Formaldehyde In Aqueous Solution Research Articles

Design of a process for the provision of methanolic formaldehyde solutions of low water content from aqueous formaldehyde solutions

Formaldehyde is an essential and widely used intermediate in the chemical industry. It is mostly handled and stored in aqueous solutions. However, some processes require methanolic formaldehyde solutions of low water content as feedstock, among them the production of the synthetic fuel poly(oxymethylene) dimethyl ether (OME). This work presents the conceptual design for a process to provide methanolic formaldehyde solutions with high yield, avoiding aqueous solution as a side product. The separation of water is achieved by a combination of thin-film evaporation and distillation. Process simulations and optimal operating points with respect to energy demand and residual water content are determined. A residual water content of 0.09 g/g in the product could not be undercut.

The Effects of Formalin (Formyl Tetrahydrofolate) on CDK1 Protein on the Oocyte Maturation Process: Quantitative Structure Toxicity Relaionships (QSAR) In Silico Analysis

Formalin is an aqueous solution of formaldehyde. Formalin can trigger the formation of ROS causingoxidative stress, and has an impact on changes in theCDK1 protein which has a role in oocyte maturation.The researchers were able to predict in silico mutagenicityand formyl tetrahydrofolate toxicity to CDK1protein in oocyte cell maturation using the Molegro VirtualDocker computer program and the comparisoncompound fipronil. The receptor CDK1/CyclinB1/CKS2,code PDB: 4Y72, was used with the LZ9 ligand.Using the pkCSM online tool program, investigate in silicoqualitative structure activity relationships (QSAR)to predict pharmacokinetic properties (ADME), toxicity ofpotential medicinal compounds, environmentalcontaminants, and poisons. The bond energy resulting from docking between formalin, LZ9 ligand, andfipronil comparators at the target receptor was compared for data analysis. The more stable the bonds are,the lower the bond energy of the ligands to the target receptor. The bond energy of formalin = -130.832kcal/mol, ligand LZ9 301 [A] = -120.118kcal/mol, and fipronil = -101.069 kcal/mol, according to the in silico testresults. Formalin has the ability to increase ROS production and affect CDK1 protein more than LZ9 andfipronil ligands, according to the above test results. Thefindings of the in silico test utilizing the pkCSMonline tool software demonstrate that formyl tetrahydrofolate molecules are hazardous and quicklyenterand absorb into the human body.

AMINOMETHYLATION OF DIHYDROXYACETOPHENONES

Aminomethylation of trifunctional 2.5-dihydroxyacetophenone (2.5-DHA) and 2.4-dihydro¬xy¬aceto-phenone (2.4-DHA) by free primary and secondary amines in the presence of formaldehyde has been conducted for the first time. It has been established that 2.5-DHA is aminomethylated with secondary heterocyclic amines - piperidine and morpholine and with aqueous formaldehyde solution in alcohol medium at 500C. The reaction proceeds simultaneously via all three functions forming stable C,O-substitution products − β-amino-2-aminomethoxy-4-aminomethyl-5-hydroxypropiophenones. The aminomethylation reaction of 2.4-DHA proceeds by phenolic function only under the action of methylene bis-amines piperidine and morpholine in absolute alcohol at 200C with the formation of 2.4-dihydroxy-3-aminomethylacetophenones. Aminomethylation of 2.4-DHA with primary aromatic amines - n-to¬luidine and n-anisidine proceeds in absolute alcohol under the action of formaldehyde in the form of paraform in the presence of catalytic amounts of KOH at 500C. The reaction products are 3.4-dihydro-2H-1.3-benzoxazines. 2.5-DHA does not react with primary aromatic amines and formaldehyde. The composition and structure of compounds synthesized have been established according to the data of ele¬mental and spectral methods of analysis

Effects of formaldehyde ( Parasite‐S ®) on biofilter nitrification from a cold and a warm freshwater RAS

