纳米TiO_2修饰的涂碳型PVC膜汞离子选择电极的研制与应用

制备了以纳米TiO2为修饰剂的涂碳型PVC膜汞离子选择电极,并用于汞离子的测定。对比裸碳电极、普通涂碳型汞离子选择电极和纳米TiO2修饰的涂碳型PVC膜汞离子选择电极在1.0×10-3 mol/L铁氰化钾溶液中的循环伏安图,发现纳米TiO2修饰的涂碳电极的氧化还原峰电流明显增加,且可逆性良好。对比普通涂碳电极和纳米TiO2修饰涂碳电极的响应曲线,发现纳米TiO2修饰涂碳型汞离子选择电极的Nernst响应范围更广,为1.0×10-2~1.0×10-6 mol/L,级差为30mV/pC。而且,纳米TiO2修饰涂碳型汞离子选择电极比普通涂碳电极的pH值范围更广。此外,与普通电极相比,修饰电极的检测下限更低,为4.5×10-7mol/L。常见的离子如Cu2+、Cd2+、NH4+、Zn2+、Cl-、Ca2+、Fe3+、K+、Na+、I-、Fe2+、Mg2+、Al 3+、SO42-、CH3COO-、NO3-等的选择性系数均小于0.01,在室温下电极的使用寿命约为3个月。电极用于电位分析法测定实际污水样品中汞离子,测定结果与原子吸收光谱法结果相一致,相对标准偏差为1.9%~2.4%。

Preparation and application of carbon-coated PVC membrane mercury ion selective electrode modified with nano-titanium dioxide

The carbon-coated PVC membrane mercury ion selective electrode was prepared using nano-TiO₂ as modifier and applied to the determination of Hg²⁺. The cyclic voltammograms of bare carbon electrode, normal carbon-coated mercury ion selective electrode and carbon-coated PVC membrane mercury ion selective electrode after modification by nano-TiO₂ were compared in K₃Fe(CN)₆ solution with concentration of 1.0×10^-3 mol/L. It was found that the redox peak current of carbon-coated electrode after modification by nano-TiO₂ increased significantly and have a good reversibility. The response curves of normal carbon-coated electrode and nano-TiO₂ modified carbon-coated electrode were compared. The results showed that the Nernst response range of carbon-coated mercury ion selective electrode after modification by nano-TiO₂ was wider, i.e., 1.0×10^-2-1.0×10^-6 mol/L with stage difference of 30 mV/pC. Moreover, the carbon-coated mercury ion selective electrode after modification by nano-TiO₂ exhibited wider pH range than that of normal carbon-coated electrode. In addition, the detection limit of modified electrode was lower, i.e., 4.5×10^-7 mol/L. The selectivity coefficient of common ions (such as Cu²⁺, Cd²⁺, NH₄⁺, Zn²⁺, Cl^－, Ca²⁺, Fe³⁺, K⁺, Na⁺, I^－, Fe²⁺, Mg²⁺, Al³⁺, SO₄^2－, CH₃COO^－ and NO₃^－) was less than 0.01. The lifetime of modified electrode at room temperature was about three months. The prepared electrode was applied to the determination of Hg²⁺ in actual wastewater samples by potentiometric analysis. The found results were consistent with those obtained by atomic absorption spectrometry. The relative standard deviation (RSD) was between 1.9% and 2.4%.