Hannebachite- a rare and important Sulphite - Term Paper Example

? HANNEBACHITE- a rare and important Sulphite Hannebachite Hannebachite is an important natural mineral. The composition of Hannebachite is CaSO3.H20.It is also known as calcium sulfite hemihydrates. It is one of the most stable forms of Calcium sulphate and basically is categorized in the sulphite group. It is the second recorded sulphite mineral. In fact Hannebachite among the two most important naturally occurring sulfites, the other being Orschallite (Ca3(SO3)2(SO4).12H2O). Hannebachite, Orschallite, scotlandite (PbSO3) and gravegliaite are rare sulphite minerals that come under the class of Sulphites. The name “hannebachite” has been derived from the place it was first discovered in i.e.at Hannerbacherly, near Hannebach, West Germany. Sulfite groups have the generalized formula Am[SO3]pZq·xH2O and AmBn[SO3]pZq·xH2O, where A and B both are cations and Z represent anion. The most commonly occurring cations groups binding includes Na+, K+, Cu2+, Mg2+, Al3+, Ca2+, Pb2+, and Ba2+. The molecular arrangement of sulphite is such that the sulfur molecule is at the apex of the pyramid thereby making sulfites really unstable. This is the reason why sulphite minerals are rarely found in nature. Hannebachite is an important component of fixated scrubber sludge. The structure of Hannebachite has several applications and forms the basis of further investigation since the applications of the mineral are yet to be determined and hence immense scope of research lies in this area. Introduction Hannebachite received its IMA status in 1983 following which the first ever publication on it was produced by G.Hentschel, E.Tillmanns and W. Hofmeister in 1985 (Hentschel et al, 1985); however, the first person to detect the presence of this mineral was P.Orschall who was also the discoverer of Orschallite mineral. He found these minerals in a place named Hannerbacherly in West Germany. In nature Hannebachite is mostly found along with another sulfite mineral called Orschallite. Other minerals found in the porous cavities of quaternary melilite nepheline leucitite are clinopyroxene, apatite and phillipsite COMPOSITION The mineral –hannebachite, gained importance owing to commercial research on sulfite rich scrubber materials. Studies have shown that sulfite rich scrubber material extracted from power plants were rich in Hannebachite crystallites (Malhotra,2010). In nature Hannebachite is found as sharp, almost clear crystalline structure. The composition of the mineral is SO2 49.60%,CaO 43.42%, H2O 6.98% which corresponds to its molecular formula (Anthony et al,2000).Sulfites in nature are highly unstable owing to the pyramidal structure where the sulfur is seen at the apex while the oxygen sits on the other corners of the arrangement; thereby these unstable products change into sulfates. However, CaSO4.0.5H2O can substitute into the CaSO3.0.5H2O structure up to a mole fraction of at least 0.12 (Jones et al., 1977). Structure of Hannebachite It is already known that the chemical composition of the mineral includes carbon, hydrogen sulfur and oxygen. The molecular weight is about 258.30gm. Hannebachite is orthorhombic. Its space group is Pbna (2m/2m/2m). Extensive studies have been done to determine the exact structure of the mineral. Powder diffraction was conducted to calculate the single crystal profile (figure 3). The optical class of the mineral was seen to be biaxial. It was recorded that a= 6.46A, b= 7.765A and c=10.650A which means that in the orthorhombic crystal system of hannebachite alpha=90°, beta= 90° and gamma=90°. The J-mol structure gives a clear interpretation of this structure (Figure:3). Spectroscopic studies conducted brought forward a clear idea of the bonding between the atoms present (Figure 1). The structure of hannebachite mineral was studied through Raman Spectroscopy by Frost and Keefe. The sample for hannebachite was supplied by Mineralogical Research Company who sourced in from the Hannebacher Ley volcano in Germany. The bands are observed at 1005cm-1, 969cm-1, and 655cm-1 (Frost &Keefe, 2009). Based on this study it was determined that the sulphite ions in the mineral bind to calcium through sulfur owing to which the SO bands