G. Ofori-Sarpong

Going for gold: transitional livelihoods in Northern Ghana

This article critically reflects on what impact a supported and formalized artisanal and small-scale mining (ASM) sector could have in Northern Ghana, where poverty is deeply-rooted, the outcome of decades of government neglect. Since country independence in 1957, numerous attempts have been made to improve the living standards of the populations in the country’s North but deteriorated human resource bases and shortages of infrastructure have limited their effectiveness. A recent upsurge in ASM activity, however, has catapulted the region on to another – previously unimaginable – growth trajectory entirely. As findings from research carried out in the township of Kui in Bole District of the country’s Northern Region illustrate, ASM has injected considerable wealth into many of Ghana’s Northern localities, in the process, helping to stabilize their economies and in the process, alleviating the hardships of tens of thousands of farm-dependent families. The intensification of support to, and the formalization of, ASM, could prove to be an important step toward eradicating a poverty problem that has plagued this region of sub-Saharan Africa for more than a century.

Oil Well Cement Additives: A Review of the Common Types

Abstract Additives play significant role in oil and gas well cementing operations. There are varieties of cement additives that have been developed to allow the use of Portland cement in many different oil and gas well operations. In an attempt to formulate the appropriate cement slurry for any cementing job, the right additive must selected and the right quantity must be added. Additives have different functions and are broadly classified as accelerator, retarders, extenders, fluid loss agents, dispersants and many more. Each of the broad classification has different categories of additives that have been developed to perform almost the same function during cement slurry design. However, there some additives under each major type that are commonly used in cement slurry design for oil and gas well cementing operations. This paper reviews the broad classification of oil well additives giving emphasis to the commonly used additives during oil and gas well cementing operations.

Pretreatment of Refractory Gold Ores Using Cell-Free Extracts of P. chrysosporium: A Preliminary Study

The fungus Phanerochaete chrysosporium has been proven to biotransform refractory gold ores, leading to increase in gold recovery. This transformation has been attributed to enzymes secreted by the microbe. This paper reports the findings of preliminary investigations aimed at assessing the use of hydrogen peroxide and cell-free extracts from the fungus, P. chrysosporium, to effect biotransformation of sulphidic refractory gold ores. The investigations show that the total dissolved arsenic, iron and sulphur in solution were up to 5.2 wt%, 0.9 wt% and 6.0 wt% respectively from flotation concentrate after 72 hrs of treatment. Analysis for sulphide sulphur in the residual solids of the gold concentrate indicated about 25 wt% oxidation within 24 hours of treatment. In general, cell-free decomposition of the samples did not increase beyond 24 hours of contact time, possibly due to exhaustion of the active components. Gold extraction by cyanidation increased by 24% after 24-hr treatment with the cell-free extracts. Comparatively, cell-free (in vitro) treatment recorded 66% overall gold recovery as against 61% for whole cell (in vivo) after 72 hours of treatment. These initial results indicate clearly that in vitro processing is a promising alternative to in vivo processing of refractory gold ores using P. chrysosporium.

Assessing the Parameters for Optimum Biotransformation of Carbonaceous Matter by Phanerochaete chrysosporium

Refractory carbonaceous gold ores pose challenges during cyanidation of gold due to the presence of carbonaceous matter (CM) which preg-robs dissolved gold, and this results in a decreased recovery. In an on-going study, the fungus, Phanerochaete chrysosporium has been used to deactivate CM and decrease its ability to preg-rob aurocyanide. P. chrysosporium has been reported to biotransform CM by surface oxidation, which leads to disruption of the continuous graphitic structure necessary for adsorption, and alteration of the pores suitable for aurocyanide adsorption. The present study focused on using anthracite coal as surrogate for CM, and establishing fungal-treatment parameters that bring about maximum decrease in preg-robbing by the anthracite-grade CM. The results indicate that P. chrysosporium can survive in several growth media, and possesses the ability to deactivate anthracite in a wide range of time, pulp density, temperature, pH, and level of agitation. A processing time of 5-7 days at pH 4 and 37°C gave the best conditions. The best pulp densities for stationary and shake culturing respectively were 60% and 25%.

The effect of comminution equipment on gravity gold recovery in small-scale mining operations

As a strategy to improve gold recovery in the small-scale mining industry of Ghana, comminution equipment utilised in grinding was investigated. Morphological studies show that gold particles liberated by hammer mills were globular, disc mills produced cigar-shaped particles, and stamp mills created flaky units. Up to 5% of the gold particles liberated using a disc mill were coated with iron due to smears from the grinding surfaces. Based on shape-factors, the efficiency of subsequent gravity concentration operations increased in the order of flakes < cigars < spheres. A proposed flowsheet increased the gold extraction by over 15%.

Utilization of Microwave Energy in the Calcination and Agglomeration of Nsuta Manganese Carbonate Ore

The application of microwave energy in the calcination and agglomeration of manganese carbonate ore from Nsuta, Ghana, has been investigated. The real and imaginary permittivities, which may be used to determine a substances response to microwave heating, were measured and the permittivities of both the ore and calcine were relatively low at low temperatures. Beyond 600oC, both the real and imaginary permittivities increased more rapidly with that of the calcine reaching relatively high values. The degree of microwave absorption and thus the temperature attained by the samples during microwave heating increased with sample mass, processing time and incident microwave power. Processing temperatures of over 1500oC could be attained under optimum microwave coupling. Calcination and agglomeration tests were performed and the calcine obtained readily absorbed microwaves. The tumbler index of the agglomerated material was 90 and the average crushing strength was 2550 KN. Ghana Mining Journal Vol. 9 2007: pp. 54-61