N-nitrosodimethylamine In Water Research Articles

Effects of transition-metal ions on the reduction of N-nitrosodimethylamine in water by zinc

The influencing factors, products and mechanism of N-nitrosodimethylamine (NDMA) reduction by zinc (Zn) in the presence of transition-metal ions (Mn2+, Co2+ and Ni2+), were investigated. The NDMA removal by Zn was significantly improved by them, and the promoting effect of Co2+ and Ni2+ were better than Mn2+. With the decrease of pH values and dissolved oxygen concentrations, the removals of NDMA were enhanced in all reaction systems. NDMA was mainly reduced to unsymmetrical dimethylhydrazine (UDMH) in Zn and Zn/Mn2+ systems. It was mainly reduced to dimethylamine (DMA) and ammonium (NH4+) in Zn/Co2+ and Zn/Ni2+ systems. There were undetected products in all reaction systems. Catalytic hydrogenation was the main mechanism, and active hydrogen atom was the main active species. The presence of Mn2+, Co2+ and Ni2+ promoted the corrosion of Zn and changed the surface morphology of Zn. The formation of type I film on Zn surface was promoted in the presence of Co2+ and Ni2+, which was conducive to the continuous corrosion of Zn and hydrogen generation. While type II film which would inhibit the corrosion of Zn formed on Zn surface in the presence of Mn2+. MnO2, Co3O4 and Ni(OH)2 were formed in Zn/Mn2+, Zn/Co2+ and Zn/Ni2+ systems, respectively. They would facilitate more generation of active hydrogen atoms.

Accelerated Ultraviolet Treatment of Carbamazepine and NDMA in Water under 222 nm Irradiation.

Krypton chloride (KrCl*) excimer ultraviolet (UV) light may provide advantages for contaminant degradation compared to conventional low-pressure (LP) UV. Direct and indirect photolysis as well as UV/hydrogen peroxide-driven advanced oxidation (AOP) of two chemical contaminants were investigated in laboratory grade water (LGW) and treated secondary effluent (SE) for LPUV and filtered KrCl* excimer lamps emitting at 254 and 222 nm, respectively. Carbamazepine (CBZ) and N-nitrosodimethylamine (NDMA) were chosen because of their unique molar absorption coefficient profiles, quantum yields (QYs) at 254 nm, and reaction rate constants with hydroxyl radical. Quantum yields and molar absorption coefficients at 222 nm for both CBZ and NDMA were determined, with measured molar absorption coefficients of 26 422 and 8170 M-1 cm-1, respectively, and QYs of 1.95 × 10-2 and 6.68 × 10-1 mol Einstein-1, respectively. The 222 nm irradiation of CBZ in SE improved degradation compared to that in LGW, likely through promotion of in situ radical formation. AOP conditions improved degradation of CBZ in LGW for both UV LP and KrCl* sources but did not improve NDMA decay. In SE, photolysis of CBZ resulted in decay similar to that of AOP, likely due to the in situ generation of radicals. Overall, the KrCl* 222 nm source significantly improves contaminant degradation compared to that of 254 nm LPUV.

Surface modification of coconut shell activated carbon for efficient solid-phase extraction of N-nitrosodimethylamine from water.

A practical and cheap methodology in modifying commercial coconut shell activated carbon for solid-phase extraction of N-nitrosodimethylamine in water was developed through an understanding of activated carbon surface chemistry. In comparison with commercial activated carbon, extraction recoveries by activated carbon treated with sulfuric acid decreased by 50%, while those of activated carbon heated at 800°C improved by more than 100%. Acid treatment increased the oxygen content on the carbon's surface. In contrast, heat treatment decreased the surface oxygen content, resulting in a more hydrophobic surface, which favoured adsorption and extraction of N-nitrosodimethylamine. The influence of different activated carbon sizes, amount of modified activated carbon, and pH on the N-nitrosodimethylamine recoveries was assessed and compared with the commercial solid-phase extraction cartridge. The recommended amount of powder activated carbon treated at 800°C was 3g to yield an optimum recovery of 130%, which was superior to the commercial solid-phase extraction cartridges. The method validation results confirmed the high accuracy, reproducibility, and precision of the method. The study indicated that chemisorption plays a significant role in the adsorption of N-nitrosodimethylamine on activated carbon, and the optimization of its surface chemistry can enhance N-nitrosodimethylamine adsorption/extraction from water.

