Formaldehyde In Aqueous Solution Research Articles

Use of formalin in intensive aquaculture: properties, application and effects on fish and water quality

AbstractFormalin (aqueous solution of formaldehyde stabilized with methanol) is one of the most used disinfectants in aquaculture. It is used to eliminate infectious agents but may be responsible for negative effects on fish and water quality. This work focuses on physical–chemical properties of formalin and on its reactions and its use in intensive aquaculture and in environment. The types of treatments and the action mode of formalin are also described. The main consequences of formalin exposure to fish are damage in gills and alterations in mucous cells. Formalin also interacts with some treatments adopted in aquaculture establishments, for example biological filter, where the nitrification process seems to be strongly affected. With respect to formalin inactivation, formaldehyde (effluent) may be diluted with water or specific treatments should be conducted to decrease the concentration levels before its discharge into the environment. The common methodologies applied to aquaculture are not completely efficient on formalin removal from water, and the advanced oxidation processes may be a good alternative.

A computational study on the reaction mechanism of neutral phenol with formaldehyde in aqueous solution

The reaction mechanism of neutral phenol with formaldehyde in aqueous solution was studied theoretically by using the GGA-PW91/DNP+COSMO method. In previous studies, it was found that the water molecules can mediate proton transfer from nitrogen to oxygen, but the results of this study show that water molecules can also catalyse proton transfer from carbon to oxygen. With the mediation of water, the energy barriers were greatly lowered. The calculated energy barriers indicate that the para-position of phenol has higher reactivity than the ortho-position. The reaction occurs in a concerted mechanism. However, the process exhibits asynchronous characteristics, particularly the C–C bond formation precedes the proton transfer and the proton transfer from water molecules to the carbonyl oxygen is ahead of proton abstraction from the benzene ring.

Movement anatomy of the gluteal region and thigh of the giant anteater Myrmecophaga tridactyla (Myrmecophagidae: Pilosa)

Abstract: Locomotion reveals the displacement and behavior manner of the species in their daily needs. According to different needs of the several species, different locomotor patterns are adopted. The shapes and attachment points of muscles are important determinants of the movements performed and consequently, the locomotion and motion patterns of living beings. It was aimed to associate anatomical, kinesiology and biomechanics aspects of the gluteal region and thigh of the giant anteater to its moving characteristics and locomotor habits. It was used three specimens of Myrmecophaga tridactyla, settled in formaldehyde aqueous solution at 10% and subsequently, dissected using usual techniques in gross anatomy. The morphological characteristics of the gluteal region and thigh that influence the patterns of movement and locomotion of animals, were analyzed and discussed in light of literature. All muscles of the gluteal region and thigh of giant anteater show parallel arrangement of the muscular fibers, being flat or fusiform. These muscles are formed in the joint which the interpotent type biolever act. These morphological characteristics indicate a greater predominance of amplitude and movement speed at the expense of strength. On the other hand, features such as osteometric index and the observation of giant anteater motion indicate the opposite, what reflects this animal lack of expertise in locomotor habits and shows the need of future realization of more detailed studies in this subject.

Metal–organic chemical vapor deposition growth of β-FeSi2/Si composite powder via vapor–liquid–solid method and its photocatalytic properties

Semiconducting iron disilicide (β-FeSi2) island grains of a few hundred nanometers in diameter were formed on the surface of Si powder by metal–organic chemical vapor deposition. On Au-coated Si powder, the Au–Si liquidus phase was obtained by melting the Si surface via the Au–Si eutectic reaction, which contributed to the formation of island grains. The dramatic decrease in the defect density in β-FeSi2, which was due to this growth mechanism, was confirmed by the photoluminescence properties. The β-FeSi2/Si composite powder could evolve hydrogen from formaldehyde aqueous solution under irradiation of visible light with wavelengths of 420–650 nm.

Anatomic Bases for Brachial Plexus Block of Capuching (Sapajus libidinosus)

