Study Of Alkali Reduction Wastewater Treatment With Integrated Membrane Process And Influence Of Treated Water Reuse On Polyester Decrement

In this work, application of ultrafiltration and nanofiltration membrane process on alkali reduction wastewater treatment and hydraulic backwashing and sodium hydroxide-sodium dodecyl benzene sulfonate chemical cleaning of membrane was experimental studied. The results showed that under the pressure of 0.1 Mpa, the removal rate of COD and turbidity of wastewater could reach 30% and 98%, the membrane flux was stably maintained at more than 30 L·m-2h-1 by the ultrafiltration membrane treatment. Under the pressure of 0.8 Mpa, the removal rate of COD and turbidity of wastewater was about 85% and 15%, the membrane flux was stably maintained at more than 15 L·m-2·h-1 by the nanofiltration membrane treatment. Effect of hydraulic backwash cleaning to the two kinds of films was not ideal, the pure water flux of the membrane recoveried under 85% of the initial flux. But sodium hydroxide-sodium dodecyl benzene sulfonate cleaning had a better cleaning effect, it could make the pure water flux of the membrane recovery to more than 90% of initial flux.Acidification experiment of concentrated liquid of nanofiltration was compared with the direct acidification method, the results showed that after the treatment of nanofiltration membrane, the wastewater was concentrated and decreased, the volume of sulfuric acid which was needed to add to the wastewater was decreased. Compared with the direct acidification method, COD removal rate of filtrate was above 80% by acidification after membrane treatment, it meant that a higher terephthalic acid sodium(TADS) concentration was in nanofiltration concentrated liquid. Ash content, acid value and transmittance of the recuperated terephthalic acid(TA) sample of acidification experiment of membrane treatment was 630 ppm,641.5 mg(KOH)/g and 89.6%, compared with the recuperated TA sample of direct acidification method, the quality had been greatly improved.Influence of water reuse by membrane treatment(the accumulation of ethylene glycol content)may caused to the polyester reduction process was analysed. The results showed that the increase of the content of ethylene glycol(EG) could promote the polyester decrement process. In the optimal reduction conditions, in order to achieve the same reduction effect when the content of EG reached a certain level, shortening the reduction time would be feasible. The reduction rate of polyester increased with the increase of alkalinity, temperature and time. And alkalinity was the biggest effect on the reduction rate, the increase of alkalinity would increase the reduction rate greatly. Reduction rates of different material of polyester fabric was different in the same conditions.