IntroductionBirnessite 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.