Effect of organic solvent on recovery of terephthalic acid from alkali deweighting wastewater of polyester

For the purpose of effective recovery of terephthalic acid( TPA) from polyester alkali deweighting waste water,dissolving-crystallization method is applied to separate the TPA from the waster residue,using N,N-dimethylformamide( DMF) as solvent,distilled water as precipitating agent and active carbon as decoloriser. The functional groups in the recovered product are identified by infra-red spectrum( IR),and the purity and acid value are determined by UV spectrophotometry and acid value titration,respectively. The rational mass ratios of the waste residue to DMF and the activated carbon to the waste residue are 1: 12 and 0. 6: 1,respectively. The purity of recovered TPA is close to that of the standard TPA reagent( purity ≥ 99%). The acid value reaches 96. 43% of that of the standard TPA reagent. The recovery rate is 86. 54%. The research shows that the TPA in alkali deweighting wastewater can be recovered effectively by using DMF solvent.