World Gold 91
Integral Pressure Stripping
CHRIS CAMPBELL•HICKS 1 AND GAVIN BEER2
ABSTRACT
The recent re-emergence of an Integral Pressure Stripping system which operates with both cell and column in closed circuit at elevated temperature and pressure, requires no cyanide in the eluate solution and has greatly reduced carbon reactivation requirements in seen as a progressive step in this area.
Several of these re-configured IPS systems have-been placed in service
in Australia and overseas in the last three years, with the first of the new generation units constructed and commissioned by Como Engineers Pty. Ltd. at Mt. Fisher in the East Murchison of W.A. in September 1987. This plant was relocated to a new ore body a_tDarlotW.A. in February 1989. Use is made of a data base of raw plant performance figures from both Mr. Fisher and Darlot and its performance compared with other operating plants.
Initial commissioning difficulties of the Mt. Fisher prototype and dis cussed together with the modifications and operational procedures required to overcome these problems. Stripping times of less than 6 hours at 145 degrees have been achieved with barren carlxm values less than 1Oppm from loaded carbon values above 3000 ppm and with cell pass efficiencies reaching 90 per cent.
The plant has demonstrated the following additional advantages: lower capital cost, lower consumable materials and energy costs, greatly reduced waterrequirements, reduced carbon reactivation requirements athigh circuit recovery rates, simplicity of design and improved electrowinning efficien cies.
INTRODUCTION AND BACKGROUND
The commissioning of more than 50 new gold treatment plants in Australia from 1980 onward has seen much research, development and innovation. Primary research organisations, design engineers, consultants, engineering and construction organizations and producers themselves have all made significant contributions as the full impact of the rapid growth in the industry was felt. This is seen as an excellent example of the academic and research institutions working side by side with industry in a mutually supportive and co-operative atinosphere which has inevitably accelerated growth of both expertise and revenue.
Conventional elution plant designs such as the Zadra (or Homes take) plants (Zadra et al1952) and the AARL type (Davidson R.L. 1977) are continually being reviewed, are well understood and have gained widespread acceptance in the gold industry. Both plant designs have proven track records and work well. The choice between these two quite different designs being largely governed by leach circuit chemistry, the presence or absence of other ionic species such as silver, copper, nickel etc and specific ore types.
The large water demands of comparably sized Anglo plants, i.e. 60 tonnes compared with 6 tonnes for the Zadra plants, have required large and expensive reverse osmosis or other water treat-ment installations at site where ground wear T.D.S.levels at time exceed 100,000 ppm.
Other factors affecting elution plant selection and geographical location, financial constraints and plant size with the Zadra plants generally being favoured in North America and the AARL plants being the preferred option in South Africa.
Nicol M.J., 1985, gives a useful general summary of the three main pathways for de-sorption touching on the thermodynamics and kinetics. More recently, in Australia, Muir, Avraamides, Labrooy and others 1982-1987 have proposed the use of both ion specific resins and non aqueous solvents other than methanol such as acetonitrile (AN) and dimethylsulphoxide (DMSO) as alternative adsorption/elution pathways for noble metals. In the case of resin co’Iumns advantage is taken of ambient temperatures and selective ion adsorb/desorb sequencing. Muir admits to some difficulties in de-sorption rates and research continues with some encouraging results being produced in S.A. in 1990. Gold producers may typi cally express “fear of the unknown” (read fear of new technology), where the handling of organic chemicals will present potential hazards. Given the very high safety statistics of oil refmeries the problem is probably more apparent than real. This attitude is disap pointing given the extremely high chemical activities measured for noble metal ions in aqueous/non-aqueous solution mixtures. (Hinchcliff, Muir 1986).
THEORETICAL CONSIDERATIONS
Adsorption is favoured by low temperature,. low free cyanide, low pH, high ionic strength, and the presence of Calcium.