Ultrasonic assisted-dispersive solid-phase extraction for rapid enrichment of N-nitrosodimethylamine in water

a novel and rapid analytical method was established for the extraction of N-nitrosodimethylamine in large-volume water samples. Pretreatment was on the basis of ultrasonic-assisted-dispersed solid phase extraction. Coco housing activated carbon was incorporated into the water samples, and the rapid enrichment of N-nitrosodimethylamine was realized by implementing ultrasonic-assisted dispersion. After that, the suspension was filtered by suction, and the residue was eluted by dichloromethane. The eluate was collected and then concentrated to dry using rotary evaporation. Ultra-high performance liquid chromatography tandem mass spectrometer, which equipped with atmospheric pressure chemical ionization source was employed for determination under the multiple reaction monitoring mode. Limit of detection and quantification for N-nitrosodimethylamine in 500 mL water was 2. 0 ng/mL and 6. 0 ng/mL, respectively. Throughout the validation, good linearity with R~2>0. 999 were achieved with the range from 0. 5 ng/mL to 150. 0 ng/mL. Satisfactory recovery(95. 7%-100. 8%) and inter-day reproducibility(<4. 2%) were obtained by three-level spiking experiments in different water matrices. Finally, the established method was applied for analysis of 48 real samples, the detectable concentrations of positive samples were in the range of <2. 0 ng/L to 14. 4 ng/L. Compared with the traditional solid-phase extraction method, this method ology showed the characteristics of rapid and more efficient, and could save at least 50% of the pretreatment time. Meanwhile, the result of method ology validation were satisfactory.

Degradation of N-nitrosodimethylamine by Palladium/ Iron Bimetallic Composite Catalytic Fiber

N-nitrosodimethylamine (NDMA) in the water environment is a carcinogenic organic contaminant, which can be converted to hypotoxic compounds by zero-valent iron degradation. For the removal of trace NDMA in water, the theory and efficiency of zero-valent iron degradation should be intensely researched. In this study, the polypropylene (PP) fibers were chosen as substrate materials and the composite catalyst fibers containing Pd/Fe0 bimetal were prepared by the UV irradiation-coordination method for the removal of trace NDMA. Pd/Fe0/PP-g-AA was characterized by scanning electron microscope, inductively coupled plasma atomic emission spectrometry, and X-ray photoelectron spectroscopy. The NDMA removal by Pd/Fe0/PP-g-AA under different conditions was investigated. The results indicated that when the acrylic acid monomer mass fraction was 20%, the composite catalytic fiber Pd/Fe0/PP-g-AA showed a better degradation effect on NDMA. The removal of NDMA followed the pseudo-first-order reaction kinetics model. The initial NDMA concentration and the pH of the solution could not greatly influence the catalytic degradation of trace amounts of NDMA. The presence of 3CO2- and NO3- significantly inhibited the degradation of NDMA. However, the NDMA degradation had been less affected by SO42-, HCO3-, and nature organic matter (NOM) existing in the solution.

A New Method Using Liquid Chromatography Tandem Mass Spectrometry to Detect NDMA in Water

This study focused on using liquid Chromatography Tandem Mass Spectrometry to detect N-Nitrosodimethylamine (NDMA) at trace concentrations in water. The water sample was preconcentrated by solid-phase extraction method. To find an elution which can obtain higher recovery, three reagents with different organic solvents were examined. After comparing the recoveries and the standard deviation of the elution, finally the dichloromethane was determined as the elution of the experiment. Then the concentrated sample was analyzed by a method combining SPE pretreatment and LC separation with tandem mass spectrometry using multiple reaction monitoring (MRM).

Reduction of N-Nitrosodimethylamine (NDMA) in Aqueous Solution by Nanoscale Fe/Al2(SO4)3

N-Nitrosodimethylamine (NDMA) is recently defined as one of nitrogenous disinfection by-products with high carcinogenicity and can be frequently detected in finished water. The decomposition of NDMA in water using nanoscale zero-valent iron (NZVI) in the presence of aluminum and iron salts was investigated in this paper. The results showed that some salts can enhance the removal of NDMA by commercial NZVI in the order of Al2(SO4)3 >> AlCl3 > FeSO4 > Na2SO4 ≈ NZVI alone, and the highest NDMA removal was 87.3 % in the presence of Al2(SO4)3. NDMA removal varied with the addition of Al2(SO4)3, NZVI dosage, initial NDMA concentration, solution pH, and temperature. The reduction of NDMA increased with the dosage of Al2(SO4)3 and NZVI, which follows a pseudo-first-order kinetics model. The removal of NDMA by NZVI was higher in acidic pHs than in alkaline ones, and the highest removal was found at pH 5. Higher reaction temperature can improve the removal of NDMA and reduce the reaction time. Based on the total nitrogen balance, most nitrogen of NDMA was converted to ammonium and dimethylamine.

