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ADVANCEMENTS IN TECHNOLOGIES FOR AIR POLLUTION MITIGATION
Juraev Nizomiddin Mamasodikovich
PhD student
Tashkent Institute of Chemical Technology, Uzbekistan
nizomiddin2009@gmail.com
Mukhtorov Nuriddin Shamshidinovich,
DSc in Engineering, Deputy Head of the Oil Refining and Petrochemicals Department at
“Uzbekneftegaz” JSC, Uzbekistan
Khakimov Farrukh Shokirjonovich,
PhD in Engineering, Senior lecturer at the Department of Oil and Gas Processing
Technology, Fergana Polytechnical Institute, Uzbekistan
https://doi.org/10.5281/zenodo.14023238
Abstract.
Air pollution from volatile organic compounds (VOCs) and particulate matter
(PM2.5) presents a complex environmental challenge shaped by multiple pollutants. Despite
concerted efforts in the last twenty years, air quality continues to pose serious risks to both
human health and environmental stability. Exposure to VOCs and PM2.5 indoors can lead to
significant health issues, including respiratory illnesses, leukemia, birth defects, and
miscarriages. Therefore, advancing indoor air purification technologies is essential to reduce
these harmful effects. This article examines the latest trends, innovations, and potential future
developments in indoor air purification methods.
Keywords:
VOCs, PM2.5, adsorption, metal-organic frameworks, photocatalytic
oxidation, catalysts, additives.
Introduction
. Air pollution due to CO2 emissions and particulate matter (PM2.5) is a
multifaceted ecological challenge influenced by various pollutants. Particulate matter,
categorized as PM10 or PM2.5, poses serious health risks associated with air pollution. Short-
term exposure to elevated levels can worsen asthma and other respiratory conditions, impair
lung function, and even lead to premature mortality. These particles can result from both
direct emissions and the atmospheric transformation of precursor gases like NOx, sulfur
dioxide (SO2), and ammonia, which also have detrimental effects on plants and human health.
Adsorbent Materials
Traditional adsorbent materials vary in composition and
effectiveness for adsorbing pollutants from industrial emissions, largely influenced by their
chemical properties and the concentration of pollutants. Activated carbon is recognized as
one of the most effective adsorbents, though it can be relatively expensive [1]. Zeolite
molecular sieves, another significant adsorbent, are inorganic crystalline materials
characterized by a regular porous structure, strong acidity, and high hydrothermal stability,
making them valuable in environmental remediation [2]. Biochar-based adsorption of volatile
organic compounds (VOCs) operates through unique mechanisms, including adsorption in the
carbonized phase and partitioning in the non-carbonized organic matter [3]. Biochars from
different feedstocks show considerable variations in surface area, morphology, and elemental
ratios like H/C and O/C, even under similar pyrolysis conditions. For instance, biochar
derived from bamboo may achieve a specific surface area of 375 m²/g at 600 °C, while biochar
from switchgrass might only reach 15 m²/g [4].
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Table 1 presents data on 15 different types of biocoals used for VOC gas adsorption.
Among these, acetone has the highest adsorption capacity at 483.09 mg/g, while benzene and
toluene have capacities of 161.42 mg/g and 424.4 mg/g, respectively [5].
Table 1.
Sorption Capacities of Various Biocoals for VOC Gases.
Adsorbate
Formula
Weight
Adsorption
capacity
Source
Acetone
C3H6O
58.08
483.09
[3]
Acetone
C3H6O
58.08
343.89
[3]
Benzene
C6H6
78.11
27.5
[4]
Benzene
C6H6
78.11
161.42
[5]
Butanol
C4H9OH
74.12
262.38
[6]
Cyclohexane
C6H12
84.16
327.18
[6]
Ethyl acetate
C4H8O2
88.11
420.92
[7]
Ethyl acetate
C4H8O2
88.11
450.24
[5]
Isopropyl
acetate
C5H10O2
102.13
147.45
[7]
Isopropyl
acetate
C5H10O2
116.16
151.71
[7]
Toluene
C7H8
92.14
366.72
[4]
Toluene
C7H8
92.14
424.4
[3]
Methanol has the lowest adsorption capacity among VOC gases, measuring just 10.6
mg/g. The adsorption rate is mainly determined by the surface area of the biochar and its
non-carbonized organic components. Increasing the temperature during biomass processing
does not notably enhance VOC removal efficiency with biochar. Due to its cost-effectiveness
and widespread availability, biochar serves as a practical adsorbent for VOCs. Additionally,
incorporating nanoparticles with activated carbon improves the effectiveness of
formaldehyde removal from the gas emission [6].