The effect of Parasite-S® (an aqueous formaldehyde solution) on the nitrification processes of biofilters was evaluated in two recirculating aquaculture systems (RASs). Rearing tanks in the warmwater RAS contained yellow perch (Perca flavescens) and grass carp (Ctenopharyngodon idella) with an initial weight of 166.8 kg and a mean density of 39.5 kg/m3. Rearing tanks in the coldwater RAS contained rainbow trout (Oncorhynchus mykiss) and lake trout (Salvelinus namaycush) with an initial weight of 1377.8 kg at a system density of 41.9 kg/m3. Parasite-S® was administered to the entire system on four consecutive days in both trials to achieve a nominal concentration of 14.8 mg/L formaldehyde (40 mg/L formalin) at the biofilter. Removal efficiencies for total ammonia nitrogen (TAN) and nitrite nitrogen were measured as indicators of biofilter nitrification processes. The active ingredient in Parasite-S®, formaldehyde, was measured until it was below the method detection limit of 0.8 mg/L. TAN volumetric removal rate was significantly decreased in both systems after formaldehyde addition and remained below pre-exposure efficiency in the coldwater RAS. Nitrite nitrogen volumetric removal rate was not significantly different, but the slope and intercepts were less after formaldehyde addition indicating an effect on the nitrifying bacteria. Although removal rates were decreased, no mortality occurred after four consecutive formaldehyde indefinite bath exposures in either system.

Obtaining of Formaldehyde Modified Tars and Road Materials on Their Basis

The process of chemical modification of tar and oxidized bitumen with formalin (a 37% aqueous solution of formaldehyde) in a hermetic container was investigated and the effectiveness of the proposed process was proven. It is shown that the most effective raw material for the process is tar, not oxidized bitumen. The expediency and impact of using different types of solvents (toluene, p-xylene and petroleum solvent, and n-octane) in the modification process were studied. It was established that the solvent should be used in the modification of oxidized bitumens, not tars. The low efficiency of the process of tar modification with formaldehyde without the use of a catalyst was proven, and it was shown that the most active catalyst in the process is sulfuric acid. The influence and optimal values of the main factors controlling the process of chemical modification of tar with formaldehyde were established, namely temperature, duration, and content of the modifier—formaldehyde. On the basis of the found regularities and optimal conditions of the modification process, samples of binding materials (of different brands) with different operational characteristics were obtained, and their comprehensive research was carried out. With the help of FTIR spectroscopy, the chemical interaction of tar with formaldehyde in the presence of an acid catalyst was confirmed. The design of the compositions of asphalt concrete mixtures using formaldehyde-modified tar was carried out, from which cylindrical samples of stone mastic asphalt (SMA-15 brand) were obtained, which were tested according to the main indicators: average density, water-saturation, compression strength at 20 and 50 °C, compression strength after water-saturation (MPa) at 50 °C.

Morphological importance of coronary ostia in equine.

The position of the coronary ostia was investigated in 70 segments of the aorta from young adult crossbred horses. After fixation with a 4% buffered aqueous formaldehyde solution and cautious dissection of the aortic bulb, the morphometric relationships between the coronary ostium and the aortic valvar elements were digitally analysed with the support of Image-Pro Plus® software. In horses, the left coronary ostium was near to the right valvular commissure in all cases (100%) analysed in this study. The left coronary ostium was at the level of the intercommissural line in 57.1% and below it in 42.9%. The right coronary ostium was near to the left valvular commissure in 58.6% (2.14 ± 0.32 cm) and close to the right valvular commissure in 41.4% (2.27 ± 0.40 cm). Concerning the intercommissural line, the right coronary ostia was at its level in 24.3% and below it in 75.7%. Accessory coronary ostia were observed in 8.6% of the specimens. In view of the results, it was possible to assume that the positions of the coronary ostia in equines tend towards a standard morphological disposition. Thus, perfusion of the left coronary artery occurs partly more frequently in ventricular systole and complete perfusion occurs less frequently in ventricular diastole. For the right coronary artery, perfusion is mostly complete in diastole and partially in ventricular systole.

Synthesis and Characterization of Cyclodextrin-Based Polyhemiaminal Composites with Enhanced Thermal Stability.

