An efficient and mild recycling of waste melamine formaldehyde foams by alkaline hydrolysis

Melamine formaldehyde foam(MFF)generates many poisonous chemicals through the traditional recycling methods for organic resin wastes.Herein,a high MFF degradation ratio of ca.97 wt.%was achieved under the mild conditions(160℃)in a NaOH–H2O system with ammelide and ammeline as the main degradation products.The alkaline solvent had an obvious corrosion effect for MFF,as indicated by scanning electron microscopy(SEM).The reaction process and products distribution were studied by Fourier-transform infrared spectroscopy(FTIR),X-ray photoelectron spectroscopy(XPS),and ^(13)C nuclear magnetic resonance(NMR).Besides,the MFF degradation products that have the similar chemical structures and bonding performances to those of melamine can be directly used as the raw material for synthesis of melamine urea-formaldehyde resins(MUFs).Moreover,the degradation system demonstrated here showed the high degradation efficiency after reusing for 7 times.The degradation process generated few harmful pollutants and no pre-or post-treatments were required,which proves its feasibility in the safe removal or recovery of waste MFF.

Effect of Humidity on Formaldehyde Oxidation over Ce_(0.8)Zr_(0.2)O_(y)Catalyst

In the preparation of a series of Ce_(0.8)Zr_(0.2)O_(y)catalysts catalyzing the removal of formaldehyde,BET,H2-TPR,IR,SEM,XPS,and XRD were used to characterize the catalyst,and the influence of humidity on the catalyst activity was studied by adjusting the humidity during the process.The experimental results showed that the formaldehyde removal rate increased with the increase of humidity.When the humidity was higher than 50%,the formaldehyde removal rate decreased by 3%over that when the humidity was 50%.The characterization results showed that humidity facilitated the activation of oxygen and the formation of hydroxyl groups,which both promoted the formation and oxidative decomposition of intermediates and prevented the deposition of intermediates that clogged the pores,allowing more formaldehyde to be adsorbed and oxidized,which increased the activity of the catalyst.This provides new mechanistic evidence for the oxidation of formaldehyde and helps in the development of relatively low-cost materials for formaldehyde purification.

Indoor Formaldehyde Removal Techniques through Paints: Review

Due to its ability to cause illnesses and discomfort even at low concentrations, formaldehyde pollution of indoor air poses a significant risk to human health. Sources of formaldehyde in indoor environments include textiles, paints, wallpapers, glues, adhesives, varnishes, and lacquers;furniture and wooden products like particleboard, plywood, and medium-density fiberboard that contain formaldehyde-based resins;shoe products;cosmetics;electronic devices;and other consumer goods like paper products and insecticides. According to the World Health Organisation, indoor formaldehyde concentrations shouldn’t exceed 0.1 mg/m3. The methods include membrane separation, plasma, photocatalytic decomposition, physisorption, chemisorption, biological and botanical filtration, and catalytic oxidation. Materials based on metal oxides and supported noble metals work as oxidation catalysts. Consequently, a paint that passively eliminates aldehydes from buildings can be developed by adding absorbents and formaldehyde scavengers to the latex composition. It will be crucial to develop techniques for the careful detection and removal of formaldehyde in the future. Additionally, microbial decomposition is less expensive and produces fewer pollutants. The main goal of future research will be to develop a biological air quality control system that will boost the effectiveness of formaldehyde elimination. The various methods of removing formaldehyde through paints have been reviewed here, including the use of mixed metal oxides, formaldehyde-absorbing emulsions, nano titanium dioxide, catalytic oxidation, and aromatic formaldehyde abating materials that can improve indoor air quality.

