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 populartextile industrial wastewater in China due to its high concentration of terephthalie acid (TA)and the poorly biodegradable polyester oligomer and chemical promoters. And nowadays, theglobal TA production can not be satisfied with the industrial needs, The recovery of TA fromisland-sea fabric alkali-hydrolysis process wastewater, as well as different recoverytechnologies and TA reuse criterion factors were investigated in this article. The results wereshowed in the following.Basing on wastewater from the island-sea fabric alkali-hydrolysis process, fiberweightlessness rate, COD concentration, TA concentration and other pollutants wereinvestigated. The optimal hydrolysis process condition was temperature 90^C, alkali solutionconcentration 3 percent, hydrolysis time 30min. In the condition, the sea component has beendissolved completely. The fiber weightlessness rater was from 30 to 35 percent. Islandcomponent can be seen dearly. The main pollutants in wastewater were TA and ethyleneglycol (EG). The quality and quantity of wastewater changed with different hydrolysiscondition. COD and TA concentration in most amount wastewater was 25000 mg/L and18000 mg/L. The lab experiment results were same with the factory monitoring.The wastewater from island-sea fabric alkali-hydrolysis process was acidified withsulfuric acid. The acidification process included three progress which were starting progress,quick acidification progress and ending progress. TA concentration was stable when pH wasno more than 3.47, so the acidification pH was controlled to 3. During the acidification, thedeposition risistance decreased with temperature increase and improved with the sulfuric acid concentration. The adding velocity was slowly, the more time was needed to acidify. Duringthe stirring progress, solvent will volatilize. The more time will reduce the solvent. Thedegree of supersaturation will increase with the acidification time. The smaller particle willbe produced. The optimal condition was temperature 70^C, adding sulfuric acid velocity wasfrom 5 to 8ml per minute, sulfuric acid concentration was from 10 to 20 percent, the stirringvelocity was from 260 to 390 r per minute. In this condition, TA particle diameter could bemore than 45urn and it was easy to be deposited.Basing on the effect of single acidification factor on the characters of TA, the researchwas showed in the following. The TA ash content decreased with the temperatureimprovement and increased with the sulfuric acid concentration. The 34Ohm transmittanceincreased with temperature improvement and decreased with the sulfuric acid concentration.When sulfuric acid concentration was 10 percent, the TA ash content was small, TA 340nmtransmittance was high. When sulfuric acid velocity was 5ml/min, the TA ash content washigh and 340nm transmittance was small. When stirring velocity was 390r/min, the ashcontent was good. The value of ash content was 1000×10^-6, value of 340nm transmittancewas 86.7%. The optimal acidification condition was temperature 70℃, adding sulfuric acidvelocity was 4ml/min, sulfuric acid concentration was 10 percent, the stirring velocity wasfrom 260 to 390 r per minute. In this condition, TA characters were good.Active carbon was good to adsorb TA in wastewater from island-sea fabricalkali-hydrolysis process. The adsorption could be characterized by Langmuir wasothermand Freundlieh wasotherm. The equations were showed in the following. Langmuir,1/q=0.0037+0.7165/Ce, correlation coefficient was 0.9348, Freundlich q=4.67Ce^<sup>0.6167,correlation coefficient was 0.9308. The active carbon amount had much effect on TAcharacters. To high concentration wastewater, when active carbon amount was small, theeffect on decrease impurities was small, and when the amount was too high, the recovery rateof TA was too small. In order to make the effect maximization, the amount of active carbonwas from 3 to 5 g per liter. During the optimal active carbon amount, the adsorption time alsohad effect on the TA characters. Only in the optimal adsorption time, the impurities could bepurified. The optimal adsorption time was 60 minute. When wastewater quality changed, theamount of active carbon and the adsorption time had the same effect on the TA characters. When the COD and TA concentration was less than 15000 mg per liter and 8000 mg per liter,the amount of active carbon and the adsorption time were 3g per liter and 30min.When theCOD and TA coneentration was more than 15000 mg per liter and 8000 mg per liter, theamount of active carbon and the adsorption time were 5.5 g per liter and 90min.When wastewater from island-sea fabric alkali-hydrolysis process was treated with thecombined technology by optimal acidification technology and active carbon adsorption, TAcharacters were improved. But treated by a single technology, TA character can not besatisfied the actual use criterion. The impurities stored in the sample. Used by the combinedtechnology, comparing with the directed acidification technology, optimal acidificationtechnology and active carbon adsorption, the TA ash content was increased 64, 52 and 43percent, the 340nm transmittance was improved 25, 24 and 23 percent. The total acidcontent reached to 97%, the acid value reach to 670.2 nag KOH/g. Some factor had beenreached the fiber grade.Basing on the recovery waste material and reuse, from different use criterion, the TAreuse factors were brought out. The main factors were appearance, purity, total acid content,the acid value, colour and 340nm transmittance. This will give some information to TArecovery and reuse.Environmental benefit, economic benefit and social benefit were discussed in theresearch. TA recovery and reuse were satisfied with the circular economy and sustainabledevelopment stratagem.