Background: In captivity, capuchin monkeys compete for space and rank. Fights can result in traumas, especially to the limbs, requiring interventions that are often outpatient. Local anesthesia as a tool in these procedures, as an aid to chemical restraint, is very relevant for small outpatient surgeries, or even for pain relief. Knowledge of peripheral nerve anatomy is essential to perform local anesthesia. Thus the objective of the present study was to determine, by anatomical studies of the brachial plexus region, the best access pathways for anesthetic blocking of the nerve.Materials, Methods & Results: Seven adult capuchin monkeys (Sapajus libidinosus) were used, weighing 2-3 kg, fixed and preserved in formaldehyde aqueous solution at 10%. In five of these animals the supraclavicular, infraclavicular and axillar regions were dissected to visualize the muscles, clavicle and bracchial plexus nerves. An analogical pachymeter was used to measure the depth of the plexus in relation to the cranial and caudal clavicle face and axillary fossa, comparing the length of two hypodermic needles (13x4.5 mm and 15x5 mm). Simulation of the anesthetic block was tested in two animals: before dissecting an acrylic varnish solution was injected using a syringe and 13x4.5 mm needle in the supraclavicular, infraclavicular regions and axillary fossa. To assess the positioning points of the syringe, dissection was performed and the varnish perfusion in the plexus was observed. For the anesthetic block in the supraclavicular region the dorsal median of the clavicle with a 95º deltoclavicular angle with the needle perpendicular to the skin was taken as point of reference. In the infraclavicular the reference point was the caudal face of the median clavicle with an 80º deltoclavicular angle. In the axillar region, with the limb at 90º, the syringe was positioned perpendicular to the axillar at the height of the mid portion of the thorax. The mean and standard deviation of the skin-brachial plexus distance for the supraclavicular, infraclavicular and axillar techniques were, respectively, 1.76 ± 0.1387 cm, 1.12 ± 0.239 cm and 1.59 ± 0.365 cm. These data showed the viability of executing the anesthesia technique by three access pathways. However, in the supraclavicular access pathway in the anesthetic simulation with the 13x4.5 mm hypodermic needle, the stain diffused to the plexus, showing, when compared with the 1.76 cm mean skin- plexus distance a safe distance to prevent the needle from perforating the nerve.Discussion: The techniques reported in the human literature for brachial plexus block presented a series of complications, with incomplete blocks and hemorrhages when the axillar access pathway was used and presented risk of pneumothorax in the supraclavicular. In the capuchin monkey the supraclavicular access pathway in anesthetic simulation with 13x4.5mm hypodermic needle showed a safe distance for the needle not to perforate the nerve, so that the use of this needle could be indicated in 2-3 kg animals. However, hypodermic needles are not recommended for use in this area because of the risk of perforating the subclavicular artery close to the plexus. As an alternative some anesthesiologists use the infraclavicular access pathway with atraumatic needles recommended for brachial plexus block, with relative success and fewer complications. Although the supraclavicular region showed the best depth in relation to the technique used here, anesthetic tests should be made to confirm the efficaciousness of executing the brachial plexus anesthetic technique in capuchin monkeys using atraumatic needles for nerve block.

Immobilizing AgPd alloy on Vulcan XC-72 carbon: a novel catalyst for highly efficient hydrogen generation from formaldehyde aqueous solution

A novel bimetallic catalyst, AgPd nanoalloy supported on Vulcan XC-72 carbon (AgPd@C-72), has been successfully fabricated and used for catalyzing H2 generation from formaldehyde aqueous solution at room temperature for the first time.

Multiporous open-cell poly(vinyl formal) foams for sound absorption

A series of multiporous open-cell poly(vinyl formal) (PVF) foams were obtained by crosslinking poly(vinyl alcohol) (PVA) with different contents of formaldehyde in aqueous solution.

Fluorinated antimony(v) derivatives: strong Lewis acidic properties and application to the complexation of formaldehyde in aqueous solutions.

As part of our ongoing studies of water tolerant Lewis acids, we have synthesized and investigated the properties of Sb(C6F5)3(O2C6Cl4), a fluorinated stiborane whose Lewis acidity approaches that of B(C6F5)3. While chloroform solutions of this Lewis acid can be kept open to air or exposed to water for extended periods of time, this new Lewis acid reacts with P t Bu3 and paraformaldehyde to form the corresponding formaldehyde adduct t Bu3P-CH2-O-Sb(C6F5)3(O2C6Cl4). To test if this reactivity can also be observed with systems that combine the phosphine and the stiborane within the same molecule, we have also prepared o-C6H4(PPh2)(SbAr2(O2C6Cl4)) (Ar = Ph, C6F5). These yellow compounds, which possess an intramolecular P→Sb interaction, are remarkably inert to water but do, nonetheless, react with and accomodate formaldehyde into the P/Sb pocket. In the case of the fluorinated derivative o-C6H4(PPh2)(Sb(C6F5)2(O2C6Cl4)), formaldehyde complexation, which occurs in water/dichloromethane biphasic mixtures, is accompanied by a colourimetric turn-off response thus highlighting the potential that this chemistry holds in the domain of molecular sensing.

