Effect of pH in the natural degradation process of cyanide

摘要

In this paper, the effects of pH in the naturaldegradation real waste waters which was taken from the systemduring the pilot plant studies of Gümüshane-Mastra gold oresand synthetic solutions of pH 11.2 and 12. The experimentwhich started on September 25~(th) was continued until the59~(th) day when the liquid phase froze completely due toweather conditions of the season. Cyanide concentration waslowered from 392ppm CN~- to 10ppm CN~- and pH from 11.2to 9.9. The volume of the liquid phase 25percent decreasedbecause of evaporation over this two months period. Secondstep experiments were carried out to investigate the effect of pH,evaporation and rate of cyanide decreases in the cyanidedestruction. Synthetic cyanide solutions of pH 11.2 and 12 wereprepared and kept 4 months in the PVC tanks, under the openatmospheric conditions. The pH values were allowed to changeat the atmospheric conditions in the first tank. But the secondtank's pH was kept constant around pH: 12 using NaOH. Theresults showed that 99.8 percent of total cyanide ion wasdecreased at the end of 76 days. At the second tank, where pH:12 was kept constant, 99 percent of total cyanide ion wasdecreased at the end of 97 days.