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Indoor air pollutants can cause severe health problems , specifically in terms of toxicological impacts on human. Every day, a complex mixture of many air pollutants is emitted from various sources and subject to atmospheric processes that can create varied classes of pollutants such as carboxylic acids, aldehydes, ketones, peroxyacetyl nitrate, an...
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... Indoor Environment Generally, VOCs are released from various sources such as solvents, paints, workplace cleansers, pesti- cides, glues, disinfectants, and perfumes. As a result, VOCs are easily entered into the indoor environment and their possible consequences are shown in Fig. 1. It is well established that IAQ is responsible for building related illnesses (da Costa Filho et al., 2017), and mul- tiple chemical reactivity (MCR) (Lan et al., 2011), directly or indirectly causes 4.3 million premature deaths in 2012 (WHO, 2014). Sick building syndrome (SBS) one of the various diseases in humans caused due to air ...
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... Photocatalysts can function to provide both oxidation and reduction conditions; the electron reduces an acceptor and the hole oxidizes donor molecules. Photocatalysis has found a wide range of practical applications including air treatment [2,3], photocatalytic CO 2 reduction [4], wastewater treatment [5,6], drinking water treatment [7,8], conversion of solid waste into gaseous phase [9], photocatalytic treatment and removal of heavy metals [10,11], microbial disinfection [12] and so on. Some of the photocatalysts with the best performances include TiO 2 , ZnO, WO 3 , CdS, and NiO among which TiO 2 is the most widely applied because of its stability and chemical inertness, high photo-reactivity, low cost, and nontoxicity [6,13]. ...
With numerous chemical reactions involved, photocatalysis has gained a lot of attention in recent decades as a possible method for converting solar energy to value-added chemicals. The effectiveness of photocatalytic systems has been increased through the development of several methods and strategies. However, because of their poor performance and the low utility value of certain reaction products, their practical uses are quite constrained. Tandem photocatalysis has gained popularity recently as a result of its extremely selective transformations, exceptional performance, and ability to produce highly valuable compounds from its byproducts. This review summarizes the latest applications of heterogeneous tandem photocatalysis in the evolution of hydrogen, reduction of CO2, and reduction of nitrates in aqueous media. It also looks into the literature on the utilization of tandem reactions in the in-situ synthesis of useful and environmentally friendly materials sequel to previous reduction reactions.
... To reduce the health risk posed by indoor air pollution, engineers have explored diverse techniques, including adsorption, air ionization, catalysis, photocatalysis, and micro-fuel cells) (Kim et al., 2017;Raza et al., 2017). Adsorption's facile and user-friendly properties have made it a preferred option. ...
The utility of nanomaterial adsorbents is often limited by their physical features and fine particle size in particular. For example, a large bed-pressure drop is associated with fine-particle sorbents. To learn more about the effect of adsorbent morphology on uptake performance, we examined the adsorption efficiency of metal-organic framework 199 (MOF-199) in the pristine (fine powder) form and after its binding to an inert support on glass beads. Most importantly, we investigated the effect of such coatings on adsorption of gaseous benzene (0.1–10 Pa) in a dry N2 stream, particularly as a function of the amount of MOF-199 loaded on glass beads ([email protected]) (i.e., 0,% 1%, 3%, 10%, and 20%, w/w) at near-ambient conditions (298 K and 1 atm). A 1% MOF-199 load gave optimal performance against a 0.1 Pa benzene vapor stream in 1 atm of N2, with a two-to five-fold improvement (e.g., in terms of 10% breakthrough volume [BTV] (46 L atm (g.MOF-199)⁻¹), partition coefficient at 100% BTV (3 mol [kg.MOF-199]⁻¹ Pa⁻¹), and adsorption capacity at 100% BTV [8.8 × 10⁻⁷ mol m⁻²]) compared with those of 3%, 10%, and 20% loading. The relative performance of benzene adsorption was closely associated with the content of [email protected] (e.g., 1% > 3% > 10% > 20%) and the surface availability (m² (g.MOF-199)⁻¹) such as 291 > 221 > 198 > 181, respectively. This study offers new insights into the strategies needed to modify finely powdered MOFs to extend their range of environmental applications.
... Volatile organic compounds (VOCs) are an important class of atmospheric pollutants with immense impact on air quality and thereby on human health. VOCs are emitted from a wide range of industrial processes, transport vehicles, insulation materials, paints, indoor objects, as well as from natural sources (Berenjian et al. 2012;Raza et al. 2017). They are known to cause a spectrum of illnesses in humans and animals like respiratory diseases, skin/eye irritation, neurotoxicity, and even cancers (Khan and Ghoshal 2000). ...
