Trace Amounts Of Formaldehyde Research Articles

Effect of Ni doping on methane removal from hydrogen in ZrMnFe alloy and mechanism analysis

Getter alloy has the advantages of low cost and high hydrogen purity in small and medium-scale hydrogen purification. However, the commonly used ZrMnFe alloy is reactive to various impurities in hydrogen, and requires a temperature above 600 °C to remove methane. To improve reactivity with methane and ensure a high hydrogen adsorption platform pressure, partial substitution of Fe with Ni, which has a smaller bonding energy with methane ligand, is beneficial. In this work, we prepared ZrMnFeNi alloys with different Ni stoichiometric ratios by suspension induction melting and investigated their performance in purifying hydrogen containing trace amounts of methane. All alloys maintain C14 Laves phase, and the interplanar spacing of the (103) crystal planes decreases with the replacement of Ni. It is proved that ZrMnFeNi alloys can significantly improve the absorb efficiency of methane in hydrogen and reduce the removal temperature. At 450 °C, ZrMnFe0.7Ni0.3 can remove 10 ppm methane to 0.124 ppm. The purification efficiency of hydrogen at 450 °C can reach 96.94%, while the purification efficiency of ZrMnFe alloy is only 27.12%. The ZrMnFe0.7Ni0.3 alloy decomposes methane into carbon and hydrogen during purification, and the carbon diffuses into the alloy at high temperature to form a metal carbide with zirconium. The XPS results show that the electron-rich state of Ni is more beneficial for activating the C–H bond breaking of methane.

Assembly of a Fluorescent Chiral Photonic Crystal Membrane and Its Sensitive Responses to Multiple Signals Induced by Small Molecules.

Chiral liquid crystal materials that are responsive to environmental stimuli are in demand. A chiral photonic crystal membrane based on cellulose nanocrystals (CNCs) was prepared by molecule assembly in the present work. A fluorescent molecule containing a cationic group, [N-(3-N-benzyl-N,N-dimethylpropyl ammonium chloride)-1,8-naphthalimide]hydrazine, was assembled on the surface of the CNCs. The new chiral photonic crystal membrane possesses supersensitive multiresponses to small molecules, such as water and formaldehyde molecules. The appearance, liquid crystal texture, fluorescence, and color of the chiral membrane have sensitive changes induced by small molecules. By increasing RH from 30 to 100%, the reflectance peak of the membrane red-shifted from 498 to 736 nm. In particular, the iridescent texture and fingerprint structure of the membrane could change markedly under trace amounts of formaldehyde, and the chiral membrane can form an extremely sensitive off-on fluorescence switch. The relationship between the fluorescence intensity and the trace concentration of formaldehyde satisfied the linear equation with the association coefficient of 0.9997. The changes in fluorescence and color are visible to the naked eye, and the membrane can quantitatively recognize trace formaldehyde at a molecular level in a humid environment. The mechanism by which the fluorescence switch operates was investigated using density functional theory at the B3LYP/6-31G(d) level. The membrane has potential for use in the fields of advanced functional materials and biomaterials.

Impact of applied cell voltage on the performance of a microbial electrolysis cell fully catalysed by microorganisms

The effect of the operating voltage on the performance of a microbial electrolysis cell (MEC) equipped with both a bioanode and a biocathode for hydrogen production is reported. Chronoamperometry tests ranged between 0.3 and 2.0 V were carried out after both bioelectrodes were developed. A maximum current density up to 1.6 A m−2 was recorded at 1.0 V with hydrogen production rate of nearly 6.0 ± 1.5 L m−2 cathode day−1. Trace amounts of methane, acetone and formate were detected in cathode's headspace and catholyte which followed the same trend as hydrogen production rate. Meanwhile substrate consumption in anolyte also followed the trend of hydrogen production and current density changes. The bioanode could utilise up to 95% of acetate in the tested voltage ranges, however, at a cell voltage of 2.0 V the bioanode's activity stopped due to oxygen evolution from water hydrolysis. Cyclic voltammograms revealed that the bioanode activity was vital to maintain the functionality of the whole system. The biocathode relied on the bioanode to maintain its potential during the hydrogen evolution. The overall energy efficiency recovered from both bioanode and external power in terms of hydrogen production at the cathode was determined as 29.4 ± 9.0%, within which substrate oxidation contributed up to nearly 1/3 of the total energy marking the importance of bioanode recovering energy from wastewater to reduce the external power supply.

