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Minutes of the Annual General Meeting held at the St. Helena Club on Wednesday, 27th July, 1977, at 7.30 p.m. Book review Advances in extractive metallurgy, 1977. Proceedings of the third symposium organised by the Institution of Mining and Metallurgy held from 18-20th April 1977. London, the Institution of Mining and Metallurgy, 1977. 244 pp. £18,50. Coal preparation A meeting of the Organising Committee of the Eighth International Coal Preparation Congress took place in Moscow on 24th and 25th May, 1977.

Jan 1, 1978

By D. Harbottle, D. Rhodes, T. F. Jones, S. R. Biggs

Multiphase process design and optimization often depends upon the rheological properties of sludges and slurries. In practice the task of determining these important properties is usually carried out by removing small samples from a process line or process unit and performing tests with proprietary bench-top analysers near to site or at a remote laboratory. Sampling will remain an important procedure in industrial processes, but there is also a strong case for augmenting the routine information obtained using an in situ sensor, as suggested below. ?Sampling protocols can result in extensive turnaround periods from sample collection to the generation of results. The delay can have an effect on a variety of factors such as product quality, process operability and efficiency. ?Sampling of toxic or radioactive material can prove an even greater challenge to minimize human involvement. ?Removal often changes the rheology of a specimen, and might lead to incorrect conclusions being drawn about the condition of a sludge. ?Sludge and slurry in a containment suffers a gravitational gradient, so that a removed sample should be paired with its location, particularly in the vertical dimension.

Jan 1, 2007

By M. M. Ali, C. Musingwini, R. A. Phillips

The long-term open-pit mine production scheduling problem (OPMPSP) is typically solved in two broad stages. The first stage entails optimisation of the ultimate pit limit, which delimits the economical final pit and maximises the undiscounted value of the deposit. The second stage entails optimisation of the long-term open-pit mine production scheduling, which maximises the discounted value of the deposit. The long-term OPMPSP is a type of an NP-hard problem, such as the travelling salesman problem (TSP), because it is intrinsically complex to solve since it incorporates both hard and soft constraints. Therefore, metaheuristic approaches have been used to find global optimum solutions to the long-term OPMPSP. This paper presents a metaheuristic approach utilising a dual interchange algorithm (DIA) to solve the long-term OPMPSP. The DIA is a parent algorithm which supervises two subservient algorithms, namely, simulated annealing (SA) and Tabu search (TS). The DIA selects the better solution generated in each run from the two algorithms, and simultaneously penalises the algorithm that produced an inferior solution, while rewarding the one that produced a better solution. The DIA was tested on the three-dimensional Arizona Copper Deposit (KD) dataset, which is publicly available for research purposes from the online MineLib repository. It was set to generate net present values (NPVs) in five-minute intervals and the solution improved until it plateaued at about 30 minutes of runtime. The NPVs compared favourably to those obtained on the same KD dataset but obtained over 24-hour runtimes, when solved using simulated annealing and Tabu search algorithms, and the NPV generated from the work of Muñoz (2012) using the modified TopoSort as found on the MineLib repository at the time of this study. Therefore, this paper demonstrates that DIAs can be developed and used to solve the three-dimensional long-term OPMPSP.

Sep 1, 2021

By M. Splaine, W. Davison, D. C. Atkinson

"Since 1964, Nchanga Consolidated Copper Mines, Ltd., has been developing and using production scheduling methods for optimizing its metallurgical operations in the short term (up to one year). Medium-range metallurgical planning has been possible only by successive evaluations of a single-year L.P. A modified version of Rosenbrock's direct search technique has now been developed to allow multi-year optimization of both mining and metallurgy for medium-range planning. The modifications to the search technique have produced a marked increase in computational efffciency for this heavily constrained problem in many variables and the system is a usable planning tool, given a reasonably powerful computer. The plans are 'optimum' in the sense that they yield the maximum present value of the operations.Each of the resulting five-yearly mine plans forms the basis for further detailed metallurgical evaluation by the established production scheduling system."