In simple thermodynamics terms, the physi-sorption of gold onto
carbon proceeds with a nett decrease in free energy, and using
del G = del H -:- T del S
for this process we see that H is -ve for the decreased disorder of the system and this is immediately felt when activated green carbon is added to a light, nonpolar organic solvent. The mixture, if hand held, becomes warn to the touch as the exothermic physi-sorption take place.
The adsorption of Au(CN)2′ proceeds by the same mechanism
generating heats of adsorption of the order of 14kJ/mole, compared to say Hydrogen association H + H = H2 at around 100 kJ/mole.
Figures l(a),(b)&(c) below illustrate the basic arguments
Q ..bC”
Q = adsorption on solid substrate
G = concentration in solution b, n = constants
1Plant General Foreman, Canadian Bogosu Resources Ltd., Ghana (West
Kinetics And Equilibrium
after D.M. Muir
Africa). Previously Metallurgical Superintendent, Forsayth Mining
Services, Perth, Western Australia
2.Piant Superintendent, Sundowner Minerals, Perth, Western Australia
Activated carbon closely follows the Langmuir and Freundlich isotherm. The equilibrium isotherms above show a decrease in the activity of carbon as the temperature is raised indicating a direct line
Au in solution
5
Carbon loading 30,000 ppm Au
14,000 ppm
0 6 12
18
TIME
24 hours
5,000 ppm
Fig .1(a).Kinetics (independent of stirring).
I
30,000
Freundlich Equation
10,000 Q =
154
Gold on carbon
1,000
100
i.e. log Q = const + n log C
0.01 0.10 1.0 10.0 ppm
GOLD IN SOLUTION
Fig. I (b). Equilibrium.
Cairns, April21-25
INTEGRAL PRESSURE STRIPPING
80,000
Au on carbon
20,000
EQUILIBRIUM ADSORPTION ISOTHERMS
100
Au in solution
200 ppm
Fig.l (c). Effect ofTemperature.
,,
of thought to the development of high temperature methods of stripping carbon.
Excellent work in this field was carried out by Salisbury and
others from 1952 onwards at the USBM and Homestake using laboratory pressure stripping apparatus as below and generating the useful isotherms of Figure 3.
Pressure Stripping Apparatus
The test apparatus (Fig. 2.) consisted of:
1. 25mm diameter by 850nun long stripping column.
2. Strip solution reservoir.
3. Nitrogen tank for system pressurization and solution flow.
Heat for the system was provided by thermometrically controlled electric tape.
Testing Parameters
1. Isotherm data were collected at temperatures of 112, 125, 135, 185, 200 and 220’C. Curves for 200 and 220’C were extrapo lated since at these temperatures cyanide destruction w:as com plete and gold was reduced on the carbon. This is logical since the aqua ion of Au+ is not stable (e.g. the reduction potential for free, ionic gold(I) in the aqueous phase is greater than that of HzO, therefore gold was reduced).
2. System pressure was maintained at 52 psi (350 kPa).
3. Elution solution makeup – Aqueous 0.1% NaCN/1.0% NaOH.
4. Loaded carbon- 920 ounce Au/ton C (31,542g Au/tonne C):
approximately 100 g per stripping batch.
5. Column elution there was 10 minutes retention per bed (column) volume.
6. Data reported -percent of 920 ounce Au/ton C recovered versus number of bed volume through column.
It was the work of Baxter and Macaulay., 1983, that saw the design, development and subsequent commissioning of the first integral pressure strip/electrowin unit at the Hickey mine near Blaney in N.S.W.
Despite the success of the Hickey stripping plant as detailed by
Baxter, however, little to no further development or attention seems to have been given to this novel design for several years until Siddall (OMC), offered a re-configured version to Sundowner Minerals
N.L. in 1987 as a superior option to conventional pressure Zadra
plant.