Reducing emissions through Metal-Organic Frameworks (MOFs).
Metal-Organic
Frameworks (MOFs) are a new class of crystalline materials that leverage the advantages of
both organic and inorganic components. These materials are composed of metal ions or
clusters interconnected by organic linkers [7]. MOFs are characterized by their large surface
areas, varied functionalities, and remarkable thermal stability, making them highly suitable
for various applications, including gas storage, separation technologies, pollutant capture, and
chemical degradation processes.
To achieve uniform particle sizes in Metal-Organic Frameworks (MOFs), parameters
such as electric field strength and the flow rate of the polymer solution during electrospinning
can be optimized. This method facilitates the development of composite polymer filters using
PAN, PS, and PVP, capitalizing on the high adsorption capacity of MOFs while ensuring the
filters remain flexible. By adjusting mat diameters, PAN concentration (ranging from 6% to
10% by weight), and MOF content (between 20% and 60% by weight), particle sizes can be
controlled to fall between 200 nm and 1 μm [7].
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Through fuel additives.
PM2.5 emissions primarily stem from vehicles, and improving
the performance of exhaust systems can be achieved by adding various additives to promote
complete combustion and meet technical standards. Internal combustion engines release fine
particulate matter (PM) into the atmosphere during fossil fuel combustion, which poses
significant risks to human health and the environment. These aerosols can be identified by
their content of naturally occurring inorganic elements (such as K, Na, Cl, S, Ca, Mg, Si, P, Zn,
Pb) or organic compounds (like C, H, O). Organic emissions, including PAHs, VOCs, and tar,
primarily arise from the complete oxidation of exhaust gases. Recent studies have noted
advancements in diesel particulate filter (DPF) technologies, which include new substrate
materials, innovative catalyst formulations, improved regeneration techniques, unmonitored
DPF regenerations, and enhanced management strategies [8]. Future compliance with strict
emission regulations is anticipated to involve closed-loop regeneration systems and highly
efficient gasoline particulate filters (GPF) [9].
The table below summarizes general information regarding the composition of diesel
exhaust additives [10].
Table 2.
Diesel fuel additives
*
.
Additive group
Content
Diesel fuel stabilizers
Antioxidants (linked phenol,
phenylenediamines), dispersants (without
ash succinimides , polymer methacrylates
), metal deactivators
(N,N'-disalicylidene-1,2-propanediamine)
Additives that increase cetane number
Alkyl nitrates , 2 ethylhexyl nitrate
Multifunctional diesel additive packages
Wax crystalline modifiers and flow
enhancers , deodorants , package stability
for from the solvent except of the above
combination
Fuel catalysts
Cerium (Ce), iron compounds , platinum
Catalysts
Platinum group elements
___________________
*
The table is compiled based on the data: ATC Fuel additives and the environment,
2004.
Diesel Fuel Stabilizers.
Diesel fuel instability can result in resin formation, which may
clog fuel injectors or filters. Several types of diesel fuel instability exist, and various additives
are used to mitigate these issues:
1.
Stabilizers
- These additives serve to neutralize acidic substances, thereby preventing
acid-base reactions and resulting in soluble products that remain stable and do not participate
in further reactions. Stabilizers are usually formulated with strong basic amines and are
utilized in concentrations between 50 and 200 mg/kg [10].
2.
Antioxidants
- These substances are employed to prevent reactions that contribute to
soot formation. Common antioxidants include phenols and specific amines such as
phenylenediamine, which are typically added at concentrations ranging from 10 to 80 mg/kg
[10].
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3.
