Preparation And Characterization Of Thiol-pva And Its Application To The Dgt

Diffusive gradients in thin-films technology (DGT) is one kind of promising in-situ passive sampling techniques, as well as DGT is also a technique for the measument of labile heavy metals. Compared with the traditional equilibrium passive sampling technique, DGT is a dynamics sampling technique.A new functional thiol-polyvinyl alcohol (PVA-SH) was prepared with thioglycolic acid to import-SH group into a polyvinyl alcohol framework. The optimum processing conditions were investigated by single factor experiment with material ratio, the amount of catalyst, reaction temperature, reaction time and other factors to serve as targets. The structure of PVA-SH was measured by IR, DTA and TGA spectroscope. The accumulation and measurement of DGT device with the liquid binding phase and a dialysis membrane diffusive layer for Cd2+ were studied. The liquid binding phase was 0.0010 mol/L PVA-SH solution (PVA-SH DGT). The selective accumulation of PVA-SH DGT for metal ions were investigated. The validation of PVA-SH DGT for Cd2+ were investigated. The effects of pH and ionic strength on binding capacity of PVA-SH DGT were investigated. The validation of the DGT devices for Cd2+ in synthetic lake water, spiked river water and spiked industrial wastewater was systematically investigated.The experiment results showed that the presence of the SH deformation peak at 2593 cm-1 on PVA-SH in IR graph, and the content of sulfur of PVA-SH was 1.65%(wt). The DGT device had a substantial binding capacity at pH 5.5-9 and concentrations of competitive Na+ from 0.0001 to 0.7 mol/L. The binding capacity of PVA-SH for Cd2+ was 233.7μmol/L. There was a good selectivity of PVA-SH DGT for Cd2+. The relative selectivity coefficients of accumulation for Zn2+, Co2+ and Ni2+ with respect to Cd2+ at the same deployment time were 10.45,16.34 and 23.01, respectively. The Cd2+ concentration in synthetic lake water was determined by the DGT device (recovery=100.7%, R2=0.9901). The concentrations of DGT-labile Cd2+ in the spiked river water and industrial wastewater were determined by the PVA-SH DGT (recovery=65.52%, R2=0.9983 for spiked river water and recovery= 72.32%, R2=0.9988 for spiked industrial wastewater). The recovery of spiked river water and industrial wastewater was lower because of the complexation of the dissolved orgnic carbon (8.43 mgC/L for river water and 40.32 mgC/L for industrial wastewater) with the spiked Cd2+ in the waters. The PVA-SH is maybe suitable as the binding phase of DGT technique.