Open File Report # 307

Transcription

1 New Mexico Bureau of Mines and Mineral Resources Open File Report # 307 Column Leach Testing of Gold Ore from the Ortiz gold mine: The effect of surfactant additions to the leaching solution. Michael J. Harris Metallurgist New Mexico Bureau of Mines and Mineral Resources September 1987

2 Abstract Five column leaching tests were carried out to determine the effects of adding various surfactants (at a level 15 of ppn) to the cyanide leaching solution, on the extraction of gold from ore taken from the Ortiz gold mine, located near Cerrillos, N.M. Based on this test work the surfactant additions did not have a significant effect on the over all extraction of gold from the ore.

3 Introduction This open file report is based on work carried out for the Orti gold mine during the period of October 1984 to February The Ortiz gold mine (owned by Consolidated Gold Fields) provided the materials needed for this study. Summary 1. The ore as received had been crushed to 100 percent parsing 1 inch. The material was moderately damp with an 8.3 percent moisture. Triplicate fire assays yielded a head analysis of 0.02 troy ounces of gold per ton of ore. 2. The cyanide leaching solution contained 1 gram per liter sodium cyanide at a ph 11.8 of with a residual gold concentration of ppm ( oz/ton of solution). 3. Five column leaching tests were carried out to test the effects of various surfactants on the extraction of gold. The surfactants tested and the extraction results are shown below: Column Surfactant None Nalco 2DA375 Nalco 7811V1179 Nalco 3DA78s Nalco 8801B3159 Gold Extracted. (mg Au/ Kg of ore)

4 4. The extraction rate of gold as a function of effluent flow rate was determined to be a constant during the initial portion of each of the five column leaching tests. This constant value was 5.00 mg of gold per liter of leaching solution. 5. The quantity of gold dissolved in solution was found to peak early in the test and declined there after. This peak in the concentration of dissolved gold in the leaching solution was found to occur between the 5th and 8th liter of effluent for each of the column tests. 6. In each of the five tests, 90 percent (or better) of the gold was extracted with the first 20 liters of leaching solution. 7. Based on these results the surfactant additions had little if any, effect on the extraction of the gold at a surfactart addition of 15 ppm. Discussion Ore Description: The gold ore used in this test work was provided by the Ortiz gold mine. The sample consisted of about pounds of wet material contained in 55 a gallon drum. A head sample was split out rom the bulk sample for prelimicary

5 analysis. Tests were carried out on the head sample to determine gold content, percent moisture and particle size distribution. The results are shown below: Gold Content (triplicate fire assay) 0.02 oz/ton Percent Moisture (air dry) 8.3 Particle Size Distribution Percent Weight Mesh Tyler 1 inch 3/4 inch 1/2 inch 4 m 10 m 20 m 28 m 35 m 48 m 65 m 100 rn Cumulative Passing Leaching Solution: The leaching solution as provided by Ortiz consisted of approximately 110 gallons of one gram per liter sodium cyanide solution, 11.8, ph with a residual gold concentration of ppm (0,0025 oz/ton of solution). Tfis solution was modified for the test work by the addition of the surfactants, which were also provided by Ortiz. Each surfe.ctant was added at a rate of 15 ppm by weight. The surfactant wed in each test is shown below: Test Surfactant None (control) Nalco 2DA375 Nalco 7811V1179 Nalco 3DA785 Nalco 8801B3159

6 Bulk samples of each leaching solution were prepared by mixing five gallons of the cyanide solution with enough surfactant to make the designated 15 ppm concentration. The bulk solutions were stored in stoppered five gallon containers and used as needed each day. Column Desoription: Five columns were used in this test work. Each column consisted of a ten foot long, 6 inch ID, schedule 40 PVC pipe. On the bottom of each column 6 a inch schedule 40 PVC cap was installed to contain the in ore the column. Each cap was drilled and fitted with a short length 1/2 inch of PVC tubing to allow the leaching solution to flow out of the column. Inside the cap a small wad of glass wool was placed over the exit hole. The glass wool was held in place by a section of screen which was laid over the wool and gilled then in place with PVC solvent. This arrangement allowed the solution to flow out of the column while retaining the ore particle?. The columns were mounted on a wooden 14 frame inches above the floor and the tops of the columns were secured to the sec0r.d floor tailing with metal straps and screws. Column Loading Procedure: Ore was taken from the 55 gallor drum by shovelfuls and placed sequentially into one of five numbered buckets (one bucket for each column). After every three rcunds a shovelful was placed into a sixth bucket to serve as a head sample, When the ore buckets were filled they were weighed and the contents were loaded into the respective columns. After

7 loading the ore contained the columns varied in height between 7.5 and 8 feet. Leaching procedure: Approximately two liters of leaching solution was introduced into each column each day. The solutions were held in two liter flasks which were suspended above the columns in a rack which was attached to the ceiling. The solution flowed out of the flask through tubing and into the column. The flow rate was regulated by a screw clamp on the tubing. By tightening the clamp the solution flow rate was decreased. Each day the flasks were filled and the column effluents were collected. Each effluent sample was weighed and portions vere taken for cyanide, ph and dissolved gold determinations. The bulk effluent sample was then disposed of after the residuf.1 cyanide had been destroyed with sodium hypochlorite. The columns were leached for 42 days, drained for two days, washed with two liters of water, drained for days, five waphed, drained for five days and washed a final time. The columnr were then drained for seven days after which the leached residues were removed and air dried for several days. The residues were then split into quarters and a fire assay sample was split out from each quarter, the bulk residues were then stored. Test Results: The test results are summarized in Table I and