stretches to much higher wave numbers. Hannebachite is structurally similar to another naturally occurring, sulfite bearing mineral-Orschallite. In fact, in nature these two minerals are found together. Orschallite was discovered from the same place from which Hannebachite was first found i.e. Hannebacher ley volcano. Orschallite is a colorless and transparent mineral. The crystalline structure of Orschallite is hexagonal (Hentschel et al, 1993). Comparing the Raman spectroscopy of hannebachite and Orschallite, the latter has an extremely complex structure owing to band overlapping of sulphate and sulphite in Orschallite. Relatively the structure of Scotlandite is simpler whose band in Raman spectroscopy is attributed to stretching of S03. Physical properties When the mineral was first discovered it appeared as thin bladed crystals. The color of the mineral is recorded as ranging between colorless to white and occurrence of no other color at all. The crystal changes color from almost transparent to milky white when it is exposed to air (Mineral data, 2005).Its luster is vitreous almost glassy in appearance. Owing to the placement of the molecules the hardness of the mineral has been calculated as 3.5 mohrs. The specific gravity of the mineral has been calculated to be 2.52 gm/cc. Hannebachite is not a radioactive mineral. PLACE OF ORIGIN The place of origin of hannebachite is Hannebacher Ley, near Hannebach, Eifel, Germany. The site is known to be really rich in many minerals. In fact several minerals have been detected in this site for the first time because of the volcanic origin of the area. Other important minerals such as Orschallite have also been discovered here. GEOLOGIC OCCURRENCE Hannebachite is always found along with other sulphate-sulphite bearing minerals such as Orschallite and scotlandite. Typically the mineral occurs compactly in the porous volcanic rocks along with apaptite, phillipsite and clinopyroxene (Jambor, 1994, p 572). Both hannebachite and Orschallite are preserved during an underwater volcanic eruption in a melilite nepheline leucitite. Scotlandite is also found in association with other rare sulphite metalslanarkite and susannite and is a result of weathering deposition and natural oxidation processes (Paar et al,1984). Besides this it has been proposed that sulphite minerals are formed from reactions between greenhouse gases and slaked lime or quick lime (Frost & Keefe, 2009). SPECIAL CHARACTERISTICS Hannebachite has a few special characteristics which have proven to extremely beneficial for practical as well research purposes. ROLE IN SOIL DE-SULPHATION The spectroscopic results conducted on Hannebachite and Orschallite showed that the two minerals were closely associated and shared a possible relation ((Frost &Keefe, 2009). 3(CaSO3)2.H2O + 1/2O2 + 9H2O > Ca3[SO4](SO3)2.12H2O + 3(SO3 )2- +3Ca2+ Soil contaminated with sulfates/sulfites may be treated with addition of Cao or calcium hydroxide. Owing to which hannebachite maybe formed, this in turn can be easily removed thereby helping in de-sulfating the soil of the area. 2CaO + 2SO2 +H2O > (CaSO3)2.H2O (hannebachite) Hannebachite in Mars-Geologic Process Planet Mars has been the focus of many researches for a few decades now and hannebachite has played a crucial role in helping scientists determine the past and present temperate conditions of the Martian surface and the occurrence of liquid water on its surface. Halevy and Schrage (2009) conducted a series of mineral precipitation experiments to establish that So2 was capable of prohibiting precipitation of calcium carbonate because hannebachite, a hydrated form was formed and these experiments helped explain the dearth of carbonates in the Martian surface today. The experiments showed that thermodynamically pSO2/pCO2 ? ~5.0 ? 