4. DISCUSSION4.1 CHEMICAL COMPOSITION ANALYSISThe chemical composition analysis of itakpe iron oreas represented in Table 1 show that Itakpe contains iron, silicate, aluminium,magnesium, potassium and sodium elements, while Table 2 represents the chemicalcomposition of Ajabanoko deposit which is composed of iron, silicate,aluminium, magnesium, potassium and sodium as well. It should be noted thatpotassium, aluminium, magnesium and sodium occurs in a very small amount forthe two deposits. The chemical composition also confirmed that Itakpe iron orehas average iron concentration of 36.18 % before carrying out any beneficiationon it, while the Ajabanoko iron ore has average iron concentration of 34.
4 %before processing as presented in Table 1 and Table 2. The results revealedthat Itakpe has higher iron concentration than Ajabanoko prior tobeneficiation.4.2 MINERALOGICAL ANALYSISTable 3 and Table 4 show the mineralogical analysesof Itakpe and Ajabanoko iron ore respectively. Table 3 shows that Itakpe hashigher composition of hematite (29.67 %) than magnetite (24.
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18 %) with asub-metallic lustre. Table 4 which represent the Ajabanoko mineralogicalanalysis has a higher composition of magnetite (26.54%) compare to hematite(20.41 %). Although, both ore has higher composition of quartz mineral which canbe consider as the dominant gangue mineral of the ore. 4.
3 BENEFICIATION STUDIESThegeneral observations in the study show that separating fluid plays vital rolesin the separation of iron minerals from its ore and that the particle sizesalso aid the recovery. Although, there is appreciable recovery at fine particlesizes, but the recovery was increased at coarse particle sizes. 4.3.1 Effects of Dilution RatioTheinfluence of dilution on the recovery of iron ore using Spiral is as revealed inTables 7, 8, 9, 10, 11, and 12. The highest grade of iron mineral was achievedat 30% solid using the spiral gravity technique. The 40 % solid which is a lowdilution (higher percent solids) experienced a decrease in the falling rate ofparticles leading to overcrowding of the particles during separation processwhich makes the separation iron minerals from the gangue minerals to be less effective.The volume of water in the agitator provides the necessary dilution requiredfor particles separation.
Highest grade of Itakpe iron ore was gotten at 30 %dilution using spiral separator as presented in Table 8 and Figure 11respectively. Although, 20 % dilution ratio also recorded a reasonable grade,but 30 % dilution is determined to be the optimum for Itakpe iron ore depositwhich has 62.0 % recovery using spiral separator. Beneficiation of Ajabanokoiron ore recorded the highest grade at 30 % dilution using the spiral with arecovery of 66.95 %.
These indicate that separating fluid has a greater effecton recovery using spiral separator. 4.3.
2 Effects of Particle SizeTheeffect of the particle size on the recovery of iron ore is also shown in Tables7, 8, 9, 10, 11, and 12. The highest iron grade for Itakpe iron ore wasachieved at +300 ?m particle sizeand +300 ?m was also determined to be optimum for Ajabanoko iron ore usingspiral separator as presented in Tables 8 and 11 respectively. Lower separationefficiency in finer particles was observed and believed to be caused by thenegligible mass associated with these size particles. Particles so small thatsettle in accordance with Stroke’s law are unsuitable for concentration (Wills,2006).
4.3.3 Separation EffectivenessTheresults, as shown in Figures 4, 6, 8, 10, 12, and 14 revealed that iron oreconcentrate was effectively separated from the tailings, which are dominatedwith quartz minerals. Theoretically, effective separation was possible becausethe quotient of the difference in their specific gravities is greater than 2.5(equation 1).
From the same results, it was observed that the overflow, i.e.the tailings still have a higher percentage of Fe at the end of the four stageconcentration processes. This Fe in the gangue may come from magnetite in theore, which was not effectively separated. The specific gravity of magnetite isbetween 4.
9 and 5.2, indicating that the quotient varies is between 2.4 and2.8.
Should there be more magnetite of specific gravity 4.6, the efficiency ofseparation decreases. Recall from the above equation, as the quotient reduces,the effectiveness of the separation reduces. Also, from the mineralogicalstudies, it could be recalled that the Itakpe ore has higher percentage ofhematite and lower percentage of magnetite, while the Ajabanoko ore has higherpercentage of magnetite and lower percentage of hematite. 5. CONCLUSIONIthas been observed that the quartz mineral present in the iron ore from the twolocations is the major gangue mineral, hence the nature of this mineral (quartz)affected the recovery of iron minerals. The results revealed that theconcentration criterion is fulfilled for the effective separation of thevaluable minerals from the gangues using spiral gravity separation technique.
These results shows that gravity separation can as well be carried out in alarge scale on the two deposits which will be economical and profit driven ifinvested on.Theresults of this study have clearly shown that optimum separation of iron oreconcentrate from Itakpe and Ajabanoko iron ore by spiralling operations ispossible. It is clearly revealed that the optimum separation was greatlyinfluenced and can be efficient with optimum dilution ratio and smallerparticle size of the ores. The result of the study has also shown that theoptimum Fe recovery could be achieved when the particle size is at +300 µm particle sizeat 30 % dilution for Itakpe and +300 µm particle sizesat 30 % dilution for Ajabanoko iron ore using 6-bowl spiral separator. Thespiral gravity separation technique was able to upgrade this type of ore to themarketable grade as a result of the reasonable difference in specific gravitybetween the iron mineral and the main associated minerals. Gravity separationwas a possible solution for pre-concentrating such ore before using otherconcentrating technique in taking it to super concentrate.
The result of bothdeposits show little or no difference in terms of their recovery, whichinterprets to both deposit having the same physicochemical properties. The result of beneficiation using spiralseparator shows particle size and dilution ratio plays a vital role on therecovery of the iron minerals. Increase in dilution ratio gives increase inrecovery and grade of iron minerals but to a limit.
Also, the smaller theparticle size the better the result of grade, but there is a limit at whichgravity concentration will be efficient when the dilution ratio is too high orthe particle size is too fine.