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

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.

The Influence of Copper on Halogenation/Dehalogenation Reactions of Aromatic Compounds and Its Role in the Destruction of Polyhalogenated Aromatic Contaminants

“…The effective role of copper-based catalysis in hydrodechlorination (HDC) processes applicable for wastes contaminated with low concentrations of polychlorinated pollutants has been described [142][143][144][145][146][147][148][149][150][151][152][153][154][155][156][157][158].…”

“…Pyrolysis and combustion are often applied to dismantle e-wastes. The incineration of BFRs-containing e-wastes usually produces, however, polybrominated dibenzo-p-di- Partial HDC of polychlorinated benzenes and regioselective HDC of some chlorinated phenols and chlorinated anilines using Devarda's Al-Cu-Zn alloy in an alkaline aqueous solution at room temperature was studied by Weidlich et al [158]. The HDC activity was explained by the galvanic oxidation of Al from Devarda s Al-Cu-Zn alloy in an aqueous 1 wt.% NaOH solution.…”

“…Scheme 39. Cu-catalyzed HDC of chlorobenzene using NaBH 4 as the reduction agent[156].Similar to the above mentioned HDC mediated by Cu using NaBH 4 reductant, the HDC of DDT (50 ppm in H 2 O) and 2,4,6-TCP (50 ppm in H 2 O) was achieved using a mixture of Devarda's alloy (50% Cu + 45% Al + 5% Zn in quantity 0.5 g/L) and sodium borohydride alloy (1 g NaBH 4 /L) at 80-100 • C[157].Partial HDC of polychlorinated benzenes and regioselective HDC of some chlorinated phenols and chlorinated anilines using Devarda's Al-Cu-Zn alloy in an alkaline aqueous solution at room temperature was studied by Weidlich et al[158]. The HDC activity was explained by the galvanic oxidation of Al from Devarda s Al-Cu-Zn alloy in an aqueous 1 wt.% NaOH solution.…”

Applicability of Nickel-Based Catalytic Systems for Hydrodehalogenation of Recalcitrant Halogenated Aromatic Compounds

“…This alloy contains 50 wt% of Al and 50 wt% of Ni bound in the form of Al 3 Ni and Al 3 Ni 2 . Different bases such as NaOH or KOH [88][89][90][91][92][93][94][95][96][97][98][99][100][101][102][103][104], alkali metal carbonates [89,94,95], NaF [100] or some alkaline salts of complexing agents [91,101] were proved for HDH processes. It was observed that Raney Al-Ni alloy is, especially in diluted aq.…”

The Effect of Shape-Controlled Pt and Pd Nanoparticles on Selective Catalytic Hydrodechlorination of Trichloroethylene

“…Chlorine containing organic molecules have been widely used in industry as dry cleaning solvents for degreasing, as intermediates for the production of refrigerants [1,2] or for micro structured silicon carbide films in semiconductor production [3]. However, the contamination by chlorinated organic compounds is very hazardous for the environment and causes pollution of underground water, depletion of the ozone layer and threats the human health because of toxicity and carcinogenic effects [3][4][5][6][7][8][9][10].…”