Removal of N-nitrosodimethylamine by ultraviolet treatment and anodizing TiO2 membrane processes

N-Nitrosodimethylamine (NDMA) is a disinfectant by-product shown to be carcinogenic, mutagenic, and teratogenic. The objective of this study is to compare NDMA removal efficiencies in water using conventional technologies (microfiltration, nanofiltration, reverse osmosis, and UV treatment) and innovative hybrid technology, which combines UV treatment with anodizing TiO2 membrane (UV/A-Ti-M) technology. In the UV/A-Ti-M photoreaction, the affecting factors such as UV intensity, the initial concentration of NDMA, and initial pHs were investigated. Even though membrane processes were ineffective in removing NDMA compounds, UV irradiation used in combination with an anodizing TiO2 membrane were achieved to remove NDMA completely from water. When NDMA was decomposed by UV/A-Ti-M process, dimethylamine yield increased and methylamine yield decreased with an increase in initial NDMA concentration. The successful removal of NDMA was specific to acidic conditions (pH 4–6). UV/A-Ti-M process is useful and powerful tools to remove NDMA in water. © 2011 American Institute of Chemical Engineers Environ Prog, 2011

Ingestion Exposure to Nitrosamines in Chlorinated Drinking Water

ObjectivesN-Nitrosodimethylamine (NDMA) is classified as a probable human carcinogen by the United States Environmental Protection Agency (US EPA) and is formed during the chlorination of municipal drinking water. In this study, selected nitrosamines were measured in chlorinated drinking water collected from Chuncheon, Kangwon-do, Republic of Korea, and a risk assessment for NDMA was conducted.MethodsTwelve water samples were collected from 2 treatment plants and 10 household taps. Samples were analyzed for 6 nitrosamines via solid-phase extraction cleanup followed by conversion to dansyl derivatives and high-performance liquid chromatography-fluorescence detection (HPLC-FLD). Considering the dietary patterns of Korean people and the concentration change of NDMA by boiling, a carcinogenic risk assessment from ingestion exposure was conducted following the US EPA guidelines.ResultsNDMA concentrations ranged between 26.1 and 112.0 ng/L. NDMA in water was found to be thermally stable, and thus its concentration at the end of boiling was greater than before thermal treatment owing to the decrease in water volume. The estimated excess lifetime carcinogenic risk exceeded the regulatory baseline risk of 10-5.ConclusionsThis result suggests that more extensive studies need to be conducted on nitrosamine concentration distributions over the country and the source of relatively high nitrosamine concentrations.

Enhancement of the photodegradation of N-nitrosodimethylamine in water using amorphous and platinum manganese oxide catalysts

The enhancement of the photodegradation of toxic N-nitrosodimethylamine (NDMA) in water using amorphous manganese oxide (AMO) and platinum manganese oxide (Pt/Mn3O4) catalysts was investigated. Characterization of the catalysts was carried out using XRD, FESEM, TEM, EDXS, BET, XPS, and AOS. Pt/Mn3O4 and its precursor AMO, synthesized by a redox reaction of Mn2+ and Mn7+, showed similar morphologies. High surface area AMO was confirmed to be amorphous, whereas Pt/Mn3O4 was a mixture of two crystalline structures. The optimum catalyst loading was 25mg per 100mL NDMA solution for which the photocatalytic activity was maximized. The average hydrodynamic particle size of a given amount of catalyst increased due to aggregation as a result of an increase in temperature during UV illumination (λ=254nm). Photocatalytic studies showed that NDMA degraded according to zero-order kinetics under air saturation at pH 7.0. AMO and Pt/Mn3O4 showed photostability and comparable activities with pure TiO2 and platinized TiO2. Mixed valencies of Mn and the presence of O2 on the surface of the catalysts, which reacts with photogenerated electrons to form reactive oxygen species (hydroxyl and superoxide anion radicals), played significant roles in the enhancement of the photodegradation of NDMA in water.

