凹凸棒土对镉(Ⅱ)和镍(Ⅱ)吸附行为的研究及分析应用

Study on the adsorption behavior of attapulgite to cadmium(Ⅱ) and nickel(Ⅱ) and its analytical application

利用凹凸棒土比表面积大,吸附能力强的特点,以火焰原子吸收光谱（FAAS）法为检测手段,探讨了凹凸棒土对Cd（Ⅱ）和Ni（Ⅱ）的吸附行为,考察了静态饱和吸附容量,研究了影响其吸附和解吸的主要因素,以及共存离子的影响情况。当pH 4.0、凹凸棒土用量为0.50g时,凹凸棒土对Cd（Ⅱ）、Ni（Ⅱ）的吸附率达到94%以上;以20 mL 0.5 mol/L的HCl可将吸附在凹凸棒土上的Cd（Ⅱ）、Ni（Ⅱ）定量洗脱。凹凸棒土对Cd（Ⅱ）和Ni（Ⅱ）的静态饱和吸附容量分别为32.5 mg/g、25.0 mg/g;本法对Cd（Ⅱ）和Ni（Ⅱ）的检出限分别为31 ng/mL、0.19 ng/mL;相对标准偏差分别为1.1%和0.94%（Cd（Ⅱ）：0.30μg/mL,n=11;Ni（Ⅱ）：0.80μg/mL,n=11）。在优化的实验条件下,本法用于天然水样中Cd（Ⅱ）和工业废水中Ni（Ⅱ）含量的测定,加标回收率分别为92%~98%和87%~102%。

Based on the characters of high surface area and strong adsorption capacity of attapulgite,a method was established to determine the content of trace Cd（Ⅱ） and Ni（Ⅱ） by combining enrichment and separation of attapulgite with flame atomic absorption spectrometry（FAAS） in this paper.The adsorptive behavior of attapulgite to Cd（Ⅱ） and Ni（Ⅱ） was discussed while some problems were studied,including the static saturated adsorption capacity,the main factors influencing adsorption and desorption,and the interference of coexisting ions.The adsorption rate of Cd（Ⅱ） and Ni（Ⅱ） by 0.50 g of attapulgite was over 94% at pH 4.0 and the metal ions could be quantitatively eluted from attapulgite with 20 mL of hydrochloric acid（0.5 mol/L）.Under the optimum conditions,the maximum static adsorption capacity of attapulgite to Cd（Ⅱ） and Ni（Ⅱ） were 32.5 mg/g and 25.0 mg/g;the detection limits were 31 ng/mL and 0.19 ng/mL;the relative standard deviations（RSD） were 1.1 % and 0.94 %（Cd（Ⅱ）：0.3 μg/mL,n=11;Ni：0.80 μg/mL,n=11）.The proposed method was applied to the determination of Cd（Ⅱ） in natural water samples and Ni（Ⅱ） in industrial wastewater.The recoveries were 92 %-98 % and 87 %-102 %,respectively.