A Comparison of Airborne Formaldehyde Field Measurements Collected in an Anatomic Pathology Laboratory

Environmental monitoring of airborne formaldehyde (FA) using sensitive methodologies is fundamental to prevent health risks. The objective of this study was to compare three different FA monitoring methods during the daily activities of an anatomic pathology laboratory. Daily eight-hour measurements deriving from Radiello® passive diffusive samplers (PDS), NEMo XT continuous optical sensor (COS), and multi-gas 1512 photoacoustic monitor (MPM) were simultaneously compared over a period of 14 working days. Given the different daily distributions of the measurements performed by the three devices, all measurements were time-aligned for comparison purposes. The 95% limit of agreement (LOA) method was applied to estimate the degree of concordance of each device with respect to the others. Formaldehyde arithmetic mean measured using PDS was 32.6 ± 10.4 ppb (range: 19.8 - 62.7). The simultaneous measures performed by COS and MPM were respectively 42.4 ± 44.8 ppb (range: 7.0 - 175.0) and 189.0 ± 163.7 ppb (range: 40.0 - 2895.4). The MPM geometric mean (171.3 ppb) was approximately five times higher than those derived from COS (32.3 ppb) and PDS (31.4 ppb). The results of the LOA method applied to log-transformed FA data showed the same systematic discrepancies between MPM and the other two devices. A good agreement between PDS and COS could lead to a tailored approach according to the individual specificity of these techniques. This tool may be useful for accurately assessing the risk of FA exposure among healthcare workers. However, the limited specificity of the MPM does not support its use as a monitoring method for FA in the workplace.

Comprehensive Analysis of Indoor Formaldehyde Removal Techniques:Exploring Physical,Chemical,and Biological Methods

This research focuses on the evaluation of diverse approaches for removing formaldehyde from indoor environments,which is a significant concern for indoor air quality.The study systematically examines physical,chemical,and biological methods to ascertain their effectiveness in formaldehyde mitigation.Physical methods,including air circulation and adsorption,particularly with activated carbon and molecular sieves,are assessed for their efficiency in various concentration scenarios.Chemical methods,such as photocatalytic oxidation using titanium dioxide and plasma technology,are analyzed for their ability to decompose formaldehyde into non-toxic substances.Additionally,biological methods involving plant purification and microbial transformation are explored for their eco-friendly and sustainable removal capabilities.The paper concludes that while each method has its merits,a combined approach may offer the most effective solution for reducing indoor formaldehyde levels.The study underscores the need for further research to integrate these methods in a practical,cost-effective,and environmentally sustainable manner,highlighting their potential to improve indoor air quality significantly.

Advances of manganese-oxides-based catalysts for indoor formaldehyde removal

Formaldehyde(HCHO)has been identified as one of the most common indoor pollutions nowadays.Manganese oxides(MnO_(x))are considered to be a promising catalytic material used in indoor HCHO oxidation removal due to their high catalytic activity,low-cost,and environmentally friendly.In this paper,the progress in developing MnO_(x)-based catalysts for HCHO removal is comprehensively reviewed for exploring the mechanisms of catalytic oxidation and catalytic deactivation.The catalytic oxidation mechanisms based on three typical theory models(Mars-van-Krevelen,Eley-Rideal and Langmuir-Hinshelwood)are discussed and summarized.Furthermore,the research status of catalytic deactivation,catalysts’regeneration and integrated application of MnO_(x)-based catalysts for indoor HCHO removal are detailed in the review.Finally,the technical challenges in developing MnO_(x)-based catalysts for indoor HCHO removal are analyzed and the possible research direction is also proposed for overcoming the challenges toward practical application of such catalysts.

Effect of polytetrafluoroethylene hollow fiber microstructure on formaldehyde carbonylation performance in membrane contactor

