水中痕量全氟化合物的分析检测及纳滤膜去除特性研究
发布时间：2018-11-15 21:59
【摘要】：全氟化合物(PFCs)在土壤、水体及生物体内广泛存在,具有持久性、污染性、生物积累性和难降解性等特点,其中全氟辛基磺酸及其盐已经引起了国内外学者的广泛重视,并且被列为持久性有机污染物(POPs)。本文将四种全氟化合物作为研究目标,建立了四种全氟化合物的环境样品前处理及仪器分析方法,并通过小型错流纳滤膜过滤装置研究了无机盐、有机物存在条件下,纳滤膜对不同分子量全氟化合物的去除效果。通过试验研究,得出以下结果:(1)样品前处理的最优化固相萃取条件为:活化溶液为氨水甲醇和去离子水,滴速为2滴/s,水样滴速为2滴/s;淋洗液为40%甲醇水(pH=5),滴速为2滴/s;洗脱液为0.1%氨水甲醇溶液,滴速为1滴/s,以上步骤溶剂体积均为4m L。采用超高效液相色谱-质谱联用(UPLC-MS/MS)对水中痕量PFCs进行了测定,方法检出限为0.06ng/L-0.22ng/L,加标回收率为73.1%-91.3%,相对标准偏差为7.4%-14.3%。测定结果显示,该方法线性好,准确度高,能满足环境水样中痕量PFCs的测定要求。(2)分别采用纯水、添加无机盐(氯化钠,氯化钙)、添加有机物(海藻酸钠SA、牛血清白蛋白BSA、腐殖酸HA)以及同时添加无机盐与有机物的溶液与PFCs标准物质配成一定浓度的PFCs原水,研究纳滤在这几种水质条件下对PFCs的去除特性。研究发现下列因素影响纳滤膜对PFCs的去除效果:(1)纯水条件下,由于较高的相对分子量,纳滤膜对全氟辛基磺酸(PFOS)的筛分作用强于全氟丁基磺酸(PFBS)。(2)添加无机盐条件下,膜面双电层被压缩,静电斥力的减小导致截留率下降,膜孔收缩导致截留率上升,钙离子会在PFCs之间,PFCs与膜面之间产生架桥作用,污染物体积增大,提高截留率,综合作用下,纳滤膜对PFOS的截留率较纯水时增大,对PFBS的截留率较纯水时下降。(3)有机物存在时,SA与HA提高膜面电位,则静电斥力增大,使得PFCs的截留率提高;BSA主要通过其复杂的空间结构及较大的分子量使PFCs吸附于其表面,来提高膜对于PFCs的截留率,最终膜对于PFOS的截留率较纯水时有所提高,PFBS的截留率较纯水时基本相同。(4)无机盐与有机物共存时,膜电位的变化引起的静电斥力的变化是影响膜对PFOS以及PFBS的主要作用,同样膜孔收缩增强的筛分作用也有一定的影响。同时相比于(2),由于SA中含一定量的羧基和羟基,HA含有一定量的羧基及少量羧基,BSA中含少量的羧基和氨基,钙离子还会使有机物分子发生络合作用,以上综合作用,使膜对于PFOS的截留率较纯水时增大,而膜对于PFBS的截留率较纯水时基本相同。
[Abstract]:Perfluorooctane sulfonic acid (PFOS) and its salts are widely used in soils, water bodies and organisms, and have the characteristics of persistence, pollution, bioaccumulation and non-biodegradability, among which perfluorooctane sulfonic acid and its salts have attracted extensive attention of scholars at home and abroad. And listed as persistent organic pollutant (POPs). In this paper, four kinds of perfluorinated compounds were taken as the research object, the methods of environmental sample pretreatment and instrumental analysis of four perfluorocarbons were established, and the inorganic salts and organic compounds were studied by means of a small cross-flow nanofiltration membrane filtration device. Removal of perfluorocarbons with different molecular weight by nanofiltration membrane. The results are as follows: (1) the optimal solid-phase extraction conditions for sample pretreatment are as follows: the activated solution is ammonia water methanol and deionized water, the droplet rate is 2 drops / s, and the water sample droplet velocity is 2 drops / s; The eluent was 40% methanol-water (pH=5) at a drop rate of 2 drops / s, and the elution solution was 0.1% ammonia water methanol solution with a drop rate of 1 drop / s, and the volume of the above steps was 4 mL. UPLC-MS/MS was used to determine trace PFCs in water. The detection limit was 0.06 ng / L -0.22 ng / L, and the recovery rate was 73.1% -91.3%. The relative standard deviation was 7.4- 14.3cm. The results show that the method has good linearity and high accuracy, and can meet the determination requirements of trace PFCs in environmental water samples. (2) Inorganic salts (sodium chloride, calcium chloride) and organic compounds (sodium alginate, SA,) are added respectively in pure water, inorganic salts (sodium chloride, calcium chloride) and organic compounds (sodium alginate). Bovine serum albumin (BSA) BSA, humic acid (HA), the solution of inorganic salt and organic matter and PFCs standard material were used to prepare PFCs raw water of a certain concentration. The removal characteristics of PFCs by nanofiltration under these water conditions were studied. It is found that the following factors affect the removal efficiency of PFCs by nanofiltration membrane: (1) under pure water conditions, due to higher relative molecular weight, The screening effect of nanofiltration membrane on perfluorooctane sulfonic acid (PFOS) was stronger than that on perfluorooctane sulfonic acid (PFBS). (_ 2). When the inorganic salt was added, the double electric layer on the membrane surface was compressed, and the reduction of electrostatic repulsion resulted in the decrease of the rejection rate. The shrinkage of membrane pore led to the increase of rejection rate, and calcium ion would bridge between PFCs, PFCs and membrane surface. The volume of pollutants increased, and the rejection rate of PFOS increased. The rejection rate of nanofiltration membrane was higher than that of pure water. The rejection rate of PFBS was lower than that of pure water. (3) in the presence of organic matter, SA and HA increased the potential of membrane surface, the electrostatic repulsion increased, and the rejection rate of PFCs increased. The adsorption of PFCs on the surface of BSA is mainly due to its complex spatial structure and large molecular weight, which can improve the retention rate of PFCs on the membrane. Finally, the rejection rate of the membrane to PFOS is higher than that of pure water. The rejection rate of PFBS is almost the same as that of pure water. (4) the change of electrostatic repulsion induced by the change of membrane potential is the main effect of membrane on PFOS and PFBS when inorganic salt and organic matter coexist. At the same time, the screening effect of membrane pore shrinkage enhancement also has certain effect. At the same time, compared with (2), because SA contains a certain amount of carboxyl group and hydroxyl group, HA contains a certain amount of carboxyl group and a small amount of carboxyl group, BSA contains a small amount of carboxyl group and amino group, and calcium ion also makes organic molecule complex. The rejection rate of membrane to PFOS was higher than that of pure water, but the rejection rate of membrane to PFBS was almost the same as that of pure water.