The effect of elevated temperatures on either cyanide free elution on in combination with cyanide and caustic is well documented, Labrooy et al., and’numerous AMIRA reports 1985-1989, where the operation at higher temperature compensates for the lack of added cyanide in the eluate, at 4 per cent caustic on higher. The higher pH (greater than 13) also ensured adequate conductivity and protection against anode corrosion. Combining this with the work summarised by Rogans J., a useful table results:
r t ecluM
– T “\
s…,tel!u<or-. LJ
\
50UJT10N Rt: VOAI’\
Nl TA.Nl
.c..:.
w
100
90
80
Fig. 2. Laboratory Apparatus for Pressure Stripping.
(.) I I //'””t25°C
Q.
d’ 70
UJ
11..
11..
(f) 50 / I
– _.
……
— –
0
…J
8 .,.. – –
-“-…
185 °C
40 r;
30
r—-
…..
.,.;
2 ‘i 6 8 10 12 1″1 16 18 29 22
ELUATE, Column Volumes ( 10 min retention time)
Fig. 3. Stripping Isotherms for Au from Activated Carbon.
156
INTEGRAL PRESSURE STRIPPING
I
r .1… –
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ti II “,,
.!
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Fig.4.
IPS PLANT DESIGN AND OPERATION
Gardiner’s Rule
“The society which scorns excellence in plumbing because plumb ing is a humble activity and tolerates shoddiness in process engineering because it is an exalted activity will have neither good plumbing nor good engineering. Neither its pipes nor its theories will hold water.”
(With apologies to Kelly, Spotiswood and Gardiner)
The Como Engineering (pilot) plant as installed at Mt. Fisher (Fig. 4 and 5), utilized a 1.2tonne PTFB lined stainless teel column in closed circuit with a pressurized electrowinning cell (Flow diag. 5). Heat was provided by a direct gas fired Marshall boiler without heat exchangers.
The cell was of mild steel and originally lined with high density polypropylene. This material proved to be inadequate for tempera tures of 140 degrees when the additional heat of conduction of the cathodes was felt and resulted in serious distortion of the liners and cathode trays which were fabricated from the same material.
A more severe problem was complete melting of the insulating
strips allowing contact of the cathode and anode bars with the steel cell itself. While this did not constitute a safety hazard since the cell was well insulated from the pressure shell it did allow short circuit ing and current dumping with consequent loss of cell efficiency. The polypropylene was replaced with PTFB and the problem resolved.
After a few months service the PTFB column liner also delaminated due to a combination of poor original lamination and vacuum conditions within the column during the cooling cycle. This lining was completely removed and the carbon loading hopper laminated with acid resistant rubber for acid washing outside the
column and the stainlesssteel column run without a lining. Column corrosion has bt<en nilas expected in the very high pH environment and in the absence of cyanide addition to the eluate.
Other problems encountered early were the difficulty inbalancing the cell level at the elevated temperature and pressure and sustained performance of the elute circulation pump, which was not surprising given the high availability demands discussed later.
The Darlot I.P.S unit operating at Mr. Fisher on the very “hard and clean” archean chert ore body ((::ampbell-Hicks., 1988/1989.) maintained acceptable carbon loading in excess of3000 g/t for over twelvemonths without any thermalreactivation. Acid washing was also discontinued for the last seven months of the operation while still maintaining acceptable loading suggesting further investiga tion was merited.
Poor operations control twice during the Mt. Fisher project resulted in massive anode failure with the anodes sustaining more than 50 per cent corrosion in both cases in only a few strips. In the first case the corrosion was attributed to chlorine attack from poorly rinsed carbon after acid washing and in the later case was attributed to direct acid attack at low cell pH.
Subsequent attention to ensuring pH was maintained above 13 and thorough rinsing of carbon saw little to nil further anode attack. An interesting feature of the IPS plant at Mt. Fisher (and Darlot) was the decision not to include areactivation kiln in the design. This decision was based on the following:
a fast tracked short term project (12 months)
• clean organic free ore body.
• sweet water
elevated temperature stripping to reduce re-activated require ments.
• expensive high activity coconut shell carbon.