Membrane contactor is regarded as a promising method for reaction and process intensification. The feasibility of formaldehyde carbonylation to synthesize glycolic acid using polytetrafluoroethylene(PTFE)membrane contactor has been proved in our previous study. In this paper, the effect of membrane microstructure on process performance was further investigated. Three porous PTFE hollow fibers with different pore sizes and one polydimethylsiloxane(PDMS)/PTFE composite membrane with dense layer were fabricated for comparison. The physical and chemical properties of four membranes, including chemical composition, morphology, contact angle, liquid entry pressure, thermodynamic analysis and gas permeability, were systemically characterized. Experiments of formaldehyde carbonylation under different reaction conditions were conducted. The results indicated that the yield of glycolic acid increased with decreasing pore size for porous membranes, which was due to the improvement of wetting behavior. The dense layer of PDMS in composite hollow fiber could effectively prevent the solvent from entering membrane pores, thus the membrane exhibited the best performance. At reaction temperature of 120℃ and operation pressure of 3.0 MPa, the yield of glycolic acid was always higher than 90% as the mass ratio of trioxane and phosphotungstic acid increased from 0.2:1 to 0.8:1. The highest turnover frequency was up to 26.37 mol·g^(-1)·h^(-1). This study provided a reference for the understanding and optimization of membrane contactors for the synthesis of glycolic acid using solvent with low surface tension.

Rheological and physicomechanical properties of rod milling sand-based cemented paste backfill modified by sulfonated naphthalene formaldehyde condensate

Rod milling sand(RMS)—a coarse sand aggregate—was recycled for cemented paste backfill(CPB)for the underground mined area at the Jinchuan nickel deposit,named rod milling sand-based cemented paste backfill(RCPB).The adverse effects of coarse particles on the transportation of CPB slurry through pipelines to underground stopes resulting in weakening of the stability of the backfill system are well known.Therefore,sulfonated naphthalene formaldehyde(SNF)condensate was used for the performance improvement of RCPB.The synergistic effect of solid content(SC),lime-to-sand ratio,and SNF dosage on the rheological and physicomechanical properties,including slump,yield stress,bleeding rate,uniaxial compressive strength(UCS),as well as mechanism analysis of RCPB,have been explored.The results indicate that the effect of SNF on RCPB performance is related to the SNF dosage,lime-to-sand ratio,and SC.The slump of fresh RCPB with 0.1wt%-0.5wt%SNF increased by 2.6%-26.2%,whereas the yield stress reduced by 4.1%-50.3%,indicating better workability and improved cohesiveness of the mix.The bleeding rate of fresh RCPB decreased first and then rose with the increase of SNF dosage,and the peak decrease was 67.67%.UCS of RCPB first increased and then decreased with the increase of SNF dosage.At the optimal SNF addition ratio of 0.3wt%,the UCS of RCPB curing for 7,14 and,28 d ages increased by 31.5%,28.4%,and 29.5%,respectively.The beneficial effects of SNF in enhancing the early UCS of RCPB have been corroborated.However,the later UCS increases at a slower rate.The research findings may guide the design and preparation of RCPB with adequate performance for practical applications.

Curing Process of Phenol Formaldehyde Resin for Plywood under Vacuum Conditions

The study characterized the curing behaviors of phenol formaldehyde(PF)resin under different vacuum degrees and explored the properties of 9-ply plywood panels hot-pressed under both vacuum and atmospheric conditions.The changes in core temperature and moisture content of the plywood mats during hot pressing were investigated as well.It was found that the gel times and gel temperatures of PF resin decreased with the increase of vacuum degree using a self-made device.FTIR spectra indicated the degree of polycondensation of hydroxymethyl gradu-ally increased with the increase in temperature.It was also observed that a higher degree of vacuum led to a slower polycondensation reaction rate of PF resin.During different hot-pressing processes,the bonding strengths in the innermost and uppermost gluelines of the vacuum hot-pressed plywood panels were up to 30%–50%higher than their counterparts of conventional hot-pressed products.A less difference in the bonding strengths between these two gluelines was also observed for vacuum hot-pressed products.In addition,the core of vacuum hot-pressed plywood was found to have a greater heating rate and higher temperature at thefinal stage of hot pressing,which was beneficial to cure the PF resin.The results from this study indicate a promising potential of introducing a vacuum during hot pressing to improve the quality and productivity of plywood products and provide a basis for adopting vacuum to hot press wood composites.