PdO/LaCoO3 heterojunction photocatalysts for highly hydrogen production from formaldehyde aqueous solution under visible light

PdO/LaCoO3 heterojunction photocatalyst was prepared by sol gel process and deposition precipitation method under mild condition, used for H2 production from formaldehyde aqueous solution without any additives at low temperature. We demonstrate through PdO doping that creation of heterojunction on LaCoO3 particles surface can effectively adjust band-gap and Fermi energy levels to apply in hydrogen production from formaldehyde solution under visible light. The work indicate that the heterojunction structure can greatly enhance the charge generation, largely improve the visible light absorptive quality and effectively restrain the recombination of photogenerated electron–holes pairs to exhibit a higher photocatalytic activity. The optimal photocatalytic activity of PdO/LaCoO3 in H2 production from formaldehyde solution under visible light was ten times of LaCoO3 (1.26 mmol h−1 g−1). The photocatalysts composition and optical properties were characterized by XRD, TEM, EDS, XPS, TPR-H2, UV–vis (DRS) and Photoluminescence (PL).

Applying Modified Chemical Equilibrium Constants for Improving Equilibrium Species Distribution and Vapor–Liquid Equilibrium (VLE) Prediction of Formaldehyde Aqueous Solutions

This paper presented a revised model for calculating the chemical and vapor–liquid equilibria (VLE) of the formaldehyde + water system. Chemical equilibrium constants for the formation of poly(oxymethylene) glycols (HO(CH2O)iH, MGi, i > 1) were reviewed, and selected models were modified to reliably predict the species distribution of formaldehyde aqueous solutions and describe the influence of overall formaldehyde concentration. Besides, the UNIFAC equation for the Gibbs excess energy was combined with the chemical reaction equilibria to represent the experimental VLE data in the literature. In addition, some model parameters were redetermined from the corresponding data fits.

Identification of Di(oxymethylene)glycol in the Raman Spectrum of Formaldehyde Aqueous Solutions by ab Initio Molecular Dynamics Simulations and Quantum Chemistry Calculations.

Di(oxymethylene)glycol forms in formaldehyde aqueous solutions by polymerization of methanediol. The structure and hydrogen bond interactions of di(oxymethylene)glycol with water were characterized by performing Car-Parrinello molecular dynamics simulations. The anharmonic vibrational frequencies of di(oxymethylene)glycol in solution were determined with ab initio calculations considering explicitly the hydrogen-bonded water molecules, while other interactions with solvent were described within a polarizable continuum model approach. The calculations allow for a detailed interpretation of the experimental Raman spectrum of formaldehyde aqueous solutions, leading to the assignment of the band at 920 cm(-1) to the symmetric CO stretching mode of di(oxymethylene)glycol.

Thin films exhibiting multicolor changes induced by formaldehyde-responsive release of anionic dyes

A novel methodology for the sensing of formaldehyde that displays a response using distinct and diverse color changes is reported. Through copolymerization of a primary amine monomer with additional co-monomers on a pattern-printed microscope slide, primary amine-containing thin films were obtained. After the absorption of a range of colors of anionic dyes, the thin films were immersed in aqueous formaldehyde solutions. It was demonstrated that the color of the thin films changed depending on the formaldehyde concentration in the solution. As the anionic dyes were released from the thin films at varying formaldehyde concentrations, a set of thin films exhibiting a range of color-change patterns was observed. The response selectivity of the thin films towards carbonyl compounds was examined, and sensitivity in the order of formaldehyde»acetaldehyde>acetone was observed. In addition, the effect of amine structure was examined, and it was found that thin films bearing tertiary amino groups show virtually no formaldehyde response. These observations clearly indicate that the existence of primary amino groups is essential for color changes to be observed, and that the formation of an imine is the crucial step in generating a response against formaldehyde. The formaldehyde-responsive system presented herein is advantageous, as its preparation is relatively simple and does not require complex organic synthesis. In addition, a wide range of anionic dyes is compatible with the system, and can be selected in terms of color, charge, toxicology profile, and cost, for example.

