Acid Leaching for Metallic Impurities

Acid Leaching for tinny ImpuritiesAcid Leaching for Metallic Impurities pay grade of Some Mineral Ores in Nigeria*R.L. Tyohemba1 S. K. Emgba2AbstractThere is every direct to access the scoria ratio of mineral ores in order to render investors and industrialists with information infallible to weigh the gains of venturing into their exploration. Metallic ores including Zinc ore (Sphalerite), conjure ore (Magnetite), compact ore (Heamatite), bull ore (chalcocite), get ore (Galena) and gypsum were obtained from the National Geological Survey Kaduna. The ore samples were grounded and digested with aqua regia dissolvent to leach their metal-looking constituents use standard method. The main bi all-metal components of the ores viz Zn, Fe, Cu, Pb and Ca were determined by the flame atomic compactness spectrophotometer (Biotech FAAS phoenix 986) alongside their associated impurities. Galena (Lead ore) recorded the steepest metallic slag substance of ab turn out 28.64 % and was followed by Sphalerite with about 6.31 % metallic impurities. The other ores recorded ZnMgNiPb. The impurity matter of heamatite and magnetic contract-ore were of the same trend in the order MnCuZnNiPb. However, heamatite recorded nobleer(prenominal) Fe sate than magnetite. Galena contained 534.50 mg/Kg (71.36 %) adopt content with its associated impurities bring out in the order ZnMnCuCd. Sphalerite contained 8362.22 mg/Kg (93.69 %) as atomic number 30 while its associated impurities were present in the order of CuFeCaMnPb. In gypsum, its Calcium content was (97.15 %) with its associated metallic impurities in the order MgFeKCrPb. The examine ores had a very high level of their major metallic constituents with only Galena which had a high level of impurities. Thus these ores could be good feedstock to mine their principal components.1.1 INTRODUCTIONNigeria is luxuriously endowed with a variety of mineral resources, fossil fuelsand solid minerals ranging from unparall eled metals, miscellaneous stones to industrial minerals such as Lead(Pb), Feldspar(xAl(Al,Si)3O8), ron magnetite(Fe3O4), adjure hematite(Fe2O3), gypsum(CaSO4.2H2O), bulls eye(Cu), Kaolinite(Al2O5(OH)4Si), Zinc(Zn), Limestone(caco3) e. t. c. Most of these argon yet to be exploited. Statistically, the level of exploitation of these minerals is very low in relation to the extent of deposits establish in the country. The presence of impurities in ores is inevitable due the nature of their particular. Impurities in minerals may be caused by elemental admixtures or by crystal chemical substitutions 1. Impurities atomic number 18 often liable for colour changes. Natural impurities argon super acid in minerals, as is the impulse for one element to slip into the crystalline structure in domicile of some other element. Exchanges of these forms do not cause a adaptation in mineral name as long as the replacements ready up only a small proportion of the entire structure.Oxides nod ules of Ni, Co and Cu fork over been strand to occur in lattices of cast- straighten out and atomic number 25 2. Associated impurities of coat(II) such as lead, press, dogshit, Silver etc., contained in be said to be found present in Nigerian sphalerite mineral3. The high manganese content of the sphaleritesleave them incongruous for touch by conventional smeltingtechniques, facilitating the inevitability to jut out and construct an onsiterefinery that is specifically suited for Gamsberg ores and concentrates 4. Naturally occurringsphalerite commonly incorporates variable niggardlinesss ofimpurities (e.g. Fe, Cd, Mn, Cu, Co, Ni, Ge, In) that rest atomic number 30in lattice sites. For example, FeS concentrations can range up to25 mol. %, while MnSseldom reaches up to 14 mol.