Abstract:

In this paper, a kind of smart microgels, poly(N-isopropylacrylamide-co-allylthiourea) (PNA), for the detection and removal of Hg²⁺ was prepared by using N-isopropylacrylamide (NIPAM) and allylthiourea (ATU) as copolymer monomers, N,N'-methylenebisacrylamide (MBA) as a crosslinking agent, and 2,2'-azobis(2-methylpropionamidine) dihydrochloride (V50) as an initiator through precipitation polymerization. The chemical composition and morphology of the microgels were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The particle size distribution and temperature responsiveness of microgels were studied by dynamic light scattering nanoparticle analyzer (DLS). The effects of interfering ions, pH and temperature on the Hg²⁺-response of microgels were investigated. The adsorption and removal efficiency of PNA microgels for Hg²⁺ were explored by using atomic absorption spectrometer (AAS). The results show that, the PNA microgels have a temperature sensitivity and specific responsiveness to Hg²⁺. The shrinkage ratio (R_D) caused by Hg²⁺-response decreases with the increase of ATU monomer ratio. The optimal detection temperature was determined to be 30℃. With the increase of Hg²⁺ concentration, the R_D value gradually decreased. According to the corresponding relationship between the Hg²⁺ concentration and the R_D of microgels, the calculation formula of Hg²⁺ concentration was fitted. The lowest detection concentration of PNA microgels can reach 10^-8 mol·L^-1. In the adsorption experiment, the adsorption capacity of the PNA microgel was found to increase with the Hg²⁺ concentration. An adsorption rate of over 80% was achieved for Hg²⁺ solutions below 10^-4 mol·L^-1, and the minimum concentration of Hg²⁺ could be reduced to 0.0005 mg·L^-1. Compared with Zn²⁺, Cd²⁺and Pb²⁺, the adsorption rate of PNA microgels for Hg²⁺ is about 7 times more than other metal ions. The research results provide a new method for the detection and removal of harmful metal Hg²⁺.

Key words: N-isopropylacrylamide, allylthiourea, microgels, Hg²⁺ response

摘要：

以N-异丙基丙烯酰胺（NIPAM）和烯丙基硫脲（ATU）为共聚单体，N,N'-亚甲基双丙烯酰胺（MBA）为交联剂，2,2′-偶氮二（2-甲基丙基咪）二盐酸盐（V50）为引发剂，通过沉淀聚合法制备了一种可用于Hg²⁺检测与去除的聚（N-异丙基丙烯酰胺-共聚-烯丙基硫脲）（PNA）智能微凝胶。利用傅里叶变换红外光谱仪（FT-IR）、X射线光电子能谱仪（XPS）和扫描电镜（SEM）对微凝胶进行了化学成分和形貌表征。利用动态光散射纳米粒度分析仪（DLS）对微凝胶的粒径分布及温度响应性进行了研究。探究了干扰离子、pH和温度对微凝胶Hg²⁺响应性能的影响。利用原子吸收光谱仪（AAS）探究了PNA微凝胶对Hg²⁺的吸附去除效果。结果显示，PNA微凝胶具有良好的温敏性以及对Hg²⁺的特异响应性，响应Hg²⁺后引起的收缩比（R_D）随着ATU单体比例的增加而减小，并确定了最佳检测温度为30℃。随着Hg²⁺浓度的增加，R_D值逐渐减小，根据Hg²⁺浓度与R_D之间的对应关系拟合出相应的Hg²⁺浓度计算公式。该PNA微凝胶最低检测浓度可达10^-8 mol·L^-1。在吸附实验中，PNA微凝胶的吸附容量随着Hg²⁺浓度的增加而增加，对10^-4 mol·L^-1以下的Hg²⁺溶液，吸附率可达80%以上，最低可使Hg²⁺浓度降至0.0005 mg·L^-1。相比Zn²⁺、Cd²⁺和Pb²⁺，微凝胶对Hg²⁺的吸附率是其他金属离子的7倍左右。研究结果为有害金属Hg²⁺的检测和去除提供了新方法。

关键词: N-异丙基丙烯酰胺, 烯丙基硫脲, 微凝胶, Hg²⁺响应