8 Figures 14. A complete listing of the leaching test data for each column is presented in the appendix. From these results there would seem to be little to differentiate these tests. Figure 1 shows gold extraction (based on percent) as a function of effluent flow. The data are grouped in a narrow band without more than 8 percent an difference at any time. Figure 2 shows gold extraction (in milligrams) as a function of effluent flow for the initial 15 liters of each test. The most interesting feature of these results is the linear aspect of the extraction between 2 liters and 11 liters. A least squares fit of these results gave an equation = of 5.00 y (X) rlith a coefficient of fit of The coefficient of fit is very good, again indicating that there was little difference between the five tests. The slope of the line gives a value for tk.e rate of extraction during the initial stage of the test. The value of 5.00 mg of gold per liter of solution is equivalert to oz of gold per ton of solution. Figure 3 shows the concentration of dissolved gold as a furction of effluent flow rate. Of primary interest is that the amcunt of gold in solution reached a peak very early in the test work and then declined gradually through out the rest of the time. This peak occurred between 5 and 8 liters total effluent flow, which corresponds to between 6.7 and 10.8 gallons effluent per

9 square foot. The only real difference in these results is shown in 4 Figure which presents total gold extraction (mg) a as function of effluent flow. Yet even this difference is only a function of the weight of ore placed in the column. Column 4 yielded the lowest overall extraction and had the lowest total weight of ore. Column 5 yielded the highest overall extraction and had the highest total weight. The ratio of gold extracted (mg) to total weight of ore was calculated to overcome the effect of the different weights of ore in each test. The results are shown below: Column Surfactant Gold Extracted ( m g Au/ Kg of ore) None DA375 Nalco 7811Vl179 Nalco DA78s Nalco Nalco 8801B These results vary (lowest to highest) by only 3 percent, c.gain indicating very little difference in the test results, Finally using the total amount of gold dissolved in each test to calculate a head assay gave the following results. Column Calculated Head Assay (oz/ton)

10 These results are somewhat higher than the fire assay result of 0.02 oz/ton, but still within experimental limits. Therefore it is the conclusion of this study that the use of the various surfactants at a level 15 of ppm did not significantly effect the extraction of gold from this sample of the Ortiz ore.

11 Table 1 Summary of Column Leaching Results Column Test Number Gold Extracted (mg) Effluent flow (liters) Cyanide consumed (gms) Feed Weight (wet, kg) Feed Weight (dry, kg) Gold Extraction mg Au/liter mg Au/kg of ore Calculated Head Assay (oz/ton) O Leached Residue Assays (oz/ton) trace 0.00 trace trace trace trace trace trace trace trace 0.02 trace trace trace less than 0.01 oz/ton

12 I! a 0 0 i.l a I I

13

14 '3r Figure 3 Dissolved Gold Concentration as Function of Total Effluent a A I I i 0 V 0 " I 0 I IO I I I FTFL.!!FNT FI OW (Ii tors) I I

15 CT 59 E v z 58 0 Q E X W 0 _I 57 t w V I I I I I I I 0 IO EFFLUENT FLOW (liters)

16 APPENDIX

17 sumrnvy of Leaching Data Column 1 Control Effluent SampleSampleWelght (g) Date NO. Individual cumulative (ppm) Individual Cumulative per liter Consumed Gold Gold Extraction (ug) Cyanide (w) 11/ / 1 1/2/ Offi " < e GO OG M h) " ' m ,

18 ,diumn 2 SurTactant Lu~3/5 smry of Leaching Data 11f / /2/ ? M) a 5 <O NO OW 7Eo J 1Go GI GO3 ;: C)l % J G *

19 column 3 Surfactant 7811VU79 summary of Leaching Data 7 e Sample Wei ht ( ) Gold Gold Extraction (ug) anido(mg) "" D3 tc No. Individual &rulittive (ppm) Individual Cumulative per liter CYConsumal CkmulilLivc. pll 11/ < m hl ll s GM W I9lGG / IO I4 336 I GE ' /2/ W

20 column 4 Surfactant 3a4785 summsry of Leaching Data sample Sample Weight (3) Gold Gold EXtractim (ug) Cyonidc (mrj)" Effluent a2 tc NO. Individunl Cumulative (pp) Individual Cumulative per liter ConSlUned C~lmUlntlVf P( / 1 1/2/ , GO Go (0.5 ( GOO ow G M ~ura m m 2561 GI371 5r>on l0ln ~'3.1 I,llrn*> I Grill I TxI%l1 19, Gl '1 I fl nclg GO

21 Column 5 Surfactant 88OlB3159 Sunlmary of Leaching aata Effluent Sample Sample Weight (g) Gola Gold Extraction (ug) Cyanide (tq) n1 tc No. Individual Cumulative (ppn) Individual Cumulative per liter Consumed ~~mu].ativa p~ ". 11/ < I ?I 'X H % j G " G " G G7 594 " I fl , ~0.7 IO.,^ /2/ " fl G I