%. Consequently,the high extent of stoichiometric inconsistency observedhas a mark effect on the processing, as high levels of theseimpurities in some zinc concentrates, i.e. Gamsberg, renders themu nsuitable for processing by traditional operations.Copper is associated with basemetals such as nickel and cobalt.Studies have likewise been carried out on representative samples of Kre (Turkey) where long rich copper ore were leached in astringentic ferrous sulfate solutions in order to recover copper and its associated metals (Zn, Co, Ni) present in the ore5.The minerals of lead and zinc ar naturally associated with eachOther.In many parts of the world, significant deposits of these mixedsulphideoxide lead and zinc ores are found with the main sulphideand/or oxidized ore bodies. Because of their complex mineralogy,these ores are very difficult to deal with from a mineral processingpoint of go steady and they are very often left untreated as a essence of themetallurgical difficulties encountered in rending lead and zincfrom them. Although the primary sources of the metals are leadand zinc concentrates from sulphide and oxidised ores, as suppliesof these deplete, the proces sing of mixed ores must be considered6. Also, the lead-zinc ore from a mine is featured by complicated copper-lead-zinc intergrowth and uneven dissemination size. Besides, the minerals containing copper depart by nature the mineral containing zinc, causing difficulty of separation of copper, lead and zinc minerals 7.There also published data on the presence of metallic impurities including Fe, Se, Mg, Al, Si, Cu, Zn, Pb, Cr, La, Ce, Nd and Y which were removed from desulpurized gypsum 8.Hayward and Quincy 9 developed a method for the give-and-take of iron ores containing impurities such as aluminium, silicon, chromium, nickel and cobalt from iron ores of the emblem which contain nickel in redundancy of 0.25% and chromium in excess of 0.5%, such as for example those ores found in Cuba known as Mayari ores. The impurities which are present in all iron ores such as sulphur, phosphorus, manganese and silicon appear in iron and steel make there from. Such impurities are generally un desirable in iron alloys, still it has not been possible to remove them completely, and only high grade iron ores are used at present in the issue of iron. For this reason, various low grade iron ores have been wholly rejected, each because of their high table of contents of the impurities mentioned or because they contain varying criterions of base metals 10. These bulks of impurities mentioned in the essay have obvious unattractive characteristics that will increase the comprise of mineral processing.There exist speculations that mineral ores in Nigeria are characterized by high levels of impurities. It then becomes imperative to access these mineral ores and their impurity ratios to cater investors and industrialists with information that will help to estimate cost of production as well as to find suitable methods applicable for their purification.2.1 METHODOLOGY2.1.1 sample Collection and PreparationMineral ores including Zinc ore (Sphalerite ZnS), Iron ore (Magnetite F e3O4), Iron ore (Heamatite (Fe2O3)), Copper ore (chalcocite Cu2S)), and Lead (Galena-PbS) were obtained from the National Geological Survey Kaduna. The samples were stored in the laboratory for the study. The ore samples were grounded using a porcelain mortar and pistol sieved and digested to leach their metallic constituents using the procedure described below.2.1.2 Acid leaching of ore samples for metallic content determination.This was carried out as described by the ISO (1998)procedure 11. 1g of the grounded air dehydrated ore sample was transferred into a 250 ml reaction vas (Teflon digestion bomb). 10ml of the mixture of nitric acid and hydrochloric acid in a ration of 13 (aqua regia) was added unto the reaction vessel containing 1g of dried sample and heated using hot plate inside a fume hood until white fume was observed and allowed to cool.The reaction vessel was allowed to stand so that most of any insoluble residue settles out of suspension. The relatively sediment- free extract was decanted carefully onto a filter paper, collecting the puree in a 100 ml volumetric flask. All the sign filtrate was allowed to pass through the filter paper, and the insoluble residue was wash onto the filter paper with a minimum amount of nitric acid (0.5 mol/l). The filtrate so collected was collected alongside the initial filtrate and the volume of the flask was made up to mark with