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William A Mitch - One of the best experts on this subject based on the ideXlab platform.
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predicting the contribution of Chloramines to contaminant decay during ultraviolet hydrogen peroxide advanced oxidation process treatment for potable reuse
Environmental Science & Technology, 2019Co-Authors: Zhong Zhang, Yi-hsueh Chuang, Nan Huang, William A MitchAbstract:Chloramines applied to control membrane biofouling in potable reuse trains pass through reverse osmosis membranes, such that downstream ultraviolet (UV)/H2O2 advanced oxidation processes (AOPs) are de facto UV/H2O2-Chloramine AOPs. Current models for UV/Chloramine AOPs, which use inaccurate Chloramine quantum yields and ignore the fate of •NH2, are unable to simultaneously predict the loss of Chloramines and contaminants, such as 1,4-dioxane. This study determined quantum yields for NH2Cl (0.35) and NHCl2 (0.75). Incorporating these quantum yields and the formation from •NH2 of the radical scavengers, •NO and NO2–, was important for simultaneously modeling the loss of Chloramines, H2O2, and 1,4-dioxane in the UV/H2O2-Chloramine AOP. Although the level of radical production was higher for the UV/H2O2-Chloramine AOP than for the UV/H2O2 AOP, the UV/H2O2 AOP was at least 2-fold more efficient with respect to 1,4-dioxane degradation, because Chloramines efficiently scavenged radicals. At low Chloramine concen...
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Predicting the Contribution of Chloramines to Contaminant Decay during Ultraviolet/Hydrogen Peroxide Advanced Oxidation Process Treatment for Potable Reuse
2019Co-Authors: Zhong Zhang, Yi-hsueh Chuang, Nan Huang, William A MitchAbstract:Chloramines applied to control membrane biofouling in potable reuse trains pass through reverse osmosis membranes, such that downstream ultraviolet (UV)/H2O2 advanced oxidation processes (AOPs) are de facto UV/H2O2-Chloramine AOPs. Current models for UV/Chloramine AOPs, which use inaccurate Chloramine quantum yields and ignore the fate of •NH2, are unable to simultaneously predict the loss of Chloramines and contaminants, such as 1,4-dioxane. This study determined quantum yields for NH2Cl (0.35) and NHCl2 (0.75). Incorporating these quantum yields and the formation from •NH2 of the radical scavengers, •NO and NO2–, was important for simultaneously modeling the loss of Chloramines, H2O2, and 1,4-dioxane in the UV/H2O2-Chloramine AOP. Although the level of radical production was higher for the UV/H2O2-Chloramine AOP than for the UV/H2O2 AOP, the UV/H2O2 AOP was at least 2-fold more efficient with respect to 1,4-dioxane degradation, because Chloramines efficiently scavenged radicals. At low Chloramine concentrations, the UV/Chloramine AOP efficiency increased with an increase in Chloramine concentration, as the level of radical production increased relative to that of radical scavenging by the dissolved organic carbon in RO permeate. However, the efficiency leveled out at higher Chloramine concentrations as radical scavenging by Chloramines offset the increased level of radical production. The level of 1,4-dioxane degradation was ∼30–50% lower for the UV/Chloramine AOP than for the UV/H2O2-Chloramine AOP when the concentration of residual Chloramines in RO permeate was ∼50 μM (3.3 mg/L as Cl2). Initial cost estimates indicate that the UV/Chloramine AOP using the residual Chloramines in RO permeate could be a cost-effective alternative to the current UV/H2O2-Chloramine AOP in some cases, because the savings in reagent costs offset the ∼30–50% reduction in 1,4-dioxane degradation efficiency
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tradeoffs between pathogen inactivation and disinfection byproduct formation during sequential chlorine and Chloramine disinfection for wastewater reuse
Water Research, 2018Co-Authors: Kirin E Furst, Brian M Pecson, Brie D Webber, William A MitchAbstract:Treatment of fully nitrified municipal wastewater effluents with chlorine followed by Chloramines (i.e., sequential chlorine disinfection) upstream of advanced treatment trains can contribute pathogen inactivation credits for potable reuse while leaving a Chloramine residual to control biofouling on membrane units in the advanced treatment train. However, free chlorine exposures must be optimized to maximize pathogen inactivation while minimizing the formation of disinfection byproducts (DBPs) that are challenging to remove in the advanced treatment train. Using a pilot-scale disinfection contactor receiving fully-nitrified, tertiary municipal wastewater effluent, this study found that a 3 mg × min/L free chlorine CT (i.e., the product of the chlorine residual "C" and the contact time "T") followed by a 140 mg × min/L Chloramine CT could reliably achieve 5-log inactivation of MS2 bacteriophage and reduce median total coliform concentrations below 2.2 MPN/100 mL. Free chlorine disinfection was equally effective when chlorine was dosed to exceed the breakpoint for 1 mg/L of ammonia as N. At this free chlorine exposure, regulated trihalomethane (THM) and haloacetic acid (HAA) formation remained below their Maximum Contaminant Levels (MCLs), but NDMA concentrations of ∼30 ng/L were above the 10 ng/L California Notification Level. Increasing the free chlorine exposure to ∼30 mg × min/L increased THM and HAA formation, with regulated THMs approaching or exceeding the MCL. Although this free chlorine exposure prevented NDMA formation during chloramination, the ∼10 ng/L background NDMA formation in the tertiary effluent remained. Increasing the free chlorine exposure also increased the formation of unregulated halogenated DBP classes that may be significant contributors to the DBP-associated toxicity of the disinfected wastewater. The results indicate that sequential chlorination can be used to optimize the benefits of free chlorine (virus and NDMA control) and Chloramine disinfection (THM, HAA, and coliform control).
