Method for recovering and purifying terephthalic acid in alkali-minimization waste liquor

Abstract

The invention relates to a method for purifying terephthalic acid in alkali-minimization waste liquor through acidolysis and crystallization, which comprises the following steps of: adsorbing to remove organic impurities and colored substances from the alkali-minimization waste liquor by using active carbon; adding a dilute acid solution into filtrate for acidolysis, and extracting the terephthalic acid from the waste liquor; drying and grinding a filter cake to obtain coarse terephthalic acid; dissolving and crystallizing the terephthalic acid by using a strong polar organic solvent, and performing recrystallization for multiple times to more effectively improve the purity of the terephthalic acid; and washing with water, filtering, drying, and refining the terephthalic acid to make the purity more than 99.8 percent, so that the terephthalic acid can be polymerized with glycol to produce polyester. By the method, the chemical oxygen demand (COD) of discharged wastewater can be effectively reduced, high-purity terephthalic acid can be obtained through recovery and purification, and waste materials can be reutilized.

Description

technical field [0001] The present invention relates to a recycling method of alkali reduction waste liquid, in particular to a technology for obtaining high-purity terephthalic acid from waste liquid, which mainly consists of regenerating crude terephthalic acid obtained after acid analysis of waste liquid Crystallization purification techniques. Background technique [0002] Alkali weight reduction waste liquid is a waste liquid produced during the process of hydrolyzing polyester fibers with alkali in order to make the produced polyester fabric more silky and imitative. In caustic soda solvent, polyester fibers are hydrolyzed under high temperature conditions to generate sodium terephthalate and ethylene glycol, and the degraded terephthalic acid and ethylene glycol monomers in polyester fabrics exist in water to form alkali weight reduction waste liquid, process principle : [0003] [0004] [0003] This processing technology produces organic wastewater with high ...

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Problems solved by technology

Anaerobic biochemical treatment mainly adopts upflow anaerobic biological sludge bed, backflow anaerobic biological filter bed, and composite anaerobic reactor. Terephthalic acid is finally anaerobic biodegraded, but the removal rate is generally only about 40%, and the start-up It takes a long time, and at the same time, this method degrades terephthalic acid to achieve environmental benefits, but fails to recycle terephthalic acid, resulting in waste of raw materials

Aerobic biochemical treatment of alkali reduction wastewater usually uses aerobic sludge activation method, but due to the unstable water quality and quantity of alkali reduction wastewater, high concentration of organic matter, wide range of pH value, and many organic matters that are not easy to degrade, some ordinary activated sewage Sludge swelling, weak impact resistance, and large amount of excess sludge occurred during the operation of the sludge. Later, although the above shortcomings were improved by replacing the activated sludge pool with a contact oxidation tank, the energy consumption was still high, and the output of excess sludge was large. Increase the investment and operating costs of sludge treatment equipment, in addition to the higher nutritional requirements for some industrial wastewater

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