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Characterisation of different ore types and determination of optmum operation conditions for treating Kansanshi ores through the leaching circuit.
(2015-09-07) Chilando, Chanda A
Different ore types react differently when leached under the same leaching conditions. The extent to which minerals go into solution is a function of several parameters. In this project, emphasis was on determining the mineralogical characteristics of different ores, the optimum residence time, the quantity of acid needed to leach the different ore types and the dissolution of some impurities in the leach solutions. The leaching parameters that were studied were: (a) % solids of the slurry (28%), (b) particle size distribution (80% passing 150[im), (c) pH about 1.60, and, (d) mass of ore leached (1.5kg) and were kept constant for different types of ore. The mineralogy of the ores was investigated and the ore were found to be of predominately composed of malachite, pseudomalachite and Chrysocolla.The optimum residence time for HGB, LGB and HGG was found to be 2hrs. The highest acid consumption was observed in LGB and was 93kg H2SO4 per tonne of ore. The acid consumption can be reduced by increasing the concentration of the solids in the feed to the leaching circuit. Increasing the concentration of solids from 55% to 65% solids in the feed the consumption would reduce acid consumption by 4.2kg HaSCV tonne ore. From 55% to 75% and 85% solids the consumption would reduce by 7.3 and 9.4 kg / tonne of ore respectively.
Comparison of LIX 984NC versus acorga M5774 for copper extraction process.
(2015-09-07) Mwale, Adolph N.
This report looks at the selection of the best extractant amongst the available options on the market. It particularly focuses on the comparison of the two extractant, Lix 984N and Acorga M5774. Mopani copper mines Nkana cobalt plant has a copper solvent extraction plant as one of the by processes to extract and produce copper in the quest to purify the pregnant solution into a cobalt concentrated solution. Therefore it is in the best interest of the company to minimise operation cost. Test works were carried out to come up with a very economical but effective extractant that will extract copper from the pregnant leach solution. Test works were done on a bench scale by comparing the two extractants at the same conditions to see which one extract more and which one has better economics if all factors are considered. Acorga M5774 is cheaper than Lix 984N in terms of price per kilogram. The test works have shown that Lix 984N easily extracts the copper from the pregnant leach solution but it is not easily striped by the spent electrolyte than Acorga M5774. Even though this is the case, Lix 984N has shown that on the overall, it is better than Acorga M5774 because it loses less copper to the tails and the economics are good.
Deportment of bismuth, nickel, lead, cobalt, gold and silver
(2015-09-07) Malama, Kenani
The project was carried out to assess the distribution of impurities during the converting stage. The assays of these impurities are summarized into a mass/material balance to account for all elements of interest. These metals are bismuth, silver, gold, nickel, lead and cobalt and the balance were carried out over the converter. Samples were collected from various strategic points of streams such as at the matte settling furnace tap, converter mouth and under a ventilation discharge pipe. These were then taken to the laboratory for analysis. The results obtained showed that these metals occur in very small quantities although they might have some negative effect on the production of copper. These results were given in percentages. From the conclusion, it will be seen that the metals of interest are a very small fraction of the whole mass of materials in and out of the converter. Among the elements of interest it can be observed that cobalt occurs in larger amounts than others. Otherwise various amounts depend on the type of blend carried out on a particular blow. In particular, flue dust particles contain bismuth. Recommendation will be made that the next time the project is proposed it should be extended from the concentrate shed were blending occurs to the smelter section. Perhaps it can further be extended to the refinery section were effects are felt. The best way to control high levels of these impurities is to apply evaporative precipitation.
Development of an impurities based profile or model for Nchanga Electrowon Cathodes
(2015-08-27) Pule, Gershom
The project was carried out at the Tailings Leach Plant of Konkola Copper Mine Pic in Chingola Zambia. The major objectives were to establish regions on the surface of the cathode that were prone to impurities such as lead, iron, sulphur and oxygen and to evaluate an existing mathematical model or develop a new one that computed the extent of affected regions on the cathode surface. This came from the background of having poor quality cathodes that did not meet market specifications. The poor quality cathodes revealed the exact locations of the said impurities through the study of their concentrations on cathodes. A square grid was plotted to cover the entire cathode surface and each grid point was analysed for the major impurities that have been contaminating the cathodes. The results were used to develop a physical model (Figure 4.3) and also to evaluate the existing mathematical models in literature (equations 4.2.1 and 4.2.2). The need to estimate or quantify the levels of impurities occurring on electrowon copper cathodes at Nchanga Tailings Leach Plant is important.