Polyhemiaminal (PHA) polymers are a new class of thermosetting polymers that have recently gained attention owing to their high mechanical strength and excellent recycling behavior. However, low thermal stability is a common issue in PHA polymers due to the thermally labile crosslinked knots. Herein, crosslinked PHA polymer composites were synthesized by reacting formaldehyde with a precursor solution of 4,4ʹ-oxydianiline (ODA) and cyclodextrins (CDs) (α-, β-, and γ-). The material obtained under optimal conditions (ODA:CD molar ratio of 1:0.5, 37% aqueous solution of formaldehyde (formalin)) exhibited good film formability and high thermal stability with two characteristic decomposition phenomena and a high char yield. The early decomposition of CDs and char formation led to high thermal stability. Time-resolved NMR analysis was conducted to study hemiaminal bond formation via a condensation reaction between ODA and formaldehyde. Furthermore, PHA matrix formation was confirmed by the dissolution of the deposited CD layer in a solution of N-methyl-2-pyrrolidinone containing 8–9 wt.% LiBr at 80 °C and FTIR analysis. Based on the elemental analysis results, PHA network formation was confirmed by considering a single unit of the PHA network with CD composition, including the solvent and water.

Nonenzymatic formaldehyde sensors using nickel oxide based electrode fabricated by electrochemical method

NiO materials were fabricated by electrochemical exfoliation combined with ultrasonic vibration to produce nano-sized particles. By electrophoresis, NiO particles dispersed in IPA solvent (isopropyl alcohol) were precipitated on the ITO substrate acting as the cathode. The morphology and structure of the materials were characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD). The role of electrophoresis potential, electrophoresis time on electrode formation was investigated when studying the effect on electrochemical properties of the electrode for formaldehyde in aqueous solution. As a result, with the NiO dispersion system (0.1 g NiO in 50 mL IPA), the distance between the ITO electrode (negative electrode) and the Pt plate (positive electrode) of 2 cm, the electrophoresis potential of 10 V, electrophoresis time of 3 min is optimized for fabrication of NiO/ITO electrode in formaldehyde electrochemical sensor. Sensitivity and linear range at different electrode potentials were investigated when determining the concentration of formaldehyde in water.

Solid–Liquid Equilibria and Kinetics of the Solid Formation in Binary and Ternary Mixtures Containing (Formaldehyde + Water + Methanol)

Solid precipitation from aqueous formaldehyde solutions is a major technical problem, leading to troubles such as plugging and fouling. While these problems are ubiquitous in formaldehyde technology, it is hard to predict them, so their mitigation is difficult. Data on the formation of a solid phase in formaldehyde-containing systems are scarce and basically only available for the system (formaldehyde + water); even these few data are contradictory. We have tackled these problems from different sides in the present work. First, a new method for measuring the solid–liquid equilibria and kinetics of solid formation in formaldehyde-containing systems was developed, and it was shown that, for technically relevant conditions, long-term effects are essential: it may take over 1000 days until equilibrium is reached. Using this new technique, reliable data for the solid–liquid equilibrium of the system (formaldehyde + water) were obtained. The liquidus line in the phase diagram of that system has two branches meeting in a eutectic point: one where the solid is water, and one where it is formaldehyde-rich. The formaldehyde solubility is found to be much lower than in most previous works. As methanol is often used for stabilizing aqueous formaldehyde solutions, we also investigated solid–liquid equilibria in the systems (formaldehyde + methanol) and (formaldehyde + water + methanol). Furthermore, data on the kinetics of the formation of formaldehyde-rich solids were acquired for the studied systems. Based on the new data and extensive previous work on the chemical equilibria and reaction kinetics, a physico-chemical model was developed, which describes both the solid–liquid equilibria as well as the kinetics of the solid formation. It is shown that the very slow kinetic effects in the studied systems are mainly caused by the interaction of the slow liquid phase reaction kinetics and the precipitation of a single oligomer of formaldehyde with water for which the solubility limit is reached.

