Julien LE ROUX - Academia.edu (original) (raw)

Papers by Julien LE ROUX

Research paper thumbnail of Efficient peroxydisulfate activation process not relying on sulfate radical generation for water pollutant degradation

Environmental science & technology, Jan 20, 2014

Peroxydisulfate (PDS) is an appealing oxidant for contaminated groundwater and toxic industrial w... more Peroxydisulfate (PDS) is an appealing oxidant for contaminated groundwater and toxic industrial wastewaters. Activation of PDS is necessary for application because of its low reactivity. Present activation processes always generate sulfate radicals as actual oxidants which unselectively oxidize organics and halide anions reducing oxidation capacity of PDS and producing toxic halogenated products. Here we report that copper oxide (CuO) can efficiently activate PDS under mild conditions without producing sulfate radicals. The PDS/CuO coupled process is most efficient at neutral pH for decomposing a model compound, 2,4-dichlorophenol (2,4-DCP). In a continuous-flow reaction with an empty-bed contact time of 0.55 min, over 90% of 2,4-DCP (initially 20 μM) and 90% of adsorbable organic chlorine (AOCl) can be removed at the PDS/2,4-DCP molar ratio of 1 and 4, respectively. Based on kinetic study and surface characterization, PDS is proposed to be first activated by CuO through outer-sphere interaction, the rate-limiting step, followed by a rapid reaction with 2,4-DCP present in the solution. In the presence of ubiquitous chloride ions in groundwater/industrial wastewater, the PDS/CuO oxidation shows significant advantages over sulfate radical oxidation by achieving much higher 2,4-DCP degradation capacity and avoiding the formation of highly chlorinated degradation products. This work provides a new way of PDS activation for contaminant removal.

Research paper thumbnail of Tracing disinfection byproducts in full-scale desalination plants

Desalination, 2015

The aim of this study was to assess the formation and the behavior of halogenated byproducts (reg... more The aim of this study was to assess the formation and the behavior of halogenated byproducts (regulated THMs and HAAs, as well as nitrogenous, brominated and iodinated DBPs including the emerging iodo-THMs) along the treatment train of full-scale desalination plants. One thermal multi-stage flash distillation (MSF) plant and two reverse osmosis (RO) plants located on the Red Sea coast of Saudi Arabia. DBPs formed during the prechlorination step were efficiently removed along the treatment processes (MSF or RO). Desalination plants fed with good seawater quality and using intermittent chlorine injection did not show high DBP formation and discharge. One RO plant with a lower raw water quality and using continuous chlorination at the intake formed more DBPs. In this plant, some non-regulated DBPs (e.g., dibromoacetonitrile and iodo-THMs) reached the product water in low concentrations (< 1.5 μg/L). Regulated THMs and HAAs were far below their maximum contamination 2 levels set by the US Environmental Protection Agency. Substantial amounts of DBPs are disposed to the sea, low concentrations of DBPs were indeed detected in the water on shore of the desalination plants.

Research paper thumbnail of Chloramination of nitrogenous contaminants (pharmaceuticals and pesticides): NDMA and halogenated DBPs formation

Water Research, 2011

Disinfection with chloramines is often used to reduce the production of regulated disinfection 15... more Disinfection with chloramines is often used to reduce the production of regulated disinfection 15 by-products (DBPs) such as trihalomethanes (THMs) and haloacetic acids (HAAs). However, 16 chloramination can lead to the formation of N-nitrosamines, including N-nitrosodimethylamine 17 (NDMA), a probable human carcinogen. Previous research used dimethylamine (DMA) as a model 18 precursor of NDMA, but certain widely used tertiary dimethylamines (e.g. the pharmaceutical 19 ranitidine) show much higher conversion rates to NDMA than DMA. This study investigates the 20 NDMA formation potential of several tertiary amines including pharmaceuticals and herbicides. The 21 reactivity of these molecules with monochloramine (NH 2 Cl) is studied through the formation of NDMA, 22

Research paper thumbnail of NDMA Formation by Chloramination of Ranitidine: Kinetics and Mechanism

Environmental Science & Technology, 2012

Research paper thumbnail of Formation of NDMA and Halogenated DBPs by Chloramination of Tertiary Amines: The Influence of Bromide Ion

Environmental Science & Technology, 2012

The formation of NDMA and other DBPs (including THMs, HANs, HKs) has been investigated by chloram... more The formation of NDMA and other DBPs (including THMs, HANs, HKs) has been investigated by chloramination of several tertiary amines in the absence and in the presence of bromide ion. NDMA formation from the most reactive tertiary amines (e.g. dimethylaminomethylfurfuryl alcohol or DMP30) was enhanced in the presence of bromide due to the formation of brominated oxidant species such as bromochloramine (NHBrCl) and the hypothetical UDMH-Br as an intermediate. The formation of 2 NDMA by chloramination of less reactive model compounds was inhibited in the presence of bromide. This can be explained by competitive reactions leading to the production of brominated DBPs (i.e. THMs). In the presence of bromide, the formation of brominated THMs during chloramination can be attributed to the presence of small amounts of HOBr produced by the decomposition of chloramines and bromamines. The results are of particular interest to understand NDMA formation mechanisms, especially during chloramination of wastewaters impacted by anthropogenic tertiary amines and containing bromide ion.