Drinking water quality assessment in Basic Schools in Peri-Urban areas - a case of Mtendere Township in Lusaka, Zambia.
(2013-01-18) Tembo, Evans Mwamba
Mtendere Township (meaning a peaceful township) is one the unplanned settlements situated on the eastern side of Lusaka, Zambia. The township is charecterised with over-crowding, lack of adequate safe water, poor sanitation, poor hygiene practices, poverty, and poor waste management practices. The township has four Government basic schools with a total population of 10,164 pupils, and these schools are also charecterised by the same challenges. At present the studied schools are using borehole water with an assumption that it is safe water and requires no treatment. It is against this background that this study on drinking water quality assessment in four Schools in Mtendere Township was carried out to determine the suitability of the borehole water for use by the pupils and teachers. In general, the results of this study showed that the concentration of nitrates and microbiological parameters of drinking water for New Mtendere, Mtendere and Chitukuko Basic Schools range from 19.6 mg/1 - 29.66 mg/1 and 4 CFU/100ml - 28CFU/100ml respectively. In comparison with the recommended ZABS / WHO guidelines for nitrates (i.e. l0mg/l) and microbiological parameters (0 CFU/l00ml), these contaminants are above the recommended standards and thus making the water in studied schools unsafe for human consumption. Hence need for the school management to treat the water prior to consumption. The study therefore recommends that drinking water quality assessment in schools should be given a priority by Ministry of Health. Additionally, the ministries of Education and Health should work together in implementing an effective health and hygiene education programme in schools in peri-urban areas. The respective school managements should be treating their water in storage tanks and also should introduce sustainable handwashing programmes with soap in schools to alleviate water re-contamination by the pupils at the point of use. Further studies should be undertaken by the Ministry of Health in collaboration with Colleges and Universities in order to investigate the trends of groundwater contamination in schools in Lusaka, and then be scaled-up to other peri-urban areas in the country particularly the Copperbelt.
The effect of grind and increased residence time on the floatability of Mufulira copper ore.
(2015-09-07) Sinkala, Suwilanji
The purpose of this project was to evaluating the effect of grind time and increased Residence time on the floatability of the Mufulira copper ore on a laboratory scale. The project was proposed mainly because of periodic fluctuations in the mineralogy of this complex copper sulphide ore. The aim was therefore to address this problem and generally improve the flotation performance of the Mufulira concentrator. Systematic sampling was employed where copper ore samples were cut from six different selected conveyor belts each feeding the ball mills. Grinding time was done from 15 to 40 minutes at an interval of 5 minutes. Thereafter, flotation testworks were carried out to determine the effect of increased residence time on the flotation performance. However, 25 minutes grind time was the optimum mesh of grind with corresponding copper recovery of 94.8% and a grade of 24.9%. At 4 minutes rougher and 8 minutes scavenger was the optimum residence time with copper recovery and grade of 88.9% and 21.2% respectively. All other parameters were kept constant such as reagent dose rate at 30 gram per litre and pulp density except for time which was under evaluation. It is recommended that the optimum mesh of grind should be 25 minutes at flotation time of 4 minutes rougher and 8 minutes scavenger and testworks should be done at a decreased grind time and decreased residence time to determine the floatability of the Mufulira copper ore.
Full release of analysis of ore from all Nkana Mopani company mine shafts
(2015-09-07) Mutika, Richard
Due to low copper and cobalt recoveries that were being experienced, and thus a considerable rise in mineral losses to the tailings, this study was proposed. The specific objective was to establish the optimum mesh of grind for all Nkana copper and cobalt sulphide ores. This was done through laboratory batch flotation test work. Therefore the current work is an extension of previous work done by Mutentwa (2001) who investigated Chibuluma, South Ore Body and Mindola ores. This study was done through laboratory flotation tests conducted under different experimental conditions for all Mopani Copper Mine sulphide ores. Mineral samples were collected, prepared and subjected to grinding and flotation tests. The average head grades were 1-2.5% copper and about 0.2% cobalt. From the results obtained, the optimum mesh of grind for central shaft ore was 70% passing 75|jm with recoveries of 97.6% and 88.2% for copper and cobalt respectively. That for South Ore Body ore was also 70% passing 75|jm giving recoveries of 95% and 80% for copper and cobalt respectively. Mindola Subvertical ore had 60% passing 75|jm as the optimum mesh of grind with recoveries of 96.4% and 87.6% for copper and cobalt respectively. The optimum mesh of grind for Mindola North ore was also 60% passing 75gm with recoveries of 94.6% and 93.8% for copper and cobalt respectively. These results are different from the optimum mesh of grind being practiced which was 65% passing 75|_im for all the shaft ores. It was therefore concluded that the low copper and cobalt recoveries, as well as the considerable rise in mineral losses to the tailings were due to the change in the optimum meshes of grind for the different shaft ores. Therefore, it is recommended that the plant personnel may implement the above optimum meshes of grind as established in this study.