157
Yl
soo•p,_ …_.,.,…._t ..,
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In house activity (k) measurement was initially a low (50-60) per cent but throughout the project quickly tnmslated to (65-70) per cent that of green carbon and carbon continued to load to 3000 g/t until exhaustion of the orbed in October 1988., i.e. without incurring any further measurable drop in recovery attributable to organic or inorganic foulants.
At the end of the Mt. Fisher project, however, the carbon was removed from the circuit and sent out for custom stripping and reactivation.
To assist in the investigation of this abnormally low regeneration
requirements amples were also sent to the Chemistry Centre in WA, Avraamides 1988/Siddall 1988/89, where activity and foulant levels were examined and the carbon reactivated in a test kiln along with a Northern Territory plant carbon, also using a Zadra operation at 140 C, but using only atmospheric electrowinning and where a regeneration kiln was in service.
The summarized results indicated that the Mt. Fisher plant operated adequately without a carbon regeneration system since start up in September 1987. Acid washing of the carbon had not been practiced since April1988, seemingly without adverse effect. Site carbon activity testing was carried out on a routine basis, with results indicating a steady, gradual improvement in activity since the IPS plant overcame the operational and teething problems at the end of 1987. As part of the study into the benefits of utilising an Integral Pressure Stripping (IPS) Plant, using the facilities of the Mineral Processing Laboratory of the WA Chemistry Centre, (MPL), samples of strip liquor were also examined in order to assess the ability of the IPS plant to assist removal of organic/inorganic fouling and to remove cyanide.
Testwork Results
Activity testing utilising the Mineral Processing Laboratory (MPL) activity test method yielded the following results.
Activity k(h-1) Activity Relative,%)
Mt Fisher “areen” 815±4 100
Mt Fisher loaded 86+ 1 17
Mt Fisher barren 55±14 12
Mt Fisher barren + acid wash 47±11 10
NT “areen” 480±31 100
NT loaded (699) 86+6 24
NT barren (699) 93±13 26
The summarised results also indicated that the K-values for loaded carbon are similar from both Mt. Fisher and NT, and differ slightly for barren carbon. However, the “green” carbon values are very different at 815 for Mt. Fisher and 480 for NT, reflecting the us of high quality carbon at Mt. Fisher. As a result, the commonly ‘reported relative activity actually translated to 24-26 per cent for NT carbon and 10-17 per cent forMt. Fisher.
A comparison of activity test techniques between Mt. Fisher site
and MPL also indicated the following:
METHOD MT FISHER MPL
Relative Activity, % of barren Mt Fisher carbon
35
12-15
Large discrepancies are obvious, and the reported activity of 65-70 per cent obtained at Mt. Fisher was not substantiated.
For the Strip Liquor Analysis the following trends were observed:
G
0 ,
L ;;!’=
D /
0
N
c
A R B
0
N
g
I 10
t -¥ I
1
0 0.003 0.03 0.3 3 10
GOLD IN SOLUTION mg/1
-EQUILIBRIUM •+•ACTUAL C-1-P
Fig. 6.Equilibrium Relationship. Gold on Carbon vs Gold iwSolution.
As expected, conductivity fell as a result of hydrolysis during electrowinning and although no cyanide was added to the eluant, the initial free cyanide level was 280 ppm. As stripping progressed, the level dropped to 15 ppm, and analyses showed the following efficiencies:
TIME HEAD
Au ppm TAIL
Au PPm EFFICIENCY
(%)
0 285 268 6
2 150 53 65
5 44 13 70
7 18 6 67
10 5 3 25
Analysis of Ca, Mg, and Na had shown virtually consistent levels over the duration of the strip.
Activity Testing
The method adopted by Mt. Fisher relied on a single point value after fifteen minutes of adsorption. The method produced a very different answer to the MPL method, which is based on a multi point assessment. The large discrepancy between the site value of 65-70 per cent activity, and the 35 per cent obtained with the same technique by MPL was attributed to be due to the use of gold chloride at site whereas the correct solution should have been gold cyanide. For the Darlot project, it was recommended that the MPL multi-pointmethod be adopted, since this appears to be the standard in the WA industry. It was apparent then that the non-regenerated carbon that was currently in use at Mr. Fisher, still had reasonable acceptable activity and was seen as equivalent to the regenerated carbon from the NT operation.
