-adsorbed oxygen with negligible transient currents. For Pt(100), this strong specific adsorption also induces a surface atomic rearrangement toward a more stable surface with a more densely packed structure similar to the (5 x 20) reconstruction observed in the gas phase. 

K.A. Kraus and G.E. Moore, Anion exchange studies. V. Adsorption of hydrochloric acid by a strong base anion exchanger, J. Am. Chem. Soc., 1953, 75, 1457-1460 F. Nelson and K.A. Kraus, Anion exchange studies. XXIII. Activity coefficient of some electrolytes in the resin phase, J. Am. Chem. Soc., 1958, 80, 4154. 

K.A. Kraus and G.E. Moore, Anion exchange studies. V Adsorption of hydrochloric acid by a strong base anion exchanger, J. Am. Chem. Soc., 1953, 75, 1457-1460. 

Wilhelm Ostwald with A. Kelberin showed that the adsorption of hydrochloric acid by charcoal is reversible, the same equilibrium state being reached if a concentrated solution is diluted after adsorption as if a dilute solution were used initially, and the results were reproducible. The adsorbed amount plotted against the dilution of the solution gave a hyperbolic curve. Ostwald pointed out the importance of adsorption in dyeing and the retention of salts in soil. He refers to experiments by van Bemmelen, who at first inclined to a chemical theory, whereas Ostwald suggested that the phenomena were due to mechanical affinity . 

On the addition of a neutral chloride to the solution the chlorine ion concentration is increased, and provided that the cation of the added chloride does not affect the adsorption of the hydrogen ion, i.e. on addition of a weakly adsorbed cation, such as potassium, the adsorption of the hydrogen ion can now proceed to its normal equilibrium value without having to retain any adsorbed chlorine ions by electrostatic attraction. The addition of potassium chloride to a hydrochloric acid solution will thus augment the adsorption of the acid by the charcoal, a result confirmed by Michaelis and Rona. 

Zirconium Arsenates.—Zirconium Orthoarsenate, Zr3(As04)4. 5H20, has been obtained 5 as a voluminous white precipitate by adding sodium monohydrogen orthoarsenate to a solution of zireonyl fluoride in hydrochloric acid. Zirconium monohydrogen orthoarsenate, Zr(HAs04)2, appears to be formed slowly by adsorption of arsenic acid by zirconium dioxide.6... 

Figure 2. Finite-bath rates of adsorption for hydrochloric acid...

Figure 13. Finite-bath rate of adsorption for hydrochloric acid at 2°C.

The specific surface area of only the pyrocarbon (Sc) was determined by p-nitrophenol (PNP) adsorption (assuming preferable adsorption of PNP onto carbon deposits) from an aqueous solution of hydrochloric acid, studied using a Specord M-40 (Karl Zeiss, Jena) UV/vis spectrophotometer at 400 nm. This technique was described in detail elsewhere.12... 

Kargin, 1928 Kargin and Kiseleva, 1938) believes that sols of Fe(OH)3 always contain a certain amount of hydrochloric acid which acts as the stabilizing electrolyte, and the positive charge of the granule is produced by adsorption of ions. The opinion prevailing at present is that the stabilizer is the product of incomplete hydrolysis of perchlorate of iron (FeOCl) formed according to the equation ... 

SAFETY PROFILE A highly corrosive irritant to the eyes, skin, and mucous membranes. Mildly toxic by inhalation, Explosive reaction with alcohols + hydrogen cyanide, potassium permanganate, sodium (with aqueous HCl), tetraselenium tetranitride. Ignition on contact with aluminum-titanium alloys (with HCl vapor), fluorine, hexa-lithium disilicide, metal acetylides or carbides (e.g., cesium acetylide, rubidium ace-tylide). Violent reaction with 1,1-difluoro-ethylene. Vigorous reaction with aluminum, chlorine + dinitroanilines (evolves gas). Potentially dangerous reaction with sulfuric acid releases HCl gas. Adsorption of the acid onto silicon dioxide is exothermic. See also HYDROGEN CHLORIDE (AEROSOL) and HYDROCHLORIC ACID. 

Both hydrochloric acid and barium chloride cause occlusion of chloride. Hydrochloric acid is worse than barium chloride in this respect. Therefore the sulfate solution before the precipitant is added should not contain more than 0.1% of hydrochloric acid by volume 17, J]. A further complication caused by excess acidity is adsorption of H ions, which causes liberation of sulfuric acid when barium sulfate is ignited [2, J]. In addition to this, high acidity of reaction solution will cause error because of the solubility of barium sulfate in hydrochloric acid. The solubility of barium sulfate in water, though small, is not negligible (4 mg/ L at 20°C). The presence of mineral acid increases the solubility to a considerable extent, that is, in 0. IN hydrochloric acid the solubility of barium sulfate is about 10 mg/L at 20°C [4]. This limits the amount of hydrochloric acid that can be used. A concentration of O.OSN with respect to hydrochloric acid before precipitation has been found to be most suitable [4,5]. 

