Method for Suppressing the Leachability of Certain Metals
The interaction of Sn, Sb and Pb with tungsten in contact with an aqueous medium has a synergistic effect in which the leachability of each metal is suppressed. This means that tungsten has the ability to suppress the leachability of these same metals, in particular lead. For example, tungsten may be added to the lead-contaminated soil in order to suppress lead contamination of the ground water by forming lead tungstate which has a very low solubility.
1 . A method of suppressing leachability of certain metals, comprising:
contacting an aqueous medium with tungsten metal and at least one other metal selected from tin, antimony, and lead whereby the leachability of the tungsten metal into the aqueous medium is suppressed.
2 . The method of claim 1 wherein the aqueous medium has a pH of less than about 9.
3 . The method of claim 2 wherein the pH of the aqueous medium is from about 5 to about 9.
4 . The method of claim 1 wherein a tungstate of the other metal is formed.
5 . The method of claim 1 wherein lead tungstate is formed.
6 . The method of claim 1 wherein the contact with the aqueous medium causes an aqueous tungstate anion and an aqueous cation of the other metal to form whereby the tungstate anion and cation of the other metal react to form a tungstate of the other metal which is not substantially soluble in the aqueous medium.
7 . A method for reducing lead contamination of ground water comprising:
adding tungsten to an area of land where lead is present in the soil or ground water.
8 . The method of claim 7 wherein the area of land comprises an outdoor shooting range.
9 . The method of claim 8 wherein the outdoor shooting range has soil that contains lead bullets.
10 . The method of claim 7 wherein the tungsten is added by spraying a solution of sodium tungstate on the area of land.
11 . The method of claim 7 wherein solid tungsten-containing articles are added to the soil.
12 . A method for removing a soluble lead species from aqueous solution comprising contacting the aqueous solution containing the soluble lead species with tungsten metal to form a lead tungstate precipitate.