Operating experience at Mt. Fisher also indicated that the keys to low solution losses which maximised recovery were:
• low level of residual gold on barren carbon
• low cyanide tenor in the CIL circuit.
Typical values were 35 ppm Au and a cyanide level of less than
0.02 per cent. Any significant increase in either of these values led to detectable solution losses.
This was also an interesting observation since discussions with a number of other operators reflected a consensus that barren loadmg up to 150 ppm Au didnotresult in significant gold values desorbmg and reporting to tails.
The typical CIP adsorb/desorb equilibriums implied in Figures 6 and 7 , however, appear to substantiate the Mt. Fisher observation.
Strip liquor analyses results confirmed that cyanide was stripped from the carbon and eliminated in the electrowinning circuit.
Gold was handled by the IPS plant with an overall efficiency of (65-70) per cent for the particular strip under consideration.
This compares with the typical30 per cent efficiency for atn10s pheric pressure cells.
The IPS plant did not remove inorganic foulants during stripping. The good quality circuit water and low lime addition rates appear to be the reason why the carbon retained its activity without acid washing. No change in activity was measured when the carbon was acid washed, inqicating behaviour typical of new carbons. It was only when a carbon was badly fouled that there was apositive effect on its activity following acid washing. Visual inspection of this test sample indicated only moderate levels of foulant were present. Acid washing prior to regeneration during the move to Darlot was recommended.
FEED
CARBON
LOADED CARBON TO ELUTION AND REGEN
FEED • 4.0 mg/1
4
5
STAGES
6
TAILS
1 2 3 4 5 6
TENOR
mg/1
2.0
0.8
0.32
0.13
0.05
0.02
LOADING
g/T
5000
2500
1200
650
360
205
/
Fig. 7. Carbon in Pulp Adsorption Circuit.
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160
Cairns, April21-25
WORLD GOLD ’91
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THE DARLOT PROJECT
The Mt. Fisher ore body was exhausted by October 1988 and the entire plant including the I.P.S unit was shut down de-commis sioned and handed over the disassembly on 21-11-88. It was transported to the Darlot ore body 140 km south of Mr. Fisher re-assembled and recommissioned 13 weeks l ter, 24-2-89, on a clay/quartz ore body where it immediately exceeded both budget and design targets achieving 145per cent of budget tonnage within 10 days of commissioning and 129 per cent of budgeted fme gold within 6 weeks. (Campbell-Hicks,1989.,) Plant modifications re quired for the Darlot operation were minor but important and are sununarised below:
The plant remained essentially “skid mounted” (Fig. 5) to facilitate furtherrelocation and transportation if and when required. The contribution made by the IPS unit to the pleasing metallur gical results, and the high plant recovery values, (Figs 8 and 9) was significant in helping to offset the slow carbon loading kinetics indicated by early testwork. This testwork, carried out by Orway Mineral Consultants had indicated slow carbon loading kinetics on all samples tested. A fast carbon turnaround strategy was thus implemented early in the project in an effort to physically flush the macropores of this fine clayey material which was 50% – 25 microns ex the crusher and with a significant proportion in the micron range as later revealed by microscopy. 10-12 strips quickly became routine with up to 14×1.3 tonne batches in one week on
several occasions.
Metallurgical performance data (Figs. 8 and 9) showed a ”bottom line”improvementinrecoveriesbetweenAprilandNovemberfrom
92.5 per cent to 95.73 per cent with 97.3 per cent being recorded for December. These figures were substantiated by recovered (fine oz.), gold produced when balanced against calculated (assayed) grade and recovery figures. Umpire laboratories were also used on a routine basis to confirm abnormally high/low assay results.
