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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.14027904
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,
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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].
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
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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].
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].
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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].
3.
Dispersants
- These agents are designed to prevent the clumping of soot
particles and their subsequent deposition by inhibiting adhesion and
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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.
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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 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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