Jan 1, 2014

By Jonty Tshipa

The Mine Site Technologies, MST BlastPED ST is a wireless/remote blasting system used in more than sixty (60) mines (including two mines in Zambia and one in Tanzania) since its release in 2002. The system consists of a controller and signal tube initiator which communicate wirelessly using spread spectrum frequency. This technique ensures a robust and secure wireless link between the controller and the signal tube initiator. The configuration of the system ensures ease of use with all the instructions for initiating the blast printed on the equipment. This means little or no formal training is required to use the system. The technology enables you to have your blasting point at a distance of up to 4 km, line of sight (LOS), as opposed to the traditional distance of 500m from the blast. This ensures the blast takes place from a safer and secure location. The paper and presentation will provide the audience with the benefit of many years of international mining know-how in this technology as well as more recent local African experiences. There will be references to demonstration blasts done in South Africa, current users in Africa and elsewhere. Practical Return on Investment (ROI) calculations and references to safe blasting practice will also be included.

Jan 1, 2008

By More-O&apos, R. C. Ferrall, J. W. Wilson

SYNOPSIS The theory of elasticity has been shown to provide a means of determining the stresses and displacements induced by mining in deep level hard rock mines. This theory has been incorporated into an electrical resistance analogue on which the plane of a reef or ore-body can be modelled to enable the rapid determination of stresses and displacements at points in the plane of the reef. This electrical analogue has been used to determine energy release rates caused by scattered mining, which, to some extent, is a measure of the degree of hangingwall fracture. A correlation between predicted energy release rates and actual underground conditions in stopes in the O.F.S. goldfields has been encouraging enough to define parameters on which future stoping layouts can be based. The use of the elastic theory through the analogue has been extended to the assessment of the influence of stoping operations on off-reef excavations. Underground conditions at damaged and undamaged areas have been compared with predicted elastic stresses at the positions under review, resulting in the derivation of design parameters for use in siting off-reef excavations in the prevailing geological conditions in the O.F.S. and Klerksdorp goldfields. The analogue has also been used to assess the vulnerability of certain un mined dykes to bursting. Correlations between stresses induced on dykes by stoping and dyke behaviour underground has enabled critical stress levels to be determined for several persistent dykes occurring in the O.F.S. and Klerksdorp goldfields. A number of long and short term planning projects at mines operating in the Anglo American Corporation and General Mining and Finance Groups are described, where the data derived from the electrical resistance analogue is processed by computer programmes and assessed on the strength of the design factors derived from the correlation of field work and the elastic theory.

Jan 1, 1970

By H. Brüggemann

The exploration of deposits generates geological data which are suitable for creating a preliminary tectonic and stratigraphic model. Linked with the topographical map and analysis data from exploration drillings, this information forms a numeric representation of the deposit. The following example demonstrates an expert system which connects chemical quality requirements and quarrying criteria, and develops a quarrying strategy based on the calculated model. Additional constraining factors like process technology, quarrying methods, landscape protection regulations, etc. are included. The goal is to guarantee a long-term, homogeneous material flow from the quarry at acceptable production costs - even in the case of an extraordinarily inhomogeneous deposit. In order to fulfil this requirement it is necessary to consider a large number of rules, criteria and instructions which can be structured as an expert system and programmed with LISP at a comparably low cost. The chosen strategy is not necessarily final, but can be changed any time by altering or varying the framework of conditions. The output consists of a block-working sequence which best satisfies the set requirements for appropriate points of quarry opening.

Jan 1, 1987

By L. J. Park, A. D. Thomas

Gladstone Pacific Nickel Limited (GPNL) is proposing to develop the Marlborough nickel deposit in central Queensland and the Yarwun Refinery in Gladstone, Australia. The project proposes to connect the two sites with a DN 500, single pump station slurry pipeline, transporting up to 4 Mtpa of nickel laterite ore as slurry 180 km from Marlborough to Gladstone. Slurry viscosity is a key parameter influencing pipeline design. Not only is the slurry viscosity relatively high, requiring pumping at low concentrations, around 30% by weight, but the viscosity (yield stress and plastic viscosity) increases with shearing or agitation. It is argued that the viscosity changes can be analysed in terms of total energy input, including energy input during grinding. The slurry viscosity is therefore expected to increase along the pipeline and the pumping concentration must be low enough such that the increase in yield stress does not cause transition to laminar flow towards the end of the pipeline. The base viscosity of two ore types is determined using a rotational viscometer for minus 212 micron slurries. Viscosity variations with ore particle sizes of d99 212, 425 and 600microns are investigated. For each of these particle sizes the expected increase in viscosity during pipeline transport is simulated on a laboratory scale by agitation with a turbine mixer in a baffled container to give the same equivalent unit energy input as will occur in the pipeline. Tests were also conducted on the d99425 micron slurry in a 2.7 metre diameter DN 200Wheelstand, rotated for the 23 hour transit time and at a similar relative velocity as in the pipeline. Based on the Wheel stand test results the yield stress is expected to increase by a factor of 3.1during pipeline transit. The preliminary design allows for a reduced pumping concentration to accommodate this increase in yield stress towards the end of the pipeline.

