Wet Peroxide Oxidation of Chlorobenzenes Catalyzed by Goethite and Promoted by Hydroxylamine

Abstract

In this work, the abatement of several chlorobenzenes commonly found as pollutants in the aqueous phase has been carried out by catalytic wet peroxide oxidation using goethite as the catalyst and hydroxylamine as the promotor. Spiked water with monochlorobenzene and different positional isomers of dichlorobenzene, trichlorobenzene, and tetrachlorobenzene, at concentrations ranging from 0.4 to 16.9 mg L−1 was treated. Runs were carried out batch-way, at room conditions, without headspace. The heterogeneous catalyst was commercial goethite, with a specific surface area (SBET) of 10.24 m2 g−1 and a total iron content of 57.3 wt%. Iron acts as a catalyst of hydrogen peroxide decomposition to hydroxyl radicals. Hydroxylamine (in a range from 0 to 4.9 mM) was added to enhance the iron redox cycle from Fe (III) to Fe (II), remarkably increasing the radical production rate and therefore, the conversion of chlorobenzenes. Iron was stable (not leached to the aqueous phase) even at the lowest pH tested (pH = 1). The effect of pH (from 2 to 7), hydrogen peroxide (from 1 to 10 times the stoichiometric dosage), hydroxylamine, and catalyst concentration (from 0.25 to 1 g/L) was studied. Pollutant removal increased with hydroxylamine and hydrogen peroxide concentration. An operating conditions study demonstrated that the higher the hydroxylamine and hydrogen peroxide concentrations, the higher the removal of pollutants. The optimal pH value and catalyst concentration was 3 and 0.5 g L−1, respectively. Operating with 2.4 mM of hydroxylamine and 10 times the stoichiometric H2O2 amount, a chlorobenzenes conversion of 90% was achieved in 2.5 h. Additionally, no toxic byproducts were obtained.

A novel and stable hydroxylamine salt generated from betaine hydrochloride and its application in the synthesis of cyclohexanone oxime

“…Hydroxylamine (NH 2 OH) is a versatile chemical, which plays an important role in various applications ranging from degradation of organic pollutants to pharmaceutical production, as well as in large-scale synthesis of cyclohexanone oxime for nylon 6 manufacture. [1][2][3][4][5] However, it contains an N-oxyenamine moiety, which is quite unstable and decomposes even at room temperature due to the low N O ⊞-bond energy at ca 57 kcal mol −1 , meaning that the handling of NH 2 OH as a free base is a challenge. [6][7][8][9] Two well-known catastrophic industrial explosions involving NH 2 OH occurred in Pennsylvania, USA, and in Gunnma, Japan, in 1999 and 2000, respectively.…”

Abatement of 1,2,4-Trichlorobencene by Wet Peroxide Oxidation Catalysed by Goethite and Enhanced by Visible LED Light at Neutral pH

“…In this way, it was found that hydroxylamine (HA) enhanced the redox cycle of the iron contained in goethite when this mineral was used to abate organic pollutants by CWPO [18]. The addition of HA has also been successfully tested in chlorobenzenes abatement by hydrogen peroxide and goethite [29]. This material was stable, and no iron leaching was found despite the acid pH used (acid pH was required for oxidising the chlorobenzenes) [29].…”

“…The addition of HA has also been successfully tested in chlorobenzenes abatement by hydrogen peroxide and goethite [29]. This material was stable, and no iron leaching was found despite the acid pH used (acid pH was required for oxidising the chlorobenzenes) [29]. However, although this reducing agent greatly increases the efficiency of the process, the addition of HA to the reaction system introduces an additional cost and risk to the environment, so other options should be explored.…”

Application of Chelating Agents to Enhance Fenton Process in Soil Remediation: A Review

“…The interest in using heterogeneous catalysts in the Fenton process (known as catalytic wet peroxide oxidation process, CWPO) has significantly increased in recent times [12]. CWPO uses natural iron-containing materials [12][13][14], supported catalysts with high surface area-supports (pillared clays, zeolites, silica, activated carbon, etc. ), allowing the dispersion of the active phase (mainly Fe, but also Cu, Mn, Au, etc.)…”