| Purified terephthalic acid (PTA) is an important raw chemical material. For the effects of the craft, materials and other factors, a large mount of wastes are released during the manufacturing of PTA. They can be classified into oxidization residue, purification residue and pool residue. Landfill and incineration to the waste pollutes the environment and also wastes the resource, however, separation and recovery from the waste gain a good economic and environmental benefits. The waste residue is from the Yi Sheng Ltd. ,Ning Bo, as material in this paper. Three recovery methods-solvent extraction, base-dissolution and acid-precipitation, base-dissolution and thermal decomposition, were systematically studied and the results show the base-dissolution and acid-precipitation method can recover TA effectively. The main results of this research were summarized as follows:1 This waste residue is composed by TA (92.35%～93.53%), PT (2.69%～3.27%), BA(less than 0.85%) and other impurities. (in mass fraction)2 For the Boiled Water Extraction method, four times extraction can dissolve the PT of the PTA waste mostly. The final product of TA is gained with yield of 95.87%, purity of 95.87%. For the Acetic Acid Extraction method, one extraction is enough, and the final product of TA with yield of 95.80%, purity of 95.85 is gained as well,3 For the base-dissolution and acid-precipitation method, 455g 5% NaOH solution and 554g 5% sulfur acid are used up by recovering 50g waste reside, which releases 1.6L wastewater with COD conc. of 924mg/L and 1.59g insoluble residue. The gained TA yield is 91.74%, purity is 99.40%.4 For the base-dissolution and thermal decomposition method, 125℃and 76 min heating time are the optimization of reaction condition. The final gained TA yield is 91.74%, purity is 99.40%.5 Base-dissolution and acid-precipitation is the optimum method among three recovery methods. Each ton of the PTA waste residue can earn profit of 4645 yuan by this method. |
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