Formaldehyde decomposition of air purification functional interior wall paint

A novel nano-TiO2-xNx composite was used as photocatalyst and added to the interior wall paint. The average diameter of nano-TiO2-xNx was about 20 nm. The majority crystal component of the sample was anatase and its optical absorption edge was shifted from 387 nm to 520 nm significantly. Nano-composite paint containing different dosage of nano- TiO2-xNx was investigated to study the properties of formaldehyde decomposition in the air. Testing results show that the formaldehyde decomposition ratio of that nano-paint can almost reach above 80%, especially for that of the paint containing 3% （w/w） nano-TiO2-xNx which exceeded 90%. The primary investigation on the reaction kinetics of photocatalytic formaldehyde decomposition indicated that the experiment data well fit the model of first-order reaction kinetics.

Air Purification Using Mists Generated by an Efficient Multi-fluid Mixer

Sadatomi and Kawahara developed a special twin-fluid atomizer called a multi-fluid mixer, which can spray mists by supplying air alone because water is automatically sucked by a vacuum pressure arisen inside the mixer. In the present paper, firstly, some applications of the mists sprayed by the atomizer are described. Secondly, the performance of the twin-fluid atomizer with best performance was compared with those of the commercial twin-fluid MMA100 type together with the single-fluid swirl type. In the CO2 adsorption tests, mists were sprayed five minutes by the respective types in turn in a test room, and time variations of CO2 concentration in air after the introduction of CO2 in the room were measured at the bottom of the room to compare the CO2 adsorption rates by the mists for the respective cases. In addition, diameters of droplets for the respective types were measured with a microscope. As a result, superiority of our twin-fluid atomizer was confirmed, because 40% droplets were 20 to 40 μm in diameter, and the CO2 adsorption rate by the mists with our twin-fluid atomizer was 25% higher than that with the commercial ones.

Solar-assisted selective separation and recovery of precious group metals from deactivated air purification catalysts

The mitigation of environmental and energy crises could be advanced by reclaiming platinum group precious metals(PGMs) from decommissioned air purification catalysts. However, the complexity of catalyst composition and the high chemical inertness of PGMs significantly impede this process. Consequently,recovering PGMs from used industrial catalysts is crucial and challenging. This study delves into an environmentally friendly approach to selectively recover PGMs from commercial air purifiers using photocatalytic redox technology. Our investigation focuses on devising a comprehensive strategy for treating three-way catalysts employed in automotive exhaust treatment. By meticulously pretreating and modifying reaction conditions, we achieved noteworthy results, completely dissolving and separating rhodium(Rh), palladium(Pd), and platinum(Pt) within a 12-h time frame. Importantly, the solubility selectivity persists despite the remarkably similar physicochemical properties of Rh, Pd, and Pt. To bolster the environmental sustainability of our method, we harness sunlight as the energy source to activate the photocatalysts, facilitating the complete dissolution of precious metals under natural light irradiation. This ecofriendly recovery approach demonstrated on commercial air purifiers, exhibits promise for broader application to a diverse range of deactivated air purification catalysts, potentially enabling implementation on a large scale.

Study of three-dimensional spatial diffuse discharge in contact electrode structure applied to air purification

In this work,based on the role of pre-ionization of the non-uniform electric field and its effect of reducing the collisional ionization coefficient,a diffuse dielectric barrier discharge plasma is formed in the open space outside the electrode structure at a lower voltage by constructing a three-dimensional non-uniform spatial electric field using a contact electrode structure.The air purification study is also carried out.Firstly,a contact electrode structure is constructed using a three-dimensional wire electrode.The distribution characteristics of the spatial electric field formed by this electrode structure are analyzed,and the effects of the non-uniform electric field and the different angles of the vertical wire on the generation of three-dimensional spatial diffuse discharge are investigated.Secondly,the copper foam contact electrode structure is constructed using copper foam material,and the effects of different mesh sizes on the electric field distribution are analyzed.The results show that as the mesh size of the copper foam becomes larger,a strong electric field region exists not only on the surface of the insulating layer,but also on the surface of the vertical wires inside the copper foam,i.e.,the strong electric field region shows a three-dimensional distribution.Besides,as the mesh size increases,the area of the vertical strong electric field also increases.However,the electric field strength on the surface of the insulating layer gradually decreases.Therefore,the appropriate mesh size can effectively increase the discharge area,which is conducive to improving the air purification efficiency.Finally,a highly permeable stacked electrode structure of multilayer wire-copper foam is designed.In combination with an ozone treatment catalyst,an air purification device is fabricated,and the air purification experiment is carried out.