deionized water. The extract thus prepared was ready for the determination of the studied metals, by an atomic absorption spectrometer (Biotech FAAS Phoenix 986).3.1 RESULTS AND DISCUSSION3.1.1 Metallic Content of Copper Ore (Chalcocite).The result of metallic content of copper ore is presented in table 1. The concentration of copper in the ore was found to be 10341.73 (mgkg-1) representing about 97.7% of its metallic content covered by this wager. Other metallic constituents which are considered to be impurities were also found present. Hence, Ca (99.65 (mgkg-1), Mg (63.89 mgkg- 1), Ni (9.38 mgkg-1), Pb (1.99 mgkg-1) and Zn (73.26 mgkg-1) in the order CaZnMgNiPb. These metallic ions exists in their +2 oxidation states as copper and could replace the Cu2+ in its lattice sites. In a similar work by 5, massive rich copper ore was leached in acidic ferric sulphate solutions and was able to recover copper and its associated metals (Zn, Co and Ni). plug-in 1 Metallic content of Copper ore (mg/Kg)3.1. 2. Metallic content of the studied Iron ores (Heamatite and Magnetite)Presented in table 2 are the available metallic contents of the studied iron ores. The mount of iron in the heamatite ore was found to be 6488.19 mgkg-1, representing (97.3) % of the quantity metallic content evaluated in the study. The iron content of magnetite was 5571.81 mgkg-1, representing 96.99%. However, an interesting trend was observed in the variation in the amount of metallic impurities which were found present in these iron ores. Both heamatite and magnetite varied in their level of i mpurities in the order MnCuZnNiPb. Oxides nodules of Ni, Co and Cu have been found elsewhere to occur in lattices of iron and manganese ores 2. Hayward and Quincy 9 had already identified impurities such as Aluminium, Silicon, Chromium, Nickel and cobalt from iron ores of the type which contained nickel in excess of 0.25%. The values inform in this study for both iron ores are lower in nickel content than those recorded above (0.21 and 0.18) % nickel for heamatite and magnetite respectively.As earliest stated in literature, iron alloys are generally undesirable but it has not been possible to remove them completely, and only high grade iron ores are used at present in the production of iron. For this reason, various low grade iron ores have been wholly rejected, either because of their high contents of the impurities mentioned or because they contain varying amounts of base metals 10. From the results presented in this study, Nigerian iron ores are of high iron content with very negligible impurity content in the ratio of (135 and 132) iron to metallic impurities content of heamatite and magnetite. confuse 2 Metallic content of iron ores (HeamatiteMagnetite) (mg/Kg)**H Heamatite **M Magnetite3.1. 3 Metallic Content of Lead Ore (Galena)The recorded amount of Pb in the galena ore was 534.50 mgkg-1, representing (71.36) % Pb content of the studied metallic components. Also, other metallic components considered to be impurities including Cadmium, Copper, Manganese and Zinc were found present in the ore as presented in table 4 in the order ZnMnCuCd. The metallic impurities of Zn and Mn were present in relatively large amounts. (i.e. 14.21 and 12.85) %. The minerals of Lead and zinc are naturally associated with each other. In many parts of the world, significant deposits of these mixed sulphide-oxide lead and zinc ores are found with the main sulphide and/or oxidized ore bodies. Because of their complex mineralogy, these are very difficult to deal with from mine ral processing point of view and they are very often left untreated as a result of the metallurgical difficulties encountered in extracting lead and zinc from them 6.Table 4. Metallic content of Lead ore (mg/Kg)3.1.4 Metallic Content of Zinc ore(Sphalerite)The results are found in table 5. Zinc content was determined to be 8362.22 mgkg-1 (93.69) % of the ores metallic content studied. Other metallic components which are considered to be common impurities associated with zinc ores were also found present in the other CuFeCaMnPb. The occurrence of zinc with such impurities has earlier been