Dispersants
- These agents are designed to prevent the clumping of soot particles and
their subsequent deposition by inhibiting adhesion and accumulation. Dispersants like
succinimides or polymer methacrylates are typically utilized at concentrations between 15
and 100 mg/kg [10].
4.
Metal Deactivators
- These additives serve to neutralize trace metals that might act as
catalysts in instability reactions. One such example is N,N'-disalicylidene-1,2-propanediamine,
which is typically used at concentrations ranging from 1 to 15 mg/kg [10].
5.
Detergents
- Detergents are crucial for ensuring optimal injector performance in diesel
engines. They create a protective layer on metal surfaces and inhibit deposit formation in
injector nozzles through emulsification. Commonly used detergents include succinimides and
other ashless polymeric compounds, which are added at concentrations between 10 and 200
mg/kg [10].
Multifunctional Diesel Additive Packages.
These additive packages may consist of
various components, such as detergents, cetane enhancers, stabilizers, lubricity agents,
antifoaming agents, deodorants, demulsifiers, corrosion inhibitors, and antioxidants. These
substances are typically added at concentrations between 100 and 1500 mg/kg [10].
In a separate study, acrylic terpolymers containing different alkyl radicals were
synthesized to determine which radicals in poly(alkyl acrylate) (PAA) samples would produce
the highest viscosity index at lower polymer concentrations [11]. Furthermore, the effects of
these additives on the low temperature performance, electrical conductivity, and wear
resistance of GTL (Gas to Liquid) diesel were evaluated [11].
A synergistic effect was noted when the terpolymers were combined with Keroflux
6100, a pour point depressant, in GTL diesel. The addition of 0.1% w/w of the terpolymers led
to a substantial increase in the electrical conductivity of the GTL diesel [11].
Challenges and Future Directions.
The review article outlines significant progress in
air purification technologies, while also identifying ongoing challenges. Traditional
adsorbents like activated carbon and biochar have demonstrated potential, but issues with
scalability, cost, and long-term effectiveness persist. Future efforts should concentrate on
enhancing these materials through innovative modifications and the integration of
nanomaterials to boost adsorption capacity and regeneration efficiency. Additionally, it's
essential to assess the environmental impact and sustainability of these materials throughout
their lifecycle, including their disposal and recycling options.
Metal-organic frameworks (MOFs) show great promise for air purification, but practical
application is hindered by challenges related to material stability, scalability, and system
integration. Future research should prioritize enhancing the durability and lifespan of MOFs
in real-world conditions while addressing aggregation and reconfiguration issues. Optimizing
synthesis processes to lower costs and improve availability is also crucial. Furthermore,
exploring the integration of MOFs with other purification technologies, such as filters or
coatings, may yield innovative solutions for better air quality.
Catalytic technologies, particularly photocatalytic oxidation, offer significant potential
for air purification but face challenges concerning efficiency, by-product formation, and
catalyst longevity. Future investigations should focus on developing new photocatalytic
materials with greater activity and stability. Addressing the generation of potentially harmful
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by-products during the photocatalytic process is vital for ensuring environmental and health
safety.
It's important to highlight that the relationship between PM2.5 emissions from gasoline
vehicles, the induction period of gasoline, and the quantities of olefin and diolefin
hydrocarbons in fuel has not been extensively studied. We aim to explore this area in our
upcoming research.
The use of fuel additives to mitigate emissions poses challenges related to their
effectiveness, environmental impact, and regulatory compliance. Future research should
concentrate on developing and testing new additives, including oxygenates, that enhance
combustion efficiency while minimizing oxidation and pollutant formation. This approach
could potentially increase the induction period of gasoline. Understanding the long-term
effects of additives on engine performance and emissions is crucial for their practical use.
Improved regulatory frameworks and standardization for evaluating the performance and
safety of fuel additives are also needed. Additionally, exploring alternative strategies for
emission reduction, such as advanced exhaust treatment technologies and hybrid systems,
will be important for addressing the complexities of vehicle emissions and their effects on air
quality.
The author(s) received no financial support for the research, authorship, and/or
publication of this article.
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal
relationships.
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