Advances and challenges of photocatalytic technology for air purification

With the acceleration of the urban industrialization process,air pollutant emission has increased sharply,which seriously endangers the ecological environment and human beings.Solar-driven photocatalysis has the broad-spectrum activity for various inorganic to organic pollutants at ambient temperature without harsh reaction conditions,which shows a very broad application prospect in air purification.However,the photocatalysis technology suffers from the unrevealed reaction me-chanism and the deactivation of photocatalysts,which severely limits its practical application.Currently,there is still a huge gap between basic research and industrial application in the field of photocatalytic air purification.This review summarizes recent progress on photocatalytic degradation of air pollutants and categorizes them based on the types of photocatalytic materials and air pollutants,with a focus on photocatalytic reaction mechanisms and the application scenarios of photocatalytic air purification to identify this gap.We also critically discussed the major challenges for promoting applications of photo-catalytic technology and put forward the development prospect.

China Begins Air Purification Programme

Government institutions have been called on to im-prove urban air quality in a bid to create a healthier en-vironment for people. On April 6～7, Vice Premier Li Lanqing made an important speech on the national con-ference of "Air Purification Programme——cleaning motor vehicle operation", he said that the improvement should start with accelerated development of cleaner fu-els and reducing pollution exhausted from motor vehi-cles. Industrial and domestic coal-burning and vehicle e-missions have produced large amounts of pollutants in-cluding sulphur dioxide, dust and nitrogen oxide. Air pollution has become a major factor which

Research and development on mechanism of removal of indoor volatile organic compounds by plants