The Geology and Water Quality Study of The Mwakambiko Hill and Adjacent Areas,Mapatizya mining area,Kalomo District,Southern Province,Zambia
(2015-10-05) Chanda, Chabala
The area north of Kariba Minerals Ltd is underlain by igneous rocks (pegmatite and dolerite) and metasedimentary rock units that have been ascribed to the Basement Complex Supergroup and Muva Supergroup. The rock units ascribed to the Basement Complex Supergroup include gneiss and marble whilst schist belongs to the Muva Supergroup. It is not clearly known whether amphibolite is of sedimentary or igneous origin and thus it has not been ascribed to any formation but it has been placed in Muva Supergroup. There is strong evidence that the marble is of magmatic origin and this ideology is based on the fact that marble contains xenoliths of assimilated country rock. The lithologies have been metamorphosed to upper almandine amphibolite facies and equally show evidence of retrogressive metamorphism though the grade has not been determined due to lack of indicator minerals in analyzed thin sections. Mapatizya Mining area generally occurs in a region that receives rainfall of below 700mm. Most of the rivers and streams that drain the area are intermittent. The poor water retains of the rock formations and rapid drying up of streams is attributed to; (1) high degree of weathering that has affected the lithologies, (2) faster flows of water in streams due to the steepness and rugged nature of the terrain and (3) high degree of fracturing and jointing exhibited by some of the rock formations. The primary sedimentary porosity of the rock formations have been obliterated by two episodes of metamorphism that affected the lithologies hence groundwater movement is limited to secondary porosity defined by fractures, joints, lithological contact boundaries, foliation and fault planes. Water availability is generally poor but field observation has shown that there is high possibility that the area might have good underground water reserves. Water for both domestic and industrial use is sourced from; boreholes, wells, natural springs and stream bed wells. The chemistry of the sampled water shows predominance of Calcium cation and Bicarbonate anion showing that there is a marked interaction of underground water with marble; this suggests that marble is possibly the aquifer. Lack of proper sewage system (use of pit latrines), bad garbage disposal habits and bad choice of feeding and drinking areas for live stocks have been found to be the major contributing factors to both surface and underground water contamination. This rapid contamination of underground water with fecal matter points to the fact that the aquifer is unconfined with its water table rising very close to the surface. Siltation of the only existing dam (Mbiko) is the visible evidence of the careless solid waste management by the existing mines which in the long run will also add elevated quantities of dissolved and suspended solids in both surface and underground water.
The Geology and Water Quality Study of The Mwakambiko Hill and Adjacent Areas,Mapatizya mining area,Kalomo District,Southern Province,Zambia
(2015-09-11) Chanda, Chabala
The area north of Kariba Minerals Ltd is underlain by igneous rocks (pegmatite and dolerite) and metasedimentary rock units that have been ascribed to the Basement Complex Supergroup and Muva Supergroup. The rock units ascribed to the Basement Complex Supergroup include gneiss and marble whilst schist belongs to the Muva Supergroup. It is not clearly known whether amphibolite is of sedimentary or igneous origin and thus it has not been ascribed to any formation but it has been placed in Muva Supergroup. There is strong evidence that the marble is of magmatic origin and this ideology is based on the fact that marble contains xenoliths of assimilated country rock.The lithologies have been metamorphosed to upper almandine amphibolite facies and equally show evidence of retrogressive metamorphism though the grade has not been determined due to lack of indicator minerals in analyzed thin sections.Mapatizya Mining area generally occurs in a region that receives rainfall of below 700mm. Most of the rivers and streams that drain the area are intermittent. The poor water retains of the rock formations and rapid drying up of streams is attributed to; (1) high degree of weathering that has affected the lithologies, (2) faster flows of water in streams due to the steepness and rugged nature of the terrain and (3) high degree of fracturing and jointing exhibited by some of the rock formations.The primary sedimentary porosity of the rock formations have been obliterated by two episodes of metamorphism that affected the lithologies hence groundwater movement is limited to secondary porosity defined by fractures, joints, lithological contact boundaries, foliation and fault planes.Water availability is generally poor but field observation has shown that there is high possibility that the area might have good underground water reserves. Water for both domestic and industrial use is sourced from; boreholes, wells, natural springs and stream bed wells.The chemistry of the sampled water shows predominance of Calcium cation and Bicarbonate anion showing that there is a marked interaction of underground water with marble; this suggests that marble is possibly the aquifer.Lack of proper sewage system (use of pit latrines), bad garbage disposal habits and bad choice of feeding and drinking areas for live stocks have been found to be the major contributing factors to both surface and underground water contamination. This rapid contamination of underground water with fecal matter points to the fact that the aquifer is unconfined with its water table rising very close to the surface.Siltation of the only existing dam (Mbiko) is the visible evidence of the careless solid waste management by the existing mines which in the long run will also add elevated quantities of dissolved and suspended solids in both surface and underground water.
