BIOCYANIDE DEMONSTRATION PROJECT Activity III ; Project 5

PROBLEM Cyanide is used to extract precious metals from ores Cyanide is an acute poison and can form strong complexes with several metals Conventional treatment processes can be expensive and chemical intensive

ADVANTAGES Natural Biological Process Low Application Costs Relatively Quick Method

OBJECTIVES Obtain a significant reduction of weak acid dissociation (WAD) cyanide in gold mine process water Evaluate effectiveness of heavy metal removal Develop operating costs for treatment

TREATMENT RESULTS The total cyanide decreased from 275 ppm to 60 ppm The WAD cyanide decreased from 240 ppm to 40 ppm Nitrates decreased from 32 ppm to 1 ppm

COST ANALYSIS OPERATING COSTS PER 1,000 GALLONS OF MODERATE CYANIDE CONCENTRATION IS $0.81

CONCLUSIONS Significant reduction of total and WAD cyanide in gold mine process water Effective removal of heavy metals in mine process water Cost effective treatment technology

Cyanide Heap Biological Detoxification Activity III; Project 11

Background Cyanide is used in the mining industry throughout the world to improve the efficiency of metals separation in extracting precious metals from ore

Background Cyanide has the ability for form strong complexes with several metals therefore increasing the mobility of those metals. As such, cyanide can contribute to environmental concerns

Project Objectives Obtain a significant reduction of weak acid dissociable (WAD) cyanide Evaluate the effectiveness of heavy metal removal

Technology In general, biological cyanide degradation is accomplished by stimulating indigenous bacteria through nutrient addition and optimizing growth conditions (i.e. pH, temperature and the end product produced) These bacteria have the natural ability to degrade cyanide

Technology Advantages Cyanide compounds are naturally present in the biosphere Biological treatment is nontoxic to the environment as the bacteria return to natural levels when the cyanide is depleted Detoxification ends possible long- term liability and monitoring

Column construction Column Preparation

~9.1 tons of ore per column

Column Operation Initial testing December 3, 1998 Process solution application rate of gpm/ft 2 Hydrogen peroxide application of 5:1 stoichiometric requirement

Column Operation Column operation suspended on December 22, 1998 due to extreme weather conditions causing the columns to freeze Columns restarted on December 28, 1998

Parameters Monitored WAD and Total Cyanide Ag, As, Au, Cd, Co, Cu, Fe, Mn, Mg, Hg, Ni, Se and Zn Nitrate pH Temperature

WAD CN

Total CN

Copper

Nitrate

Zinc

Results Hydrogen peroxide column reached the compliance level of 0.2 mg/l for WAD CN within 36 days Whitlock & Associates reached compliance within 151 days. Applied Microbiology, Compliance Technology and Little Bear Laboratories were all approaching the regulatory limit when the demonstration ended

Conclusions Worst case scenario as the initial CN concentration of ~700 ppm was higher than the expected concentration of ppm Under optimal conditions, it is speculated that three of the biological processes would have performed significantly faster and reached the regulatory limit

Photolysis for Cyanide & Nitrate Remediation of Water Activity IV ; Project 3

OBJECTIVES Use Photolysis to Remediate CN - & NO 3 - Test & Compare Photolytic Methods Compare results published in literature Determine reaction mechanisms using Eh-pH diagrams as well as ion chromatography and ion selective electrode measurements

RESULTS & CONCLUSIONS Photolysis is a viable approach for remediation Direct Photolysis is not applicable for cyanide Homogeneous Photolysis (with H 2 O 2 ) was found to work the best for cyanide oxidation but product analysis showed heterogeneous photocatalysis (with TiO 2 ) was more efficient

RESULTS AND CONCLUSIONS Cyanide oxidation occurs as a series of oxidation reactions Photo-reduction of nitrate can be accomplished