Required Modifications
The modification made to the IPS unit for Darlot operations were: An improved eluate circulation pump with consideration for eventual replacement with a magnetically coupled gland less type with a stainless steel wet end.
• Installation of a reversible worm and stator balance pump looped to a level switch for maintaining constant cell level.
• Insulation upgrade to reduce heat losses during operation above 150’C after installation of the high temperature heater scheduled for late 1990.
A fast strip turnaround strategy requiring 200 per cent of original design availability together with stronger (coarser) cathode wool allowing 10:1 gold:woolloading.
Plant Test Performance Data
Typical plant data for a series of strips are given in Table 1, with the plotted isotherm (Fig. 10) showing good agreement with the work of Salisbury et al. Five only sequential strips were carried out under maintained cell closure conditions and at the following parameter settings.
110
100
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0
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authors withdrawal from the project in June 1990. Due to the consistently sound financial performance of the Darlot project consideration was given to the addition of the kiln to the elution facility.
80 /.:
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I
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Fig. 10. %Au Stripped vs Time
From late December 1989 to February 1990 considerable time was spent at the Forsayth Lawlers gold project where a Promintec vertical tube thermal reactivation kiln had been in operation since the project was commissioned in 1986. Typical of many operators faced with high circuit carbon inventories coupled to “first genera tion” reactivation kiln operation, the re-activated carbon was little to no higher activity after treatment. (Muir D.M. 1987) Muir sug gested that many operators, were producing mediocre to poor results from their kilns simply because they were not able to achieve the mandatory bed temperatures which, in the presence of steam, are necessary for restoration of acceptable activities. The W.A Chemistry Centre, (MPL) was suggested as an appropriate body to consult.
MPL’s results on many field carbons and their in house carbon
testing research, using a laboratory test kiln produced results rang ing from 85 per cent to 125 per cent of green carbon activity after
Column Temp.: 145 C Column Pressure: 380 kPa Amps: 185A
Cell Temp. : 145 C
Column Pressure: 380 kPa Voltage : 2.8 V
thermal regeneration. (Avraamides 1990). These results were seen
as excellent and prompted a resolution to achieve the same results, after appropiate modifications, from the Lawlers kiln, or to replace it with a new Combustion Air unit. In this case the old kiln was to be relocated to Darlot.
Como Engineers (Perth W.A) were also requested to reCOffi!Ilend and make modifications to the existing Lawlers kiln to duplicate the results achieved by the MPL.
After the discussions with MPL appropiate modifications were made to the existing kiln, including:
• removal of the thermocouple probe from placement vertically
up the tube, where it restricted the velocity of carbon passage and relocated 50mm below the outlet, thus ensuring the temperature sensing probes were representative of the temperature gradient of all kiln tubes. A second probe was similarly located below the tube outlet on the opposing side. Unrestricted carbon flow,and hence bed temperature, repre sentative of all tubes was finally achieved.
• four off, water injection points at the bottom of the kiln to provide the necessary pyrolysis steam.
• a water rotameter and controller to make water injection rate adjustments as required.
• ducting of waste boiler heat to further pre-drying application.
Plant Performance Results
The modifications were completed within a week and several series of s’amples again submitted to the MPL for determination of both activity and hardness.
The results of carbons tested after reactivation in the reconfigured
Elution Isotherm for the Darlot operation at 145 ‘C.
Average costs for strips over a two month period (Dec/Jan- 89/90), gave figures, including power,chemicals and labour at
$316/strip or $243/tonne. Water requirements including the acid
wash, if performed, were less than 4 cubic metres although high quality water was required.
At this time of reporting, no further plant performance figures for
the Darlot operation at the re-designed+ 160’C temperature opera tion were available to the author for analysis or comment but will be presented (if available) in April1991.
Thermal Reactivation
Contract custom thermal reactivation of Darlot barren carbon was still being carried out at the rate of 2-3 tonnes/month until the
kiln are contained in appendix A. •
At 7 Vs water injection rate and and bed temperature of 70Q’C., activities ranged from 89-123 per cent of green carbon activity and
without significant deterioration of hardness in line with the MPL test kiln results. To the authors knowledge the kiln typically con tinues to produce better than 1OOper cent activities from the stripped circuit carbons after reactivation.