Использование твердофазной микроэкстракции в качестве пробоподготовки для определения n-нитрозодиметиламина в воде, загрязненной в результате проливов гидразинового ракетного топлива

A paper describes a method for determination of N-nitrosodimethylamine in water, polluted by spills of 1,1-dimethylhydrazine, based on solid phase microextraction coupled to gas chromatography/mass spectrometry. A method detection limit was determined to be 1 ug/kg, relative error was below 20%. A method is very sensitive and selective as well as quite simple, relatively cheap and fully automated.

High-Performance Liquid Chromatography for Determination of N-Nitrosodimethylamine in Water

High-Performance Liquid Chromatography for Determination of N-Nitrosodimethylamine in Water

Flow injection chemiluminescent determination of N-nitrosodimethylamine using photogenerated tris(2,2′-bipyridyl) ruthenium (III)

A flow injection configuration was developed and evaluated for the chemiluminescent determination of N-nitrosodimethylamine. The method is based on the on-line cleavage of the N NO bond of the nitrosamine by irradiation with ultraviolet light. The dimethylamine generated was subsequently reacted with tris(2,2′-bipyridyl) ruthenium (III), which was generated through the on-line photo-oxidation of tris(2,2′-bipyridyl) ruthenium (II) with peroxydisulfate. After selecting the best operating parameters, the emitted light showed a linear relationship with the concentration of N-nitrosodimethylamine between 1.5 and 148 ng ml −1, with a detection limit of 0.29 ng ml −1. The repeatability was 1.6% expressed as relative standard deviation ( n = 10) and the reproducibility, studied on five consecutive days, was 3.2%. The sample throughput was 50 injections per hour. The method was applied to studying the recoveries of N-nitrosodimethylamine in water and different cured meat products.

Free radical destruction of N-nitrosodimethylamine in water.

Absolute rate constants for the reactions of the hydroxyl radical, hydrated electron, and hydrogen atom with N-nitrosodimethylamine (NDMA) in water at room temperature have been determined using electron pulse radiolysis and transient absorption spectroscopy (*OH and e- aq) and EPR free induction decay attenuation (*H) measurements. Specific values of (4.30 +/- 0.12) x 10(8), (1.41 +/- 0.02) x 10(10), and (2.01 +/- 0.03) x 10(8) M(-1) s(-1) were measured, respectively. DMPO spin-trapping experiments demonstrated that the hydroxyl radical reaction with NDMA occurs by hydrogen atom abstraction from a methyl group, and the rate constant for the subsequent reaction of this radical transient with dissolved oxygen was measured as (5.3 +/- 0.6) x 10(6) M(-1) s(-1). This relatively slow rate constant implies that regeneration of the parent nitrosoamine from the oxidized transient could occur in natural waters containing dissolved organic compounds. The reaction of the hydrated electron with NDMA was to form a transient adduct anion, which could subsequently transfer this excess electron to regenerate the parent chemical. Such regeneration reactions would significantly reduce the effectiveness of any applied advanced oxidation technology remediation effort on NDMA-contaminated natural waters.

N-nitrosodimethylamine in drinking water using a rapid, solid-phase extraction method

A simple, rapid method for the extraction of N-nitrosodimethylamine (NDMA) from drinking and surface waters was developed using Ambersorb 572. Development of an alternative method to classical liquid-liquid extraction techniques was necessary to handle the workload presented by implementation of a provincial guideline of 9 ppt for drinking water and a regulatory level of 200 ppt for effluents. A granular adsorbent, Ambersorb 572, was used to extract the NDMA from the water in the sample bottle. The NDMA was extracted from the Ambersorb 572 with dichloromethane in the autosampler vial. Method characteristics include a precision of 4 % for replicate analyses, an accuracy of 6 % at 10 ppt and a detection limit of 1.0 ppt NDMA in water. Comparative data between the Ambersorb 572 method and liquid-liquid extraction showed excellent agreement (average difference of 12 %). With the Ambersorb 572 method, dichloromethane use has been reduced by a factor of 1,000 and productivity has been increased by a factor of 3-4. Monitoring of a drinking water supply showed rapidly changing concentrations of NDMA from day to day.