The Structural Features and Characteristics of Birnessite Family of Minerals - Essay Example

Birnessite Mineral Name: Instructor: Institution: Date: Introduction Birnessite represented by the chemical formula Na0.3Ca0.1K0.1)(Mn4+, Mn3+)2O4 · 1.5 H2O is an oxide mineral that is made of manganese coupled with potassium, sodium, and calcium. The mineral is characterized by a color that ranges from black to dark brown with a submetallic patina. The formation of Birnessite results from the precipitation process in oceans, lakes, and groundwater. The mineral Birnessite has an approximated Mohs hardness of 1.6 and is very soft. Birnessite belongs to the family of phyllomanganate which is a family of felloalloy components that consists of deep sea manganese and desert varnish nodules (Athouël, Moser, Dugas, Crosnier, Bélanger, and Brousse, 2008). In recent years, Birnessite has attracted significant attention due to its diversified geological setup it occurs and its unique sorption, redox properties and its cation exchange capability.Specifically morphology or structural control capacity of birnessite and birnessite related materials has attracted significant focus and attention (Yin, Li, Wang, Ginder-Vogel, Qiu, Feng, Zheng, and Liu 2014). Birnessite was described originally by Milne and Jones as made up of black grains. Recent research done using scanning electron microscope has provided some significant features that are a continuation of the previous done by the two authors. The scanning has indicated a profusion of surface structures that is deemed to be with a distance of few microns or even less than a micron. Also, researchers have indicated that the mineral consists of disks, plates, box-work that made up of intersecting disks or plates, a botryoidal or aggregate cluster of spherulites and sponge-work. The present material make-up of the mineral has significantly shown the above features only that the majority features of the surface structure is intergrown curved surface or plates which is seen and appears as vermiform. Even though the main chemical and structural features of the mineral are somehow assessed, many of details regarding the crystal and structural chemistry of birnessite remains poorly explained and thus understood specifically crystal-chemical formula, diffraction characteristics and chemical-physical features (Yin, Li, Wang, Ginder-Vogel, Qiu, Feng, Zheng, and Liu 2014). The phyllomanganate family of minerals are considered similar to expandable smectites (phyllosilicates) and are deliberated as microporous solids. As phyllosilicates, a phyllomanganate family of minerals can be interpolated with a range of both inorganic and organic compounds to develop pillared structures or multilayer nanocomposites. Several studies have attributed phyllomanganate family of minerals and components to play a key role in the formation of heavy yet destructive minerals as well as other pollutants in the contamination of water body system and soils because of the crystal chemical features it contains which consults the extensive redox and sorption features. The bigger range of birnessite varieties with a diverse chemical and structural features can be synthesized in the modern laboratory. To come up with a surrogate birnessite materials of natural samples, recommendations is at this moment provided that such synthesis should be done at a low temperature. Birnessite produced in low-temperature environments are usually characterized by their finely dispersed nature with a presence of a low level of structural order. The last two decades has depicted an increasing interest for high-temperature birnessite that is produced with the temperatures of as high as 1000 degree centigrade. This has ended up escalated their promising capabilities as electrodes to be used in secondary lithium batteries for both local and commercial use. Birnessite which is characterized by a higher structural faultlessness can be manufactured at an extremely high temperatures, these features being more stable and durable than those commonly applied in the electrochemistry. Specifically, the transition to a spinel arrangements is not visible after the cell cycling. Also, the manufacture of a highly oxidizing species in the process of birnessite production prevents the creation of suboxides and because of this, a novel variety of synthetic potassium that is rich in birnessite that consists of a two-layer periodicity is manufactured. Figure 1: Structure of Birnessite Preparation of layer-Structure Birnessite Several processes have been applied in the preparation of layer-Structure Birnessite that consists of micron size. The most common is the oxidation of Manganese (Mn) II that is in its basic solution using Hydrogen Peroxide, Oxygen or Potassium Phosphate, redox reaction between MnO4 ions and Mn II, the reaction of MnO4 ions and hydrochloric acid coupled with a cationic exchange. The mentioned methods of preparation of layer-Structure Birnessite requires the addition of one or more catalyst at one point or another in the process of the mineral preparation. The structure features of Birnessite consists of grain like morphology structure that differs in size with synthetic component significantly determining the size. Just like the majority of nanoparticles and micro, the selection conditions or mechanism that will lead to a particular choice of Birnessite structure is yet to be discovered and understood by researchers in this field. To date, the synthesis process of black birnessite nanofibers or nanoparticles with dendritic morphology using the direct method of reduction process of