Abstract: For the purpose of recycling terephthalic acid (TPA) in polyester alkali peeling wastewater, solventing-out crystallization method is applied to separation of the TPA from the wastewater residue, using N, N-dimethylformamide (DMF) as solvent, distilled water as precipitating agent and active carbon as decoloriser. The functional groups in the product are identified by infra-red spectrum (IR), and the purity and acid value of the product are determined by UV spectrophotometer 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 recycled 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. Recycling rate is 86.54%. The research shows that the TPA in alkali peeling wastewater can be recycled effectively by using DMF solvent through solventing-out crystallization method.

Key words: alkali deweighting, terephthalic acid, recovery, organic solvent