摘要
聚乙烯醇(PVA)是印染废水有机污染物的主要来源,同时含铬显影剂的使用导致部分印染废水含有六价铬(Cr(Ⅵ)),高浓度PVA及高毒性Cr(Ⅵ)的协同处理技术亟待突破。利用过硫酸盐热活化可引发聚合物发生自由基交联反应的特点,研究印染废水中PVA及Cr(Ⅵ)协同处理的方法。考察了过硫酸盐投加量、反应温度、初始pH值、Cr(Ⅵ)初始浓度等因素对二者去除效率的影响,借助X射线光电子能谱、凝胶渗透色谱等手段分析了反应沉淀物及剩余废水中残留物,探索了PVA及Cr(Ⅵ)的协同处理机制。结果表明:当过硫酸盐质量浓度为8.0 g/L、反应温度为70℃、废水pH值小于6时,模拟印染废水的化学需氧量去除率达91.9%,PVA去除率可达98.0%,Cr(Ⅵ)还原率为94.3%;过硫酸盐热活化引发PVA自由基交联及PVA的还原性是PVA高效沉淀及Cr(Ⅵ)有效还原的主要原因,此类浆料与重金属污染物的协同处理在印染废水方面具有一定的应用前景。
Objective Polyvinyl alcohol(PVA),a major sizing agent used in textile weaving,is eluted in the pretreatment of textile wet processing and becomes the main source of organic pollutants in textile wastewater.Meanwhile,textile industries sometimes adopt chromium-containing developers for the printing screen,leading to Cr(Ⅵ)pollution in the textile wastewater.The simultaneous treatment technology of high concentration of PVA and highly toxic Cr(Ⅵ)in printing and dyeing wastewater is of great concern.Persulfates can initiate the free radical crosslinking of the polymeric chain,which is considered as one of the solutions for the crosslinking-induced precipitation of PVA.Additionally,under high temperature and acidic conditions,PVA can reduce Cr(Ⅵ)to Cr(Ⅲ)which is less toxic.Thus,in the thermally activated persulfate system,with the rapid precipitation of high concentration of PVA,the effective reduction of Cr(Ⅵ)becomes possible.Method To achieve the simultaneous removal of PVA and Cr(Ⅵ)from wastewater,persulfate(K_(2)S_(2)O_(8))was chosen as free radical crossling initiator.Simulative wastewater containing the high concentrations of PVA(10 g/L)and the coexisting Cr(Ⅵ)was the object of treatment.The thermal activation was used to activate K_(2)S_(2)O_(8) because desizing wastewater is often processed at high temperatures(70-80°C)and Cr(Ⅵ)is more easily reduced under high temperature.The remoal performance of PVA and chemical oxygen demand(COD)and the reductive efficiency of Cr(Ⅵ)were studied,with specific attention paid to the performance of free radical-induced crosslinking of PVA and the production of free radicals and explored the critical factors controlling their efficacy by electron spin-resonance spectroscopy(ESR).In addition,the possible underlying mechanism was studied using X-ray photoelectron spectroscopy(XPS),gel permeation chromatography(GPC),and gas chromatography-mass spectrophotometry(GC-MS).Results The K_(2)S_(2)O_(8) dosage,reaction temperature,and pH value of the solution were the key factors affecting the removal efficiency of PVA and Cr(Ⅵ).When the concentration of K_(2)S_(2)O_(8) was 8.0 g/L,the reaction temperature was 70°C and the pH value of wastewater was less than 6,the COD value of simulated printing and dyeing wastewater were reduced from 18000 to 1458 mg/L with a removal rate of 91.9%,the removal rate of PVA could reach 98.0%and the reduction rate of Cr(Ⅵ)was 94.3%.As a crosslinking agent,K_(2)S_(2)O_(8) can induce the generation of PVA carbon radicals and promote the effective crosslinking.Meanwhile,the oxidation of-OH groups of the PVA polymer could enhance the production of O_(2)^(·-) radicals.This property which is analogous to catalyst could effectively promote the crosslinking of PVA.In addition to the reduction property of PVA itself,the reactive oxygen species(ROS)such as O_(2)^(·-) produced from the process of inducing radical cross-linking of PVA can also reduce Cr(Ⅵ)to Cr(Ⅲ).Conclusion Based on the free radical cross-linking technologies for polymers,a synergistic treatment technique for PVA and Cr(Ⅵ)pollutants removal using thermally activated persulfate system was proposed.The radical induced cross-linking and the reducibility of PVA under high temperature is found to be the main reason for efficient precipitation of PVA and synergistic reduction of Cr(Ⅵ),which has a certain application prospect in the treatment of textile wastewater.The advantages of this technology are as follows.1)The thermally activated K_(2)S_(2)O_(8) can efficiently induce the radical based crosslinking of PVA and promoted the precipitation.2)As a strong oxidant,K_(2)S_(2)O_(8) can oxidize the hydroxyl groups in PVA to promote the crosslinking efficiency.3)The oxidation of-OH groups of the PVA polymer can enhance the production of ROS,which facilitates the simultaneous reduction of coexisting Cr(Ⅵ).Under optimal conditions,the maximum removal efficiencies of PVA and COD reached 98.0%and 91.9%,and the reduction rate of Cr(Ⅵ)was 94.3%.This process is technically highly efficient and cost effective,and provides new insights for the simultaneous treatment technology of high concentration of PVA and highly toxic Cr(Ⅵ)in printing and dyeing wastewater.
作者
李方
潘航
章耀鹏
马慧婕
沈忱思
LI Fang;PAN Hang;ZHANG Yaopeng;MA Huijie;SHEN Chensi(College of Environmental Science and Engineering,Donghua University,Shanghai 201620,China;Shanghai Municipal Engineering Design Institute(Group)Co.,Ltd.,Shanghai 200092,China)
出处
《纺织学报》
EI
CAS
CSCD
北大核心
2023年第3期147-157,共11页
Journal of Textile Research
基金
上海市自然科学基金项目(21ZR1401500)
中央高校基本科研业务费专项资金资助项目(2232021G-11)。
关键词
聚乙烯醇
六价铬
过硫酸盐
印染废水
协同处理
polyvinyl alcohol
Cr(Ⅵ)
persulfate
dyeing and printing wastewater
synergistic removal
