Abstract
At many mining sites process (milling) and drainage waters escape treatment and cause receiving waters to become contaminated above avoidance or even toxic levels for fish.
The present know-how on chemical agents which can be used to complex with copper and zinc to form non-toxic compounds is limited to chelating agents such as NTA or EDTA. Preferential reaction with trivalent ions such as iron means that such ions must be tied up before complexation of copper and zinc can occur. As the amount of iron in contaminated water is usually two to eight times higher than that of copper and zinc, high dosages of chelating agents are usually required.
In this project, the use of salts of anthranilic acid, especially calcium anthranilate, was investigated. The consumption of anthranilateions was found to be about the same as that of NTA or EDTA, i.e. four milligrams per milligram of copper or zinc. The total dosage to be applied to contaminated waters would be, however, several times lower as iron is not involved in the reactions and copper and zinc are complexed in that order.
Toxicity tests to compare the efficiency and dasages of calcium anthranilate and NTA or EDTA are presently being carried out.