KMnO4 while using H2SO4 has not yet come to a conclusion despite the extensive studies in the field. However, speculations all over indicate that the dendritic morphology structures manufactured can result from either be inorganic or organic reactants. The preparation of a black birnessite nanofibres or nanoparticles can be done through thorough stirring of the resultant solution at its initial phase of synthesis. However, in modern days, birnessite is prepared through the reduction of KMnO4 while using H2SO4 as the principal catalyst in the closed vessel while depriving the vessel from extreme light exposures. Preliminary caution needed involves the grading of all analytical chemicals to avoid the inclusion of impurities and other components that might affect resultant results. To obtain such levels of desired results, all pieces of glasswares to be used in the experimental process of preparation of birnessite are cleansed using acid combined with ultrapure water devoid that is made up of organic components under room temperature. The process of preparation of birnessite was first done by Coe and Clark while preparing manganese oxide. Foreign ions of sodium, potassium, and calcium in their synthetic form are deliberated as non-important and can be manufactured without the presence of Birnessite. Despite this the majority of synthetic types of such mineral ions loss a significant amount of water when subjected to extreme temperatures. The structure of Birnessite is believed to be comparable to that of chalcophanite, but researchers on the same are yet to come with a certain structure for the same. However, the commonality between studies is found on the part of the structure component is believed to be made up of molecules of water that is believed to be found layers of edge-sharing MnO6 octahedra molecules. Previous Structural Studies of Birnessite As mentioned earlier, among the challenges previous researchers have encountered in their study of birnessite mineral is the fact that the mineral is made up of several synthetic and natural varieties making it difficult to understand it. In addition, the mineral comes in an exceedingly dispersed condition and generally at a reduced level of structural perfection. Due to these grounds, until recent decade, even the single cell parameters of the various outlined birnessite changes were not concluded explicitly. Several research done recently have proposed that the structure of birnessite is corresponding to that of chalcophanite and for each layer of chalcophanite one for every seven Manganese ions octahedral sites is empty. Extensive studies have been done on the manganese oxide birnessite due to its ion exchange capabilities. Several studies have indicated that the cation exchange capabilities of manganese oxide birnessite increase at an almost linear scale with the Ph range with an approximated range of between of pH 3.2 to pH 7.6. In addition, the exchange coefficient value of alkali to proton caution exchange has been deliberated to increase over the orders of intensity as the pH increases towards the value of 7.6. It is unfortunate that the above changes have become increasingly difficult to be captured using a classical ion exchange formula that assumes a constant exchange coefficients and exchange capabilities; thus an adapted formula has been adapted by several studies done on the same. Previous studies done under the surface complexation model has included a pH charge that is considered hooked on the exchangers has been considered as the more suitable model that offers a description of how ions exchange in the birnessite mineral. In is unfortunate the surface complexation model covered in a range of previous studies done fails to provide a ground to make a comparison. Also, the model presented various research done on the same fails to give a consistent approach to rely on them. Despite this recent studies have made significant strides by providing information that is more detailed regarding the properties and structures of the sorption sites contained in the birnessite surface structure which previous studies failed significantly to offer an explanation. New information has been provided by the development of a new structural content that has offered an extensive re-assessment of the surface complexation model previously studied. Recent studies have been driven by at least one objective that is to provide a consistent applicable model structure for cations on the birnessite mineral. Several researchers have come to a conclusion that the most common structure of birnessite mineral resembles that of mineral chalcophanite which consists of layers of MnO6 that are edge sharing and are octahedra in structure with an alternate layer of a water molecule. The atoms of zinc are positioned in the octahedral dexterity spheres that is surrounded with MnO6 and water layer. As mentioned earlier, previous studies also made a conclusion that one for every seven manganese atoms consists of empty space (Julien, Massot, Baddour-Hadjean, Franger, Bach, and Pereira-Ramos, 2003). Each layer of Mn-O and both below and above the empty manganese layer are zinc ions that are positioned in somewhat a distorted position in the octahedral void that is surrounded by a three oxygen atoms in the adjacent water layer as depicted in the below figure. Figure 2: Layered structure of sodium birnessite Figure 3: the Molecular model is incorporating Zinc ions. According to the research concluded by Johnson, E.A., and Post (2006), the authors illustrated that the zinc atoms contained in the chalcophanite are directly associated with structural