Computationally Exploring and Alleviating the Kinetic Bottlenecks of Anaerobic Methane Oxidation

The anaerobic oxidation of methane by methanotrophic archaea offers a carbon- and electron- efficient route for the production of acetate, which can be further processed to yield liquid fuels. This acetate production pathway is initiated by methyl-coenzyme M reductase, but this enzyme can only oxidize trace amounts of methane ex situ. Efforts to improve the kinetics of methyl-coenzyme M reductase through enzyme engineering have been, in part, limited by low-throughput assays. Computational enzyme engineering can circumvent this limitation through the design of smaller, more focused libraries, which have a higher probability of success. By drawing from a new consensus reaction mechanism for Mcr and newly published data, the first complete kinetic characterization of the Mcr reaction mechanism is proposed. In the developed kinetic description, the rate of methyl-coenzyme M unbinding is proposed to limit Mcr overall kinetics. A revised computational method was devised to improve the rate of product release while not disrupting the reaction’s activated complex. Large, hydrophobic amino acids that can assume multiple conformations were predicted to be most effective at reaching this design goal. Other rate-limiting scenarios were examined, such as (i) high-temperature (> 45 °C), (ii) methyltransferase-limiting case, and (iii) ineffective Cofactor F430 binding. A separate library of designs is put forth for each one of these cases. These efforts mark the first computational attempt at redesigning methyl-coenzyme M reductase for reversed or improved activity, which if experimentally validated, would have a cross-cutting impact across the biotechnology and biochemistry fields by debottlenecking anaerobic methane oxidation.

Rapid and sensitive detection of formaldehyde based on AC electrokinetic effects

Formaldehyde is a toxic water-soluble organic matter. Its detection methods and detection limit have been attracting more attentions. An AC electrokinetic (ACEK)-enhanced capacitive sensing method for rapid detection of trace formaldehyde in liquid is presented using commercial microelectrode chips. By this method, a detection limit is achieved as low as 0.01 ppm (μg/ml) within a 60 s response time. It is proved that the trace amount of formaldehyde in common solvents can also be effectively detected. As a complement, the capacitance change rate dependence on testing voltage and frequency is investigated. Compared to other existing detection methods, this ACEK-based capacitive method is a low cost, high sensitive and fast detection means, which shows a great application prospect in industry and research such as food safety and specimen cleaning.

Enzyme Mediated Increase in Methanol Production from Photoelectrochemical Cells and CO2

While success has been shown in utilizing photocatalytic systems to reduce CO2 in water, most of these studies have yielded formic acid as the major product with trace amounts of formaldehyde or methanol. One reason for this is the strong equilibrium of formaldehyde toward the hydrate methanediol. To increase methanol yields from CO2, we show here the combined use of the biological catalyst alcohol dehydrogenase (ADH) from Saccharomyces cerevisiae with CO2 reduction products obtained from photoelectrochemical cells (PEC). We first show that ADH can reduce very low micromolar amounts of formaldehyde in solution. Upon adding ADH to the PEC products, a rapid three- to four-fold gain in methanol production was observed, which we also attribute to the lack of back reaction by the enzyme. Lastly, because formaldehyde dehydrogenase (FalDH) showed very low reactivity with formate, the addition of FalDH and ADH to the PEC products demonstrated no difference in methanol yields as compared to ADH alone.

