Millions of tons of tailing dump at Rayfield mine in Jos in North Central Plateau state of Nigeria have been found to contain large quantity of columbite. Initial attempts to recover columbite concentrates by local mi...Millions of tons of tailing dump at Rayfield mine in Jos in North Central Plateau state of Nigeria have been found to contain large quantity of columbite. Initial attempts to recover columbite concentrates by local miners and mineral speculators from the columbite rich tailing dump failed due to the ineffective processing route employed. Using cone and quartering sampling method, 0.5 kg of the columbite tailing was obtained for sieve and chemical analyses. 50 kg of <1mm fraction of the sample was subjected to a first stage magnetic concentration in a three poles Dry High Intensity Magnetic Separator (DHMS) that separated the columbite in the third pole. The re-grind of the + 0.355 mm rougher concentrate fraction (containing interlocking columbite) to pass the sieve aperture was treated on the DHMS in the second stage. The rougher concentrate undersize and columbite pre-concentrate of the first stage magnetic separation were then gravity concentrated on the air float machine. The Rayfield tailings and final concentrate were assayed using ED-XRFS to obtain 12.5% and 69.6% Nb2O5, respectively. The recovery and separation efficiency were 77.95% and 77.88% in that order. The magnetic and gravity concentrations were found effective at 77.95% recovery for columbite from the Rayfield tailing dump. This study also provided database for optimum recovery of columbite from tailings of mining sites of similar composition.展开更多
The effect of bitter leaf (Vernonia amygdalina) extract as an inhibitor for aluminium silicon alloy in 0.5 M solution of caustic soda using weight loss method has been investigated. The alloy of composition 9% Si and ...The effect of bitter leaf (Vernonia amygdalina) extract as an inhibitor for aluminium silicon alloy in 0.5 M solution of caustic soda using weight loss method has been investigated. The alloy of composition 9% Si and 91% Al was sand cast at the Foundry Shop of the National Metallurgical Development Centre, Jos, Nigeria. The cast alloy was cut and machined to corrosion coupons and immersed into 0.5 M NaOH solution containing varying inhibitor concentrations (0.1%, 0.2%, 0.3%, 0.5% v/v) within a period of fifteen days. From the result, it was found that the adsorption of Vernonia amygdalina reduced the corrosion rate of this group of alloy in the alkaline medium. The inhibitive action of this plant extract was explained using inhibition efficiency and degree of surface coverage. The most suitable inhibitor concentration was found to be 0.5% with inhibition efficiency of 87%. The mechanism of inhibition is by physical adsorption and the adsorbed molecules of the inhibitor lies on the surface of the alloy blocking the active corrosion sites on the alloy, hence, giving the alloy a higher corrosion resistance in the studied environment.展开更多
文摘Millions of tons of tailing dump at Rayfield mine in Jos in North Central Plateau state of Nigeria have been found to contain large quantity of columbite. Initial attempts to recover columbite concentrates by local miners and mineral speculators from the columbite rich tailing dump failed due to the ineffective processing route employed. Using cone and quartering sampling method, 0.5 kg of the columbite tailing was obtained for sieve and chemical analyses. 50 kg of <1mm fraction of the sample was subjected to a first stage magnetic concentration in a three poles Dry High Intensity Magnetic Separator (DHMS) that separated the columbite in the third pole. The re-grind of the + 0.355 mm rougher concentrate fraction (containing interlocking columbite) to pass the sieve aperture was treated on the DHMS in the second stage. The rougher concentrate undersize and columbite pre-concentrate of the first stage magnetic separation were then gravity concentrated on the air float machine. The Rayfield tailings and final concentrate were assayed using ED-XRFS to obtain 12.5% and 69.6% Nb2O5, respectively. The recovery and separation efficiency were 77.95% and 77.88% in that order. The magnetic and gravity concentrations were found effective at 77.95% recovery for columbite from the Rayfield tailing dump. This study also provided database for optimum recovery of columbite from tailings of mining sites of similar composition.
文摘The effect of bitter leaf (Vernonia amygdalina) extract as an inhibitor for aluminium silicon alloy in 0.5 M solution of caustic soda using weight loss method has been investigated. The alloy of composition 9% Si and 91% Al was sand cast at the Foundry Shop of the National Metallurgical Development Centre, Jos, Nigeria. The cast alloy was cut and machined to corrosion coupons and immersed into 0.5 M NaOH solution containing varying inhibitor concentrations (0.1%, 0.2%, 0.3%, 0.5% v/v) within a period of fifteen days. From the result, it was found that the adsorption of Vernonia amygdalina reduced the corrosion rate of this group of alloy in the alkaline medium. The inhibitive action of this plant extract was explained using inhibition efficiency and degree of surface coverage. The most suitable inhibitor concentration was found to be 0.5% with inhibition efficiency of 87%. The mechanism of inhibition is by physical adsorption and the adsorbed molecules of the inhibitor lies on the surface of the alloy blocking the active corrosion sites on the alloy, hence, giving the alloy a higher corrosion resistance in the studied environment.
