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Open AccessArticle

Microstructural Transformation and Hydrogen Generation Performance of Magnesium Scrap Ball Milled with Devarda’s Alloy

by Olesya A. Buryakovskaya and Mikhail S. Vlaskin

Materials 2022, 15(22), 8058; https://doi.org/10.3390/ma15228058 - 15 Nov 2022

Cited by 9 | Viewed by 2404

A method for magnesium scrap transformation into highly efficient hydroreactive material was elaborated. Tested samples were manufactured of magnesium scrap with no additives, or 5 and 10 wt.% Devarda’s alloy, by ball milling for 0.5, 1, 2, and 4 h. Their microstructural evolution and reaction kinetics in 3.5 wt.% NaCl solution were investigated. For the samples with additives and of scrap only, microstructural evolution included the formation of large plane-shaped pieces (0.5 and 1 h) with their further transformation into small compacted solid-shaped objects (2 and 4 h), along with accumulation of crystal lattice imperfections favoring pitting corrosion, and magnesium oxidation with residual oxygen under prolonged (4 h) ball milling, resulting in the lowest reactions rates. Modification with Devarda’s alloy accelerated microstructural evolution (during 0.5–1 h) and the creation of ‘microgalvanic cells’, enhancing magnesium galvanic corrosion with hydrogen evolution. The 1 h milled samples, with 5 wt.% Devarda’s alloy and without additives, provided the highest hydrogen yields of (95.36 ± 0.38)% and (91.12 ± 1.19)%; maximum reaction rates achieved 470.9 and 143.4 mL/g/min, respectively. Such high results were explained by the combination of the largest specific surface areas, accumulated lattice imperfections, and ‘microgalvanic cells’ (from additive). The optimal values were 1 h of milling and 5 wt.% of additive. Full article

(This article belongs to the Special Issue Metallurgy of II-VI Groups Metals)

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25 pages, 5385 KB

Open AccessArticle

Cu-Catalyzed Hydrodehalogenation of Brominated Aromatic Pollutants in Aqueous Solution

by Tomáš Weidlich, Barbora Kamenická, Ludvík Beneš, Veronika Čičmancová, Alena Komersová, Jiří Čermák and Petr Švec

Catalysts 2021, 11(6), 699; https://doi.org/10.3390/catal11060699 - 31 May 2021

Cited by 4 | Viewed by 3661

Abstract

The catalytic effect of copper in Devarda’s Al-Cu-Zn alloy (Dev. alloy) and sole metallic copper, copper salts and copper oxides in the coaction of NaBH₄ within the hydrodehalogenation (HDH) of polybrominated phenols, such as the herbicide Bromoxynil in alkaline aqueous solution has been investigated. Namely, the hydrodebromination (HDB) activity of Dev. alloy/NaOH system has been compared to heterogeneous Cu-based catalysts using NaBH₄ as a reductant. Differences in the solid-state structures of used Cu-based heterogeneous catalysts after the mentioned HDB process have been studied using the powder XRD and SEM techniques. It was found that some of the used copper-based catalysts are reusable and reasonably effective even at room temperature. Efficiency of the most promising copper-based reduction systems (Dev. alloy/NaOH and Cu-based catalysts/NaBH₄) have been successfully tested within the HDB of industrially important brominated flame retardant tetrabromobisphenol A (TBBPA). Dev. alloy/NaOH and Cu-based catalyst generated in-situ within the CuSO₄/NaBH₄ produced were recognized as the most active HDB agents for complete debromination of both BRX and TBBPA. Full article

(This article belongs to the Special Issue Gold, Silver and Copper Catalysis)

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21 pages, 5274 KB

Open AccessArticle

Hydrodechlorination of Different Chloroaromatic Compounds at Room Temperature and Ambient Pressure—Differences in Reactivity of Cu- and Ni-Based Al Alloys in an Alkaline Aqueous Solution

by Tomáš Weidlich, Barbora Kamenická, Klára Melánová, Veronika Čičmancová, Alena Komersová and Jiří Čermák

Catalysts 2020, 10(9), 994; https://doi.org/10.3390/catal10090994 - 1 Sep 2020

Cited by 16 | Viewed by 4564

Abstract

It is well known that the hydrodechlorination (HDC) of chlorinated aromatic contaminants in aqueous effluents enables a significant increase in biodegradability. HDC consumes a low quantity of reactants producing corresponding non-chlorinated and much more biodegradable organic compounds. Two commonly used precious metals free Al alloys (Raney Al-Ni and Devarda’s Al-Cu-Zn) were compared in reductive action in an alkaline aqueous solution. Raney Al-Ni alloy was examined as a universal and extremely effective HDC agent in a diluted aqueous NaOH solution. The robustness of Raney Al-Ni activity is illustrated in the case of HDC of polychlorinated aromatic compounds mixture in actual waste water. In contrast, Devarda’s Al-Cu-Zn alloy was approved as much less active for HDC of the tested chlorinated aromatic compounds, but with a surprisingly high selectivity on cleavage of C-Cl bonds in the meta and sometimes the ortho position in chlorinated aniline and sometimes chlorinated phenol structures. The reaction of both tested alloys with chlorinated aromatic compounds in the aqueous NaOH solution is accompanied by dissolution of aluminum. Dissolved Al in the alkaline HDC reaction mixture is very useful for subsequent treatment of HDC products by coagulation and flocculation of Al(OH)₃ caused by simple neutralization of the alkaline aqueous phase after the HDC reaction. Full article

(This article belongs to the Special Issue Progress in Catalytic Hydrodechlorination)

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13 pages, 1775 KB

Open AccessArticle

Development of Colorimetric and Ratiometric Fluorescence Membranes for Detection of Nitrate in the Presence of Aluminum-Containing Compounds

by Hong Dinh Duong, Han Lae Kim and Jong Il Rhee

Sensors 2018, 18(9), 2883; https://doi.org/10.3390/s18092883 - 31 Aug 2018

Cited by 10 | Viewed by 4551

Abstract

In this study, a quantitative analysis of nitrate in aqueous solution was performed through the combination of an oxazine170 perchlorate–ethyl cellulose (O17-EC) membrane with aluminum-containing compounds. Aluminum of Devarda’s alloy (DA) or a clay hydrotalcite (HT) was employed for the reduction of nitrate to produce ammonia, and the produced ammonia was detected by the O17-EC membrane. The method of combining the O17-EC membrane with aluminum compounds has showed a broad detection range of nitrate. That is, the DA was combined with the O17-EC membrane and showed the linear nitrate detection ranges of 1–10 mM and 10–100 mM, while the O17-EC membrane immobilized with the clay HT showed a linear detection range of 0.1–1 mM nitrate. The visual color transition of the nitrate-sensing membranes at different nitrate concentrations was clearly observed under sunlight or irradiation of a light-emitting diode (LED) at an excitation wavelength of 470 nm (LED470). Full article

(This article belongs to the Special Issue Colorimetric and Fluorescent Sensors 2018)

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