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reverse osmosis shifts Chloramine speciation causing re formation of ndma during potable reuse of wastewater
Environmental Science & Technology, 2017Co-Authors: Daniel L Mccurry, William A Mitch, Kenneth P. Ishida, Gregg L. OelkerAbstract:UV-based advanced oxidation processes (AOPs) effectively degrade N-nitrosodimethylamine (NDMA) passing through reverse osmosis (RO) units within advanced treatment trains for the potable reuse of municipal wastewater. However, certain utilities have observed the re-formation of NDMA after the AOP from reactions between residual Chloramines and NDMA precursors in the AOP product water. Using kinetic modeling and bench-scale RO experiments, we demonstrate that the low pH in the RO permeate (∼5.5) coupled with the effective rejection of NH4+ promotes conversion of the residual monoChloramine (NH2Cl) in the permeate to diChloramine (NHCl2) via the reaction: 2 NH2Cl + H+ ↔ NHCl2 + NH4+. DiChloramine is the Chloramine species known to react with NDMA precursors to form NDMA. After UV/AOP, utilities generally use lime or other techniques to increase the pH of the finished water to prevent distribution system corrosion. Modeling indicated that, while the increase in pH halts diChloramine formation, it converts am...
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Reverse Osmosis Shifts Chloramine Speciation Causing Re-Formation of NDMA during Potable Reuse of Wastewater
2017Co-Authors: Daniel L Mccurry, Kenneth P. Ishida, Gregg L. Oelker, William A MitchAbstract:UV-based advanced oxidation processes (AOPs) effectively degrade N-nitrosodimethylamine (NDMA) passing through reverse osmosis (RO) units within advanced treatment trains for the potable reuse of municipal wastewater. However, certain utilities have observed the re-formation of NDMA after the AOP from reactions between residual Chloramines and NDMA precursors in the AOP product water. Using kinetic modeling and bench-scale RO experiments, we demonstrate that the low pH in the RO permeate (∼5.5) coupled with the effective rejection of NH4+ promotes conversion of the residual monoChloramine (NH2Cl) in the permeate to diChloramine (NHCl2) via the reaction: 2 NH2Cl + H+ ↔ NHCl2 + NH4+. DiChloramine is the Chloramine species known to react with NDMA precursors to form NDMA. After UV/AOP, utilities generally use lime or other techniques to increase the pH of the finished water to prevent distribution system corrosion. Modeling indicated that, while the increase in pH halts diChloramine formation, it converts amine-based NDMA precursors to their more reactive, neutral forms. With modeling, and experiments at both bench-scale and field-scale, we demonstrate that reducing the time interval between RO treatment and final pH adjustment can significantly reduce NDMA re-formation by minimizing the amount of diChloramine formed prior to reaching the final target pH
Shumin Zhu - One of the best experts on this subject based on the ideXlab platform.