Jan 1, 2007

By M. A. Ford

This paper reviews the history, sources, mineralogy, extraction metallurgy, conversion, and enrichment of uranium in South Africa. Over the past 40 years extraction plants were built at 27 sites, an9.over 140 kt of uranium have been produced. Older plants have had to adapt to changing market conditions, no single technology has had the opportunity to become entrenched, and costs have been reduced to a third of those of the original flowsheet. The research efforts aimed at developing the country s nuclear raw materials have been particularly rewarding, as they have enabled South Africa to become a world leader in the extraction of uranium from low-grade ores and to develop methods for uranium enrichment and the production of nuclear fuels.

Jan 1, 1993

By B. Jack, A. Vervoort

During pillar extraction, sidewall fracturing and spalling at some collieries constitute a severe stratacontrol problem. In order to obtain a better understanding of this phenomenon, a survey of pillar corner conditions before and during pillar extraction was conducted at one particular site. For the various successive mining steps, the vertical stresses on the pillar corners were calculated by use of a three-dimensional boundary element program. A significant correlation was found between the calculated vertical stress prior to the extraction of the panel and the sidewall conditions. During the extraction of the panel, a significant deterioration of the sidewall conditions at a pillar occurred only when the adjacent pillar was mined, causing an increase in vertical stress on the remaining pillar.

Jan 1, 1992

By J. W. Wilson, P. C. Graham

Raise-boring experiences in the gold mines of the Anglo American Corporation Group by J. W. Wilson M.Sc., M.I.M.M., F.S.A.I.M.M., M.A.I.M.E. and P. C. Graham M.Sc. (Eng.) Gold mining is being carried out at ever-increasing depths in South Africa. For reasons of safety and human comfort, it is becoming imperative for raises to be developed by means other than conventional drilling and blasting. Raise-boring is an attractive alternative method. Initial raise-boring experiences in South African gold mines showed disappointingly high costs due to the abrasivity and difficulty of drilling Witwatersrand quartzites. Consequently, a research and development project was instigated with the objective of making raise-boring an economically viable technique in hard abrasive rock. A Robbins 61R raise-borer was made available to the Research and Development team and a number of raises have been drilled. During these trials two advances in cutter design were tested. This paper presents the results obtained, including drilling costs, and provides details of the equipment used.

1. Book reviews Mining and metallurgical practices in Australasia. Melbourne, Australian Institute of Mining and Metallurgy, 1981. $40 (incl. surface postage). Reviewer: M. G. Atmore Coal mine ground control, by Syd. S. Peng. 1978. Reviewer: C. F. Engelbrecht Sixth Annual International Conference on Coal Gasification, Liquefaction and Conversion to Electricity, July 31 -August 2, 1979. Pittsburgh, School of Engineering of the University of Pittsburgh, 1980. Reviewer: S. T. J. van Rensburg This book is a useful general reference volume on the topics covered provided a great deal of technical detail is not required from it. It consists of 29 papers, which are arranged under 6 headings. Flotation agents and processes. Technology and applications, edited by M. W. Ranney. Park Ridge, D.S.A., 1980. $48. Reviewer: R. P. King 2. New books Project control manual, by Sven R. Red. 250 pp. in loose-leaf binder. U.S. Al47. (Obtainable from the author at Bray Studios, Windsor Road, Windsor SL45 UG, England.) Manganese deposits, by Supriya Roy. London, Academic Press, 1981. 400 pp. Joint preparation for welding (set of overhead-projector transparencies). Abington (England), The Welding Institute, 1980. £34 per set. Electron micrographs of clay minerals, by T. Sudo,S. Shimoda, R. Yotsumoto, and S. Aita. Amsterdam, Elsevier, 1980. 228 pp. Dfl.150. Weld pool chemistry and metallurgy. Abington (England), The Welding Institute, 1980. 357 pp. $27. 3. New journal ...being known as Gliickauf + Translation, at an annual subscription of 396 DM for 24 issues per year. It is available from Verlag Gliickauf GmbR, D-4300 Essen I, P.O. Box 103945, Federal Republic of Germany. 4. Canadian MRI publications During 1980 the Mineral Policy Sector introduced a new series of reports identified by the prefix MRI. These cover internal studies and analytical works on a wide variety of subjects, that for one reason or another, do not reach the publication stream of the regular series yet may be of interest to readers in this 'unpublished form'. Twenty-four such titles are listed below. Exploration planning A series of professional advancement seminars for the mineral industry is to be held at Rhodes University from 12th to 20th August, 1981. The series, entitled 'Economic Guidelines for Exploration Planning', will be conducted by Professor B. W. Mackenzie, and the attendance will be limited to 30 participants. The seminars are intended Seminar on Geostatistics A seminar for mining executives on Geostatistics and Decision Making in the Mining Industry is to be held in Toronto from 23rd to 25th September, 1981. v