Evaluation of Formaldehyde as a Potential Cause of Olfactory Dysfunction in Hairdressers

Objective: The aim of this study was to compare the olfactory function between hairdressers exposed to formaldehyde and unexposed controls, as exposure to toxic agents is a potential cause of olfactory disorders in humans. Hairdressing professionals frequently encounter formaldehyde, a component found in hair products that are known to have various toxic effects on the human body, including alterations in the sense of smell. Methods: A total of 32 hairdressing volunteers exposed to formaldehyde and 32 non-exposed volunteers matched for age, sex, education and smoking status underwent the University of Pennsylvania Smell Identification Test (UPSIT®). Results: The findings demonstrated a decrease in UPSIT® olfactory test scores and a higher degree of olfactory loss among hairdressers exposed to formaldehyde (mean UPSIT® scores: 30.6 vs 35.1, p Conclusion: Occupational exposure of hairdressers to formaldehyde is associated with diminished olfactory function. Education approach and promotion of personal protective equipment usage should be encouraged.

Evaluation of Formaldehyde as a Potential Cause of Olfactory Dysfunction in Hairdressers

Objective: The aim of this study was to compare the olfactory function between hairdressers exposed to formaldehyde and unexposed controls, as exposure to toxic agents is a potential cause of olfactory disorders in humans. Hairdressing professionals frequently encounter formaldehyde, a component found in hair products that are known to have various toxic effects on the human body, including alterations in the sense of smell. Methods: A total of 32 hairdressing volunteers exposed to formaldehyde and 32 non-exposed volunteers matched for age, sex, education and smoking status underwent the University of Pennsylvania Smell Identification Test (UPSIT®). Results: The findings demonstrated a decrease in UPSIT® olfactory test scores and a higher degree of olfactory loss among hairdressers exposed to formaldehyde (mean UPSIT® scores: 30.6 vs 35.1, p Conclusion: Occupational exposure of hairdressers to formaldehyde is associated with diminished olfactory function. Education approach and promotion of personal protective equipment usage should be encouraged.

Low-temperature catalytic oxidation of formaldehyde over Co_3O_4catalysts prepared using various precipitants

Co3O4 catalysts prepared with different precipitants（NH3·H2O,KOH,NH4HCO3,K2CO3 and KHCO3）were investigated for the oxidation of formaldehyde（HCHO）.Among these,KHCO3-precipitated Co3O4（KHCO3-Co） was the most active low-temperature catalyst,and was able to completely oxidize HCHO at the 100-ppm level to CO2 at 90℃.In situ diffuse reflectance infrared spectroscopy demonstrated that hydroxyl groups on the catalyst surface were regenerated by K~＋ and CO3^（2-）,thus promoting the oxidation of HCHO.Moreover,H2-temperature programmed reduction and X-ray photoelectron spectroscopy showed that employing KHCO3 as the precipitant increased the Co^3＋/Co^2＋molar ratio on the surface of the Co3O4 catalyst,thus further promoting oxidation.Structural characterization revealed that catalysts precipitated with carbonate or bicarbonate reagents exhibited greater specific surface areas and pore volumes.Overall,these data suggest that the high activity observed during the Co3O4 catalyzed oxidation of HCHO can be primarily attributed to the presence of K~＋ and CO3^（2-） on the Co3O4 surface and the favorable Co^3＋/Co^2＋ ratio.

Progress in research on catalysts for catalytic oxidation of formaldehyde

Formaldehyde（HCHO）is carcinogenic and teratogenic,and is therefore a serious danger to human health.It also adversely affects air quality.Catalytic oxidation is an efficient technique for removing HCHO.The development of highly efficient and stable catalysts that can completely convert HCHO at low temperatures,even room temperature,is important.Supported Pt and Pd catalysts can completely convert HCHO at room temperature,but their industrial applications are limited because they are expensive.The catalytic activities in HCHO oxidation of transition-metal oxide catalysts such as manganese and cobalt oxides with unusual morphologies are better than those of traditional MnO2,Co3O4,or other metal oxides.This is attributed to their specific structures,high specific surface areas,and other factors such as active phase,reducibility,and amount of surface active oxygens.Such catalysts with various morphologies have great potential and can also be used as catalyst supports.The loading of relatively cheap Ag or Au on transition-metal oxides with special morphologies potentially improves the catalytic activity in HCHO removal at room temperature.The preparation and development of new nanocatalysts with various morphologies and structures is important for HCHO removal.In this paper,research progress on precious-metal and transition-metal oxide catalyst systems for HCHO oxidation is reviewed; topics such as oxidation properties,structure–activity relationships,and factors influencing the catalytic activity and reaction mechanism are discussed.Future prospects and directions for the development of such catalysts are also covered.