Elemental analysis was carried out by inductively coupled plasma using a TJA IRIS-HR spectrometer after dissolving the compounds in a minimum amount of hydrochloric acid. X-ray diffraction spectra (XRD) were recorded on a Siemens D-500 diffractometer with a graphite-filtered CuKa radiation (1,5405 A). ESR spectra were recorded at 77 K using an ER 200 tt Brucker spectrometer. An ASAP 2000 Micrometries apparatus measured specific surface areas by nitrogen adsorption at 77K after degassing the samples in situ at 353 K for 4h. 

The benzoylation of resorcinol to produce 2,4-dihydroxybenzo-phenone has been previously performed with benzotrichloride, which implies the coproduction of 3 mol of hydrochloric acid and consequently a large amounts of acid waste. " Alternative routes to 2,4-dihydroxyben-zophenone involve direct acylation of resorcinol with benzoyl chloride (BC) or the Hoesch reaction with benzonitrile, which also suffer from acid waste production. In a more ecoefficient approach, the reaction was performed with benzoic acid (BAC) in the presence of some solid catalysts, with a special focus on BEA zeolite (Scheme 5.9). The progress of the reaction in para-chlorotoluene is examined, and after 18 h, 2,4-dihy-droxybenzophenone (2,4-DHB) is isolated in 70% yield, together with 20% of resorcinol monobenzoate (RMB), 3% of resorcinol dibenzoate, 5% of BAC, and 2% of resorcinol. The fact that the concentration of resorcinol in the final mixture is somewhat lower than that of BAC is probably due to the preferred adsorption of the former. The process is then studied by using different substituted BACs the different conversions of 2-methyl-,... 

Figure 6.29 Change in adsorption behavior of hydrochloric acid and sulfuric acid on anion exchange membrane with acid concentration. Anion exchange membrane NEOSEPTA AFN (strong basic anion exchanger).

Before conducting the quantitative analysis of carboxylic acids, especially of their bifunctional derivatives, as well as high-boiling acids, they are converted into more stable and less adsorptionally active derivatives. Methyl esters are frequently used as derivatives of acids in GC analysis. To obtain methyl esters of carboxylic acids, diazomethane [101, 148, 150, 335], a methanolic solution of hydrochloric acid [164, 336], a methanolic solution of boron trifluoride [f51, 152, 337], pyrolysis of tetramethyl-ammonium salts [166, 338, 339] and other methods [181,340-344] have been used. In a number of instances [345—347] higher esters are used. The sensitivity of detection with an BCD is increased when halogen-containing reagents are used to obtain esters... 

Losses of Os can occur during evaporation of hydrochloric acid solution of chloroosmate(IV) and during fusion of geomaterials. Os(IV) can be isolated by hydrous precipitation of the hydrous oxide. A 10% NaHCOs solution is added to the boiling solution until a precipitate appears and suddenly coagulates. Os(IV) can be separated from base metals by adsorption of the latter on a strong-acid cation-ex-change resin (Dowex 50W-X8) from an HCl solution of pH 0.8-1.5. Os(Vni) oxide can be extracted from aqueous medium by carbon tetrachloride and chloroform and also distilled (see Ru section). The distillate is collected in 6 mol 1 HCl saturated with SO2. 

Crystallization is able to recover the desired product (in solid or crystal form) without many process control operations. After removal of cell biomass and organic impurities by centrifugation and activated carbon absorption, respectively, a direct vacuum distillation-crystallization is used for succinic acid recovery from broth by Luque et al. (2009). The pH of the aqueous broth is adjusted to 4.2 by addition of hydrochloric acid before vacuum distillation. Some volatile by-product carboxylic acids, such as acetic, formic acids, in broth are removed under vacuum distillation at 60 °C. The followed crystallization of succinic acid is carried out at 4 °C. When this method is used in a simulated broth, the highest succinic acid yield and purity are 75 % and 97 %, respectively. Another direct crystallization method at normal pressiue bases on the principle that carboxylic acids have different distribution with their dissociated and undissociated forms at different pH, and the undissociated carboxylic acid has different solubility (Li et al. 2010b). The solubility of succinic acid is 3 % at 4 °C, pH 2.0, while the other acid by-products, such as lactic acid, acetic acid, and formic acid, are still fully water miscible. Thus, crystallization of succinic acid can be carried out at 4 °C and pH < 2. While acidic by-products remain in the solution, succinic acid could be selectively crystallized. By this one-step recovery technique, succinic acid yield and purity are 70 % and 90 %, respectively. However, much succinate is still residual in the broth, and the product of low piuity cannot be used as a monomer for polymerization. To obtain a higher purity of succinic acid, coupled purification processes such as adsorption or membrane separation are needed for broth to remove residual impurities (Wang et al. 2014). 

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