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Role of reactive nitrogen species in ranitidine degradation in UV/Chloramine process: Transformation pathways and NDMA formation
Chemical Engineering Journal, 2021Co-Authors: Shumin Zhu, Jue Wang, Jing Deng, Shiqing ZhouAbstract:Abstract Chloramine under UV photolysis could not only produce the widely known hydroxyl radical (HO•) and reactive chlorine species (RCS; e.g., ClO•, Cl2•− and Cl•), but also produce reactive nitrogen species (RNS; e.g., •NH2, •NO and •NO2). In this study, the kinetic mechanisms, degradation products, N-Nitrosodimethylamine (NDMA) formation of RAN in the UV/Chloramine process were investigated. The RAN degradation by UV/Chloramine process well fitted the pseudo-first order kinetic model and exhibited a synergistic improvement compared with UV photolysis and chloramination alone. HO• is the predominant radical that contributes to RAN degradation in the range of solution pH from 6.0 to 8.0 (from 43.4% to 56.3%), and RNS was confirmed to contribute to RAN degradation through experiments. As the concentrations of HCO3−, Cl− and NO3− (0 ~ 4 mM), Chloramine dosage (200 ~ 300 μM), solution pH (6.0 ~ 8.0) and natural organic matter (0 ~ 4 mg-C L-1) increased, the RAN degradation in UV/Chloramine process was inhibited. Besides, the second-order rate constant between CO3•- and RAN was determined to be 8.05 × 106 M−1 s−1 in this study. A possible pathway and reaction schemes of RAN degradation by UV/Chloramine process were proposed, which could also be used to explain the role of RNS in the NDMA formation. During the treatment of RAN by chloramination alone and UV/Chloramine, NDMA has a better formation potential at both pH = 7.0 and pH = 8.0. Although RNS were responsible for NDMA formation during the RAN degradation by UV/Chloramine process, UV photolysis and extending the photolysis time from 5 to 10 min could degrade NDMA and its precursors. Overall, the high yield and toxicity of NDMA should be concerned when choosing the UV/Chloramine process.
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comparison of diatrizoate degradation by uv chlorine and uv Chloramine processes kinetic mechanisms and iodinated disinfection byproducts formation
Chemical Engineering Journal, 2019Co-Authors: Shumin Zhu, Weiqiu Zhang, Shiqing ZhouAbstract:Abstract This study compared the degradation efficiency of diatrizoate (DTA) by UV/chlorine and UV/Chloramine processes. DTA could be effectively degraded by the UV/chlorine and UV/Chloramine processes compared with chlorination and chloramination solely. Although the UV/chlorine process was more sensitive to the variations of oxidant dosages, solution pH, the concentration of bicarbonate and chloride, UV/chlorine degraded DTA more efficiently than UV/Chloramine process. The reactive chlorine species (RCS) and hydroxyl radical (HO ) are predominant contributors to DTA degradation in the UV/chlorine and UV/Chloramine processes respectively, and the specific contribution of each reactive specie changed with solution pH. The performance of UV/chlorine and UV/Chloramine processes on DTA degradation was obviously inhibited in natural waters (e.g., wastewater, rainwater, river water and tap water), however, degradation of DTA in the UV/chlorine are still satisfactory compared with UV/Chloramine process. Formation of chloroform, dichloroacetonitrile, and iodoform (IF) from DTA was observed in both UV/chlorine and UV/Chloramine processes. It is notable that formation potential of IF from DTA was significantly enhanced in UV/Chloramine process, and thus the overall cytotoxicity of generated DBPs in UV/Chloramine process is far greater than that in UV/chlorine process.
Shiqing Zhou - One of the best experts on this subject based on the ideXlab platform.
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Role of reactive nitrogen species in ranitidine degradation in UV/Chloramine process: Transformation pathways and NDMA formation
Chemical Engineering Journal, 2021Co-Authors: Shumin Zhu, Jue Wang, Jing Deng, Shiqing ZhouAbstract:Abstract Chloramine under UV photolysis could not only produce the widely known hydroxyl radical (HO•) and reactive chlorine species (RCS; e.g., ClO•, Cl2•− and Cl•), but also produce reactive nitrogen species (RNS; e.g., •NH2, •NO and •NO2). In this study, the kinetic mechanisms, degradation products, N-Nitrosodimethylamine (NDMA) formation of RAN in the UV/Chloramine process were investigated. The RAN degradation by UV/Chloramine process well fitted the pseudo-first order kinetic model and exhibited a synergistic improvement compared with UV photolysis and chloramination alone. HO• is the predominant radical that contributes to RAN degradation in the range of solution pH from 6.0 to 8.0 (from 43.4% to 56.3%), and RNS was confirmed to contribute to RAN degradation through experiments. As the concentrations of HCO3−, Cl− and NO3− (0 ~ 4 mM), Chloramine dosage (200 ~ 300 μM), solution pH (6.0 ~ 8.0) and natural organic matter (0 ~ 4 mg-C L-1) increased, the RAN degradation in UV/Chloramine process was inhibited. Besides, the second-order rate constant between CO3•- and RAN was determined to be 8.05 × 106 M−1 s−1 in this study. A possible pathway and reaction schemes of RAN degradation by UV/Chloramine process were proposed, which could also be used to explain the role of RNS in the NDMA formation. During the treatment of RAN by chloramination alone and UV/Chloramine, NDMA has a better formation potential at both pH = 7.0 and pH = 8.0. Although RNS were responsible for NDMA formation during the RAN degradation by UV/Chloramine process, UV photolysis and extending the photolysis time from 5 to 10 min could degrade NDMA and its precursors. Overall, the high yield and toxicity of NDMA should be concerned when choosing the UV/Chloramine process.