Synthesis of three-dimensional ordered mesoporous MnO_2 and its catalytic performance in formaldehyde oxidation

Three-dimensional（3D）ordered mesoporous MnO2 was prepared using KIT-6 mesoporous molecular sieves as a hard template.The material was used for catalytic oxidation of HCHO.The material has high surface areas and the mesoporous characteristics of the template,with cubic symmetry（ia3d）.It consists of a β-MnO2 crystalline phase corresponding to pyrolusite,with a rutile structure.Transmission electron microscopy and X-ray photoelectron spectroscopy showed that the 3D-MnO2 catalyst has a large number of exposed Mn4＋ ions on the（110）crystal plane surfaces,with a lattice spacing of 0.311 nm; this enhances oxidation of HCHO.Complete conversion of HCHO to CO2 and H2O was achieved at 130 °C on 3D-MnO2; the same conversions on α-MnO2 and β-MnO2 nanorods were obtained at 140 and 180 °C,respectively,under the same conditions.The specific mesoporous structure,high specific surface area,and large number of surface Mn4＋ ions are responsible for the catalytic activity of 3D-MnO2 in HCHO oxidation.

Preparation of phenol formaldehyde resin from phenolated wood

The technique for preparing phenol formaldehyde resin from phenolated wood (PWF) and its characters were studied and analyzed. Poplar (Populus spp.) wood meal was liquefied by phenol in the presence of sulfuric acid as a catalyst. After the liquefied products were cooled, alkaline catalyst and formaldehyde were added. The mixture was kept at (60?) C for 1h and then was heated to (85?) C for 1h. The influence of molar ratio of formaldehyde to phenol (F/P) was investigated. The results showed when the molar ratio of formaldehyde to phenol was over 1.8, the PWF adhesives had high bond quality, bond durability and extremely low aldehydes emissions.

Inactivation Kinetics of β-N-Acetyl-D-Glucosaminidase from Prawn (Penaeus vannamei) by Formaldehyde

β-N-Acetyl-D-glucosaminidase （NAGase, EC.3.2.1.52） is chitinolytic enzymes and disintegrate dimmer and trimer a composition of oligomers of N-acetyl-β-D-glucosamine （NAG） into monomer. Prawn （P. vannamei） NAGase is involved in digestion and molting processes. Some pollutants in seawater affect the enzyme activity causing loss of the biological function of the enzyme, which affects the exuviating shell and threatens the survival of the animal. The effect of formaldehyde on prawn （P. vannamei） β-N-acetyl-D-glucosaminidase activity for the hydrolysis of pNP-NAG has been studied. The results show that formaldehyde, at appropriate concentrations, can lead to reversible inactivation of the enzyme, and the IC50 is estimated to be 1.05mol· L^-1. The inactivation mechanism obtained from Lineweaver-Burk plots shows that the inactivation of the enzyme by formaldehyde belongs to the competitive type. The inactivation kinetics of the enzyme by formaldehyde has been studied using the progress-of-substrate-reaction method described by Tsou, and the rate constants have been determined. The results show that k＋0 is much larger than k-0, indicating the free enzyme molecule is fragile in the formaldehyde solution.

Flow injection chemiluminescence determination of meloxicam using potassium permanganate and formaldehyde system

A simple, rapid and sensitive flow injection chemiluminescence （FI-CL） method has been developed for the determination of meloxicam. The method is based on the CL-emitting reaction between meloxicam and potassium permanganate in a hydrochloric acid medium, enhanced by formaldehyde （HCHO）. Under optimum conditions, calibration curve over the range of 1.0-20.0μg/mL was obtained. The proposed method was successfully applied to the determination of meloxicam in capsules with no evi- dence of interference from common excipients. The detection limit of this method was 25.6 ng/mL. The relative standard deviation was 2.1% for 10.0 μg/mL meloxicam. The sample throughput was found to be 120 samples/h.

