The Recycling And Distillation Pretreatment Technology Research Of Synthetic Leather Industry Wastewater With DMF

Synthetic leather industry has been developing rapidly in China, which resulted in the large generation of waste liquid containing about 20% dimethyl formamide (DMF). The current distillation technology for recycling of DMF is still faced lots of problems such as large residue generation, DMF decomposition, frequent tower washing, and much wastewater production. So the exploration of a new technique for the recycling of DMF and the optimization of the distillation technology is of great significance for the energy conservation, emissions reduction and environmental protection.At first, extraction method was chose as the new technique to treat DMF waste liquor. The result shows that the extraction performance of chloroform is the best among various kinds of extraction agent and solvent ratio distribution coefficient is about 1.03. The feasible solvent ratio is 2 and the recovery rate can reach 97.5% when extraction series is 5.Then the pretreatment of waste liquid of DMF for the distillation technology was investigated based on ultra filtration(UF). Turbidity of the waste liquid could all decrease from original 600 NTU to about 1 NTU while the waste liquid was processed by membrane materials like PA, PVDF, PVDFs, PES or PP. Considering both of membrane flux and cost, PP membrane was superior to the others. It can be concluded that the optimal operation pressure is 0.1 MPa and a larger surface velocity should be chosen by comparing the flux and recovery performance of PP membrane under different conditions. The clean effluent could be used as the flushing liquor in the backwash process and sodium hypochlorite solution (0.1%) was the optimal choice in the chemical cleaning process. Studies showed that the decline of membrane flux can be retarded by increasing the frequency of backwash appropriately to one minute per hour, under which a flux recovery rate of 95.8% can be obtained. While hydraulic cleaning could remove most of the contaminations on the membrane surface but there was still little contaminations adhering to the surface and hole of the membrane.Pilot-scale experiment was carried out to obtain the technological parameters for the industrial design. Result shows that the performance of PP membrane is better than PVDF membrane, The backwashing frequencies about 2 min per 0.5 h is fitting and hypochlorous acid chosen as the chemical cleaning agent is appropriate.On the end, one set of pretreatment device was designed for pretreatment of the waste liquor from synthetic leather industry on the basis of laboratory and Pilot-scale study.