新型薄膜扩散梯度装置定量测量水环境中重金属形态

采用以纤维素透析膜为扩散相, 0.05 mol/L羧甲基纤维素钠(CMC)溶液为结合相的薄膜扩散梯度(DGT)装置(CMC-DGT)定量累积和测量水溶液中Cu²⁺, Cd²⁺和Pb²⁺的有效态; 考察了pH值和离子强度对CMC-DGT累积Cu²⁺, Cd²⁺和Pb²⁺的影响以及不同配体(乙二胺四乙酸二钠、 单宁酸和黄腐酸)对重金属有效态的影响; 测量了外加标的天然水和工业废水中重金属的有效态浓度; 并比较了不同结合相DGT装置对同一水体中重金属的有效态浓度. 实验结果表明, 0.05 mol/L CMC溶液对Cu²⁺, Cd²⁺和Pb²⁺累积容量分别为0.24, 0.11和0.45 mg/mL; 定量累积的最佳pH值范围分别为3.7～8.0, 4.7～9.0和4.7～8.0; 随着离子强度的增大, CMC-DGT对Cu²⁺, Cd²⁺和Pb²⁺的累积容量下降; CMC-DGT能够定量地累积配制水中的游离Cu²⁺, Cd²⁺和Pb²⁺, 回收率分别为92.1%, 100.6%和96.4%; 当有配体存在时, 随着配体浓度的增大, CMC-DGT测量的Cu²⁺, Cd²⁺和Pb²⁺有效态的浓度随之下降; 在过滤工业废水、 河水和湖水中, 不同结合相DGT装置对重金属有效态的测量值不同. 结果表明, CMC可作为DGT技术新的液态结合相.

New Diffusive Gradients in Thin-films Device for Quantitative Measurement of Heavy Metals in Water

Measurement of labile Cu2+, Cd2+ and Pb2+ by diffusive gradients in thin-films(DGT) device using 0.05 mol/L solution of carboxymethyl cellulose sodium(CMC) as the binding phases and cellulose acetate dialysis membrane as the diffusive layer(CMC-DGT) was systemically investigated. The effects of pH, ionic strength on the binding capacity of CMC-DGT and ligands(EDTA, tannic acid and fulvic acid) on the labile metals were investigated. Comparison of CMC-DGT device with PSS-DGT device for the measurement of labile Cu2+, Cd2+ and Pb2+ in spiked waters was assessed. The binding capacities of CMC-DGT for Cu2+, Cd2+ and Pb2+ were 0.24, 0.11 and 0.45 mg/mL, respectively. Optimal pH ranges of CMC-DGT for Cu2+, Cd2+ and Pb2+ were 3.7—8.0, 4.7—9.0 and 4.7—8.0, respectively. The binding capacities of CMC-DGT for Cu2+, Cd2+ and Pb2+ decreased with the enhancement of ionic strengths in bulk solution. The Cu2+, Cd2+ and Pb2+ concentrations were determined accurately and simultaneously in synthetic solution by CMC-DGT(recoveries 92.12% for Cu2+, 100.6% for Cd2+ and 96.43% for Pb2+). The labile concentrations of Cu2+, Cd2+ and Pb2+ by CMC-DGT decreased with the enhancement of ligands concentrations. The measured values of labile Cu2+, Cd2+ and Pb2+ concentrations by CMC-DGT were obviously more than that of PSS-DGT in spiked river water, spiked industrial wastewater and spiked lake water. Results indicated that CMC-DGT showed good prospect for the measurement of labile Cu2+, Cd2+ and Pb2+ in waters.