Cyclodextrins (CDs) and deep eutectic solvents (DESs) are emerging absorbent materials for the removal of volatile organic compounds (VOCs). In this study, we have used combination of modified CDs and levulinic acid to form four DESs analogs, referred to as supramolecular low-melting mixtures (LMMs), to study their absorption characteristics towards five VOCs, namely acetaldehyde, butanone, dichloromethane, thiophene, and toluene. The supramolecular LMMs showed up to 250-fold reduction in the vapor-liquid partition coefficients compared to water. The overall absorption capacity found to be synergistic and seemed to be dictated by the hydrophobicity of the VOCs. Toluene and dichloromethane were absorbed at 99 and 95% by the supramolecular LMMs, respectively, even at higher concentrations, with a linear relationship between the concentration and absorption capacity. The LMMs also retained their absorption capacities even after five absorption/desorption cycles.
... Nonetheless, previous research has emphasized CO2 concentration as well, recommending a concentration of not more than 800 ppm rate for an occupied room with good air exchange, as shown in TABLE II [7]. TABLE II. ...
... TABLE II. INDOOR AIR QUALITY CLASSIFICATION [7] The excellent class of indoor air quality classification will be followed during this research to achieve the best indoor air condition listed in TABLE III. IV. ...
... In this review, the recent development of photocatalysts for air purification was surveyed. It should be noted that many reviews for photocatalytic degradation (PCD) aiming at removing air pollutants have been already published, which specifically cover fundamental mechanisms of PCD [57], reactor designs [58], and photocatalysts based on TiO 2 [59] and non-TiO 2 materials such as graphene and graphitic carbon nitride (g-C 3 N 4 ) [60], and heterostructures for full solar spectral responses [61]. This review focuses on developments in this field for the last few years. ...
Air pollution by toxic chemicals and pathogens (bacteria, viruses, and fungi) has become one of the most critical problems worldwide because it has strong negative impacts on human health, both indoors and outdoors. Photocatalysis is a promising candidate to purify the atmosphere by removing pollutants among several physicochemical and biological methodologies. In this review, we discuss photocatalytic materials used for air purification, advanced methodologies for photocatalysts synthesis, and principles of photocatalytic nanoparticles that decompose pollutants, which include inorganic and organic compounds as well as dangerous pathogens. Recent achievements, outlook, and future directions in the field are discussed.
... Although most of these options are efficient at treating such pollutants, their practical applications are often limited by high cost and/or generation of secondary pollutants (through sludge and by-product formation) (Dos Santos et al., 2007). Among the many available remediation technologies, photocatalysis is regarded as a promising solution to resolve diverse types of environmental issues, such as CO 2 reduction, wastewater treatment, green energy production, and medical applications (Dos Santos et al., 2007;Ehsan et al., 2018;Ehsan and He, 2015;Raza et al., 2017). In photocatalysis, solar irradiation-based photocatalysts can be beneficial as more energy efficient and sustainable technologies than conventional treatment techniques (Malato et al., 2002). ...
The excessive amount of textile effluents disposed into the water streams is a common source of contamination of the hydrosphere. To efficiently remove pollutants in water bodies, there is growing demand for highly efficient, cost effective, and green remediation techniques. In line with such demand, a heterostructured photocatalyst (ZnO–ZnTe) has been prepared through the assembly of zinc oxide (ZnO) and zinc telluride (ZnTe). A synergistic interaction between surface adsorption and photocatalysis was explored for the removal of azo dye using a hierarchical superstructure under solar-light irradiation. Methylene blue (MB) was bleached by about 91% under visible irradiation for 2 h to support the role of the prepared heterostructures as effective photocatalysts (QY is 3.16 × 10− 7 molecules/photon). Moreover, the kinetic reaction rate of ZnO–ZnTe superstructures was 19.0 μmol g− 1 h− 1 , which was 1.54 and 1.97 times higher than those of pristine ZnO and ZnTe, respectively. These results may be ascribed to the presence of a common cation that may have helped in the diffusion of photogenerated electrons between ZnO and ZnTe, while efficiently suppressing the recombination frequency of photogenerated electrons and holes.
... Other methods such as electrophoretic deposition (EPD) [56], sol-gel method [57], and chemical vapor deposition (CVD) [58] are also reported in published literature. The dip-coating technology is an especially suitable method for flat substrates (concrete blocks, glass, etc.) to form a uniform thin layer of TiO 2 from the suspension [59] (Table 1). ...