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comparison of diatrizoate degradation by uv chlorine and uv Chloramine processes kinetic mechanisms and iodinated disinfection byproducts formation
Chemical Engineering Journal, 2019Co-Authors: Shumin Zhu, Weiqiu Zhang, Shiqing ZhouAbstract:Abstract This study compared the degradation efficiency of diatrizoate (DTA) by UV/chlorine and UV/Chloramine processes. DTA could be effectively degraded by the UV/chlorine and UV/Chloramine processes compared with chlorination and chloramination solely. Although the UV/chlorine process was more sensitive to the variations of oxidant dosages, solution pH, the concentration of bicarbonate and chloride, UV/chlorine degraded DTA more efficiently than UV/Chloramine process. The reactive chlorine species (RCS) and hydroxyl radical (HO ) are predominant contributors to DTA degradation in the UV/chlorine and UV/Chloramine processes respectively, and the specific contribution of each reactive specie changed with solution pH. The performance of UV/chlorine and UV/Chloramine processes on DTA degradation was obviously inhibited in natural waters (e.g., wastewater, rainwater, river water and tap water), however, degradation of DTA in the UV/chlorine are still satisfactory compared with UV/Chloramine process. Formation of chloroform, dichloroacetonitrile, and iodoform (IF) from DTA was observed in both UV/chlorine and UV/Chloramine processes. It is notable that formation potential of IF from DTA was significantly enhanced in UV/Chloramine process, and thus the overall cytotoxicity of generated DBPs in UV/Chloramine process is far greater than that in UV/chlorine process.
Yi-hsueh Chuang - One of the best experts on this subject based on the ideXlab platform.
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predicting the contribution of Chloramines to contaminant decay during ultraviolet hydrogen peroxide advanced oxidation process treatment for potable reuse
Environmental Science & Technology, 2019Co-Authors: Zhong Zhang, Yi-hsueh Chuang, Nan Huang, William A MitchAbstract:Chloramines applied to control membrane biofouling in potable reuse trains pass through reverse osmosis membranes, such that downstream ultraviolet (UV)/H2O2 advanced oxidation processes (AOPs) are de facto UV/H2O2-Chloramine AOPs. Current models for UV/Chloramine AOPs, which use inaccurate Chloramine quantum yields and ignore the fate of •NH2, are unable to simultaneously predict the loss of Chloramines and contaminants, such as 1,4-dioxane. This study determined quantum yields for NH2Cl (0.35) and NHCl2 (0.75). Incorporating these quantum yields and the formation from •NH2 of the radical scavengers, •NO and NO2–, was important for simultaneously modeling the loss of Chloramines, H2O2, and 1,4-dioxane in the UV/H2O2-Chloramine AOP. Although the level of radical production was higher for the UV/H2O2-Chloramine AOP than for the UV/H2O2 AOP, the UV/H2O2 AOP was at least 2-fold more efficient with respect to 1,4-dioxane degradation, because Chloramines efficiently scavenged radicals. At low Chloramine concen...