Nanomolar fluorescent quantitative detection of formaldehyde with a 8-hydroxyquinoline derivative in aqueous solution and electrospun nanofibers

A 8-hydroxyquinoline-based derivative was designed and synthesized, which is shown to act as a highly sensitive fluorescent probe for formaldehyde in aqueous solution. Based on the photo induced electron transfer (PET) process, addition of formaldehyde greatly enhanced the fluorescence of the probe. Formaldehyde can be detected quantitatively in the concentration range from 900nM to 1.3×10−4M and the detection limit on fluorescence response of the probe can be as low as 900nM. The proposed method was successfully employed for preliminary application in several commercially available foods. Moreover, it has been successfully blended with a host polymer polyvinyl alcohol and the polymer containing the probe has been made in nanofiber form via electrospinning. The fluorescence of the nanofibers could also be enhanced after they were immersed into water solution of formaldehyde.

Theoretical study of decomposition of methanediol in aqueous solution.

Methanediol is a product of the hydration of formaldehyde and is more abundant than formaldehyde in aqueous solution. We carried out a number of quantum chemical simulations to study the decomposition of methanediol in aqueous solution. The decomposition of a methanediol proceeds by transferring a proton from a hydroxyl to an oxygen atom of the other hydroxyl in the methanediol. The decomposition of the methanediol completes after the cleavage of the bond between the formaldehyde and the water molecule. The probability of the proton transfer increases by the quantum mechanical tunneling at the low temperature because the width of the potential barrier for the decomposition becomes similar to the de Broglie wavelength of the proton. We consider the catalytic effect of water molecules in aqueous solution. The structure of the methanediol is not required to change significantly when undergoing decomposition due to the active role of water molecules to transfer a proton. We consider three types of arrangement for water molecules with respect to a methanediol: (1) a ring structure formed by a methanediol and water molecules; (2) a water cluster attracted to a methanediol by hydrogen bonds; and (3) a water cluster and additional water molecules, both of which are attracted to a methanediol by hydrogen bonds. The activation energy for the decomposition is reduced by a water cluster more efficiently than water molecules in a ring structure. However, the activation energy reduced by a water cluster is still larger than that obtained from laboratory experiments. We include water molecules that are attracted to a methanediol by hydrogen bonds during the water-cluster-catalyzed decomposition of a methanediol. The hydrogen bonds with the water molecules permit little change in the structure of the methanediol during the decomposition and play a significant role to reduce the activation energy for the decomposition. The rate constant obtained from the theoretical simulation agrees well with that determined by the laboratory experiment.

Determination of the filter capture efficiency for safe use of fixative solutions in the biological glove box of the International Space Station

For fixation of biological specimen in the International Space Station (ISS) aqueous solutions of formaldehyde, glutaraldehyde and ethanol are used in a biological glove box (BGB) containment. The air circulated through the BGB unit is filtered over a bank of filters consisting of a packed bed of activated bituminous coal-based granular carbon impregnated with sodium bromate. A procedure was developed to determine the performance of these filters in the case an unexpected spill would occur. In a simulated spill scenario under earth gravity conditions finely dispersed aerosols of the aforementioned aqueous solutions were drawn through the filter unit at a flow of 75 L/min. To determine the filter capture efficiency, glass fiber membrane filters were impregnated with 2,4-dinitrophenylhydrazine (DNPH) to capture formaldehyde and glutaraldehyde by chemical binding. The filters were analyzed for the DNPH-aldehyde complex by HPLC-UV. Ethanol was collected by adsorption on activated coal and subsequently analyzed by gas chromatography flame ionization detection (GC-FID). A challenge with 10.0 mL of test solution resulted in downstream air concentrations of 0.295 ± 0.094 mg/m3 for a solution of 3% of formaldehyde in water and 0.018 ± 0.015 mg/m3 for a solution containing 3.5% of glutaraldehyde in water. For a filter load of 5.0 mL of 70% ethanol in water, the downstream concentration was 19.4 ± 7.8 mg/m3. This corresponds to filter capture efficiencies of 99.5% for formaldehyde, 99.9% for glutaraldehyde, and 97.5% for ethanol. The measured concentrations downstream of the filter unit all remained below the spacecraft maximum allowable concentrations (SMAC) for these substances. Breakthrough tests were performed at tenfold the volume of the simulated spill scenario. Complete breakthrough occurred at 35 ± 14 min for formaldehyde and at 15 ± 2 min for ethanol. For glutaraldehyde breakthrough was not observed within 75 min.

NMR studies of the equilibria and reaction rates in aqueous solutions of formaldehyde.