Background,aim,and scope Owing to the rapid development of modernisation and urbanisation,living standards have gradually improved.However,the widespread use of high-energy-consuming indoor appliances and furniture has made indoor environments a primary environmental problem affecting human health.Sick building syndrome(SBS)and building-related illness(BRI)have occurred,and indoor air conditions have been extensively studied.Common indoor pollutants include CO,CO_(2),volatile organic compounds(VOCs)(such as the formaldehyde and benzene series),NOx(NO and NO_(2)),and polycyclic aromatic hydrocarbons(PAHs).VOCs have replaced SO_(2)as the“The Fourteenth Five-Year Plan”urban air quality assessment new indicators.Indoor VOCs can cause diseases such as cataract,asthma,and lung cancer.To protect human health,researchers have proposed several indoor air purification technologies,including adsorption,filtration,electrostatic dust removal,ozonation,and plant purification.However,each technology has drawbacks,such as high operating costs,high energy consumption,and the generation of secondary waste or toxic substances.Plant degradation of VOCs as a bioremediation technology has the characteristics of low cost,high efficiency,and sustainability,thereby becoming a potential green solution for improving indoor air quality.This study introduces the research status and mechanism of plant removal of indoor VOCs and provides an experimental basis and scientific guidance for analysing the mechanism of plant degradation of pollutants.Materials and methods This study reviews studies on the harm caused by indoor pollutants to human health and related sources,mainly investigating the degradation of indoor formaldehyde,BTEX(benzene,toluene,ethylbenzene,and xylene)plant mechanisms,and research results.Results Plants can remove VOCs via stomatal and non-stomatal adsorption,interfoliar microbial,rhizosphere microbial,and growth media.Benzene,toluene,and xylene(BTX)are adsorbed by pores,hydroxylated into fumaric acid,and then removed into CO_(2) and H_(2)O by TCA.Formaldehyde enters plant leaves through the stomata and epidermal waxy substances and is adsorbed.After the two steps of enzymatic oxidation,formic acid and CO_(2) are generated.Finally,it enters the Calvin cycle and removes glucose and other nontoxic compounds.Discussion The non-stomatal degradation of VOCs can be divided into adsorption by cuticular wax and active adsorption by plant surface microorganisms.The leaf epidermal waxy matter content and the lipid composition of the epidermal membrane covering the plant surface play important roles in the non-stomatal adsorption of indoor air pollutants.The leaf margin of a plant is an ecological environment containing various microbial communities.The endophytic and inoculated microbiota in plant buds and leaves can remove VOCs(formaldehyde and BTEX).Formaldehyde can be directly absorbed by plant leaves and converted into organic acids,sugars,CO_(2) and H_(2)O by microbes.Bioremediation of indoor VOCs is usually inefficient,leading to plant toxicity or residual chemical substance volatilisation through leaves,followed by secondary pollution.Therefore,plants must be inoculated with microorganisms to improve the efficiency of plant degradation of VOCs.However,the effectiveness of interfoliar microbial removal remains largely unknown and several microorganisms are not culturable.Therefore,methods for collecting,identifying,and culturing microorganisms must be developed.As the leaf space is a relatively unstable environment,the degradation of VOCs by rhizosphere microorganisms is equally important,and formaldehyde is absorbed more by rhizosphere microorganisms at night.The inoculation of bacteria into the rhizosphere improves the efficiency of plants in degrading VOCs.However,most of these studies were conducted in simulation chambers.To ensure the authenticity of these conclusions,the ability of plants to remove indoor air pollutants must be further verified in real situations.Conclusions Plant purification is an economical,environment-friendly,and sustainable remediation technology.This review summarises the mechanisms of VOC plant degradation and presents its limitations.Simultaneously,it briefly puts forward a plant selection scheme according to different temperatures,light,and specific VOCs that can be absorbed to choose the appropriate plant species.However,some studies have denied the purification effect of plants and proposed that numerous plants are required to achieve indoor ventilation effects.Therefore,determining the ability of plants to remove indoor VOCs requires a combination of realistic and simulated scenarios.Recommendations and perspectives Plants and related microorganisms play an important role in improving indoor air quality,therefore,the effect of plants and the related microorganisms on improving indoor air quality must be studied further and the effect of plants on indoor VOCs will be the focus of future research.

Advances in Electrostatic Plasma Methods for Purification of Airborne Pathogenic Microbial Aerosols:Mechanism,Modeling and Application

The transmission of pathogenic airborne microorganisms significantly impacts public health and societal functioning.Ensuring healthy indoor air quality in public spaces is critical.Among various air purification technologies,electrostatic precipitation and atmospheric pressure nonthermal plasma are notable for their broad-spectrum effectiveness,high efficiency,cost-effectiveness,and safety.This review investigates the primary mechanisms by which these electrostatic methods collect and disinfect pathogenic aerosols.It also delves into recent advancements in enhancing their physical and chemical mechanisms for improve efficiency.Simultaneously,a thorough summary of mathematical models related to the migration and deactivation of pathogenic aerosols in electrostatic purifiers is provided.It will help us to understand the behavior of aerosols in purification systems.Additionally,the review discusses the current research on creating a comprehensive health protection system and addresses the challenges of balancing byproduct control with efficiency.The aim is to establish a foundation for future research and development in electrostatic aerosol purification and develop integrated air purification technologies that are both efficient and safe.

Enhanced air filtration performance under high-humidity condition through electrospun membranes with optimized structure

The separation stability under high-humidity is significant in practical applications for air filters.Herein,hydrophobic polyvinyl chloride(PVC)nanofiber filters with bead-on-string structure are designed to steadily remove particle matter under high relative humidity of 90%-95%.The developed hydrophobic filters possess comparable separation performance with the hydrophilic one,but greatly enhanced stability.After the introduction of beadon-string structure,the filtration performance can be furtherly improved due to the formed large cavities and hydrophobicity.Such hydrophobic PVC filters can be promising candidates for air purification in practical applications especially in wet seasons.

