新型薄膜扩散梯度技术定量采集高盐度水体中的铵离子

设计了一种基于铁氰化钴钠的新型薄膜扩散梯度(DGT)被动采样装置， 将其应用于高盐度水体中铵离子的定量采集. 采用双滴加法制备铁氰化钴钠, 并利用扫描电子显微镜(SEM)、 X射线衍射(XRD)仪和氮气吸 附-脱附测试对其表面形貌、 晶体结构和孔结构特征进行表征. 研究了铁氰化钴钠对铵离子的吸附速率和吸附容量. 建立了以琼脂糖凝胶为扩散相、 铁氰化钴钠为结合相的DGT被动采样装置. 研究了采集时间、 水体pH值和共存阳离子对基于铁氰化钴钠的DGT技术采集铵离子的影响. 实验结果表明, 铁氰化钴钠吸附铵离子在60 min时基本达到了吸附平衡; 当铵离子初始浓度为300 mg/L时其吸附容量为90 mg/g. DGT装置结合铵离子的质量随着布置时间的增加呈现线性增长(0~24 h, r²=0.994). 当pH=4~8, Na⁺浓度为0~10000 mg/L, K⁺浓度为0~25000 mg/L, Mg²⁺浓度为0~20000 mg/L, Ca²⁺浓度为0~25000 mg/L时, DGT装置累积的铵离子质量没有明显的变化. 实验结果表明， 使用基于铁氰化钴钠的DGT装置可以准确有效地采集高盐度水体中的铵离子.

Sampling of Ammonium Ion in High Salinity Waters Using Diffusive Gradients in Thin Films Technique

Eutrophication is directly related to the concentration of ammonium ion. A new diffusive gradients in thin film（DGT） technique， using sodium cobalt hexacyanoferrate， was developed and evaluated for sampling ammonium ion in high salinity waters. Sodium cobalt hexacyanoferrate was prepared using double-dropwise addition method and characterized by means of SEM， XRD and nitrogen adsorption-desorption analysis. The adsorption rate and capacity for ammonium ion by sodium cobalt hexacyanoferrate and the effects of time， pH and co-existing ions on the sampling of ammonium ion by DGT devices based on sodium cobalt hexacyanoferrate were investigated. The adsorption process reached equilibrium after 60 min and was fitted well with pseudo-second-kinetic rate model. The adsorption capacity was 90.00 mg/g at the initial concentration of ammonium ion of 300 mg/L. Langmuir and Freundlich models could both fit well the adsorption behavior. The binding gel could be eluted by 1 mol/L KCl and the elution efficiency was 85.68%（n=6）. The uptake mass of ammonium ion by DGT device as a function of time over 24 h demonstrated excellent linearity（r²=0.994）. The uptake mass of ammonium ion was quantitative over pH range 4—8 and typical ion concentration ranges（up to Na⁺ 10000 mg/L， K⁺ 25000 mg/L， Mg²⁺ 20000 mg/L， Ca²⁺ 25000 mg/L）. The results demonstrate that the DGT devices based on sodium cobalt hexacyanoferrate can accurately adsorb ammonium ion in high salinity waters.