oxygens. (Julien, Massot, Baddour-Hadjean, Franger, Bach, and Pereira-Ramos, (2003) also discovered that the manganese ions is very close to the structural oxygen atoms contained in the birnessite. The authors also mentioned that the manganese bonds contained in the structure share a triple bond of manganese and oxygen atoms thus depicting that the ions contained between the interlayers were closely associated with the structural oxygen within the mineral structures. Industrial Application Of Birnessite Birnessite which contains layers of manganese oxides are widely used for industrial purposes due to its versatile material makeup. The majority of industrial application of Birnessite is largely controlled by large particles and manganese III concentration. For the industrial purpose, Birnessite is first reduced by synthesizing the nanoparticles of Birnessite with a concentration of manganese III under a controlled environment. This is done so the properties of the mineral can be fine-tuned to a range of application. The synthesis of Birnessite can be done in the presence of oxyanions elements such as sulfate, silicate or phosphate while undertaking the process of reductive precipitation of KMnO4 by hydrochloric acid (HCL). This needs to be done using a range of electron microscopy, synchrotron X-ray methods and ultra violet spectroscopy that has a diffuse reflectance features. The outcome of such industrial process will show a general reduction of the MnO6 sheet sizes that are attributed to the three components that makes up the mineral. Manganese III concentration has the ability to significantly intesify its material componenet make up whenever there is an increase in the manganese to oxyanions ratio (Chen, Golden, and Dixon 1986). The band fissures of birnessite enlarge both indirect and direct with the decreasing size and increasing concentration of the Manganese III. Phosphate in the oxyanions influence ranking is considered to have the greatest influence among the three under study followed closely by silicate while sulfate comes last. This ranking is consistently at par with the individual property absorption capacity. A further introduction of 1 M KOH solution in the process has the ability to react with the mixture component and efficiently remove the oxyanions that are already in the solution in their absorbed states. This will result to increase in the sizes of the sheets possibly because of the particles growth process that is attachment driven (Aronson, Kinser, Passerini, Smyrl, and Stein 1999). The importance of this process in an industrial process is that helps in developing a highly performing birnessite properties, for instance, the medium sized Mn(III)-rich birnessite that is largely applied in the catalytic and photochemical processes. Also, this process is significantly applied in the understanding of the chemacal structures and composition changes of birnessite that happens to occur naturally (Drits, Silvester, Gorshkov, and Manceau, 1997). Conclusion In recent years, Roman scattering spectroscopy has gained significant usage at a global scale to study the structural features and characteristics of birnessite family of minerals. The massive use of the technology has significantly been influenced by its capability to offer an in depth analysis that directly relates to the manganese dioxide components of the structure that was previously a great challenge. Some manganese ions removed or absorbed from a given solution by birnessite mineral is reported to be significantly bigger than the general reported cation exchange capability (Lanson, Drits, Gaillot, Silvester, Plançon, and Manceau 2002). From the above study, we have analyzed birnessite as one of the most known and common manganese minerals contained in the soils that have a layer of the lattice structure. This structure is characterised by its large surface area and with the lowest degree of zero charges. Also, the coverage of the paper has described the various method of preparation of the birnessite mineral as well as its industrial application in the modern world. Work Cited Aronson, B.J., Kinser, A.K., Passerini, S., Smyrl, W.H. and Stein, A., 1999. Synthesis, characterization, and electrochemical properties of magnesium birnessite and zinc chalcophanite prepared by a low-temperature route. Chemistry of materials, 11(4), pp.949-957. Athouël, L., Moser, F., Dugas, R., Crosnier, O., Bélanger, D. and Brousse, T., 2008. Variation of the MnO2 birnessite structure upon charge/discharge in an electrochemical supercapacitor electrode in aqueous Na2SO4 electrolyte. 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Clays Clay Miner, 37(4), pp.341-7. Post, J.E., Heaney, P.J. and Hanson, J., 2002. Rietveld refinement of a triclinic structure for synthetic Na-birnessite using synchrotron powder diffraction data. Powder Diffraction, 17(3), pp.218-221. Renuka, R. and Ramamurthy, S., 2000. An investigation on layered birnessite type manganese oxides for battery applications. Journal of Power Sources, 87(1), pp.144-152. Scott, M.J. and Morgan, J.J., 1995. Reactions at oxide surfaces. 1. Oxidation of As (III) by synthetic birnessite. Environmental Science & Technology, 29(8), pp.1898-1905. Yang, L.X., Zhu, Y.J. and Cheng, G.F., 2007. Synthesis of well-crystallized birnessite using ethylene glycol as a reducing reagent. Materials research bulletin, 42(1), pp.159-164. Yin, H., Li, H., Wang, Y., Ginder-Vogel, M., Qiu, G., Feng, X., Zheng, L. and Liu, F., 2014. Effects of Co and Ni co-doping on the structure and reactivity of hexagonal birnessite. Chemical Geology, 381, pp.10-20. Read More