A Review of Metal–Organic Framework-Based Compounds for Environmental Applications

Metal–organic framework-based compounds have recently gained great attention because of their unique porous structure,ordered porosity,and high specific surface area.Benefiting from these superior properties,metal–organic framework-based compounds have been proven to be one of the most potential candidates for environmental governance and remediation.In this review,the different types of metal–organic framework-based compounds are first summarized.Further,the various environmental applications of metal–organic framework-based compounds including organic pollutant removal,toxic and hazardous gas capture,heavy metal ion detection,gas separation,water harvesting,air purification,and carbon dioxide reduction reactions are discussed in detail.In the end,the opportunities and challenges for the future development of metal–organic framework-based compounds for environmental applications are highlighted.

Applications of metal–organic frameworks for green energy and environment: New advances in adsorptive gas separation, storage and removal

The separation of gas molecules with similar physicochemical properties is of high importance but practically entails a substantial energy penalty in chemical industry. Meanwhile, clean energy gases such as H_2 and CH_4 are considered as promising candidates for the replacement of traditional fossil fuels. However, the technologies for the storage of these gases are still immature. In addition, the release of anthropogenic toxic gases into the atmosphere is a worldwide threat of growing concern. Both in academia and industry, considerable research efforts have been devoted to developing advanced porous materials for the effective and energy-efficient separation, storage, or capture of the related gases. In contrast to conventional inorganic porous materials such as zeolites and activated carbons, metal–organic frameworks(MOFs) are considered as a type of promising materials for gas separation and storage. In this contribution, we review the recent research advance of MOFs in some relevant applications, including CO_2 capture, O_2 purification, separation of light hydrocarbons, separation of noble gases, storage of gases(CH_4,H_2, and C_2 H_2) for energy, and removal of some gaseous air pollutants(NH_3, NO_2, and SO_2). Finally, an outlook regarding the challenges of the future research of MOFs in these directions is given.

A comparative study of the effects of ventilation-purification strategies on air quality and energy consumption in Beijing,China

In countries suffering from heavy ambient air pollution,ventilation is a problem,as ventilation intakes outdoor air pollutants,such as particulate matter with an aerodynamic diameter less than 2.5 μm(PM_(2.5)),while removing indoor air pollutants.Thus,it is important to identify appropriate ventilation-purification strategies to build healthy indoor environments with low energy consumption.This study reports the comparison of two sets of strategies,i.e.,mechanical ventilation with filters and natural ventilation with indoor air cleaners,in respect to energy consumption and the PMzs and carbon dioxide(CO_(2))exposure of occupants in a typical apartment in Beijing,China.A dynamic mass balance model was employed to calculate the PM2.5 and CO_(2) exposure concentrations,while the energy consumption of heating and cooling was simulated with the Designer's Simulation Toolkit.It was found that natural ventilation with air cleaners provided lower PIVhs exposure compared with that of mechanical ventilation with filters;however,mechanical ventilation achieved a lower CO_(2) exposure concentration.The annual cooling,heating,and fan energy consumption of natural ventilation strategies are lower than those of mechanical ventilation strategies.With respect to natural ventilation,an infiltration rate of 0.3-0.4 h^(-1)was the preferred setting,which led to low PM23 and CO_(2) exposure with lower energy consumption.The basic requirements for controlling indoor PM2.5 could be met if the threshold is set at 25 pg/m3.The results provide guidelines on how to combine multiple ventilation purification strategies to improve indoor air quality with lower energy usage.