Al3+ coordinated chitosan hydrogel with ultrahigh water absorbency and environmental response

To fully utilize water, there is a great demand to develop eco-friendly materials with both ultra-high water absorbency and environmental response. In this study, the Al3+ coordinated chitosan (CIS-Al3+) hydrogels were prepared by formation of coordination bonds between Al3+ and the skeleton of CIS hydrogels. AlCl3 was used to provide coordination center, and the formaldehyde aqueous solution was chosen as crosslinker. The effect of Al3+ content and mass fraction of formaldehyde on gel formation, mechanical property and water storage capacity of CIS-Al3+ hydrogels was investigated deeply. The obtained CIS-Al3+ hydrogel can store more than 500% of its own weight of water without cracking, which demonstrates its super-absorbency. Besides, the CIS-Al3+ hydrogels can swell/shrink in response to the change of external stimuli such as temperature, pH and salinity. These outstanding properties, together with the low-cost raw materials, simple preparation method and biocompatible and biodegradable properties, enable CIS-Al3+ hydrogels to be applied as water storage materials in the agriculture field and pH-responsive materials in the future.

Reversible mechanochromic studies on AIE-inspired smart materials and their applications in HCHO sensing.

Smart fluorescent materials that respond to external stimuli have received more and more attention because of their excellent optical properties in the field of anti-counterfeiting, information security and fluorescence sensing. Herein, we reported a new stimulus-responsive material, {[Zn4(TCPE)(HTCPE)(DMA)3(OH)(H2O)2]·2DMA·2H2O}n (HPU-21), which showed a series of fluorescence changes under the influence of temperature, pressure and solvents. Combined with the temperature-dependent fluorescence, 1H NMR and 13C NMR spectra, TEM and powder X-ray diffraction results, the fluorescence transformation was mainly attributed to the changes in the twisted ethyl core and the multiple rotational phenyl rings, as well as the aggregation degree. Based on these findings, we designed an adjustable formaldehyde probe with excellent performance. The detection limit of formaldehyde in aqueous solutions is calculated as 35 ppb, which is much lower than the concentration that is harmful to health (20 ppm). The extremely high sensitivity to formaldehyde makes it have potential application prospects in practical formaldehyde detection.

Quinolizinium-based fluorescent probes for formaldehyde detection in aqueous solution, serum, and test strip via 2-aza-Cope rearrangement.

Formaldehyde is an abundant contaminant in food and environments causing various diseases. Thus, the development of fast, simple, and selective formaldehyde detection is of great interest. Herein, novel quinolizinium-based fluorescent probes were designed based on a 2-aza-Cope rearrangement reaction and showed high selectivity to formaldehyde by fluorescence emission shift. We successfully reduced the detection time by increasing the bulkiness of the homoallylic moiety. The probes were applied to detect formaldehyde in aqueous solution, serum, and paper format.

Rapid preparation of gaseous methanediol (CH2(OH)2).

The simplest geminal diol CH2(OH)2 serves as an important precursor to form atmospheric formic acid. CH2(OH)2 vapour can be generated by the evaporation of an aqueous formaldehyde solution, prepared by dissolving paraformaldehyde under reflux. Its rovibrational feature at 980-1100 cm-1 is consistent with the simulation and free of the intense interferences of H2O and CH2O.

Degradation of formaldehyde aqueous solution by Bi based catalyst and its activity evaluation.

Bi based catalysts have attracted continuous attention from the scientific community because of their excellent photochemical properties and wide application in photocatalytic treatment of environmental pollution. A series of Bi based catalysts with good crystallinity and high purity were prepared by calcination and hydrothermal synthesis. In the application of degrading formaldehyde aqueous solution in a mercury lamp and xenon lamp atmosphere, it was found that BiVO4 and Bi2WO6 showed excellent photochemical properties under ultraviolet and visible light. The tests of PL, UV-Vis and EIS confirmed their high activity. In the calculation based on density functional theory (DFT), through the analysis of the energy band structure, density of states (DOS) and partial wave density of states (PDOS), it is found that the d orbital of V and W elements has a great influence on the position and size of the energy band of the catalyst, which makes it have high activity and excellent electrochemical properties.