Research paper thumbnail of Efficient peroxydisulfate activation process not relying on sulfate radical generation for water pollutant degradation

Environmental science & technology, Jan 20, 2014

Peroxydisulfate (PDS) is an appealing oxidant for contaminated groundwater and toxic industrial w... more Peroxydisulfate (PDS) is an appealing oxidant for contaminated groundwater and toxic industrial wastewaters. Activation of PDS is necessary for application because of its low reactivity. Present activation processes always generate sulfate radicals as actual oxidants which unselectively oxidize organics and halide anions reducing oxidation capacity of PDS and producing toxic halogenated products. Here we report that copper oxide (CuO) can efficiently activate PDS under mild conditions without producing sulfate radicals. The PDS/CuO coupled process is most efficient at neutral pH for decomposing a model compound, 2,4-dichlorophenol (2,4-DCP). In a continuous-flow reaction with an empty-bed contact time of 0.55 min, over 90% of 2,4-DCP (initially 20 μM) and 90% of adsorbable organic chlorine (AOCl) can be removed at the PDS/2,4-DCP molar ratio of 1 and 4, respectively. Based on kinetic study and surface characterization, PDS is proposed to be first activated by CuO through outer-sphere interaction, the rate-limiting step, followed by a rapid reaction with 2,4-DCP present in the solution. In the presence of ubiquitous chloride ions in groundwater/industrial wastewater, the PDS/CuO oxidation shows significant advantages over sulfate radical oxidation by achieving much higher 2,4-DCP degradation capacity and avoiding the formation of highly chlorinated degradation products. This work provides a new way of PDS activation for contaminant removal.

Research paper thumbnail of Tracing disinfection byproducts in full-scale desalination plants

Desalination, 2015

The aim of this study was to assess the formation and the behavior of halogenated byproducts (reg... more The aim of this study was to assess the formation and the behavior of halogenated byproducts (regulated THMs and HAAs, as well as nitrogenous, brominated and iodinated DBPs including the emerging iodo-THMs) along the treatment train of full-scale desalination plants. One thermal multi-stage flash distillation (MSF) plant and two reverse osmosis (RO) plants located on the Red Sea coast of Saudi Arabia. DBPs formed during the prechlorination step were efficiently removed along the treatment processes (MSF or RO). Desalination plants fed with good seawater quality and using intermittent chlorine injection did not show high DBP formation and discharge. One RO plant with a lower raw water quality and using continuous chlorination at the intake formed more DBPs. In this plant, some non-regulated DBPs (e.g., dibromoacetonitrile and iodo-THMs) reached the product water in low concentrations (< 1.5 μg/L). Regulated THMs and HAAs were far below their maximum contamination 2 levels set by the US Environmental Protection Agency. Substantial amounts of DBPs are disposed to the sea, low concentrations of DBPs were indeed detected in the water on shore of the desalination plants.

Research paper thumbnail of Chloramination of nitrogenous contaminants (pharmaceuticals and pesticides): NDMA and halogenated DBPs formation

Water Research, 2011

Disinfection with chloramines is often used to reduce the production of regulated disinfection 15... more Disinfection with chloramines is often used to reduce the production of regulated disinfection 15 by-products (DBPs) such as trihalomethanes (THMs) and haloacetic acids (HAAs). However, 16 chloramination can lead to the formation of N-nitrosamines, including N-nitrosodimethylamine 17 (NDMA), a probable human carcinogen. Previous research used dimethylamine (DMA) as a model 18 precursor of NDMA, but certain widely used tertiary dimethylamines (e.g. the pharmaceutical 19 ranitidine) show much higher conversion rates to NDMA than DMA. This study investigates the 20 NDMA formation potential of several tertiary amines including pharmaceuticals and herbicides. The 21 reactivity of these molecules with monochloramine (NH 2 Cl) is studied through the formation of NDMA, 22

Research paper thumbnail of NDMA Formation by Chloramination of Ranitidine: Kinetics and Mechanism

Environmental Science & Technology, 2012

Research paper thumbnail of Formation of NDMA and Halogenated DBPs by Chloramination of Tertiary Amines: The Influence of Bromide Ion

Environmental Science & Technology, 2012

The formation of NDMA and other DBPs (including THMs, HANs, HKs) has been investigated by chloram... more The formation of NDMA and other DBPs (including THMs, HANs, HKs) has been investigated by chloramination of several tertiary amines in the absence and in the presence of bromide ion. NDMA formation from the most reactive tertiary amines (e.g. dimethylaminomethylfurfuryl alcohol or DMP30) was enhanced in the presence of bromide due to the formation of brominated oxidant species such as bromochloramine (NHBrCl) and the hypothetical UDMH-Br as an intermediate. The formation of 2 NDMA by chloramination of less reactive model compounds was inhibited in the presence of bromide. This can be explained by competitive reactions leading to the production of brominated DBPs (i.e. THMs). In the presence of bromide, the formation of brominated THMs during chloramination can be attributed to the presence of small amounts of HOBr produced by the decomposition of chloramines and bromamines. The results are of particular interest to understand NDMA formation mechanisms, especially during chloramination of wastewaters impacted by anthropogenic tertiary amines and containing bromide ion.