Pulsed Corona Discharges and Their Applications in Toxic VOCs Abatement

Plasma processes are among the emerging technologies for volatile organic compounds (VOCs) abatement[1]. Both thermal plasmas and non-equilibrium plasmas (cold plasmas) are being developed for VOCs cleanup[2,3]. Particularly, pulsed corona discharges offer several advantages over conventional VOCs abatement techniques[4-7]. To optimize the existing technology and to develop it further, there is need to understand the mechanisms involved in plasma chemical reactions. Furthermore, it is strongly desirable to be able to predict the behavior of new VOCs in non-equilibrium plasma environment from the data known for a few representative compounds. Pulsed corona discharge technique is introduced here with citation of relevant literature. Fundamental principles, useful for predicting the VOCs' decomposition behavior, have been worked out from the published literature. Latest developments in the area, targeted to minimize the energy losses, improve the VOCs destruction efficiency and reduce the generation of unwanted organic and inorganic by-products, are presented.

Design of an air isolation and purification (AIP) desk for medical use and characterization of its efficacy in ambient air isolation and purification

The incidences of nosocomial infections(NIs)are increasing throughout the world,especially for those airborne diseases caused by pathogens or air particulates that float in air.In this study,we designed and manufactured a desk for clinic consultation room air purification and air isolation between doctor and patient.The air isolation and purification(AIP)desk has a high efficiency particulate air(HEPA)filter on the tope and several primary efficiency filters on the sides for air purification.The air circulating between inlet and outlet forms a wind-curtain between doctor and patient.The Computational Fluid Dynamics(CFD)model was used to calculate the speed of the air flow and the angle of sampler.We tested the air purification function of the AIP desk in rooms sized about 3.6×2.8×2.8 m(L×W×H)and found that the AIP desk could significantly remove the tested air pollutants like smoke particulates and microorganisms like Staphylococcus albus(S.albus)and human adenovirus type 5(HAdV-5).The wind-curtain can significantly block the exhale air of patient being transmitted to the respiratory area of doctor setting in the opposite of AIP desk.Thus,the AIP desk can be used in hospital setting to reduce the risk of NIs and protect both doctors and patients.

Research on the Performance of Cedarwood Essential Oil in Removing Formaldehyde

This paper tested cedar essential oil as a new formaldehyde removal ingredient on gel format,it showed a better formaldehyde removal performance,reaching equilibrium at 7 h with a formaldehyde removal rate of 64%,and at 24 h with a formaldehyde removal rate of 67%.The 24 h formaldehyde removal rate increased by 25%compared with the gel without cedar essential oil,and efficiency is improved by 60%.The ingredients come from natural sources with a woody aroma,which can soothe the body and mind.After the stability test,the formaldehyde removal gel has no odor,precipitation or discoloration.

Investigation on a vertical radial flow adsorber designed by a novel parallel connection method

Due to the increasing global demand for industrial gas, the development of large-scale cryogenic air separation systems has attracted considerable attention in recent years. Increasing the height of the adsorption bed in a vertical radial flow adsorber used in cryogenic air separation systems may efficiently increase the treatment capacity of the air in the adsorber. However, uniformity of the flow distribution of the air inside the adsorber would be deteriorated using the height-increasing method. In order to reduce the non-uniformity of the flow distribution caused by the excessive height of adsorption bed in a vertical radial flow adsorber, a novel parallel connection method is proposed in the present work. The experimental apparatus is designed and constructed; the Computational Fluid Dynamics(CFD) technique is used to develop a CFD-based model, which is used to analyze the flow distribution, the static pressure drop and the radial velocity in the newly designed adsorber. In addition, the geometric parameters of annular flow channels and the adsorption bed thickness of the upper unit in the parallelconnected vertical radial flow adsorber are optimized, so that the upper and lower adsorption units could be penetrated by air simultaneously. Comparisons are made between the height-increasing method and the parallel connection method with the same adsorber height. It is shown that using the parallel connection method could reduce the difference between the maximum and minimum radial static pressure drop by 86.2% and improve the uniformity by 80% compared with those of using the height-increasing method. The optimal thickness ratio of the upper and lower adsorption units is obtained as 0.966, in which case the upper and lower adsorption units could be penetrated by air simultaneously, so that the adsorbents in adsorption space could be used more efficiently.