CONCLUSION
At a cost of less than $130,000 installed, <$320/strip operating cost, simplicity of design, ease of transportation and very fast strip turnaround times the Fisher/Darlot IPSE unit could be seen as a superior elution, option to conventional plants. It was however not
162 Cairns, April21-25 WORLD GOLD ’91
without initial commissioning difficulties while at the same time indicating even fast r stripping times will be possible as the elution temperature is raised still higher.
AKNOWLEDGEMENTS
The author wishes to thank the following people for their significant contribution and help in the preparation of this manuscript. Greg Henderson, Snr. Metallurgist (Mr. Fisher and Darlot projects), Bernard Siddall (OMC), Assoc. Prof. David Muir and lli. Norm Stockton (Murdoch University), Dr. Jim Avraamides (Chemistry Centre W.A.) Barry Bolitho (Forsayth Mining Services), for per mission to publish the data. CBRLBogosu, Ghana for time allowed to attend the conference.
BIBLIOGRAPHY
Zadra J.B., et al. “Processes for recovering gold and silver from activated carbon by leaching and electrolysis”. U.S .B.M.R.I. No. 4843 1952.
Bailey P.R., 1985. “Elution design and operation”, (a review of the
Zadra process for the elution of gold from activated carbon)., Carbon School, S.A. Inst. of Min. andMetall., Lecture 16.
Davidson R.J., and Duncanson D. “The elution of gold from ac
tivated carbon using deionised water.” J.S. Mr. Inst. Min. and Metall., July 1977, pp 254-261.
Davidson R.J. 1985. “Elution design and operation”, (a review of
the AARL process for the elution of gold from activated carbon) Carbon School, S.A. Inst. of Min. and Metal!., Lecture 15.
Nicol M.J., 1985. “Elution theory” (Council for Mineral Technol ogy) Carbon School, S.A. Inst. of Min. and Metal!.
Muir D.M., Hinchcliff W.D and Griffin A., 1984, “research and development in the Micron Research (W.A.) solvent procedure for gold elution from carbon”, AIMM Regional Conference, Gold Mining, Metallurgy and Geology, Kalgoorie, W.A. Oct. 1984.
Muir D.M., HinchcliffW.D. and Griffin A., 1985, “Elution of gold from carbon by the Micron solvent distillation Procedure”, Hydrometallurgy 14 (1985) 151-169.
Avraamides J. and Laboratory S.R., 1989, “CIP technology recent developments in Australia”. TMS Symposium, Precious Metals 89 118 the TMS-AIME Ann. Meeting March’89 Las Vegas.
Hinchcliff W.D. et al., 1982. “Applications of aqueous-organic solvents for stripping gold at ambient temperatures” Murdoch University Seminar on the Chemistry of Gold and Activated Carbon. (July 1982)
Baxter K. and McCauley J., “Integral pressure strip/electrowin for gold recovery from activated carbon”, AIMM Regional Con ference, Gold Mining Metallurgy and Gelogy, Kalgoorlie, W.A. Oct.19 4.
Siddall B.G. and Baxter K., “Pressurised electrowinning-an ad
vance in elution circuit design”. Randol International Gold Con ference, Perth W.A 1987.
Salisbury H. et al, Verbal communication
Campbell-Hicks C.F., 1988/1989, “Autogenous grinding of ar chean chert in Western Australia”, in Advances in Autogenous and Semi-Autogenous Grinding Technology. Mular A.L. and Agar G.E. (eds), University of British Colombia, Vancouver, Canada., Sept., 1989.
Muir D.M. 1987., verbal communication. Avraamides J. 1990., verbal communication.
Rogans J., Geomet (P:V.T) Ltd., Harare, Zimbabwe- futernal report 1990.