Accumulation And Detection Of Trace Cd²⁺, Zn²⁺ In Water By Diffusive Gradient In Thin Film Technique With Two Different Liquid Binding Phases, Carboxymethyl Cellulose And Poly (4-styrenesulfonate)

Heavy metal pollutants are difficult to be removed due to their fairly high stability and difficult degradation in water. When the account of heavy metals in the water exceeds a certain limit of water, heavy metals will do a lot of harm to water body, aquatic plants and aquatic animals. Meanwhile they will also endanger human health directly or indirectly through the food chain. So we should look for a simple method in situ for measuring heavy metal ions in the water.The diffusive gradient in thin film technique has become the most promising sampling method for concentrating metal ions in the natural water, soil and river sediment since it is invented in the mid-1990s. The diffusive gradient in thin-films technique (DGT) incorporates an ion-exchange resin separated from the solution by a gel membrane and controls the ions exchange in order to obtain quantitative analytical data in situ. This technique is not only overcoming the difficulty of the pretreatment but also combining the enrichment and sampling. So the technique is very simple and fit for the simultaneity accumulation and detection of trace metal ions in water.The concentrations of Cd2+ and Zn2+ were accumulated and detected by DGT with CMC and PSS as binding phase. Diffusion coefficient of Cd2+ and Zn2+ in noncompetitive water and influencing factors (temperature, acidity, ionic strength and stirring speed) were measured. And it is ensured the appropriate binding phase concentration, then a known concentration synthetic solution was detected. EDTA metal complexes has a good thermodynamic properties, and it is a good ligand. The complexation solution with different molar ratio of Cd2+, Zn2+ and EDTA were measured and nonsteady complex compounds of Cd2+ and Zn2+ could be determined. In addition, contents of Cd2+ and Zn2+ were different as the different binding phase, which means that measurement of nonsteady complex compound depends on binding ability of binding phase of DGT.