【学位授予单位】：西安建筑科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X832
[Abstract]:Perfluorooctane sulfonic acid (PFOS) and its salts are widely used in soils, water bodies and organisms, and have the characteristics of persistence, pollution, bioaccumulation and non-biodegradability, among which perfluorooctane sulfonic acid and its salts have attracted extensive attention of scholars at home and abroad. And listed as persistent organic pollutant (POPs). In this paper, four kinds of perfluorinated compounds were taken as the research object, the methods of environmental sample pretreatment and instrumental analysis of four perfluorocarbons were established, and the inorganic salts and organic compounds were studied by means of a small cross-flow nanofiltration membrane filtration device. Removal of perfluorocarbons with different molecular weight by nanofiltration membrane. The results are as follows: (1) the optimal solid-phase extraction conditions for sample pretreatment are as follows: the activated solution is ammonia water methanol and deionized water, the droplet rate is 2 drops / s, and the water sample droplet velocity is 2 drops / s; The eluent was 40% methanol-water (pH=5) at a drop rate of 2 drops / s, and the elution solution was 0.1% ammonia water methanol solution with a drop rate of 1 drop / s, and the volume of the above steps was 4 mL. UPLC-MS/MS was used to determine trace PFCs in water. The detection limit was 0.06 ng / L -0.22 ng / L, and the recovery rate was 73.1% -91.3%. The relative standard deviation was 7.4- 14.3cm. The results show that the method has good linearity and high accuracy, and can meet the determination requirements of trace PFCs in environmental water samples. (2) Inorganic salts (sodium chloride, calcium chloride) and organic compounds (sodium alginate, SA,) are added respectively in pure water, inorganic salts (sodium chloride, calcium chloride) and organic compounds (sodium alginate). Bovine serum albumin (BSA) BSA, humic acid (HA), the solution of inorganic salt and organic matter and PFCs standard material were used to prepare PFCs raw water of a certain concentration. The removal characteristics of PFCs by nanofiltration under these water conditions were studied. It is found that the following factors affect the removal efficiency of PFCs by nanofiltration membrane: (1) under pure water conditions, due to higher relative molecular weight, The screening effect of nanofiltration membrane on perfluorooctane sulfonic acid (PFOS) was stronger than that on perfluorooctane sulfonic acid (PFBS). (_ 2). When the inorganic salt was added, the double electric layer on the membrane surface was compressed, and the reduction of electrostatic repulsion resulted in the decrease of the rejection rate. The shrinkage of membrane pore led to the increase of rejection rate, and calcium ion would bridge between PFCs, PFCs and membrane surface. The volume of pollutants increased, and the rejection rate of PFOS increased. The rejection rate of nanofiltration membrane was higher than that of pure water. The rejection rate of PFBS was lower than that of pure water. (3) in the presence of organic matter, SA and HA increased the potential of membrane surface, the electrostatic repulsion increased, and the rejection rate of PFCs increased. The adsorption of PFCs on the surface of BSA is mainly due to its complex spatial structure and large molecular weight, which can improve the retention rate of PFCs on the membrane. Finally, the rejection rate of the membrane to PFOS is higher than that of pure water. The rejection rate of PFBS is almost the same as that of pure water. (4) the change of electrostatic repulsion induced by the change of membrane potential is the main effect of membrane on PFOS and PFBS when inorganic salt and organic matter coexist. At the same time, the screening effect of membrane pore shrinkage enhancement also has certain effect. At the same time, compared with (2), because SA contains a certain amount of carboxyl group and hydroxyl group, HA contains a certain amount of carboxyl group and a small amount of carboxyl group, BSA contains a small amount of carboxyl group and amino group, and calcium ion also makes organic molecule complex. The rejection rate of membrane to PFOS was higher than that of pure water, but the rejection rate of membrane to PFBS was almost the same as that of pure water.
【学位授予单位】：西安建筑科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X832
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