| While having the nature of acidic and alkaline at the same time, glycolic acid has been widely used in the synthesis of biodegradable materials, chemical cleaning agents and household chemical products. At present, domestic enterprises mainly use hydroxyl acetonitrile hydrolysis method to produce glycolic acid, which is unable to meet requirements in organic synthesis, pharmaceutical and cosmetic industries due to its low product purity.Therefore, it’s need to establish simple and efficient way to separate and purify glycolic acid ingredient.In this paper, absorption and separation technology was used to separate and purify two components in ammonium sulfate and glycolic acid mixture solution. In the absorption process, ammonium sulfate penetrates earlier than glycolic acid, while glycolic acid later than glycolic acid in the process of desorption. According to this feature, adsorption and desorption experiments were taken by using macroporous resin. Purified ammonium sulfate component in the process of adsorption and glycolic acid in desorption process, finally to achieve the purpose of separation and purification of two components. At the same time, the theoretical analysis for the adsorption of two components was made to provide theoretical guidance for the application of absorption and separation technology in the mixture of ammonium sulfate and glycolic acid.The main research and conclusions are as follows:1. Study on analysis method of two components in ammonium sulfate and glycolic acid mixed solutionThe colored substance 3,5-diacetyl-1,4-dihydropyridine(DEDHP) was generated by the reaction of formaldehyde and acetylacetone. A improved analysis method: The combined quantitative analysis method of DEDHP spectrophotometry ~ acid-base titration which based on formaldehyde and acid-base titration, introduced the acetylacetone spectrophotometry was established for determination of two components in ammonium sulfate and glycolic acid mixed solution. The influence of the content of ammonium sulfate and glycolic acid, ethanol concentration, p H value, temperature, time on determination of the content of two components by the method were studied.Suitable conditions: p H = 5~7, CGA < 0.9 mg·m L-1, 60 ℃ constant temperature for 15 minutes, the optimal detection wavelength was 414 nm. The measurement relative deviations of the two components were less than 1.5% and 1.8% respectively.2. Study on separation of two components in mixed solution on macroporous adsorption resinDynamic adsorption and desorption were used respectively to study various properties(polarity, specific surface area, aperture) of the resin on the adsorption and desorption law of ammonium sulfate and glycolic acid. The penetration capacity difference(ΔQ), ammonium sulfate purification rate(ηs), saturation capacity difference(ΔQe), glycolic acid purification rate(ηq) as index, separation of ammonium sulfate in the process of adsorption and glycolic acid in desorption process were investigated.On the basis of change law of ΔQ and ΔQe, it was found that the separation ability of the two components was stronger if the resin had larger polarity and specific surface area or aperture approximately equal to 160A°. Combining with change law of purification rate,HPD950 resin had the best separation effect and the suitable conditions of separation and purification were determined, 1) For adsorption experiments: 40 ℃ and keep the solid-liquid flow rate at 1.5 m L·min-1; 2) For desorption experiments: 40 ℃, 20% ethanol ~ aqueous solution as eluant and keep elution flow rate at 1.6 m L·min-1. Under these conditions,ammonium sulfate purification rate ηs0.9 and ηs1.0(purity > 90%, 100%) were approximately equal to 51 mg·g-1and 85mg·g-1, and glycolic acid purification rate ηq0.7(purity > 70%,industrial grade) and ηq0.99(purity > 99%, pharmaceutical grade) were approximately equal to262 mg·g-1 and 123 mg·g-1.3. Study on adsorption mechanism of two components in mixed solution on macroporous adsorption resin HPD950Adsorption behavior of the two components on resin HPD950 was researched by static adsorption. The influence of different temperatures, resin particle size and feed concentrations on the adsorption process were studied to investigate thermodynamics and kinetics of adsorption. Adsorption mechanism of the two components was probed in the adsorption process.In the thermodynamics study, adsorption process of ammonium sulfate and glycolic acid on HPD950 resin were in accordance with Langmuir isotherm model and Freundich isotherm model, and both of them were favorable adsorption. Both adsorption process of the two components were spontaneous(ΔG < 0), entropy increase(ΔS > 0) physical exothermic process(ΔH < 0,|ΔH| < 40 k J·mol-1). In the kinetics study, the adsorption rate of the two components appears to be the second order kinetic adsorption process, and the dominant procedure is intra-particle diffusion. The total kinetic equations of the two components were as follows:ammonium sulfate: t RT FCr F ?????????????????17499exp0786.0)1(213123/29620.0硫酸铵)(glycolic acid: t RT FCr F ?????????????????20521exp1961.0)1(2)1(3123/22554.1羟基乙酸... |
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