10?8, and then hannebachite precipitates faster because it reaches saturation earlier than calcite thereby limiting availability of Ca+ ions. The experiment helped establish that the temperature required for SO2 out gassing was sufficient to maintain liquid water in Mars. Researchers claim that a similar phenomenon has occurred on the Earth’s surface leading to formation of crystalline hannebachite. HANNEBACHITE IN AEROSOLS Studies on mineral aerosol components have established that hannebachite is indeed present in mineral aerosols. Aerosols have a deep impact on the environment because they enhance pollution and decrease air visibility. XANES spectroscopy (X-ray absorption near end structure spectroscopy) studies was conducted in Asia (KEK,2010) which showed the presence of hannebachite in the interiors of aerosols which shows that oxidation of sulfur dioxide has occurred which means that adsorption of sulfur dioxide on the surface of mineral aerosols such as calcite which was followed by oxidation. BIOGENIC SULFIDE FORMATION –TREAT POLLUTION One of threats to our environment comes from acid mines drainage in coals and metal mines. Bioremediation involves production sulfate reducing bacteria which produces sulfides which in turn helps to precipitate metal ions to insoluble sulfides. It was seen that minerals such as Hannebachite, gypsum(CaSO4·2H2O), barite (BaSO4) ) and anglesite (PbSO4) acted as electron acceptors for sulfate reducing microbes giving rise to biogenic sulfide and limiting pollution (Kalnachuk, 2002). LITERATURE SURVEY/ PROSPECTS OF RESEARCH According to WILEY ONLINE LIBRARY, which is a free and fairly accessible online resource, the most commonly cited paper is Raman spectroscopic study of the sulphite bearing minerals scotlandite,2 hannebachite and orschallite – implications for the desulphation of soils (Frost & Keeffe,2009) which speaks in details about the spectroscopic properties of the sulfite minerals. This paper has been cited almost 16 times which is by far the highest number of citations as far as Hannebachite mineral is considered. However, the same resource states that journals on “SULPHITE” minerals where hannebachite may not be the focus is cited most. One of the most cited journals in German is Zur Kenntnis der Sulfite des Strontiums, Bariums, Bleis, Cadmiums und Mangans. Darstellung von Einkristallen durch Gelkristallisation (Lutz et al,1983) which has been a source of information for two decades on every sulphite mineral including hannebachite. The literature survey portrays a poor picture showing that hannebachite is a poorly reviewed mineral. It is also established that very less research has been done on the mineral and its possible applications in the field of science. However, since recently space researchers and scientists have confirmed the geological presence of the mineral in the Early Martian surface there is hope that more in depth study will be conducted on the mineral. REFERENCES Anthony, JW, Bideaux, RA, Bladh, KW, Nichols (2000) MC Handbook of 275 Mineralogy; Mineral Data Publishing: Tuscon, Arizona, USA, Vol. 4. Frost, Ray L. and Keeffe, Eloise C. (2009) Raman spectroscopic study of the sulphite bearing minerals scotlandite, hannebachite and orschallite – implications for the desulphation of soils. Journal of Raman Spectroscopy, 40(3),244-248 Havely,I, Schrag,D.P (2009) Sulfur dioxide inhibits calcium carbonate precipitation: Implicationsfor early Mars and Earth. GEOPHYSICAL RESEARCH LETTERS.36,1-5. Hentschel, G., E. Tillmanns, and W. Hofmeister (1985) Hannebachite, natural calciumsulfite hemihydrate, CaSO3 •1/2H2O. Neues Jahrb. Mineral., Monatsh., 241–250. Hentschel, G., Weidenthaler, C., & Tilmanns, E. (1993). Orschallite, Ca3(SO3)2 · SO4 · 12H2O, a new calcium-sulfite-sulfate-hydrate mineral. Mineralogy and Petrology, 48(2), 167- 177. High Energy Accelerator Research Organization(KEK) (2010) High reactivity of calcite in the atmosphere supplied by Asian dust~ Implications from speciation of calcium and sulfur using X-ray absorption near-edge structure spectroscopy. Annual Report, 1,54-55. http://ccdb5fs.kek.jp/tiff/2009/0922/0922001.pdf Jambor, J. J., Roberts, A. C., & Peziewicz, J. (1994). NEW MINERAL NAMES. American Mineralogist, 79, 570-574. Karnachuk, O. V., Kurochkina, S. Y., & Tuovinen, O. H. (2002). Growth of sulfate-reducing bacteria with solid-phase electron acceptors. Appl Microbiol Biotechnol 58, 482-486. Malhotra,V.,M (2010)Value-Added Products from FGD Sulfite-rich scrubber materials Retrieved on 21 oct 2013 W.H.Paar et al (1984). A new mineral, scotlandite (PbSO3) from Leadhills, Scotland; the first naturally occurring sulphite. Mineralogical Magazine, 48, 283-288. Read More