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Predicting the Contribution of Chloramines to Contaminant Decay during Ultraviolet/Hydrogen Peroxide Advanced Oxidation Process Treatment for Potable Reuse
2019Co-Authors: Zhong Zhang, Yi-hsueh Chuang, Nan Huang, William A MitchAbstract:Chloramines applied to control membrane biofouling in potable reuse trains pass through reverse osmosis membranes, such that downstream ultraviolet (UV)/H2O2 advanced oxidation processes (AOPs) are de facto UV/H2O2-Chloramine AOPs. Current models for UV/Chloramine AOPs, which use inaccurate Chloramine quantum yields and ignore the fate of •NH2, are unable to simultaneously predict the loss of Chloramines and contaminants, such as 1,4-dioxane. This study determined quantum yields for NH2Cl (0.35) and NHCl2 (0.75). Incorporating these quantum yields and the formation from •NH2 of the radical scavengers, •NO and NO2–, was important for simultaneously modeling the loss of Chloramines, H2O2, and 1,4-dioxane in the UV/H2O2-Chloramine AOP. Although the level of radical production was higher for the UV/H2O2-Chloramine AOP than for the UV/H2O2 AOP, the UV/H2O2 AOP was at least 2-fold more efficient with respect to 1,4-dioxane degradation, because Chloramines efficiently scavenged radicals. At low Chloramine concentrations, the UV/Chloramine AOP efficiency increased with an increase in Chloramine concentration, as the level of radical production increased relative to that of radical scavenging by the dissolved organic carbon in RO permeate. However, the efficiency leveled out at higher Chloramine concentrations as radical scavenging by Chloramines offset the increased level of radical production. The level of 1,4-dioxane degradation was ∼30–50% lower for the UV/Chloramine AOP than for the UV/H2O2-Chloramine AOP when the concentration of residual Chloramines in RO permeate was ∼50 μM (3.3 mg/L as Cl2). Initial cost estimates indicate that the UV/Chloramine AOP using the residual Chloramines in RO permeate could be a cost-effective alternative to the current UV/H2O2-Chloramine AOP in some cases, because the savings in reagent costs offset the ∼30–50% reduction in 1,4-dioxane degradation efficiency
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Comparing the UV/MonoChloramine and UV/Free Chlorine Advanced Oxidation Processes (AOPs) to the UV/Hydrogen Peroxide AOP Under Scenarios Relevant to Potable Reuse
2017Co-Authors: Yi-hsueh Chuang, Serena Chen, Curtis J. Chinn, William A MitchAbstract:Utilities incorporating the potable reuse of municipal wastewater are interested in converting from the UV/H2O2 to the UV/free chlorine advanced oxidation process (AOP). The AOP treatment of reverse osmosis (RO) permeate often includes the de facto UV/Chloramine AOP because Chloramines applied upstream permeate RO membranes. Models are needed that accurately predict oxidant photolysis and subsequent radical reactions. By combining radical scavengers and kinetic modeling, we have derived quantum yields for radical generation by the UV photolysis of HOCl, OCl–, and NH2Cl of 0.62, 0.55, and 0.20, respectively, far below previous estimates that incorporated subsequent free chlorine or Chloramine scavenging by the •Cl and •OH daughter radicals. The observed quantum yield for free chlorine loss actually decreased with increasing free chlorine concentration, suggesting scavenging of radicals participating in free chlorine chain decomposition and even free chlorine reformation. Consideration of reactions of •ClO and its daughter products (e.g., ClO2–), not included in previous models, were critical for modeling free chlorine loss. Radical reactions (indirect photolysis) accounted for ∼50% of Chloramine decay and ∼80% of free chlorine loss or reformation. The performance of the UV/Chloramine AOP was comparable to the UV/H2O2 AOP for degradation of 1,4-dioxane, benzoate and carbamazepine across pH 5.5–8.3. The UV/free chlorine AOP was more efficient at pH 5.5, but only by 30% for 1,4-dioxane. At pH 7.0–8.3, the UV/free chlorine AOP was less efficient. •Cl converts to •OH. The modeled •Cl:•OH ratio was ∼20% for the UV/free chlorine AOP and ∼35% for the UV/Chloramine AOP such that •OH was generally more important for contaminant degradation
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the contribution of dissolved organic nitrogen and Chloramines to nitrogenous disinfection byproduct formation from natural organic matter
Water Research, 2013Co-Authors: Yi-hsueh Chuang, Angela Yu-chen Lin, Xiaohuan Wang, Hsin-hsin TungAbstract:Abstract The direct incorporation of Chloramines and dissolved organic nitrogen (DON) may provide the nitrogen for nitrogenous disinfection byproducts (N-DBPs). This study explores the contributions of natural DON and Chloramine incorporation to the formation of N-DBPs during chloramination. This study also evaluates the relationship between N-DBPs and carbonaceous DBPs by investigating four sources of dissolved organic matter with different DON-to-dissolved organic carbon (DOC) ratios. During chloramination, dihaloacetonitrile (DXAN) formation is correlated with the summation of trihalomethanes (THMs) and dichloroacetic acids (DXAAs) yield in molar basis at pH > 6. This study tests the formation kinetics of THMs, DXAAs, and DXANs during chloramination, explores the changes in DBP formation potential before and after a sequence of ozonation and chloramination, and tracks the nitrogen source of dichloroacetonitrile. The results support the hypothesis that THMs, DXAAs, and DXANs mainly derive from similar precursors upon chloramination. In addition, the precursor of HANs was approximately 10% (on a molar basis) of that of THMs and HAAs combined. The N-nitrosodimethylamine (NDMA) formation potential is correlated with DON/DOC in hydrophilic and transphilic fractions. Isotope 15 N-labeled monoChloramine coupled with LC-electrospray ionization-tandem mass spectrometry was used to explore the nitrogen source of NDMA formed in chloraminated organic fractions. The results indicate that the nitroso group of the formed NDMA originates mainly from Chloramines.