The Geology of Nyangwena River South, A Confluency of the Chongwe River, Chongwe District Lusaka Province, Lusaka
(2015-09-11) Kashimu, Davies
The Nyangwena River and its adjacent areas lies in Chongwe district in the Lusaka Province of Zambia. It is part of the Southern extension of the Irumide Belt. The study area is underlain by Mesoproterozoic Basement Complex which includes gneiss, amphibolites, quartzites and schist. The Neoproterozoic Katanga Supergroup uncomfortably overlies the Basement is mainly composed of schist. The tectonic history falls into three broad episode. The first deformation (DO resulted in recumbent folding and development of planar foliation (Si) which is defined in the gneisses and amphibolites.The first deformation was accompanied by a regional prograde metamorphism(Mi) defined by the mineral assemblage being hornblende-plagioclase-biotite-quartz-gamet-sphene. The second deformation phase (D2) resulted in steep, upright folds and thrusting in a North-West direction. In addition, the second deformatiom was accompanied by a prograde metamorphism followed by a retrograde metamorphism (M2) due to cooling and fluid circulation. The mineral assemblage associated with (M2) is typical of greenschist facies defined by chlorite-quartz-biotite-epidote-sphene-actinolite-iron oxide (opaque) as observed in the chlorite schist unit. The third deformation (D3) resulted in the development of open folds and thrusting in the North-East direcfion.
Leaching of cobalt anode sludge for the production of cobalt metal using sodium sulphate as a reductant.
(2015-09-07) Malizhi, Davie M.
During electrowinning in the Nkana cobalt tank house, sludge is formed from the anodes and it is periodically collected from the cells and stored. The sludge contains appreciable amount of cobalt which is not recovered at the moment. It is for this reason that the project was proposed to investigate the possibility of recovering cobalt metal from the sludge. Therefore, the objective of this study was to establish the potential of recovering cobalt metal from the anode sludge by determining the dissolution rate of cobalt metal as a function of pH, redox potential and temperature. Leaching experiments were conducted using sulphuric acid as a leachant and Sodium Sulphite as a reductant to reduce the Co3* and for redox potential control in the cobalt anode sludge pulp to a readily leacheable Co2*. From the results, highest leach efficiencies of 52.27% cobalt at the pH of 2.0 and 68.6% at the temperature of 60°C were obtained. It can be concluded that cobalt is potentially teachable from the anode sludge but there is need to conduct more tests in order to increase the leach efficiencies. It is recommended that further tests should be done such as observing the effects of leachant concentration and use of other reductants on leaching efficiency as well as the mineralogical examinations to identify the other elements/compounds present in the cobalt anode sludge to optimise the leach efficiency.
Mass balance around floatation circuit, ascertaining copper deportment by size fraction
(2015-09-07) Mumbi, Mubanga R.
Frontier Mine s.p.r.l is a mine operating in Congo (D.R.C), which is, located 35km from Ndola, Zambia. The ore is mined from an open pit mine and has a head grade of percentage!.15 Copper. The plant treats sulphide ores and mixed ores and produces copper concentrate of up to 28% Cu grade and recoveries of up 95%. The concentrate is sold to smelter plants in Zambia and the rest of the world. The plant is new about 6 months old, but is achieving records that you normal see in old plant. The plant design is to mill 2400 t/day, the P80 of the feed going to the flotation circuit is 150u.m. My project title is 'Mass balance around the flotation circuit, ascertaining copper deportment by size fraction'.The main objective I was to account for metal distribution in the flotation circuit, so as to assess and control plant performance. The samples were collected from all the steams in the plant using a bucket. Pulp samples were taken every 30 minutes for 2 hours, this was done to have a representative sample. There were about 13 stream from which sample were taken.The recovery against size is plotted together with Copper Distribution. This is done so as help to compare the recovery for each size distribution. From the data it will be seen that the highest recoveries are between +45u.m and +75u.m. And as the particles get finer and coarse the recoveries drop. However, there is more copper -45p.m and less copper in +150u.m.
