Abstract
Para-, or 4-nitrophenol, and related nitroaromatics are broadly used compounds in industrial processes and as a result are among the most common anthropogenic pollutants in aqueous industrial effluent; this requires development of practical remediation strategies. Their catalytic reduction to the less toxic and synthetically desirable aminophenols is one strategy. However, to date, the majority of work focuses on catalysts based on precisely tailored, and often noble metal-based nanoparticles. The cost of such systems hampers practical, larger scale application. We report a facile route to bulk cobalt oxide-based materials, via a combined mechanochemical and calcination approach. Vibratory ball milling of CoCl2(H2O)6 with KOH, and subsequent calcination afforded three cobalt oxide-based materials with different combinations of CoO(OH), Co(OH)2, and Co3O4 with different crystallite domains/sizes and surface areas; Co@100, Co@350 and Co@600 (Co@###; # = calcination temp). All three prove active for the catalytic reduction of 4-nitrophenol and related aminonitrophenols. In the case of 4-nitrophenol, Co@350 proved to be the most active catalyst, therein its retention of activity over prolonged exposure to air, moisture, and reducing environments, and applicability in flow processes is demonstrated.
Highlights
Para, or 4-nitrophenol (4NP), and more broadly, compounds in the nitroaromatic family are widely used in the industrial fabrication of pharmaceuticals, explosives, pesticides, pigments, and dyes [1,2,3,4].As a result, nitroaromatics have become a very common anthropogenic pollutant arising from aqueous industrial effluent
Reduction of nitrophenols is typically carried out by either noble-metal nanoparticles, or alternatives synthesized with precise control over size and shape
This requires a significant expenditure of either material cost, experimental effort, or in many cases, both
Summary
Para-, or 4-nitrophenol (4NP), and more broadly, compounds in the nitroaromatic family are widely used in the industrial fabrication of pharmaceuticals, explosives, pesticides, pigments, and dyes [1,2,3,4].As a result, nitroaromatics have become a very common anthropogenic pollutant arising from aqueous industrial effluent. While many nitroaromatics have been shown to display acute are mutagenic, and either potential or established carcinogens [5,6,7], their reduction products, aniline toxicity, are mutagenic, and either potential or established carcinogens [5,6,7], their reduction derivatives, are typically less toxic, commercially important synthetic intermediates. Products, aniline derivatives, are typically less toxic, commercially important synthetic the reduction product of 4NP is 4-aminophenol (4AP); a useful component for the synthesis of intermediates. The aqueous catalytic reduction of component for the synthesis of dyes, agrochemicals, and pharmaceuticals [8,9,10,11]. The oxide nanoparticles have drawn significant interest as active, low-cost alternatives to the noble metal
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