摘要：Changes in the quality of domestic tap water during contact with pure copper, zinc, lead and iron as model materials were investigated by chemical and instrumental analyses. When neutral water containing 1-8 ppm free chlorine and no buffer reagent was placed in contact with pure these pieces at 20°C, the concentration of free-Cl in the water decreased rapidly with time, and pH of the water was lowered in contact with Cu and Fe pieces, but rose in contact with Zn and Pb pieces. These metals dissolved in the water were easily oxidized with free-Cl to form large precipitates of hydroxides/oxides of these metals. An increase in the metal-concentrations and a decrease in the free-Cl-concentrations in the water were suppressed by the formation of protective film on the Pb pieces when the water was placed for a long time in contact with Pb pieces. However, this suppression was not observed for Cu, Zn and Fe pieces. Results of experiment conducted in the presence of Palitzsch buffer reagent (pH of 7.0) showed that the greatest reduction in the concentration of free-Cl and the highest metal-concentration in the water were observed for Zn pieces, while the smallest and lowest values were obtained for Cu pieces. In addition, it was found that the dissolved metals were present in small precipitates (may be hydroxides and oxides) or metal ions in the water.
关键词：residual chlorine;copper;zinc;lead;iron;metal pick-up from metal material;disappearance of residual chlorine;corrosion of metal material