Optimisation of conditions for Mufulira reclaimed ore
(2015-09-07) Musonda, Chibwe Amos
The project was conducted at Mufulira Concentrator of Zambia Consolidated Copper Mines Limited (ZCCM). This concentrator treats sulphide ores whose copper mineralogy is mainly, bornite, chalcocite and chalcopyrite. Presently this concentrator is treating a mixture of fresh and reclaimed ores. Approximately about 20 OOOt per day of ore are currently treated at which about 7% was reclaimed ore as from November 1992. With this practice, it was observed that much of copper was lost to the tailings. Reclaimed ore is the ore that was originally considered to be treated because it was a low grade material. This material was therefore, left underground in stopes in preference for high grade material. The project was, therefore, aimed at optimising the flotation conditions for reclaimed ore in comparison to the existing conditions for fresh ore. It was further aimed at finding the best blending proportions of fresh and reclaimed ores. A grind of 56% - 75/xm, a pH range of 10-11 and a collector dosage rate of 20g/t/10g/t (SIPX/PAX) were found to be optimum. The blending proportion of 20% reclaimed ore and 80%- fresh ore was found to be optimum.
Optmization of acid and lime consumption at Nkana oxide leach plant.
(2015-09-07) Bwalya, Chishimba S.
Nkana Leach Plant (NLP) of the Mopani Copper Mines Pic Nkana mine site treats ore from Mindola open pit mine. Leaching is employed in the treatment of the oxide ore which is followed by solvent extraction (SX). However the leach circuit was characterized by low metal recoveries in the pregnant leach solution (PLS), while acid consumed was not equivalent to the amount of metal recovered. In an effort to lower acid consumption at the leach tanks test works were conducted on laboratory scale on the feed material to the ball mill. Sampling was done from the stock pile which feeds the belt to the sag and ball mills respectively. Parameter considered for study in leach experiments were, densities, Particle size and its distribution, Optimal pH for leeching, Rate of agitation. In order to see what effect these parameters have on acid consumption, laboratory tests were conducted on some of these parameters, the parameters selected were, densities and pH which showed significant response to acid consumption. Leaching experiments were done in a baffled tank and an agitator was used to agitate the slurry, a pH meter was used monitor the pH. Results obtained showed that an increase in the pH from 1.8-1.9 show a reduction in acid consumption from 87ml-75ml with a deference in the efficiency variations averaging 67.38%-48.79 respectively. The densities show significant change with reduction in densities, a change from 24%-27% solids showed acid consumption changes from 360ml-377ml. the metal recoveries in both cases averaged 4-6gpl Cu in solution. The ore was averaging 1.0-1.89% total copper and 0.8-1.2% acid soluble Cu, this was the ore used in the experiments. The plant maximum efficiency of about 90% on average is usually obtained, with acid consumptions of about 200tonnes per day on average. Lime was used for nuetralisation of tails after the leaching process; the two types of lime which were in use are hydrated lime and quick lime. Experiments were conducted using the two types of lime in a baffled tank and an agitator, without an agitator and using water when and during addition to the tailing. It was discovered that with quick lime, if an agitator is used the consumption averaged 23.21g in 200ml volume of tails and hydrated lime showed 25.48g in 200ml while in non agitated systems it was shown that quick lime and hydrated lime showed increases of about 26g and 30g respectively. And reaction kinetics is faster in agitated systems as opposed to non agitated systems as shown in the tables of the appendix. It was concluded from experiments that to have a good balance between acid consumed and good leach efficiency the pH of between 1.9 and 2.0 should be used with densities of below 27% solids. Tail tanks should be agitated to allow for faster kinetics and low lime consumption as experiments show that lime consumption is low when agitated tanks were used. Experiments also showed that when water is added to the lime consumption is greatly reduced hence the need to add water when adding to the tails.
Optmization of solvent extraction at Kansanshi mine with the aid of cytec pilot plant
(2015-09-07) Chibwe, Bustone C.