Hydrothermal venting and mineralization in the crater of Kick'em Jenny submarine volcano, Grenada (Lesser Antilles)

AbstractKick'em Jenny is a frequently erupting, shallow submarine volcano located 7.5 km off the northern coast of Grenada in the Lesser Antilles subduction zone. Focused and diffuse hydrothermal venting is taking place mainly within a small (∼70 × 110 m) depression within the 300 m diameter crater of the volcano at depths of about 265 m. Much of the crater is blanketed with a layer of fine‐grained tephra that has undergone hydrothermal alteration. Clear fluids and gas are being discharged near the center of the depression from mound‐like vents at a maximum temperature of 180°C. The gas consists of 93–96% CO2 with trace amounts of methane and hydrogen. Gas flux measurements of individual bubble streams range from 10 to 100 kg of CO2 per day. Diffuse venting with temperatures 5–35°C above ambient occurs throughout the depression and over large areas of the main crater. These zones are colonized by reddish‐yellow bacteria with the production of Fe‐oxyhydroxides as surface coatings, fragile spires up to several meters in height, and elongated mounds up to tens of centimeters thick. A high‐resolution photomosaic of the inner crater depression shows fluid flow patterns descending the sides of the depression toward the crater floor. We suggest that the negatively buoyant fluid flow is the result of phase separation of hydrothermal fluids at Kick'em Jenny generating a dense saline component that does not rise despite its elevated temperature.

Cone calorimeter evaluation of two flame retardant cotton fabrics

SUMMARYUnbleached (gray) cotton needle‐punched nonwoven (NW) fabrics with 12.5% polypropylene scrim were treated with two phosphate–nitrogen‐based flame retardant (FR) formulations, Southern Regional Research Center (SRRC)‐1 and SRRC‐2. The SRRC‐1 formulation contains diammonium phosphate as the FR chemical along with urea and dimethyloldihydroxyethyleneurea. Because a trace amount of formaldehyde was still expected to be released from SRRC‐1‐treated FR cotton under high heat, it was preferable to eliminate the dimethyloldihydroxyethyleneurea, leading to the revised formulation SRRC‐2. It has a higher content of diammonium phosphate and did not use the polyethylene emulsion that was in SRRC‐1. Both formulations were of low cost as they were developed at SRRC using industrial grade chemicals. The fabrics were evaluated with a cone calorimeter using three heat flux levels, 20, 30, and 50 kW/m2. On the basis of the overall cone calorimeter results for heat released and ignition times, FR NW fabrics that were treated with SRRC‐2 were found to be slightly superior in flammability properties to those treated with the earlier SRRC‐1 formulation, but the differences were statistically insignificant. Both preparations were much less flammable than the untreated control cotton NW fabrics. Compared with the untreated NW fabrics, the FR fabrics had higher visible smoke production. Copyright © 2012 John Wiley & Sons, Ltd.

Catalytic Spectrophotometric Method for Determination of Formaldehyde Based on its Catalytic Effect on the ReactionBetween Bromate and Safranin

The reaction monitored spectrophotometrically by measuring the decrease in absorbance of the reaction mixture at 533 nm. The fixed‐time method was used for the first 60s. For initiation of the reaction, under the optimum conditions, in the concentration range of 0.02‐1.5 μg mL–1 formaldehyde can be determined with a limit of detection 9.5 ng mL–1. The relative standard deviation of five replicate measurements is 2.3% for 0.5 μg mL–1 of formaldehyde. The method was used for the determination of formaldehyde in water samples with satisfactory results. A new simple and fast catalytic kinetic method for the determination of trace amount of formaldehyde is described. The method is based on the catalytic effect of formaldehyde on the oxidation of safranin by bromate in the present of sulfuric acid.

Biotransformation of N-nitrosodimethylamine by Pseudomonas mendocina KR1.

