退役锂电池放电废水特征有机污染物解析

为研究退役锂电池盐水溶液放电产生的放电废水有机物的种类与来源,首先采用单因素优化方法对萃取剂类型、pH、萃取次数3个因素进行液-液萃取前处理优化实验,获得最佳萃取预处理条件。接着采用气相色谱与质谱联用(GC-MS)程序中分流比和升温模式对比实验,建立了放电废水有机成分定性分析方法,并对检出的有机污染物进行分类与来源判断。研究结果表明,选取乙酸乙酯为萃取剂,调节放电废水pH至9.38,以8000r/min离心5min (4℃),且采用间歇三次萃取时分离效果最优。对放电废水SIM定性扫描检测出10类有机污染物,其中酸酯类、酰胺类、烷烃类物质较多,且来源于反应衍生物与电解液添加剂的占比较大,分别为33.3%与20%,包括电解质增塑剂间苯二甲酸二(2-乙基己基)酯,电解液溶剂效应产物1,4-环己烷二羧酸二甲酯、磷酸三(2-氯乙基)酯,电解液添加剂硬脂酰胺、十六碳酰胺、十四酰胺、1,4-环己烷二甲醇二乙烯醚,退役锂电池塑料外壳中抗氧剂原料3,5-二叔丁基苯酚等。这些物质对水环境均具有不同程度的毒性危害,需进一步检测各有机物浓度并揭示其迁移转化规律,建立退役锂电池放电废水重点关注有机污染物清单。

Analysis on the characteristic organic pollutants from discharge wastewater of spent lithium batteries

To study the types and sources of organic substances from wastewater generated during the discharge of spent lithium batteries by saline solution, a single-factor optimization method was used to optimize the liquid -liquid extraction pretreatment and the optimal extraction conditions were obtained by investigating the types of extraction agents, pH, and extraction times. Then, a qualitative analysis method for detecting organic substances from discharge wastewater of spent lithium batteries was established using the gas chromatography-mass spectrometry (GC-MS) program with comparative tests of splitting ratio and ramp-up modes, and the detected organic pollutants can be classified and the sources can also be determined. The results showed that the optimal separation effect could be achieved under the following extraction conditions: ethyl acetate as the extraction agent, adjusting the pH of the discharge wastewater to 9.38, centrifugalizing with 8000r/min at 4℃ for 5min, and extracting three times under intermittent mode. Ten types of organic pollutants can be detected from the discharge wastewater by SIM qualitative scanning, among which acid esters, amides and alkanes are more abundant, and those from reaction derivatives and electrolyte additives account for 33.3% and 20%, respectively. The detected organic pollutants mainly include bis(2-ethylhexyl) isophthalate deriving from electrolyte plasticizer; 1,4-cyclohexanedicarboxylic acid dimethyl ester and tris(2-chloroethyl) phosphate from electrolyte solvent effect products; stearyl amide, hexadecanamide, tetradecanamide, 1,4-cyclohexanedimethanol divinyl ether from electrolyte additives; 3,5-di-tert-butylphenol from the raw materials for antioxidant in plastic shell of spent lithium batteries. In view of their toxicity effects to the water environment caused by the detected organic pollutants, it is urgent to further test the concentration of each organic pollutant and reveal their corresponding migration and transformation rules, and establish the list of critical organic pollutants which need to be paid close attention.