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Carbon Dioxide Adsorption on Akageneite, Sphere and Particle Packing, and Ordered Amorphous and Microporous Molecular Sieve Silica
Published in Rolando M.A. Roque-Malherbe, Adsorption and Diffusion in Nanoporous Materials, 2018
Iron oxides, oxide hydroxides, and hydroxides are common compounds. These are some of the most important materials on earth because of their magnetic [1–4], catalytic [5,6], and adsorption [7,8] properties. In particular, the oxide hydroxide akaganeite is an important constituent of soils, geothermal brine deposits, and corrosion products [9–21]. The common structural building block for all the known oxide hydroxides is the Fe(O,OH)6 octahedron organized in different forms [1]. Particularly, the octahedrons that generate the framework produce a hollandite-type structure by displaying the symmetry of the I2/m (No. 12) space group in which four double chains of octahedrons create tunnels with square cross sections [9]. Further, these tunnels are in part occupied by chloride anions whose charges are compensated by protons or positive ions [11,21]. Moreover, the octahedrons are spatially organized to generate two different octahedral sites for the Fe(III) ions to produce antiferromagnetic behavior owing to the alignment of their magnetic moments [10,13]. However, the small size of the crystallites creates a situation where the direction of the magnetic moment of the crystallites turns out to be unsteady and fluctuates, producing superparamagnetism [14].
Preparation of β-FeOOH by ultrasound assisted precipitation route for aqueous supercapacitor applications
Published in Inorganic and Nano-Metal Chemistry, 2023
S. Pavithra, S. P. Keerthana, R. Yuvakumar, P. Senthil Kumar, S. Rajesh, B. Vidhya, A. Sakunthala
Akaganéite (β-FeOOH) is a type of iron oxyhydroxide, scarce in the environment and is found only in highly acidic, and chloride-rich environments such as acidic soils, saline lakes, oceans, hot brines.[13] Since the β-FeOOH has potential uses in diversified applications as discussed above, the simple methods to produce β-FeOOH nanoparticles in large quantities at laboratories are of paramount importance. Herein we report the preparation of β-FeOOH at room temperature using ultrasound assisted simple precipitation method, without the need for any toxic alcohol as solvents, or dispersing/chelating agents and any calcination temperatures. The methodology adopted in the present work has utilized only the property of ultrasound for the formation for the material, making it simple and cost effective. The distilled water was used as the solvent, and hence it makes the method to be environmental friendly, with no toxic organic solvents. Hence the method adopted is easy to scalable. So far, this material is not explored much for the supercapacitor applications. Here, the prepared β-FeOOH nanoparticles were tested for supercapacitor application in different molar concentration of KOH (1 M, 3 M and 5 M) aqueous electrolyte.
Bromate formation control by enhanced ozonation: A critical review
Published in Critical Reviews in Environmental Science and Technology, 2022
Ruchi Joshi, Thunyalux Ratpukdi, Kristofer Knutson, Amit Bhatnagar, Eakalak Khan
Complete removal of BrO3− can be achieved via the surface adsorption of akaganeite, even in the presence of organic compounds. Akaganeite can degrade organic pollutants via surface adsorption, wherein the oxygen-containing functional groups of the organic pollutants react with surface Fe(III) of the catalyst generating Fe(II) and reduce the organic pollutants (Nie et al., 2014). No specific ratio is required for the use of the catalyst with O3, thus reducing operational and monitoring efforts. However, the costs and challenges involved in the synthesis of akageneite make this catalyst less attractive. Moreover, the catalyst needs to be replenished, due to active sites being blocked after the adsorption of BrO3−.