N-Nitrosodimethylamine (NDMA) is a potent carcinogen and an emerging contaminant in groundwater and drinking water. The metabolism of NDMA in mammalian cells has been widely studied, but little information is available concerning the microbial transformation of this compound. The objective of this study was to elucidate the pathway(s) of NDMA biotransformation by Pseudomonas mendocina KR1, a strain that possesses toluene-4-monooxygenase (T4MO). P. mendocina KR1 was observed to initially oxidize NDMA to N-nitrodimethylamine (NTDMA), a novel metabolite. The use of 18O2 and H(2)18O revealed that the oxygen added to NDMA to produce NTDMA was derived from atmospheric O2. Experiments performed with a pseudomonad expressing cloned T4MO confirmed that T4MO catalyzes this initial reaction. The NTDMA produced by P. mendocina KR1 did not accumulate, but rather it was metabolized further to produce N-nitromethylamine (88 to 94% recovery) and a trace amount of formaldehyde (HCHO). Small quantities of methanol (CH3OH) were also detected when the strain was incubated with NDMA but not during incubation with either NTDMA or HCHO. The formation of methanol is hypothesized to occur via a second, minor pathway mediated by an initial alpha-hydroxylation of the nitrosamine. Strain KR1 did not grow on NDMA or mineralize significant quantities of the compound to carbon dioxide, suggesting that the degradation process is cometabolic.

Thermodynamic equilibrium calculations of hydrogen production from the combined processes of dimethyl ether steam reforming and partial oxidation

Thermodynamic analyses of producing a hydrogen-rich fuel-cell feed from the combined processes of dimethyl ether (DME) partial oxidation and steam reforming were investigated as a function of oxygen-to-carbon ratio (0.00–2.80), steam-to-carbon ratio (0.00–4.00), temperature (100 °C–600 °C), pressure (1–5 atm) and product species. Thermodynamically, dimethyl ether processed with air and steam generates hydrogen-rich fuel-cell feeds; however, the hydrogen concentration is less than that for pure DME steam reforming. Results of the thermodynamic processing of dimethyl ether indicate the complete conversion of dimethyl ether to hydrogen, carbon monoxide and carbon dioxide for temperatures greater than 200 °C, oxygen-to-carbon ratios greater than 0.00 and steam-to-carbon ratios greater than 1.25 at atmospheric pressure ( P = 1 atm). Increasing the operating pressure has negligible effects on the hydrogen content. Thermodynamically, dimethyl ether can produce concentrations of hydrogen and carbon monoxide of 52% and 2.2%, respectively, at a temperature of 300 °C, and oxygen-to-carbon ratio of 0.40, a pressure of 1 atm and a steam-to-carbon ratio of 1.50. The order of thermodynamically stable products (excluding H 2, CO, CO 2, DME, NH 3 and H 2O) in decreasing mole fraction is methane, ethane, isopropyl alcohol, acetone, n-propanol, ethylene, ethanol and methyl-ethyl ether; trace amounts of formaldehyde, formic acid and methanol are observed. Ammonia and hydrogen cyanide are also thermodynamically favored products. Ammonia is favored at low temperatures in the range of oxygen-to-carbon ratios of 0.40–2.50 regardless of the steam-to-carbon ratio employed. The maximum ammonia content (i.e., 40%) occurs at an oxygen-to-carbon ratio of 0.40, a steam-to-carbon ratio of 1.00 and a temperature of 100 °C. Hydrogen cyanide is favored at high temperatures and low oxygen-to-carbon ratios with a maximum of 3.18% occurring at an oxygen-to-carbon ratio of 0.40 and a steam-to-carbon ratio of 0.00 in the temperature range of 400 °C–500 °C. Increasing the system pressure shifts the equilibrium toward ammonia and hydrogen cyanide.

Decontamination of Gaseous Acetaldehyde over CoOx-Loaded SiO2 Xerogels under Ambient, Dark Conditions

A series of CoO(x)-doped silica xerogels with various Co(2+) loadings (Co/Si = 0, 1, 2, 4, 6, and 10 mol %) has been prepared. All xerogels exhibit large (800-1050 m(2)/g) surface areas. Narrow pore size distributions with pore size maxima around 3 nm are characteristic for Co/Si = 1, 2, 4, 6, 10 samples. As-prepared CoO(x)/SiO(2) xerogels show high catalytic activity in the air oxidation of gaseous acetaldehyde at room temperature. Carbon dioxide and trace amounts of methane are the only products detected in the gas phase. Acetic acid, a less volatile product, resides on the surface of the xerogels but can slowly desorb. The formation of CO(2) begins after an induction period. The beginning of CO(2) production coincides with the conversion of Co(2+) incorporated in the SiO(2) framework into Co(3+). Thermogravimetry/gas chromatography/mass spectrometry analysis, UV-vis and FTIR spectroscopies, as well as kinetic measurements are employed for CoO(x)/SiO(2) catalyst characterization. A possible mechanism of the reaction is discussed.