Ocular microscopy of Bradypus variegatus

Bradypus variegatus, popularly known as common sloth or brown-throated sloth, is a species with wide geographical distribution in Brazil. Expand on the literature about the species, we aimed to describe the morphology of its eye and its main annexes. For this study, six frozen specimens donated to the Animal Morphological Research Laboratory of the Federal Rural University of Amazonia were used. The specimens were fixed in a 10% aqueous solution of formaldehyde. The structures that constitute the ocular apparatus were identified and described after dissection and histological analysis using light microscopy. The bulbar conjunctiva presented a stratified cuboidal epithelium, with a considerable number of serous glands. The stroma layer and the posterior limiting lamina were found well defined in the species. The corneoscleral meshwork possessed a large opening for drainage of aqueous humour, followed by a wide retinal region, in which a layer of photoreceptors was visualized. Cones and rods could not be discriminated from each other. Microscopy of the medial angle of the eye revealed the cartilage and glands of the third eyelid, and a well-developed lacrimal gland structure. Bradypus variegatus distinguishing features and similarities in comparison with other domestic and wild mammal and bird species already described were investigated, which expounded the limited knowledge that is presently available on the morphology of wild fauna. The data extend the limited knowledge that are presently available on the ocular histology of B.variegatus.

Advanced oxidation of high concentrations of formaldehyde in aqueous solution under fluorescent and UV light

Background: Formaldehyde (FA) is a carcinogen compound, which is soluble in water. FA can be removed from aqueous solution using advanced oxidation methods. Methods: In this study, the oxidation of FA was studied under fluorescent and UV light. Hydrogen peroxide (H2 O2 ) was used as an oxidant. The pH value and H2 O2 amount of samples were optimized. The chemical oxygen demand (COD), FA concentration, and H2 O2 consumption were followed. Results: It was observed that the pH value of the sample was more significant under fluorescent light than UV light at oxidation of FA. The highest COD removal and H2 O2 reduction were 18.57 and 30.90%, respectively, at pH 12.00, with a 1:1 ratio of FA:H2 O2 under fluorescent light. 86.41% FA and 62.12% COD removal were achieved at pH 7.00, with a 1:2 ratio of FA:H2 O2 , under UV light. It was observed that H2 O2 was consumed at all pH values under UV light. On the other hand, under fluorescent light, the concentration of H2 O2 decreased only at pH 12. In control samples containing only H2 O2 , the H2 O2 reduction was 92.09% at pH 11.91, while it was 2-6% at other pH levels under fluorescent light. The H2 O2 reduction changed between 33 and 44% at different pH values under UV light. The oxidation of FA was found to be suitable for the pseudo-first-order kinetic model and Langmuir isotherm model. Conclusion: The most effective oxidation was obtained at the original pH value (7.00) and 1:2 ratio of FA:H2 O2 under UV light.

Conceptual design of a crystallization-based trioxane production process

Trioxane, a cyclic trimer of formaldehyde, is an important intermediate that is mainly used as a source of water-free formaldehyde in chemical production processes. Different routes for the production of trioxane from aqueous formaldehyde solutions have been described in the literature, which all have in common that they are energy-intensive. In this work, the conceptual design of a new production process for trioxane is presented. It is a modification of a state-of-the-art pressure swing process from the literature, where the most critical distillation step is replaced with a crystallization. The new crystallization-based process and the pressure swing process were simulated in a consistent manner based on a well-established physico-chemical model for the ternary system (formaldehyde + water + trioxane). To obtain a sound basis for the description of the crystallization, solid–liquid equilibria in the ternary system, for which previously no data was available, were measured at conditions relevant for the process. A comparison of the two processes showed that the new crystallization-based process has a considerably reduced energy demand and much smaller recycle streams. Furthermore, it was found that the crystallization can be performed efficiently at temperatures well above 273 K. All this makes the new crystallization-based process an attractive candidate for trioxane production.

