Air Pollutants Removal Using Biofiltration Technique: A Challenge at the Frontiers of Sustainable Environment

Carbon based nanocomposites, surface functionalization as a promising material for VOCs (volatile organic compounds) treatment

Urban residential and industrial growth development affects sustainable and healthful indoor environments. Environmental issues are a global problem. The deterioration of indoor air quality has prompted the creation of several air cleansing techniques. This review explains how carbon-based materials have influenced the development of air purification systems using photocatalysis. These carbon-based materials offer unique properties and advantages in VOC removal processes. Biochar, produced from biomass pyrolysis, provides an environmentally sustainable solution with its porous structure and carbon-rich composition. Carbon quantum dots, with their quantum confinement effects and tunable surface properties, show promise in VOC sensing and removal applications. Polymers incorporating reduced graphene oxide demonstrate enhanced adsorption capabilities owing to the synergistic effects of graphene and polymer matrices. Activated carbon fibers, characterized by their high aspect ratio and interconnected porosity, provide efficient VOC removal with rapid kinetics. With their unique electronic and structural properties, graphitic carbon nitrides offer opportunities for photocatalytic degradation of VOCs under visible light. Catalysts integrated with MXene, a two-dimensional nanomaterial, exhibit enhanced catalytic activity for VOC oxidation reactions. Using various carbon-based materials in VOC removal showcases the versatility and effectiveness of carbon-based approaches in addressing environmental challenges associated with indoor air pollution. Metal-organic-framework materials are carbon-based compounds. It examines the correlation between VOC mineralization and specific characteristics of carbon materials, including surface area, adsorption capability, surface functional groups, and optoelectronic properties. Discussions include the basics of PCO, variables influencing how well catalysts degrade, and degradation mechanisms. It explores how technology will improve in the future to advance studies on healthy and sustainable indoor air quality.

Exploring the potential of biofiltration for mitigating harmful gaseous emissions from small or old landfills: a review

Landfills are widely employed as the primary means of solid waste disposal. However, this practice generates landfill gas (LFG) which contains methane (CH4), a potent greenhouse gas, as well as various volatile organic compounds and volatile inorganic compounds. These emissions from landfills contribute to approximately 25% of the total atmospheric CH4, indicating the imperative need to valorize or treat LFG prior to its release into the atmosphere. This review first aims to outline landfills, waste disposal and valorization, conventional gas treatment techniques commonly employed for LFG treatment, such as flares and thermal oxidation. Furthermore, it explores biotechnological approaches as more technically and economically feasible alternatives for mitigating LFG emissions, especially in the case of small and aged landfills where CH4 concentrations are often below 3% v/v. Finally, this review highlights biofilters as the most suitable biotechnological solution for LFG treatment and discusses several advantages and challenges associated with their implementation in the landfill environment.

Advanced protein nanobiosensors to in-situ detect hazardous material in the environment

Determining hazardous substances in the environment is vital to maintaining the safety and health of all components of society, including the ecosystem and humans. Recently, protein-based nanobiosensors have emerged as effective tools for monitoring potentially hazardous substances in situ. Nanobiosensor detection mode is a combination of particular plasmonic nanomaterials (e.g., nanoparticles, nanotubes, quantum dots, etc.), and specific bioreceptors (e.g., aptamers, antibodies, DNA, etc.), which has the benefits of high selectivity, sensitivity, and compatibility with biological systems. The role of these nanobiosensors in identifying dangerous substances (e.g., heavy metals, organic pollutants, pathogens, toxins, etc.) is discussed along with different detection mechanisms and various transduction methods (e.g., electrical, optical, mechanical, electrochemical, etc.). In addition, topics discussed include the design and construction of these sensors, the selection of proteins, the integration of nanoparticles, and their development processes. A discussion of the challenges and prospects of this technology is also included. As a result, protein nanobiosensors are introduced as a powerful tool for monitoring and improving environmental quality and community safety.