Jan 1, 1981

Mr R.D. Beck attended Felsted School in Essex (England) and the Royal School of Mines, University of London, where he ob¬tained the degree of B.Sc.(Eng.), A.R.S.M. in mineral technology in 1969. His other qualifications include Pr.Eng. (1976), C.Eng (1975), and M.I.M.M. (1975). He joined Gold Fields of South Africa in December 1969, and worked at Doornfontein Gold Mine, Greenside Colliery, West Driefontein Gold Mine, Zwartkloof Fluorspar, Gold Fields Laboratories, Gold Fields Head Office, Libanon Gold Mine, and Kloof Gold Mine before being appointed Plant Superintendent at East Driefontein Gold Mine in January 1973. In June 1976, he was transferred to Head Office as Group Metallurgist, followed, in November 1978, by his secondment to Black Mountain Mineral Development Company as Plant Superintendent, to take on-site responsibilities for staff training, plant commissioning, and start up. On his return to Head Office in July 1980 as Assistant Consulting Metallurgist, he was responsible for Black Mountain and new metallurgical projects. Then, in January 1984, he was appointed General Manager of the Zinc Corporation of South Africa Limited. He became a member of The South African Institute of Mining and Metallurgy in 1973.

Jan 1, 1985

By N. G. Cook, N. C. Joughin, A. J. A. White

The rate of face advance in the gold mines is between 3 and 10 m a month, with a median value of about 5 m a month; it follows that faces are blasted less frequently than is planned. There are many advantages in the use of short holes for stoping to give face advances of from 0,7 to 0,8 m per blast. This has the potential for so increasing the frequency of blasting that monthly rates of face advance could be improved significantly. Cleaning with face scrapers is too slow to permit the maximum achievement of a complete clean, drill, and blast cycle for each shift. Short-hole blasting, combined with the use of mechanical conveyors for face cleaning, offers the possibility of completing two such cycles each day, yielding monthly rates of face advance of up to 35 m. Experiments aimed at developing safe, unitized explosive charges well-suited to produce reliable face advances of 0,7 to 0,8 m per blast under a wide range of gold-mining conditions have been notably successful. A novel method of assessing the effectiveness of a blast based on the percentage of holes that leave socket lengths of 5 cm or less was used. Unitized charges of 60 per cent Ammon gelignite, 600 mm long by 25 mm in diameter, appear to be near optimal. The explosive is de-sensitized to obviate detonation by chance mechanical impact, but requires only a 6D detonator for initiation; it has good water-resistance. Means have been developed for producing these cartridges automatically, but the necessary machines will have to be built specially and the cartridges are not yet available in large numbers. A second experiment by way of an extended pilot production trial using these cartridges in holes 0,9 m long is now under way. Preliminary results indicate that drilling and explosive efficiencies and productivity are well above average, even though face scraping is being used. Unitized charges of this type are likely to prove even more advantageous when mechanical face conveyors come into use.