reported in the previous session.Table 5. Metallic content of Zinc ore (mg/Kg)3.1.5 Metallic content of gypsumHeiska (2011) have reported the presence of metallic impurities including Fe, Se, Mg, Al, Si, Cu, Zn, Pb, Cr, La, Ce, Nd and Y in gypsum. As presented in table 6, the main metallic component of gypsum which is calcium was evaluated to be 9921.03 mgkg-1, representing 97.15 % of the totality metallic content of the studied metals. Other metals such as Cr, Fe, Mg, K and Pb were found present in the acid leached mineral in the order MgFeKCrPb. The dominance of Mg as an impurity in this ore is practically expected as the metal ion (Mg2+) is known to occur in areas where there calcium deposits exchanging at its lattice and together causing water hardness.Table 6. Metallic content of Gypsum ore (mg/Kg)3.1.6 Main metal component and impurities ratios of studied oresIn table 7 and fig. 2, the summary of these ratios are presented. Lead ore had the highest level of total metallic impurities recording about 28.69 % as impurities in its ore. Others had low metallic impurities in them. Zinc ore recorded less than 10 % as metallic impurities. On the other hand, metallic impurities in copper, heamatite, magnetite and gypsum were less than 5 %.Table 7.Metal/metallic impurity ratios of studied ores.Fig.2 Metal/metallic impurity ratios of studied ores4.1. ConclusionThe analysis of met allic content of some of the Nigerian mineral ores presented from the result indicates that the studied metallic ores are rich in their principal metallic constituent. The only exception observed is the high impurity content of galena (Lead ore). All the other mineral ores had a little section of metallic impurities in them. It is gain saying that these raw materials could serve as very rich industrial feedstock that will require little processing and thus serve cost. The high Zinc and Manganese content of the galena is inexpedient in terms of the metallurgical process that will be required to recover the major metallic content as well as the appreciable contents of the other metals which are equally of industrial importance.REFERENCES1 Smykatz-kloss, W. finish of impurities in minerals by means of Standard Differential Thermal Analysis, integrity Determination by Thermal Methods, ASTM STP 838, R.L Blaines C.K. Schoff, Eds., American society for tally and Materials, 1984, 121- 137.2 Zhang, W and Cheng, C. Y. (2007). Manganese metallurgy review. Part I Leaching of ores/secondarymaterials and recovery of electrolytic condenser/chemical manganese dioxide. Hydrometallurgy 89 (2007) 137159.3 Alafara,A. B and Folahan, A. A (2011).Beneficiation of a Nigerian sphalerite mineral Solvent extraction of zinc byCyanex272 in hydrochloric acid. Hydrometallurgy, Hydrometallurgy 109 (2011)187193.4 McClung, C. R. and Viljoen, F (2011). A detailed mineralogical assessment of sphalerites from the Gamsberg zincdeposit, South Africa The manganese conundrumMinerals Engineering 24 (2011) 930938.5 Arslan, F, Bulut, M. OlgaKangal, K. TahsinPerek, AlimGlSebahattinGrmen (2004). Studies on leaching of massive rich copper ore in acidic ferric sulfate solutions. Scandinavian Journal of Metallurgy 33(1)6-14.6 Olubambi, P.A., Ndlovu, S., Potgieter, J.H. and Borode, J.O. (2008).Mineralogical characterization of Ishiagu (Nigeria) complex sulphide ore.Int. J. Miner. Process. 87 (2008) 8389 .7Ma, J., Ren, J. and Yuan, L (2008). Flotation experimental research of multi-metal sulphide ore. Northwest Geological Research Institute of Non-ferrous metallic ores, Xian 710054, China.8 Heiska, P (2011). Methods of purifying gypsum. US Patent 20110044883.9 Hayward, C.R. and Quincy, M (1948). Treatment of iron ore containing impurities including nickel and chromium. US patent. No.45862. New York.10 Meyer, R. (1931). Process of Beneficiating iron ores. US Patent. Series No.527367. New York.11 ISO 11047. 1998. discoloration Quality Determination of cadmium, chromium, cobalt, copper, lead, manganese nickel and zinc. Flame and electrothermal atomic absorption spectrometric methods.International Organization for Standardization. Geneva, Switzerland. 6 p. (available at www.iso.ch).