A series of laboratory test work were carried out to optimize solvent extraction at Kansanshi mine. Results from the laboratory were transferred to the Cytec pilot plant which simulated the Kansanshi High Grade II solvent extraction plant. The organic and aqueous contact time was determined using a pregnant solution containing 5g/l Cu and this grade were maintained throughout the laboratory test work. pH isotherms for Cu and Fe were generated. Two extraction stages were established from the McCabe Thiele diagram generated. Also established were the temperature and reagent (LIX 984N) concentration in the organic phase constituting Shellsol as a diluent. A good result was obtained on the Cytec pilot plant with Cu recovery in the extraction stage ranging between 95 and 98%. Other parameters affecting solvent extraction were also observed. These included: crud at weir; organic and aqueous interface heights. The crud was seen to be rising in the stripping stages while decreasing in the extraction stages. To minimize aqueous entrainment, the organic and aqueous heights used were 13 and 14 cm respectively.
Optmization of the solvent extraction with the aid of the isocalc software.
(2015-09-07) Masapi, Justin
Leaching of sulphide minerals has never been successful under atmospheric conditions. Process plants that attempt to treat sulphides via the hydro metallurgical route can either pre-treat the sulphides which include roasting, to decompose to leachable oxide or leach under high pressure in the Autoclaves. In this project, the high pressure leaching was utilized. As the result of that it was projected that more acid would result in the pregnant solution, higher temperature and above all the copper tenor was also expected to improve. To quickly determine the effects of changing these operating parameters, the isocalc software was used. Preliminary testworks were done to have an overview of the plant operating conditions and also make it possible to run the software. The pH was varied to see how it affects the SX performance, organic strength, temperature and also the organic to aqueous flowrates were varied to counter the effects of improved copper grades without changing the staging. In this project it was established that, at a stabilized copper grade of 4.5gpl Cu in the pregnant solution, the optimum pH of 2 was arrived at, O/A flowrates of 1.7, and the organic strength of 27 v/v% gave the best results in that the recoveries were high. These also gave minimal copper losses in the raffmate. It was also observed that increasing the aqueous flows while keeping the organic flowrates constant resulted in high copper losses in the raffmate and the converse reduced the losses. The optimized parameters were entered into the program and gave a good result in the advance solution of SOgpl copper. This is higher than the average 43-45 gpl Cu.
Profitability : sensitivity and risk analyses of the Sabi gold project
(2012-07-25) Frimpong, Samuel
This study examines the economic viability of the Sabi gold deposit (oxide cap), basecpat Zvishavane, about 400 km south of Harare in Zimbabwe. A detailed examination of the technical and economic factors which can affect the viability of a mineral project was undertaken using sensitivity analysis. The analysis revealed that eight variables: grade of the ore, annual production rate, preproduction period, operating cost, mill recovery efficiency, inflation, the price of gold and the project discount rate are sensitive and their changes could significantly affect the project viability. Risk analysis, using the Monte Carlo Simulation technique on the probable sensitive variables, was carried out. It was established that the probability of the project failure is 29%.
Regeneration of spent activated carbon
(2015-08-11) Lesa, Ernest
Two methods for the regeneration of activated carbon loaded with sulphide anions and organic adsorbents have been studied on a laboratory scale and are described in this report. Activated carbon is used to reduce by adsorption the level of sulphide anions in cobalt advance electrolyte. During adsorption sulphide anions accumulate on free sites of activated carbon and as a result there is a progressive decline in activity of the carbon. After sometime, the activity drops to a level where very little adsorption takes place. This creates a need to regenerate the carbon and restore its activity. If the level of impurities is not reduced in the electrolyte, problems arise at the electro-winning stage of cobalt and also during use of cobalt metal . The first method of carbon regeneration described in this report is that of chemical regeneration. This method involved the use of two regenerates: hydrochloric acid and a mixture of sulphuric acid and potassium dichromate. Experiments done have shown that this method is technically feasible as a regeneration efficiency of 90 and 93% for suphuric acid plus potassium dichromate and hydrochloric acid respectively was obtainable. However, a major disadvantage of the method is the high cost of regenerants. The second method which has shown more potential than chemical regeneration is thermal regeneration. This method involves heating spent carbon to a temperature of 600 - 900 degrees celcius in an inert atmosphere. Batch experiments have indicated the technical and economic feasibility of this method. A regeneration efficiency of 93% is obtainable at a temperature of 700 degrees celcius.

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