Recovery method using membranes for terephthalic acid and sodium hydroxide from printing and dyeing alkali-reduced waste water

Abstract

The invention discloses a recovery method using membranes for terephthalic acid and sodium hydroxide from printing and dyeing alkali-reduced waste water. The method comprises (1) a step of collecting the printing and dyeing alkali-reduced waste water, and performing ultrafiltration by using a polytetrafluoroethylene hollow fiber membrane to obtain an ultrafiltration concentrated liquid and an ultrafiltration permeating liquid; (2) a step of feeding the ultrafiltration concentrated liquid into a sewage treatment plant; (3) a step of subjecting the ultrafiltration permeating liquid to nanofiltration by using a selective nanofiltration membrane component to obtain a nanofiltration concentrated liquid and a nanofiltration permeating liquid; (4) a step of adding concentrated sulfuric acid to the nanofiltration concentrated liquid to adjust the pH value to 2-3, precipitating the terephthalic acid, recovering and recycling the mother liquor after the mother liquor is treated; and (5) a step of recycling and reusing the nanofiltration permeating liquid which is a dilute sodium hydroxide solution to process production of a mercerizing machine or an alkaline machine. By the above manner, the method has simple operation and the method is capable of saving water resources, reducing production cost, and achieving a double harvest of economic benefit and environment benefit.

Description

technical field [0001] The invention relates to the field of waste water treatment, in particular to a method for recovering terephthalic acid and sodium hydroxide through a printing and dyeing alkali weight reduction waste water membrane. Background technique [0002] At present, polyester fiber has become an important raw material in the clothing industry. People use alkali weight reduction technology to endow polyester fiber fabrics with silky characteristics. With the increase of polyester fiber production in my country, polyester consumption accounts for about 50% of my country's textile market. The annual output of polyester fiber in China was 22.044 million tons in 2009, and it reached 22.784 million tons in January-November 2010. Taking the output in 2009 as an example, about 20% of the polyester fiber needs to be reduced by alkali. According to the calculation of the reduction rate of 15%, 661,000 tons of polyester fiber will be hydrolyzed in the waste water that ye...

AI Technical Summary

Problems solved by technology

Generally, the pH value of alkali reduction wastewater is adjusted to 2-4 first, TA is precipitated from the wastewater, and the removal rate reaches 70%, and the removal rate of COD is also low, less than 70%.

[0006] The above-mentioned recovery method has the advantages of simple acid analysis technology and convenient operation, but the disadvantages are: (1) the recovered terephthalic acid has many impurities and low purity. To reduce the pH of the alkali reduction wastewater from 12-14 to 2-4, inorganic The acid consumption is relatively large, and the operating cost is increased. It is reported that the treatment cost per ton of wastewater is about 8-12 yuan

(2) NaOH in wastewater is neutralized by sulfuric acid without recycling, wasting resources

(3) The TA particles precipitated by acid are very small, the particle size is mainly 5um, it is difficult to settle when suspended in water for a long time, and the precipitation and separation are difficult, and the dehydration of TA is poor

In order to overcome the deficiencies of the above-mentioned recovery process, people try to improve the purity of reclaimed TA by using solvent recrystallization after recovery, such as using pyridine, dimethyl sulfoxide, dimethylformamide, etc. as solvents to recrystallize the reclaimed TA Crystallization, but this kind of solvent is easy to combine with TA to produce by-products, and the cost is too high, which is not conducive to practical application

In addition to this, someone adopted CaCL 2 Treat alkali reduction wastewater to make TA precipitate into calcium terephthalate and reuse it, but 1-2 times of CaCl is needed to recover the same weight of TA 2 Raw materials, high cost, poor economical practicability

[0007] Nowadays, with the development of polymer material membrane science and technology, some people try to use membrane separation technology to process alkali reduction wastewater. For example, the patent publication number CN101148298A reports a method for the integrated treatment and recovery of alkali reduction wastewater membrane. Chen Huanlin et al. used pretreatment + ultrafiltration + nanofiltration to recover and utilize most of the NaOH in wastewater, and recycled 80-90% of water resources. This method requires complex processes such as flocculation and filtration before recovery, and is not easy to control , and during operation, membrane clogging caused by particulates and colloids will reduce the filtration rate

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