Removal of Low-concentration Ammonia from Ambient Air by Aluminophosphates

A series of aluminumphosphate materials was prepared and used as adsorbents for the removal of ammonia at low concentrations. The influence of various preparation parameters, including the pH value of sol, calcination temperature and molar ratio of P/A1, on the structure and surface properties as well as adsorption capacity was investigated. The results showed that large amount of P-OH present on the surface of aluminophosphates was suitable for the removal of ammonia. They were the major source of weak Br6nsted acid sites and acted as the main active centers for capturing ammonia.

Reusable and durable electrostatic air filter based on hybrid metallized microfibers decorated with metal–organic–framework nanocrystals

As global air pollution becomes increasingly severe,various types of fibrous filters have been developed to improve air filter performance.However,fibrous filters have limitations such as high packing density that generally causes high-pressure drop and ultimately deterioration in the filtration efficiency.High-pressure particulate matter precipitators are limited in terms of scope for commercialization because they require high voltage supplies and ozone generators.In this study,we develop fibrous filters with enhanced durability and improved performance using metallized microfibers decorated with metal-organic-framework(MOF)nanocrystals.Not only does the efficiency of the developed filters remain at or above 97%for 0.50-1.5μm PMs but the durability also significantly increases.In addition,using the water purification ability of the MOF,we explore the dye degradation effect of the hybrid microfibers by immersing them into Rhodamine B aqueous solution.In such an experiment the Rhodamine B aqueous solution is completely purified by the presence of the hybrid microfibers under the UV irradiation.

Electrocatalytic oxidation of gaseous toluene in an all-solid cell using a foam Ti/Sb-SnO2/β-PbO_(2) anode

Mineralization of benzene,toluene,and xylene (BTX) with high efficiency at room temperature is still a challenge for the purification of indoor air.In this work,a foam Ti/Sb-Sn O2/β-Pb O_(2)anode catalyst was prepared for electrocatalytically oxidizing gaseous toluene in an all-solid cell at ambient temperature.The complex Ti/Sb-Sn O_(2)/β-Pb O_(2)anode,which was prepared by sequentially deposing Sb-Sn O_(2)and β-Pb O_(2)on a foam Ti substrate,shows high electrocatalytic oxidation efficiency of toluene (80%) at 7 hr of reaction and high CO_(2)selectivity (94.9%) under an optimized condition,i.e.,a cell voltage of 2.0 V,relative humidity of60%and a flow rate of 100 m L/min.The better catalytic performance can be ascribed to the high production rate of·OH radicals from discharging adsorbed water and the inhibition of oxygen evolution on the surface of foam Ti/Sb-Sn O_(2)/β-Pb O_(2)anode when compared with the foam Ti/Sb-Sn O_(2)anode.Our results demonstrate that prepared complex electrodes can be potentially used for electrocatalytic removal of gaseous toluene at room temperature with a good performance.

A comparative study between ionic liquid coating and counterparts in bulk for toluene absorption

The structure-activity relationship(SAR)for toluene absorption and desorption in ionic liquids(ILs)has been investigated for seven commercial ILs in bulk and thin liquid layer.ILs with imidazolium cations of different alkyl chain lengths and a Hofmeister series of anions including[CH3COO],[I],[BF4],[HSO4],and[PF6]were included.Absorption capacity for toluene increases with increasing kosmotropicity of the cation and anion,while the absorption rate in bulk ILs is governed by viscosity and that in thin ILs layer by the oil-water partition coefficient(Kow).A regenerability coefficient(Rp)measures toluene desorption and IL regeneration.The release rate as measured by dRp/dt correlates well with the Kow and viscosity of the ILs and tx,the time required to completely desorb toluene is related to its ionic strength as measured from v(C2H)of the imidazolium cation.These properties are in turn governed by the kosmotropicity of the cation and anion pair forming the IL.