Mines

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Browsing Mines by Subject "Carbon, Activated"

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    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.