Acetic acid adsorption from aqueous solution

Techniques of Purification. The purification techniques have included column and batch adsorption, extraction, dialysis, and column and paper chromatography. Liberal use was made of the fact that the gibberellate anion is not soluble in ethyl acetate, whereas the free acid is soluble, and that charcoal will adsorb GA3 from aqueous solutions but release it with acetone (26). As a rough rule, preliminary concentration by a factor of about 105 was necessary before significant use of paper chromatography could be made. For kudzu vine and pinto bean, a known amount of GA3 was added to an aliquot of the plant extract and taken through the same procedure as the initial extract. These controls are subsequently referred to as "spiked extracts, to differentiate them from the initial or "natural extract. 

In the presence of anions which are precipitated by calcium chloride solution, proceed as follows. Precipitate the acetic acid test solution with calcium chloride solution, and collect the precipitate on a filter or in a centrifuge tube. Remove the water from the precipitate either by drying or by washing with alcohol and ether. Mix a small amount of the precipitate with diphenylamine in a dry micro test-tube, add a little concentrated phosphoric acid, and heat gently over a free flame. Calcium phosphate and free oxalic acid are formed, and the latter condenses with the diphenylamine to aniline blue and colours the hot phosphoric acid blue. The colour disappears on cooling. Dissolve the melt in alcohol, when a blue colouration appears. Pour the alcoholic solution into water thus precipitating the excess of diphenylamine, which is coloured light blue by the adsorption of the dyestuff. The dye may be extracted from aqueous solution by ether. 

As concerns the isolation of Buxus alkaloids, this was conducted by extraction of the plant material with a suitable organic solvent directly (id) or after previous treatment with acetic acid (52, 180, 187) or after basification with ammonia or soda (188). The total alkaloids were often fractionated into weak and strong basic portions by extraction from aqueous solutions of alkaloid salts at appropriate pH and then subjected to separation by means of adsorption or partition chromatography (189). 

Aripov and co-workers have studied the adsorption of carboxylic acids from aqueous solution onto untreated bentonite and bentonite treated with alkylbenzyl-, alkylnaphthyl-, and alkylanthracyl-pyridinium ions. For natural bentonite the adsorption decreased in the order acetic, butanoic, and hexanoic acid, and for the modified surface in the order hexanoic, acetic, propionic, and pentanoic acid. 

Adsorption of Iodine and Acetic Acid from Aqueous Solution... 

The need to know the chemical nature of the adsorptive is well illustrated by two simple studies, that of iodine (I2) from an aqueous solution in potassium iodide (KI) and of acetic acid (CH3COOH) from an aqueous solution. The Kl acts as a reservoir for the iodine by forming KI3 (K and IJ). It is necessary to do this because of the limited solubility of iodine, as such, in water. What is needed to be known, for the construction of appropriate isotherms is the chemical nature of the adsorptive, be it (I2) or (If) for the iodine system, or CH3COOH or CH3C00H(H20) for the acetic acid system. Further, there is the need to elucidate if (a) the iodine is adsorbed via pore filling or via capillary condensation mechanisms and (b) to demonstrate uncertainties which exist when adsorbing species can be associated with water molecules in aqueous solution, as for adsorption of acetic acid (Hill and Marsh, 1968). 

Adsorption of acetic acid from aqueous solution most probably involves competition with the water molecules. Hence, it is difficult to distinguish between adsorption restricted to the microporosity (micropore pore filling), from the adsorption of hydrated acetic acid molecules (capillary condensation). 

Hill A, Marsh H. A study of the adsorption of iodine and acetic acid from aqueous solutions on characterized porous carbons. Carbon 1968 6(l) 31-39. 

Determine the parameters of the Freundlich adsorption isotherm [(C.28)] for the adsorption of acetic acid by active charcoal. The charcoal is used to absorb the acid from aqueous solutions of different concentrations. When equilibrium is reached the amount of acetic acid was determined by titration with standardized NaOH (0.1189 M). The data is given in Table C.B. 

Next we carried out the adsorption of various substances from liquid solutions or from the gaseous state in different preparations of carbon powder. Acetic acid, hydrogen chloride, ammonia and chlorine were adsorbed from aqueous solutions. Ethyl acetate was adsorbed from an ethanol solution, and ammonia and chlorine were adsorbed from gaseous phases. 