Formaldehyde has an important role in the chemical industry and in biological sciences. In dilute aqueous solutions of formaldehyde only traces of the molecular formaldehyde are present and the predominant species are methylene glycol and in lower concentrations, dimethylene glycol. The chemical equilibria and reaction rates of the hydration of formaldehyde in H2O and D2O solutions at low concentrations were studied by (1)H and (13)C NMR at various conditions of pH (1.8-7.8) and temperature (278-333 K). These measurements became possible by direct detection of formaldehyde (13)C and (1)H peaks. The equilibrium and rate constants of the dimerization reaction of methylene glycol were also measured. The rate constants for both the hydration and the dimerization reactions were measured by a new version of the conventional selective inversion transfer method. This study, together with previous published work, completes the description of dynamics and equilibria of all the processes occurring in dilute aqueous formaldehyde solutions.

Phase equilibria of aqueous solutions of formaldehyde and methanol: Improved approach using UNIQUAC coupled to chemical equilibria

The study of the phase equilibria involving formaldehyde is still relevant because of its presence in new processes where biomass is the raw material. The coupling between physical phase equilibria and chemical reactions makes its thermodynamic description a challenging task. In this work, an improved approach using UNIQUAC coupled to chemical equilibria was developed and compared with experimental data from the literature. The first application was done for the phase equilibria of the formaldehyde–water system and distribution of oligomers in the liquid phase was computed. The second and the third applications respectively considered the phase equilibria of the formaldehyde–methanol system and the formaldehyde–water–methanol system.

Henry’s Law Constant and Overall Mass Transfer Coefficient for Formaldehyde Emission from Small Water Pools under Simulated Indoor Environmental Conditions

The Henry's law constant (HLC) and the overall mass transfer coefficient are both important parameters for modeling formaldehyde emissions from aqueous solutions. In this work, the apparent HLCs for formaldehyde aqueous solutions were determined in the concentration range from 0.01% to 1% (w/w) and at different temperatures (23, 40, and 55 °C) by a static headspace extraction method. The aqueous solutions tested included formaldehyde in water, formaldehyde-water with nonionic surfactant Tergitol NP-9, and formaldehyde-water with anionic surfactant sodium dodecyl sulfate. Overall, the measured HLCs ranged from 8.33 × 10(-6) to 1.12 × 10(-4) (gas-concentration/aqueous-concentration, dimensionless). Fourteen small-chamber tests were conducted with formaldehyde solutions in small pools. By applying the measured HLCs, the formaldehyde overall liquid-phase mass transfer coefficients (KOLs) were determined to be in the range of 8.12 × 10(-5) to 2.30 × 10(-4) m/h, and the overall gas-phase mass transfer coefficients were between 2.84 and 13.4 m/h. The influences of the formaldehyde concentration, temperature, agitation rate, and surfactant on HLC and KOL were investigated. This study provides useful data to support source modeling for indoor formaldehyde originating from the use of household products that contain formaldehyde-releasing biocides.

A novel biomass assisted synthesis of Au–SrTiO3 as a catalyst for direct hydrogen generation from formaldehyde aqueous solution at low temperature

A novel biomass-synthesized Au–SrTiO3 composite was prepared by syzygium extract and used for H2 evolution from formaldehyde aqueous solution without any additives at low temperature. The as-prepared catalyst exhibits the best performance for H2 evolution (111.15 μmol g−1) compared with the glucose–Au–SrTiO3 and UV–Au–SrTiO3. Through X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectra (FTIR), and X-ray photoelectron spectroscopy (XPS), it was found that the high activity of the syzygium–Au–SrTiO3 catalyst could be linked to the interaction between hydroxyls from biomass and the Au–SrTiO3 which resulted in the Au(I)/Au species. Also, the oxygen vacancies and organic biomass groups on the support may play an important role in the activation of formaldehyde, which was further transformed into formate intermediates and decomposed into hydrogen and carbon dioxide.

Preparation Cu-Doped Carbon Aerogels and their Adsorptive Desulfurization Performance

Cu-doped carbon aerogels were prepared by the sol-gel polymerization of resorcinol with formaldehyde in aqueous solution to produce organic gels that are supercritically dried in n-hexane and subsequently pyrolyzed in an inert atmosphere, using sodium carbonate as catalyst and copper acetate as copper source. The addition amount of the copper acetate in the initial reaction mixture has a profound effect on the surface morphology and pore texture of the resulting aerogel. It is shown that the introduction of copper lead to generation of ultrafine micropores. The desulfurization performance of the as-obtained carbon aerogels was evaluated by selective adsorption of dibenzothiophene (DBT) as a model sulfur compound and benzene as a competitive aromatic compound. It is found that the adsorption capacity for DBT is related to the volume of micropores. And the selectivity is improved with the increase of copper content, indicating the presence of copper is favorable to DBT retention on the surface via its π-complexation effect.