退浆废水中自由基引发的聚乙烯醇交联沉淀研究

Radical-induced crosslinking of poly(vinyl alcohol)from desizing wastewater

针对纺织印染工业退浆废水中含聚合度高且化学稳定性强的聚乙烯醇(PVA),是纺织工业水污染治理难点的现状,利用过硫酸盐能够引发自由基交联且氧化性强的优势,结合退浆废水高温排放的特点,使用热活化过硫酸盐体系通过自由基交联快速将PVA从废水中沉淀分离。考察了过硫酸盐投加量、反应时间、反应温度及pH值对PVA去除的影响。并利用电子顺磁共振谱、傅里叶变换红外光谱、X射线光电子能谱等对交联沉淀物进行表征分析。结果表明:在过硫酸盐投加量为10 g/L、废水温度为70℃时,处理30 min后PVA即可有效交联沉淀,化学需氧量(COD)和PVA去除率分别可达95.1%和95.6%;过硫酸钾热活化主要产生硫酸根自由基和羟基自由基,PVA被自由基夺氢产生碳自由基,碳自由基相互结合可高效交联PVA并快速沉淀。

The desizing wastewater of the textile printing and dyeing industry contains a large amount of polyvinyl alcohol(PVA)with high polymerization and strong chemical stability,which is a difficult point in the water pollution treatment.Taking advantage of persulfate′s ability to initiate free radical crosslinking and strong oxidation,combined with the characteristics of high temperature discharge of desizing wastewater,a thermally activated persulfate system was used to precipitate PVA from wastewater.The effects of persulfate dosage,reaction time,reaction temperature,and pH value on the removal of PVA were investigated.And electron paramagnetic resonance,Fourier-transform infrared spectroscopy,and X-ray photoelectron spectroscopy were used to analyze the cross-linked precipitates.The results show that when the dosage of persulfate was 10 g/L and the wastewater temperature was 70℃,PVA could be effectively cross-linked and precipitated after 30 minutes,and the removal rate of chemical oxygen demand(COD)and PVA could reach 95.1%and 95.6%,respectively.The production of sulfate radical and hydroxyl radical in thermally activated persulfate system induced the production of carbon-based radicals,and the carbon-based radicals continued to react together and produced the crosslinking product.