Methanol Chemistry on Cu and Oxygen-Covered Cu Nanoclusters Supported on TiO2(110)

The thermal decomposition of methanol has been studied on TiO2(110) as well as on Cu and oxygen-covered Cu nanoclusters supported on TiO2(110) using temperature programmed desorption (TPD). The sizes of the Cu clusters were characterized by scanning tunneling microscopy (STM). Methanol chemistry on the vacuum-annealed, reduced TiO2 surface itself produces ethylene as the main desorption product. Reoxidation of the TiO2 surface quenches the production of ethylene but also results in a new formaldehyde desorption peak at 870 K. The reactivity of methanol on small Cu nanoclusters (40.2 ± 7.0 A diameter, 12.7 ± 2.4 A height) is minimal, but trace amounts of formaldehyde, CO2, methane and H2 are detected in TPD experiments, demonstrating that the Cu nanoclusters are more active than bulk single-crystal Cu surfaces. On oxygen-covered Cu nanoclusters, methanol reaction produces formaldehyde and CO2 as the major gaseous products as well as H2, water, and methane. The yields of formaldehyde and CO2 increase as the...

Determination of Formaldehyde Traces in Fabric and in Indoor Air by a Kinetic Fluorimetric Method

A simple and sensitive kinetic fluorimetric method is reported for the determination of trace amount of formaldehyde. The proposed method is based on the catalytic effect of formaldehyde on the oxidation reaction of rhodamine B with potassium chlorate in sulfuric acid solution. Formaldehyde in the range of 0.020-0.340 µg/mL can be determined with a limit of detection of 5.73 ng/mL. The method has been used to determine trace formaldehyde in fabric and in indoor air. The results thus obtained show good agreement with those determined by acetyl acetone method.

Kinetic-Square Wave Voltammetric Determination of Formaldehyde Based on Catalytic Oxidation of Toluidine Blue by Bromate Ion

A simple, rapid and sensitive kinetic-square wave voltammetric method for the determination of trace amounts of formaldehyde (0.37–1.48 μg ml−1) based on its catalytic effect on the oxidation reaction of toluidine blue by bromate ion in acidic media at 30°C is reported. The decrease in height of the square wave voltammogram of toluidine blue in an acidic solution in the potential range of 0.02–0.2 volt (vs. Ag/AgCl) is used for monitoring the reaction. The detection limit is 68 ng ml−1 and the relative standard deviation of ten replicate determination of 0.74 g ml−1 of formaldehyde is 1.7%. No elimination of soluble oxygen in the sample solution or stopping the reaction is required.

Product distribution and reaction pathways for methylene chloride hydrolysis and oxidation under hydrothermal conditions

The product spectrum, yields, and distribution resulting from hydrolysis of methylene chloride in sub- and supercritical water and post-hydrolysis oxidation in supercritical water have been measured and analyzed to identify and prioritize likely reaction pathways of formation and destruction and their relative importance for all species observed. Reactions with dilute feeds were carried out at 246 bar in a tubular reactor system over temperatures ranging from 25 to 600°C and total residence times of 7 to 23 s. The products detected were formaldehyde, hydrochloric acid, carbon monoxide, hydrogen, methanol, and carbon dioxide, with trace amounts of methane, chloromethane, and other one- and two-carbon chlorinated hydrocarbons in the vapor phase. A complete reaction network for CH 2Cl 2 and its products under hydrolysis conditions was developed. The main route for CH 2Cl 2 breakdown was via subcritical hydrolysis to formaldehyde and HCl, followed by decomposition of formaldehyde to CO and H 2, and subsequent CO conversion to CO 2 and H 2 by the water gas shift reaction. In the presence of O 2, oxidation of HCHO, CO, H 2, and CH 3OH was significant, while CH 2Cl 2 and the chlorinated hydrocarbons exhibited no oxidation conversion below 550°C. By 600°C and a 6 s residence time under oxidation conditions, however, CO 2 and HCl were the only products observed, signifying complete destruction of all compounds (>99.99% of total carbon) under these conditions.