Jan 1, 1975

"Chairman: Dr R. E. ROBINSON Rapporteur: Dr R. P. COLBORNPapers:The simulation of crushing plants by W. J. WhitenSimulation of multi-component flotation plants by B. K. Loveday and G. R. MarchantComputer control of flotation at the Ecstall concentrator by M. P. Amsden C. Chapman and M. G. ReadingModel for the design and control of flotation plants by R. P. KingIn presenting his paper Dr W. J. Whiten outlined the basic concepts on which the control model was based and emphasized the fact that empirical models based as much as possible on theory were used to simulate each unit of the crushing plant. The final parameters of each model were computed using data collected from the plant. Unfortunately, the system did not permit accurate extrapolation but was successful when operating in the region from which the parameters were calculated.He concluded from the results of the test work that the crusher amperage was a critical parameter and that the utilization of the model gave a 15 per cent increase in the plant output. This was because the model predicted that a marginally fine grind would provide a significant increase in throughput. Dr Whiten elaborated on what constituted the multiple spline regression, explaining that it was a least-squares curve-fitting technique in one or more dimensions, where the calculation of coefficients in analytic expressions was replaced by the calculation of typical points on a very smooth curve called a spline function. The emphasis was placed on the shape and value of the curve or curves instead of on the coefficients as in analytic regression. A spline function was the line drawn between all points constituting the data set.Dr B. K. Loveday commented that the simulation was unusual in that the optimum throughput was considered to be the maximum throughput, which, surely, was limited by the crusher size. He also emphasized the importance of the interaction between both crushing and grinding circuits and added that in practice the optimum operating conditions were inter-dependent. Dr Whiten replied that in the case of the plant under consideration, the crushing process was not, in fact, the limiting operation.Mr C. E. Clifford indicated that the model was being used to simulate a number of crushing and grinding circuits at Mount Isa Mines. He reported that the model simulated the circuit satisfactorily for primary and secondary gap settings of 0,625 in. to 0,375 in., but that adjustment had to be made to the model parameters for gap settings of 0,250 in. to 0,125 in.In reply to a question from Dr D. M. Hawkins, Dr Whiten said that he preferred to use low-order splines with smaller segments rather than high-order spline functions with large segments."

Jan 1, 2014

By T. Steyn, M. Fofana

"One of the most important performance indicators of a dense medium cyclone (DMC) circuit is the Tromp curve, and by extension the separation density and Ecart Probable (Ep) values. The densimetric profiles of DMC product streams have been traditionally acquired using heavy liquid sinkfloat analysis, which has certain disadvantages, such as the associated safety and health risks. More recently, non-toxic media such as lithium hetero-polytungstates (LST) have been used, with the desired densities being achieved by maintaining the solutions at specific temperatures. However, the high costs of these liquids can be prohibitive. The long turnaround time of the sink-float analysis is a further disadvantage for timeous interventions to the operating set-points of the DMC process.The RhoVol technology can generate the density distribution of a batch of particles in a rapid, accurate, repeatable, and safe manner. Additional data of interest, such as particle size and shape, are also measured and reported on a per-particle basis. Furthermore, samples can be sorted into discrete sorting bins based on any of the measured parameters of the particle, making further analyses of the material possible.This technology has applications across all commodities that use the DMC, particularly in the size fractions –25 +8 mm and –8 +3 mm. To date, laboratory results have proved very encouraging – separation densities are within 5% of traditional sink-float results, and the technology is being introduced to diamond DMC plants. IntroductionDense medium separation is a commonly applied beneficiation technique for the density separation of valuable products from crushed ores. The industrial applications of dense medium separation have been summarized and reviewed by various authors (Scott and Napier-Munn, 2000; Bosman, 2014; Napier- Munn, 2018). Dense medium cyclones (DMCs) are widely used in the coal and diamond industries to produce clean coal or to preconcentrate kimberlitic ores, respectively. Cyclone performance (separation density monitoring) techniques are varied. In the mineral industry. Density tracer tests (Napier- Munn, 1985, 2014; Davis, Wood, and Lyman, 1985) without mineral material, are widely used, although their accuracy in predicting operating cut-points becomes limited once mineral material is introduced. More recently, radio frequency tracers have been also used for the determination of cyclone efficiency (Partition Enterprises, 2017)."

Feb 1, 2019

By H. L. Monro

Contribution by B. K. Martust I congratulate the author on his interesting paper. In my view, the establishment of the level at which South African gold output is at some kind of optimum is an interesting though somewhat academic exercise. Contribution by D. M. Hawkins* The thesis of the paper is a very interesting one, but, before it is used as the basis of any firm proposals to restructure the mining industry, which changes may be irreversible, one should be very sure that the basis of the calculations is sound. Contribution by P. J. Niewenhuizen* The hypothesis advanced by Mr Monro that the demonetization of gold in August 1971 introduced a major new policy variable, namely the supply-pricejdemand-price relationships, into the decision making process touches on a matter that has never really been given serious thought by the industry. Contribution by B. G. Kingsman* As a co-worker on the development of an econometric model for supply and demand in the world gold market with Mr H. L. Monro, it would perhaps be useful for me to make some comments on the various points raised in the discussions on his paper.