The practical utility of ternary nickel-cobalt-manganese oxide-supported platinum catalysts for room-temperature oxidative removal of formaldehyde from the air

Formaldehyde (FA), a carcinogenic oxygenated volatile organic compound, is present ubiquitously in indoor air. As such, it is generally regarded as a critical target for air quality management. The oxidative removal of FA under dark and room-temperature (RT) conditions is of practical significance. A series of ternary nickel-cobalt-manganese oxide-supported platinum catalysts (Pt/NiCoMnO4) have been synthesized for FA oxidative removal at RT in the dark. Their RT conversion values for 50 ppm FA (XFA) at 5,964 h-1 gas hourly space velocity (GHSV) decrease in the following order: 1 wt% Pt/NiCoMnO4 (100 %) > 0.5 wt% Pt/NiCoMnO4 (25 %) > 0.05 wt% Pt/NiCoMnO4 (14 %) > NiCoMnO4 (6 %). The catalytic performance of 1 wt% Pt/NiCoMnO4 has been examined further under the control of various process variables (e.g., catalyst mass, flow rate, relative humidity, FA concentration, time on stream, and molecular oxygen content). The catalytic oxidation of FA at low temperatures (e.g., RT and 60 °C) is accounted for by Langmuir-Hinshelwood mechanism (single-site competitive-adsorption), while Mars van Krevelen kinetics is prevalent at higher temperatures. In situ diffuse-reflectance infrared Fourier-transform spectroscopy reveals that FA oxidation proceeds through a series of reaction intermediates such as DOM, HCOO-, and CO32-. Based on the density functional theory simulations, the unique electronic structures of the nearest surface atoms (platinum and nickel) are suggested to be responsible for the superior catalytic activity of Pt/NiCoMnO4.

Separation processes for the treatment of industrial flue gases - Effective methods for global industrial air pollution control

The treatment of flue gases has become a crucial area of interest with the increasing air emissions into the atmosphere from industries involved in combustion of fossil fuels in their operations. In essence, there is a critical need for effective methods of treatment more than ever. Treatment and separation are now a demand for the overall industrial operations to control the rate of flue gas emissions. The major culprit in this wise is power generating industry. The major associated air pollutants are carbon dioxide, sulfur oxides, trace metals, volatile organic compounds, particulate matters, and nitrogen oxides. However, the choice of technologies to be utilized requires more than just knowledge of the separation process, but also a good understanding of the properties of the pollutants. This review explored and evaluated the various separation processes and technologies for the treatment of industrial flue gases for the control of the associated air pollutants. It also analyzed the performance with references to cost and efficiency, the advantages and disadvantages, principles for selection, research direction, and/or potential opportunities in existing separation processes and technologies.

Biochemical engineering for elemental sulfur from flue gases through multi-enzymatic based approaches - A review

Flue gases are the gases which are produced from industries related to chemical manufacturing, petrol refineries, power plants and ore processing plants. Along with other pollutants, sulfur present in the flue gas is detrimental to the environment. Therefore, environmentalists are concerned about its removal and recovery of resources from flue gases due to its activation ability in the atmosphere to transform into toxic substances. This review is aimed at a critical assessment of the techniques developed for resource recovery from flue gases. The manuscript discusses various bioreactors used in resource recovery such as hollow fibre membrane reactor, rotating biological contractor, sequential batch reactor, fluidized bed reactor, entrapped cell bioreactor and hybrid reactors. In conclusion, this manuscript provides a comprehensive analysis of the potential of thermotolerant and thermophilic microbes in sulfur removal. Additionally, it evaluates the efficacy of a multi-enzyme engineered bioreactor in this process. Furthermore, the study introduces a groundbreaking sustainable model for elemental sulfur recovery, offering promising prospects for environmentally-friendly and economically viable sulfur removal techniques in various industrial applications.