Photoreforming hydrogen production by carbon doped exfoliated g-C3N4: Optimization using design expert®software

Carbon doping was ascertained as a best strategy to improve the surface area and electronic properties of g-C3N4. Additionally, the carbon material could extend the delocalization of pi-electrons consequently fostering the photocatalytic reactions. Herein, a newly formulated carbon doped exfoliated g-C3N4 was prepared by a facile hydrothermal technique. The photocatalytic experiments using formaldehyde aqueous solution was employed to examine the effect of time and catalyst dosage. Response surface methodology (RSM) was used to optimize the reaction parameters and determine the best operating conditions using Design Expert Software Version 7.1.6. The changes in the functional groups of the catalyst before and after the reaction was characterized by FTIR analysis. As a result, the characteristic peak of tri-s-triazine located at 802 cm−1 was present in the recycled catalyst. This outcome confirms that the melon structures were not destroyed after the reaction thereby revealing better stability of the catalyst. UV–Vis DRS analysis was used to evaluate the band gap of the as-prepared catalysts. From the one-factor-at-a-time (OFAT) results, the range of the independent variables were selected as follows: time (4–8 h) and catalyst dosage (0.5–1 g/L). Based on the central composite design (CCD) matrix, the optimum conditions for hydrogen yield (920 µmol/g) were observed at 6 h using 0.75 g/L of catalyst. In the optimization process, the response of the interactions between the parameters were given by the polynomial quadratic model and 3D plot. The influencing factors on the reaction were analysed by Analysis of Variance (ANOVA). The highest R-squared value of 0.9797 and F-value of 46.31 evidenced an excellent fitting of the model. Hence, this work provides some insights on the development of Carbon doped exfoliated g-C3N4 with their contribution towards photocatalytic field.

Real-time Raman analysis of the hydrolysis of formaldehyde oligomers for enhanced collagen fixation

Formaldehyde (FA) is widely applied as a fixative for proteins such as collagen. Current studies have confirmed that the reversible oligomer-to-monomer equilibrium of FA in aqueous solution and the proportion of FA monomer is a significant factor affecting tissue fixation. Since the hydrolysis of FA oligomers is a dynamic process affected jointly by different factors, its real time monitoring has proved to be challenging. In this work, by utilizing the well-established Raman technique as an analytical platform, we identified the factors affecting the hydrolysis of FA oligomers by rationally examining the νs (OCO) and νas (OCO) modes with varying conditions, such as time, pH, temperature, and FA concentration. The optimized conditions of the highest hydrolysis rate of oligomers into monomers for fixation on collagen and tissues have been found to be relatively low FA concentration (≤5%) in phosphate-buffered saline at pH 9.0 in room temperature. In order to compare the fixation quality of the optimized conditions to that of the conventional conditions used by current medical practices (4% FA concentration in tap water under room temperature), Raman spectroscopy and chemical derivatization methods with o-phthalaldehyde and fluorescent probe FAP-1 have been investigated, and our results revealed that the FA molecules under our optimized conditions have reacted with at least 15% more amino groups within collagen compared to those under the conventional conditions mentioned above. This study provides direct evidence of the FA equilibrium in solution by Raman spectroscopy, which could be applied for the optimal use of FA in medicine, even at an industrial scale.

GENERATING A STREAM WITH A STABLE FORMALDEHYDE CONCENTRATION IN THE LABORATORY

A laboratory-scale bio-trickling filter (BTF) was initialized to evaluate the removal of formaldehyde biologically. However, generating formaldehyde gas in the lab is one of the grand challenges hindering research efforts. Formaldehyde was introduced into the gaseous phase by aerating the required air flowrate through a diluted formaldehyde solution mixed with methanol as a stabilizer by a bubbler. However, achieving stable gaseous influent concentrations of formaldehyde was challenging since it polymerizes while volatilizing. Resulting in paraformaldehyde. The resulting white powder clogged the pipes and generated uneven gaseous concentrations. To solve this problem, sodium hydroxide (NaOH) was added with a phosphate buffer to the aqueous formaldehyde solution to maintain the pH between 7.00-7.20. Additionally, the aqueous solution needed to be heated at 60℃ to eliminate the polymerization. The exhausted formaldehyde by volatilization was replaced by a continuous supply of aqueous diluted formaldehyde solution to keep the volume and mass of the aqueous solution and formaldehyde constant, respectively. Stable gaseous concentration was achieved for extended periods of time and verified by Fourier transform infrared (FTIR) spectroscopy.