活性炭吸附水中新型含氮消毒副产物二甲基亚硝胺

摘要

In water treatment, N-nitrosodimethylamine (NDMA) is a newly detected nitrogenous disinfection by-product, which is extremely cancerogenic to human health. The paper investigated the adsorption characteristics of common materials used in water treatment such as activated carbon. The result indicate that the quartz sands, zeolite and diatomaceous earth powder are barely capable of adsorbing NDMA, Coal granular activated carbon and wood powder activated carbon possesse the best adsorption performance yet activated carbon fiber and powdered activated carbon made of coal. Freundlich model was applied to describe the adsorption isotherms of coal granular activated carbon and wood powder activated carbon of NDMA absorption, with k values 1.29S and 1.462 (mg/gXL/mg), 1/n values 0.95 and 0.68, respectively, which reveal the fact that activated carbon failed to adsorb NDMA effectively. With different initial solution pH and consentration of dissolved salts, no significant changes of adsorption properity the granular activated carbon system are found. Further more, experiments of NDMA absorption by acid, alkali and nitrogen modified granular activated carbon were carried on, and the results show that none of them enhanced the adsorption efficiency, the k value of acid modified activated carbon decreased to 0.5 (mg/g)(L/mg)°, while the other two marginally reduced. Overall, it is found that some types of activated carbon act more or less effectively in the process of NDMA adsorption with low adsorption capacity. What's more, different modification methods could hardly improve the adsorption effect of NDMA by CAC. In conclusion, conventional adsorption is not useful method for NDMA removal in water treatment.%二甲基亚硝胺(N-nitrosodimethylamine,NDMA)是水处理领域中颇为关注的强致癌性新兴含氮消毒副产物.该文系统研究了常见水处理材料及各类型改性颗粒炭活性炭(GAC)对NDMA的静态吸附特征.研究发现煤质颗粒活性炭和木质粉末活性炭对NDMA具有较好的吸附效果,活性炭纤维和煤质粉末活性炭次之,而石英砂、粉末沸石和硅藻土等基本不能吸附NDMA;煤质颗粒活性炭和木质粉末活性炭吸附NDMA的等温线可采用Freundlich模型描述,其k值仅分别为1.295和1.462(mg/g) (L/mg)n,其1/n值分别为0.95和0.68,该结果说明活性炭难于有效吸附水中NDMA;起始溶液pH和不同离子背景条件下,颗粒活性炭的NDMA系统未见明显变化；对吸附效果较好的颗粒活性炭进行酸改性、碱改性和氮气热改性,结果表明三种改性方法均无法有效提高颗粒活性炭吸附NDMA的效果,酸性改性活性炭Freundlich吸附等温线的k值下降为0.5(mg/g)(L/mg)n,其它两种改性方法较原碳的吸附容量略有降低.总体研究表明,部分类型活性炭对NDMA具有一定的吸附效果,但吸附容量均较低,不同改性方法均难于有效提高GAC吸附NDMA吸附效果,水处理用常规吸附法难于应对水中NDMA污染.