Synthesis of propylene oxide from propylene and hydrogen peroxide catalyzed by titanium silicalite

The epoxidation of propylene with hydrogen peroxide in the liquid phase, in the presence of titanium silicalite catalyst (TS-1), is described. The best solvents are methanol and methanol/ water mixtures. The temperature is normally between room temperature and 60°C. Under these conditions, reaction rates are fast, yields on H 2O 2 are quantitative, and selectivity to propylene oxide is very high. Propylene glycol and its monomethyl ethers and trace amounts of formaldehyde are the only by-products formed. Selectivity is further improved and the hydrolysis of the epoxide is almost suppressed when the residual acidity of the catalyst is completely neutralized. The activity of spent catalyst is recovered by calcining at 550°C or, more simply, by washing with solvents. Complete activity recovery shows that Ti is not removed from the crystalline framework during the epoxidation reactions.

Refraction effects on the Galileo probe telemetry carrier frequency

As the Galileo probe Relay Radio Link (RRL) signal propagates outward through the Jovian atmosphere, the atmosphere will manifest itself in two ways. First, the geometric path length of the signal is increased, resulting in a small change of the RRL signal departure angle from the probe (transmitter). Secondly, the velocity of the signal is decreased. For a spherical, static atmosphere with a known profile of refractivity versus altitude the effects of refraction on the RRL frequency can be found using a variation of standard ray‐tracing techniques, whereby the ray departure angle is found by an iterative process. From the dispersive characteristics of a mixture of hydrogen and helium with trace amounts of methane and ammonia a simple model of the Jovian atmosphere is constructed assuming spherical symmetry and uniform mixing. The contribution to the RRL Doppler frequency arising from refraction is calculated, and its effect on the Doppler wind measurements is discussed.

Production and Utilization of Ethanol by the Homoacetogen Acetobacterium woodii

Acetobacterium woodii formed ethanol as a fermentation product in addition to acetate when the phosphate concentration of the medium was between 0.2 and 8.4 mM. Considerable amounts of alanine were also found (2 to 11 mM). Supplementation with phosphate caused a shift to acetate as the only end product. Ethanol could also serve as a substrate for A. woodii. The fermentation yielded predominantly acetate and was strictly dependent on high bicarbonate concentrations. 1-Propanol, 1-butanol, and 1-pentanol were converted to the corresponding fatty acids but allowed only marginal growth. A. wieringae and A. carbinolicum grown under identical conditions were also able to form ethanol, and A. wieringae could use ethanol as a substrate, too. Alcohol dehydrogenase and acetaldehyde dehydrogenase activities were determined in A. woodii. Activity stains of polyacrylamide gels with crude extracts allowed the detection of acetaldehyde dehydrogenase but not of alcohol dehydrogenase. Trace amounts of methane were detected during growth of A. woodii on glucose and ethanol.

Polarographic analysis of taurolidine, a non-antibiotic antimicrobial agent

The behaviour in aqueous solution of the non-antibiotic antimicrobial agent, taurolidine, which has marked anti-adherence properties, has been investigated by differential pulse polarography (DPP). Taurolidine gave well-defined differential pulse polarograms at pH 4.2 with a peak potential of −0.83 V vs Ag/AgCl. This behaviour was identical to that of aqueous taurultam solutions. Comparison of peak current ratios, cyclic voltammograms and peak potential/pH plots confirmed that the taurolidine signal was due to the reduction of taurultam and its hydroxymethyl derivative. A mechanism for the cathodic reduction of taurultam was proposed involving a 2-electron transfer. The signal at −0.83 V was of analytical utility, but was lost at alkaline pH. A second peak appeared in the polarogram for taurolidine solutions at alkaline pH and was identified as formaldehyde. This was quantified by a rapid DPP method. Only trace amounts of formaldehyde were found in commercial taurolidine (Taurolin) solutions and these were of no clinical significance.