Jan 1, 1984

YEAR 1943-1944 Vol. 44 Page A major change-over in the ventilation of a deep level mine, by F. G. Hill and E. C. Ranson, 27; Discussion 56, 62, 67, 71, 72, 79, 123, 129 131 A note on the quarrying of surface limestone in the Sinai Desert, by V. L. Bosazza.. .. 59 Mining with diamond drills at the Nkana Mine of the Rhokana Corporation, Limited, Northern Rhodesia, by W. A. Odgers and A. G. Stirling, 95; Discussion 117, 121, 122 123 On silicates and dusts from the Witwatersrand gold mines (some preliminary notes), by J. J. Frankel, 169; Discussion .. 178 Presidential Address-Review of the rock pressure problem, by C. Biccard Jeppe, 3; Discussion 11,15 17 The chemistry, production and application of plastics, by P. N. Lategan, 138; Discussion 151 153 YEAR 1944-1945 Vol. 45 Page A microtechnique for the size-grading of mine dust, by S. R. Rabson, 34; Discussion 49, 50, 52 55 Activated carbon for regenerating used lubricating oil, by F. J. Tromp and J. J. Matthee 90 A contribution to the study of the production of zeolites, by C. C. le Grange and A. J. Petrick 235 A laboratory method for the determination of the suitability of South African coal and coal blends for the manufacture of metallurgical coke, by R. F. J. Teichmann .. .. 202 Copper containing cements for self-sanitising surfaces, by R. S. Young and H. L. Talbot 156 Notes on some sulphide minerals from the Far East Rand, by E. Mendelssohn, 84; Discussion, 88 89 Presidential Address-A review of underground support on the Witwatersrand with its Bearing on the Problem of ultradeep mining, by P. J. Louis Bok, 3; Discussion, 24, 25 27 Scientific management with particular application to a Witwatersrand gold mine, by J. S. Ford, 63; Discussion, 77, 80, 82 83 Some aspects of rock-drilling practice (the Witwatersrand gold field), by C. J. Irving, 163; Discussion, 185, 190 *197 Temperature measurements in a mine on the Witwatersrand with an electrical resistance thermometer, by O. Weiss, 127; Discussion, 136 137 The measurement of the geo-thermic gradient by means of the clinical thermometer, by R. A. H. Flugge-de Smidt, 105; Discussion, 136 137 The micro-chemical determination of free and combined silica in mine dust, by S. R. Rabson, 43; Discussion, 49, 50, 52 55 The oxidation of pyrites associated with South African coals, by R. F. J. Teichmann 141 YEAR 1945-1946 Vol. 46 Page Air cooling plant, No. 4 Shaft, City Deep, Limited. A review of layout and results achieved, by H. W. Unwin, A. Malcolm and R. E. Campbell Pitt, 66; Discussion, 100, 102, 103, 106, 110 115 A preliminary note on the Waterberg coal field as a possible source of coking coal, by P. E. Hall 124

By A. N. Brown

Underground rock boring was the topic of the mining vacation school held at the University of the Witwatersrand in the week 4th to 8th February, 1980. The School, which dealt with the management and economics of the subject, attracted 75 delegates from all sectors of the South African mining industry, in addition to two delegates from Germany and one from Zambia.

Jan 1, 1980

The kinetics of cyanide loss were found to be first order under any given set of conditions, allowing rate constants to be easily determined. At room temperature and in the absence of activated carbon, some cyanide is lost by hydrolysis to hydrogen cyanide, but this does not occur to any significant extent at pH values higher than about 10. A higher rate of hydrolysis occurs when air agitation is used. When activated carbon is present, an additional carbon-catalysed oxidation reaction is responsible for a fairly high loss of cyanide. The evidence indicates a reaction mechanism that consumes oxygen and produces cyanate ion. Some of the cyanate thus produced decomposes to form a mixture of ammonia, carbonate, and urea, depending on the solution conditions. Additional cyanide is lost as a result of the adsorption of sodium cyanide by the activated carbon. At high temperatures, an additional hydrolysis reaction, which involves the formation of ammonium formate as an intermediate, occurs an/j is responsible for. a high loss of cyanide, leading ultimately to the formation of ammonia, hydrogen, and carbon dioxide. The presence of activated carbon has no effect on the rate of this reaction.

Jan 1, 1990