Shinobu Itoh - One of the best experts on this subject based on the ideXlab platform.
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cis 1 2 aminohydroxylation of alkenes involving a catalytic cycle of osmium iii and osmium v centers osv o nhts active oxidant with a macrocyclic tetradentate ligand
Inorganic Chemistry, 2015Co-Authors: Hideki Sugimoto, Akine Mikami, Kenichiro Kai, P K Sajith, Yoshihito Shiota, Kazunari Yoshizawa, Kaori Asano, Takeyuki Suzuki, Shinobu ItohAbstract:Catalytic activity of [OsIII(OH)(H2O)(L-N4Me2)](PF6)2 (1: L-N4Me2 = N,N′-dimethyl-2,11-diaza-[3,3](2,6)pyridinophane) in 1,2-cis-aminohydroxylation of alkenes with sodium N-chloro-4-methylbenzenesulfonamide (Chloramine-T) is explored. Simple alkenes as well as those containing several types of substituents are converted to the corresponding 1,2-aminoalcohols in modest to high yields. The aminoalcohol products have exclusively cis conformation with respect to the introduced −OH and −NHTs groups. The spectroscopic measurements including cold mass spectroscopic study of the reaction product of complex 1 and chloromine-T as well as density functional theory (DFT) calculations indicate that an oxido–aminato–osmium(V) species [OsV(O)(NHTs)(L-N4Me2)](PF6)2 (2) is an active oxidant for the aminohydroxylation. The DFT calculations further indicate that the reaction involves a [3 + 2] cycloaddition between 2 and alkene, and the regioselectivity in the aminohydroxylation of unsymmetrical alkenes is determined by the...
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cis-1,2-Aminohydroxylation of Alkenes Involving a Catalytic Cycle of Osmium(III) and Osmium(V) Centers: OsV(O)(NHTs) Active Oxidant with a Macrocyclic Tetradentate Ligand
2015Co-Authors: Hideki Sugimoto, Akine Mikami, Kenichiro Kai, P K Sajith, Yoshihito Shiota, Kazunari Yoshizawa, Kaori Asano, Takeyuki Suzuki, Shinobu ItohAbstract:Catalytic activity of [OsIII(OH)(H2O)(L-N4Me2)](PF6)2 (1: L-N4Me2 = N,N′-dimethyl-2,11-diaza-[3,3](2,6)pyridinophane) in 1,2-cis-aminohydroxylation of alkenes with sodium N-chloro-4-methylbenzenesulfonamide (Chloramine-T) is explored. Simple alkenes as well as those containing several types of substituents are converted to the corresponding 1,2-aminoalcohols in modest to high yields. The aminoalcohol products have exclusively cis conformation with respect to the introduced −OH and −NHTs groups. The spectroscopic measurements including cold mass spectroscopic study of the reaction product of complex 1 and chloromine-T as well as density functional theory (DFT) calculations indicate that an oxido–aminato–osmium(V) species [OsV(O)(NHTs)(L-N4Me2)](PF6)2 (2) is an active oxidant for the aminohydroxylation. The DFT calculations further indicate that the reaction involves a [3 + 2] cycloaddition between 2 and alkene, and the regioselectivity in the aminohydroxylation of unsymmetrical alkenes is determined by the orientation that bears less steric hindrance from the tosylamino group, which leads to the energetically more preferred product isomer