JPS6143140A - Method of recovering high-purity terepthalic acid from terephthalic acid-containing waste liquir - Google Patents

Abstract

PURPOSE:In obtaining the titled substance useful as a synthetic raw material for polyester synthetic yarn from terephthalic acid-containing waste liquir, to improve easily purity of terephthalic acid, by neutralizing the waste liquor with an acid, making it further weakly acidic, precipitating partially the titled substance, filtering it, making the filtrate acidic. CONSTITUTION:Terephthalic acid-containing waste liquor produced in a process for providing polyester synthetic fibers is neutralized with an acid, made further into 4-6pH of weak acidity, terephthalic acid is partially precipitated and fitered. The filtrate is further acidified with an acid, the precipitated titled compound is filtered, washed with water and collected. When terephthalic acid coprecipitated with impurities is filtered, and active carbon, preferably active carbon with 8-hydroxyquinoline spreader is used, to give a product having higher purity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] This invention relates to a method for recovering highly purified terephthal #2 from waste liquid generated during the manufacturing process of polyester thread synthetic fibers.

[Conventional technology]

Terephthalic acid-containing waste*V is acidified to precipitate terephthalate*V, and the crystals are filtered out and then dried and recovered.

[Problem that the invention seeks to solve]

The waste liquid generated during the manufacturing process of polyester synthetic fibers contains a considerable amount of terephthalic acid, the main raw material.
Its recovery is an important issue in terms of manufacturing costs and waste liquid treatment.

In addition to terephthalic acid, is there any catalyst in the waste liquid? Metal ions and gold JIgtII compounds used as pigments? It is not easy to obtain high-purity terephthal for practical use because it is suspected of containing impurities such as Ariiso polymer compounds.

[Means to resolve the problem]

The present inventors investigated the pH of the terephthalate-containing waste liquid at pHll-6.
It has been found that a highly pure product can be obtained by making the solution weakly acidic, precipitating terephthalic acid at <-SV, filtering it, and then collecting terephthalic acid from the filtrate (by making it acidic and filtering off the crystals). Although a small portion of the terephthalic acid that precipitates under weak acidity is lost, the above impurities are coprecipitated with the terephthalic acid and removed. Furthermore, when activated carbon, preferably g-hydroxyquinoline-impregnated activated carbon casings, were used to filter out the terephthalic acid co-precipitated with the impure acid, even more pure crystals were obtained.

[Effect]

A comparison between the conventional techniques α, h, and c and the present invention d and all was as follows.

Hereinafter, it will be abbreviated as terephthalic acid wTPA.

α, 'l' PA waste liquid acidic crystallization recovery 'j
'FA (Jil (min 023%) L## Activated carbon filtration
Acidic crystallization y [min ωθ phantom c, # # za-
Activated carbon filtration with hexyquinoline Acidic crystallization IN Classification θ/g%1, d, Iz Weak acid coprecipitation filtration TPA enzyme is precipitated with j1 and θ at 5θkg. Then filter with f&IC filter paper.

After filtration, it is washed with 00'ml of ion-exchanged water and dried.

Activated carbon/θg was added to TPAN solution 50~ and stirred, then 45
(:'Filter with filter paper. With this filthy skin!-'',
'1'PAt' is precipitated with O. Thereafter, the operation is performed in the same manner as in implementation Nl.

Example 3: g-hydroxyquinoline-impregnated activated carbon 109' is added to TPA waste liquid 5θ~, stirred, and then filtered using YaSC filter paper. In this filter * v Hct, add -L and O to precipitate 'I'PA. From then on, it will be a masterpiece as well as H/.

A part of -S da and TPA are precipitated at 11IS, O~f klQt, and filtered using a Todoroki 5C filter.

The filtrate was further purified with H in step 7 to precipitate 'At'. Since then, he has written masterpieces such as Meikyuen and Ichiku.

Practical Example 5 TpAs liquid s, OKW 15/t, TPA
A part of the solution is precipitated and filtered through 16SC filter paper. Thereafter, operations are performed in the same manner as in Example DA.

Example Mu'I'PAjtli liquid 5θhg At 1kmt, a part of TPA was precipitated, and then a part of it was deposited on activated carbon 1091.
After stirring, filter through ASC filter paper. Thereafter, the operation is the same as in the example.

Example 7 'I'FA waste liquid sokgw 15hiro and TPA
After precipitating a part of A! ;Filter with C filter paper. Thereafter, the process will be carried out in the same manner as in Example DA.

〔Effect of the invention〕

High purity terephthalic acid was recovered from this machine in Examples q to 7 of the present invention.

Claims (2)

[Claims] (1) A method in which the terephthalic acid-containing waste liquid is neutralized with an acid, then made weakly acidic to precipitate a portion of the terephthalic acid, filtered, the filtrate further acidified with an acid, and the precipitated terephthalic acid is recovered by filtration and washing with water. (2) After neutralizing the terephthalic acid-containing waste liquid with an acid, the terephthalic acid was partially analyzed by making it weakly acidic, and after filtering with activated carbon, preferably activated carbon impregnated with 8-hydroxyquinoline, the filtrate was further acidified with an acid and precipitated terephthalic acid. A method of recovering acid by filtering it and washing it with water.