Hong YK, Hong WH, Oiang HN (2(X)0) Selective extraction of succinic acid from binary mixture of succinic acid and acetic acid. Biotechnol Lett 22 871-874 Inci I, Bayazit SS, Asci YS (2011) Separation of succinic acid from aqueous solution by alumina adsorption. J Qiem Eng Data 56 4449—4453... 

Cabon tetrachloride, n-hexane, chloroform, ACN, acetone, THF, pyridine, acetic acid, and their various mixtures were applied as mobile phases for adsorption TLC. Methanol, 1-propanol, ACN, acetone, THF, pyridine and dioxane served as organic modifiers for RP-TLC. Distilled water, buffers at various pH (solutions of and dipotassium hydrogen phosphate or potassium dihydrogen phosphate) and solutions of lithium chloride formed the aqueous phase. Carotenoids were extracted from a commercial paprika sample by acetone (lg paprika shaken with 3 ml of acetone for 30 min), the solution was spotted onto the plates. Development was carried out in a sandwich chamber in the dark and at ambient temperature. After development (15 cm for normal and 7cm for HPTLC plates) the plates were evaluated by a TLC scanner. The best separations were realized on impregnated diatomaceous earth stationary phases using water-acetone and water-THF-acetone mixtures as mobile phases. Some densitograms are shown in Fig.2.1. Calculations indicated that the selectivity of acetone and THF as organic modifiers in RP-TLC is different [14],... 

In the basic solution (run 5), the reaction rate was greatly reduced and the amount of acetic acid still increased. These results indicate that the oxidation may occur preferentially on the undissociated forms of the acids (pK, of succinic acid = 4.16, pKj = 5.61), rather than on the carboxylate ions, in agreement with previous results on selective oxidation of aqueous solutions of alcohols over noble metal catalysts. Slightly basic conditions favor the desorption of the acid salt from the surface and prevents C-C bond rupture and over-oxidation, whereas acidic pH favor the adsorption of the carboxylic acid and its further oxidation [14-15]. Similar results were observed by Imamura, et al. [11] in the oxidation of formic acid or acetic acid over 5 % Ru/CeOj. 

The technique for the isolation of nicotinic acid depends on the starting material. In most cases, a preliminary hydrolysis is required either with acids or alkalies. The extractions are more complete if the material is rendered free of lipids, a necessary step when working with animal products. The free acid is extracted from the hydrolysate with organic solvents such as hot alcohol. It may then be separated as such from the organic solvent extract or in the form of an ester or as the copper salt the free acid can be recovered from the copper salt by H2S treatment. Purification is carried out by crystallization from concentrated water or alcohol solutions. Nyc et al. extracted nicotinic acid from the mycelium of Neurospora with acetone. Subsequent purification steps included the formation of the barium salt, acidification with H2SO4 and adsorption of the free nicotinic acid on charcoal. Elution was accomplished with 4% aqueous aniline and the final purification step involves recrystallization from a i 4 mixture of acetic acid and benzene. Leifer et al. have applied paper chromatography with M-butanol saturated with ammonia to separate nicotinic acid from contaminating materials. 

The samples used in the adsorption studies were subjected to a five-stage sequential extraction scheme (Davis, 2001). Solutions obtained from each extraction step were analyzed for their elemental and U isotopic concentrations. As previously described (Payne, 1999 Payne Waite, 1991), U(VI) in the relatively weak extractions (acetate buffer and Tamm s acid oxalate, referred to as TAO) can be considered accessible to the groundwater. The U(VI) released in these extractions is of importance in quantifying the total amount of U(VI) that may participate in adsorption equilibria when the soil minerals are bathed in aqueous solutions. The quantification of the accessible U(VI) in each of the samples by the extractions was also supported by excellent agreement with that determined by U(VI) isotopic exchange (Payne, 1999 Payne Waite, 1991 Davis, 2001). 

A major advance was the isolation from yeast cells by Lynen and Reichert in 1951 of an acetylated coenzyme A derivative and the demonstration that the acetyl group is in all probability attached to the sulfur atom. As already mentioned, the existence of an acetylated coenzyme A had already been postulated before,but the acetylated form had not been isolated, nor was there any indication regarding the type of acetyl compound involved. Lynen succeeded in isolating active acetic acid from yeast cells which were allowed to respire in ethanol and acetic acid, killed by boiling, and extracted with phenol. The phenol extract after addition of ether was extracted with water, and the concentrated aqueous solution was treated with barium. The further fractionation of the barium salts employing adsorption on active charcoal, elution and precipitation by acetone, yielded a compound which showed the following properties ... 

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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