Quality Synthetic Evaluation of Urea Formaldehyde Foam Substrate in Turf Establishment

[Objective]The aim of this study was to explore the feasibility of three kinds of urea formaldehyde foam substrate in tall fescue establishment as well as to study on evaluation of turf quality.[Method]The visual estimates,ecological quality estimates and utility quality estimates were used as the 1st level indicators,and the density,color,texture,uniformity,green period,cover degree,biomass,emergence energy,growth rate and turf-forming time were used as the corresponding 2nd level indicators.With T.L.Satty＇s method Analytic Hierarchy Process（AHP） and the fuzzy synthesis evaluation method,the weight ratio of matrix was obtained and the synthetic evaluation result was accorded with facts,then it could be regarded as the satisfying value of weight.[Result]The quality of three covering soil treatments was better than that of uncovering treatment and conventional treatment,the quality synthetic evaluation of F1 was the best,which was about 0.770.[Conclusion]Urea formaldehyde foam substrate showed high quality for turf establishment,which could be further spread and applied.

The effect of urea pretreatment on the formaldehyde emission and properties of straw particleboard

For manufacturing low-formaldehyde emission particleboard from wheat straw and urea-formaldehyde （UF） resins using urea treatment for indoor environments, we investigated the influence of urea treatment on the formaldehyde emission, physical and mechanical properties of the manufactured particleboard. Wheat straws were treated at three levels of urea concentration （5%, 10%, 15%） and 95℃ as holding temperature. Wheat straw particleboards were manufactured using hot press at 180℃ and 3 MPa with two types of UF adhesive （UF-45, UF-91）. Then the formaldehyde emission values, physical properties and mechanical properties were considered. The results show that the for- maldehyde emission value was decreased by increasing urea concentration. Furthermore, the results indicate that the specimens under urea treatment have better mechanical and physical properties compared with control specimens. Also specimens under urea treatment at 10% concentration and UF-91 type adhesive have the most optimum physical and mechanical strength.

Effect of LaCl_3 on Resistance and Absorptive Capacity to Formaldehyde of Indoor Ornamental Plants under Formaldehyde Stress

[Objective] This study aimed to determine the effect of rare earth biological regulator LaCl3 on the absorptive capacity to formaldehyde of four indoor ornamental plants, and to screen out the plant whose absorptive capacity to formaldehyde can be increased most greatly by LaCl3. [Method] Effect of LaCl3 on absorptive capacity to formaldehyde of four indoor ornamental plants was studied through fumigating in laboratory. Simultaneously, the indoor ornamental plant, which could significantly en- hance the degradation capacity of formaldehyde, was screened out to study the physiological and biochemical mechanisms of formaldehyde resistance. [Result] The ability to absorb formaldehyde of four indoor ornamental plants was enhanced by dif- ferent ranges after spraying with LaCl3 at suitable concentrations. The ability to ab- sorb formaldehyde of Hedera nepalensis var. sinensis, Chlorophytum comosum, Scindapsus aureun and Sansevieria trifasciata increased by 15.16%, 4.72%, 19.75% and 7.68%, respectively. In the four indoor ornamental plants, the capacity of S. au- reun to absorb formaldehyde was greatly improved by spraying LaCl3. When S. au- reun was stressed by formaldehyde, its chlorophyll content decreased by 39.87%, membrane permeability, MDA accumulation and POD activity increased by 8.17%, 56.92%, and 11.32%, respectively. However, compared the pre-spraying group with the no-spraying group under formaldehyde stress, chlorophyll content of S. aureun reduced less, membrane permeability and MDA cumulative both increased less, but POD activity increased more. [Conclusion] The formaldehyde absorption capacity of S. aureun was mostly improved after LaCl3 was sprayed.