... Thus, scale-up of large-scale PCO systems for indoor air purification based on laboratory-scale results may be inaccurate. The removal efficiency also depends upon the type of reactor design adopted due to the variation in incident radiation flux as well as the contact between photocatalyst and target pollutant [59]. Clean air delivery rate (CADR) is one method typically adopted for evaluating the air-cleaning performance of PCO reactors [34]. ...
... The major drawbacks of PCO technology are the deactivation of the photocatalyst, low photocatalytic activity, and generation of by-products [87]. Undesirable by-products can be more toxic and irritating than the target VOCs [59]. The photocatalyst lifetime is important in overall process cost as it determines the frequency of catalyst replacement [97]. ...
... Other methods such as electrophoretic deposition (EPD) [59], sol-gel method [60] and chemical vapor deposition (CVD) [61] are also reported in published literature. The dip coating technology is an especially suitable method for flat substrates (concrete blocks, glass, etc.) to form a uniform thin layer of TiO2 from the suspension [62]. ...
... Thus scale-up of large scale PCO systems for indoor air purification based on laboratory scale results may be inaccurate. The removal efficiency also depends upon the type of reactor design adopted due to the variation in incident radiation flux as well as the contact between photocatalyst and target pollutant [62]. Clean air delivery rate (CADR) is one method typically adopted for evaluating the air cleaning performance of PCO reactors [43]. ...
... The major drawbacks of PCO technology are the deactivation of the photocatalyst, low photocatalytic activity, and generation of by-products [90]. Undesirable by-products can be more toxic and irritating than the target VOCs [62]. The photocatalyst lifetime is important in overall process cost as it determines the frequency of catalyst replacement. ...
... A number of techniques have been developed over the years to treat H 2 S-laden air: (i) nondestructive approaches such as adsorption [11][12][13][14], scrubbing [15,16], and membrane filtration [17,18]; (ii) destructive approaches including photocatalysis [19][20][21][22], biodegradation [6,23,24], and thermal/catalytic oxidation [25,26]. Among the abovementioned techniques, the use of organic amine solutions (e.g., ethanolamine) was made preferably in various industries as they are an effective option to scrub acidic compounds (e.g., H 2 S) from gaseous effluents [27,28]. ...
Hydrogen sulfide (H2S) is regarded as a broad-spectrum poison associated with severe health consequences. Among the available treatment options, photocatalytic technology may be effectively applied to the production of hydrogen gas through the splitting of H2S molecules and the addition of 79.9 kJ mol-1 of energy. As a result, advanced photo-reactive media may provide a win-win strategy to treat the parent pollutant (H2S) while producing hydrogen gas. This review encompasses both TiO2 and non-TiO2 catalysts capable of operating under ultraviolet, visible, and solar light irradiation. The performances of photocatalysts are assessed in terms of quantum yield, space-time yield, and other operational variables, including mode of operation, irradiation time, and relative humidity. The concept of space velocity is used to compare photocatalysts in reference to benchmark parameters for the treatment of H2S. This review addresses current limitations and future prospects of the application of photocatalytic technology to efficiently mitigate H2S pollution.
... Photocatalytic oxidation of VOCs (PCO) is another abatement method for VOCs that has been of great interest due to their high efficiency and low energy costs, with most studies done on titania based materials [94][95][96][97]. This method is also of particular focus in indoor air quality due to low temperature conditions [98][99][100]. ...
Volatile organic compounds (VOCs) are a class of liquid compounds with low saturation vapor pressures, which enables them to change phases even at ambient conditions. This causes a huge problem when it comes to emissions. A large portion of VOCs cause catastrophic health effects such as cancer or liver damage even at very low concentrations (ppm), and the control of these compounds is vital in ensuring good air quality. Many VOCs are used in common household implements such as wood finishes or paints and can even be emitted off improperly ventilated cooking. This significantly alters indoor air quality, and as such, a large portion of research into these compounds have focused on indoor air. On the other hand, their widespread use as solvents in most industries along with their emission rates from vehicular exhausts results in contamination of outdoor air as well. The combination of these VOCs and NOx pollutants tends to cause ground level ozone formation, which has a large bio-toxicity and causes the formation of a smog. Densely populated cities have also seen a sharp rise in VOC emissions due to the increase in both vehicular traffic and industrialization. A myriad of options is available for the abatement of VOCs, and they are similar to other pollution control strategies. These methods can be broadly be classified into destruction, separation and hybrid methods. This review discusses the different perspectives to be considered for this scenario, along with descriptions of the different methods available to the industry, along with some novel technologies that have been introduced recently. The influential parameters for each method have been investigated, along with optimum catalyst/material selection. In addition to this, a mathematical modeling perspective has also been examined, with significance to simulation studies performed for the control of VOC emission technologies.
