Abstract:

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.

Key words: Diffusive gradients in thin-films, Carboxymethyl cellulose sodium, Labile, Cu²⁺, Cd²⁺, Pb²⁺