Research On The Resource Recovery From Island-sea Fabric Alkaline Hydrolysis Wastewater

The island-sea fabric alkali hydrolysis process wastewater is a kind of the popular textile industrial wastewater in China due to its high concentration of terephthalic acid (TA) and the poorly biodegradable polyester oligomer and chemical promoters. And nowadays, the global TA production can not be satisfied with the industrial needs, especially in China. The recovery of TA from island-sea fabric alkali-hydrolysis process wastewater, as well as different recovery technologies and TA reuse criterion factors are investigated in this article. The results are showed in the following.The wastewater from island-sea fabric alkali-hydrolysis process was acidified with sulfuric acid. The acidification process included three progress which are starting progress, quick acidification progress and ending progress. TA concentration was stable when pH is no more than 3.47, so the acidification pH is controlled to 3. During the acidification, temperature acid concentration adding sulfuric velocity and the stirring velocity are very important factors. By Orthogonal experiment, the extent of every factor is made to control the technics exactly. Then research the effect trend of every factor, consider the shaping velocity and growth velocity of crystal and so on which decide the quality of TA, and control the acidification condition by checking in acid number 340nm transmittance and ash content based on the acidification theory and results analysis comprehensively. At last, it get the optimal condition: temperature is 75℃, acid concentration is 15% adding sulfuric velocity is 4ml/min and the stirring velocity is 300r/min.Active carbon is good to adsorb TA in wastewater from island-sea fabric alkali-hydrolysis process. And this method is simple and cheaply. The adsorption can be characterized by Langmuir isotherm and Freundlich isotherm. The equations are showed in the following. Langmuir, 1/q=0.0037+0.7165/Ce, correlation coefficient is 0.9348, Freundlich q=4.67Ce^0.6167, correlation coefficient is 0.9308. During adsorption, the active carbon amount, temperature, adsorption time and surging velocity are very important factors. The over-low or over-high both limited the adsorption efficiency. To high concentration wastewater, when active carbon amount is small, the effect on decrease impurities is small, and when the amount is too high, the recovery rate of TA is too small. We should find the optimal amount in order to make the effect maximization. During the optimal active carbon amount, the adsorption time also has effect on the TA characters. Only in the optimal adsorption time, the impurities can be purified. At the same time, the quicker the surging velocity, the lower adsorption velocity and on the other hand, the lower the surging velocity, the lower adsorption velocity. When wastewater quality changed, the amount of active carbon and the adsorption time has the same effect on the TA characters. The research showed the optimal condition: the amount of active carbon is 3.5-4.5g/l, temperature is about 60℃, the velocity is 120- 180r/min and surging time is about 50min.Re-crystal is a common method to purification of TA. The research showed it is feasible and cheap that choose N-cymene pyrrolidone as menstruum to treat with Alkaline Hydrolysis Wastewater. Comparing the acetum, N-cymene pyrrolidone has wider district that intervenient stable and non-stable, which made condition easy to control and get the good quality of TA. And the high pressure and temperature are needless during re-crystal that saves the operation cost. The paper is also research the model of re-crystal and analyses the disciplinarian in order to provide the academic support and data.Used by the combined technology, comparing with the directed acidification technology, optimal acidification technology, active carbon adsorption and re-crystal purification technology can improve the quality of TA remarkably, and the recycled TA is reach to the industry grade and even some reach to the fiber grade.Environmental benefit, economic benefit and social benefit were discussed in the research. TA recovery and reuse satisfied with the circular economy and sustainable development stratagem.