多壁碳纳米管固相萃取快速检测水样中铅镉铜铁

Determination of Lead,Cadmium,Copper and Iron in Water by Multiwalled Carbon Nanotubes-solid Phase Extraction

传统的固相萃取填料应用于环境样品的重金属处理过程中,存在pH不稳定和不同极性萃取物共同萃取较为困难等方面的不足,因此寻找新型固相萃取填料显得尤为重要。本文采用多壁碳纳米管填充固相萃取柱,萃取水中金属元素铅、镉、铜和铁,采用石墨炉原子吸收光谱法测定铅和镉,电感耦合等离子体发射光谱法测定铜和铁。实验考察了多壁碳纳米管的性质、溶液pH值、洗脱溶液、样品流速以及基体效应对测定结果的影响。结果显示：溶液pH=9,1 mol/L硝酸为洗脱溶液,样品流速为2 mL/min时,外径〈8 nm未修饰的多壁碳纳米管有较好的萃取效率,对溶液中铅、镉、铜和铁的最大吸附容量分别为44.91、42.31、54.68和49.07 mg/g,四种元素的吸附容量均衡;钾、钠、钙、镁离子以及苯和甲苯等基质对四种金属元素的萃取影响不大。方法回收率为95.3%~99.5%,精密度（RSD,n=7）为1.2%~3.2%。本方法采用外径〈8 nm的多壁碳纳米管固相萃取,与传统萃取方法相比,富集效果好、回收率较高,而且操作简便、准确度高;与前人采用外径20~30 nm的多壁碳纳米管的性能相比,镉和铜的吸附容量更高,还可实现对铁的吸附,且铅、镉、铜和铁四种元素的吸附容量均衡,更适合用于检测水样中的金属元素。

The traditional solid phase extraction sorbent contains certain deficiencies in the progress of processing heavy metals in environmental samples,such as pH instability and co-extraction difficulty.Therefore,it is particularly important to find more efficient sorbents.A solid-phase extraction method using multi-walled carbon nanotube as absorbent materials for Pb,Cd,Cu and Fe in water has been determined.The effects of solution pH,elution solution,sample volume and matrix effects were investigated.Pb and Cd were determined by Graphite Furnace Atomic Absorption Spectrometry; alternatively,Cu and Fe were determined by Inductively Coupled Plasma-Atomic Emission Spectrometry.Experimental results show that the extraction of the metal elements is most efficient when the pH value is 9.0 and flow rate is 2 mL /min with 1 mol /L HNO3 as the elution solution by using the unmodified multi-walled carbon nanotube（ outer diameter 8 nm）.The maximum adsorption capacities of multi-walled carbon nanotube for Pb,Cd,Cu and Fe are 44.91,42.31,54.68 and 49.07 mg /g,respectively.K＋,Na＋,Ca2 ＋,Mg2 ＋,benzene and toluene have little effect on Pb,Cd,Cu and Fe extraction.The recoveries of Pb,Cd,Cu and Fe were 95.3%-99.5%,and RSD values（ n = 7） were 1.2%-3.2%,respectively.Compared with the traditional extraction method,this new method not only has high recovery and enrichment effect,but also is simple and accurate,which can be used in the detection of Cd,Cu,Fe and Pb in environmental water samples.