Research On The Removal And Application Of CO₃^2- In Waste Lye Of Mercerizing

Mercerizing is a very important process in printing and dyeing process,which will produce a lot of waste mercerizing lye.These lye are usually concentrated directly without any pretreatment for reused in mercerizing and other pretreatment processes.However,because it contains a large number of CO32-and organic impurities,not only affect the mercerization and other pretreatment effect,but also lead to the unstable quality of printing and dyeing products.Therefore,CO32-and organic impurities in lye needs to be separated to improve the purity of lye.In this study,coagulation,ultrafiltration and nanofiltration were carried out on the waste mercerized lye produced in in printing and dyeing factories,and the contents of COD,turbidity,chromaticity,OH-and CO32-in the treated lye were analyzed.The degree of crystallinity of cotton fiber,barium value of fabric and color index of dyed fabric were analyzed.The research results show that after 20 g/L CaO precipitation,When the amount of PAC is 5 g/L,after 20 g/L quicklime precipitation,PAC is stirred at 200 r/min for 1.5 min,then stirred at 80 r/min for 20 min.After flocculation pretreatment,the COD decreases from 13200 mg/L to 6460 mg/L,the turbidity from 98.0 NTU to 5.9 NTU,the chroma from 306.0 to 180.2 degrees,the basicity remains unchanged,and the content of CO32-decreases from 1.50%to 0.85%.Use of PES ultrafiltration membrane to membrane separation of alkali liquor after flocculation treatment,when the temperature of the lye is 25 ?,pressure is 4.5 bar,ultrafiltration after alkali liquor COD from 6460 mg/L to 990 mg/L,turbidity from 5.9 NTU reduced to 0,chroma from 180.2 to 66.9.In order to remove CO32-in the lye,the NF 270 lye further treatment after the above processing,the research results show that when the temperature of the lye is 20 ?,pressure is 40 bar,after processing of lye CO32-from 0.85%to 0.05%,the content of OH-slightly decreased,from 14.0%to 13.0%,COD is 290 mg/L,chroma is O.The cotton fabric was mercerized with the alkali liquor after removing the impurity of CO32-.The results show that the crystallinity of mercerized cotton fabric is 46.6%and barium value is 140.2,while that of mercerized cotton fabric with waste alkali solution is 53.4%and barium value is 111.0.The mercerizing effect is obviously improved.Dyeing mercerized fabrics results in darker,more saturated and higher K/S values.This study solves the problem of purification of mercerized waste lye,and has important practical application value for efficient reuse of mercerized lye in cotton printing and dyeing production,which is conducive to promoting clean production in the printing and dyeing industry.