Hierarchical Computational Screening of Quantum Metal-Organic Framework Database to Identify Metal-Organic Frameworks for Volatile Organic-Compound Capture from Air

The design and discovery of novel porous materials that can efficiently capture volatile organic compounds (VOCs) from air are critical to address one of the most important challenges of our world, air pollution. In this work, we studied a recently introduced metal-organic framework (MOF) database, namely, quantum MOF (QMOF) database, to unlock the potential of both experimentally synthesized and hypothetically generated structures for adsorption-based n-butane (C4H10) capture from air. Configurational Bias Monte Carlo (CBMC) simulations were used to study the adsorption of a quaternary gas mixture of N2, O2, Ar, and C4H10 in QMOFs for two different processes, pressure swing adsorption (PSA) and vacuum-swing adsorption (VSA). Several adsorbent performance evaluation metrics, such as C4H10 selectivity, working capacity, the adsorbent performance score, and percent regenerability, were used to identify the best adsorbent candidates, which were then further studied by molecular simulations for C4H10 capture from a more realistic seven-component air mixture consisting of N2, O2, Ar, C4H10, C3H8, C3H6, and C2H6. Results showed that the top five QMOFs have C4H10 selectivities between 6.3 × 103 and 9 × 103 (3.8 × 103 and 5 × 103) at 1 bar (10 bar). Detailed analysis of the structure-performance relations showed that low/mediocre porosity (0.4-0.6) and narrow pore sizes (6-9 Å) of QMOFs lead to high C4H10 selectivities. Radial distribution function analyses of the top materials revealed that C4H10 molecules tend to confine close to the organic parts of MOFs. Our results provided the first information in the literature about the VOC capture potential of a large variety and number of MOFs, which will be useful to direct the experimental efforts to the most promising adsorbent materials for C4H10 capture from air.

Catalytic degradation of benzene at room temperature over FeN4O2 sites embedded in porous carbon

Benzene and its aromatic derivatives are typical volatile organic compounds for indoor and outdoor air pollution, harmful to human health and the environment. It has been considered extremely difficult to break down benzene rings at ambient conditions without external energy input, due to the extraordinary stability of the aromatic structure. Here, we show one such solution that can thoroughly degrade benzene to basically water and carbon dioxide at 25 °C in air using atomically dispersed Fe in N-doped porous carbon, with almost 100% benzene conversion. Further experimental studies combined with molecular simulations reveal the mechanism of this catalytic reaction. Hydroxyl radicals (·OH) evolved on the atomically dispersed FeN4O2 catalytic centers were found responsible for initiating and completing the oxidation of benzene. This work provides a new chemistry to degrade aromatics at ambient conditions and also a pathway to generate active ·OH oxidant for generic remediation of organic pollutants.

1Non-thermal plasma coupled with a wet scrubber for removing odorous VOC

Odorous volatile organic compounds (VOCs) deteriorate the quality of life and affect human health. In this study, a process was developed to remove an odorous VOC using a combined non-thermal plasma (NTP) and wet scrubber (WS) system. The low removal efficiency of WSs and the large amount of ozone generated by NTP were resolved. Compared to the decomposition effects when using a WS and NTP separately, the NTP + WS system improved the removal efficiency of ethyl acrylate (EA) and significantly reduced ozone emissions. The maximum EA removal efficiency was 99.9%. Additionally, an EA removal efficiency of over 53.4% and a 100% ozone removal efficiency were achieved even at discharge voltages lower than 4.5 kV. Ozone catalysis was confirmed to occur in the NTP + WS system. Furthermore, we verified the removal of by-products such as residual ozone and formaldehyde, which is a representative organic intermediate of EA. This study demonstrates that the NTP + WS system is a green technology for removing odorous VOCs.

Removal of Volatile Organic Compounds (VOCs) from Air: Focus on Biotrickling Filtration and Process Modeling

Biotrickling filtration is a well-established technology for the treatment of air polluted with odorous and volatile organic compounds (VOCs). Besides dozens of successful industrial applications of this technology, there are still gaps in a full understanding and description of the mechanisms of biotrickling filtration. This review focuses on recent research results on biotrickling filtration of air polluted with single and multiple VOCs, as well as process modeling. The modeling offers optimization of a process design and performance, as well as allows deeper understanding of process mechanisms. An overview of the developments of models describing biotrickling filtration and conventional biofiltration, as primarily developed and in many aspects through similar processes, is presented in this paper.