Nanomaterials for Air, Water, and Soil Remediation: Review

Abstract

Overcoming the climate crisis and growing environmental pollution is a fundamental problem facing society in the 21st century. These problems have both health and economic implications. Developing an effective system for managing pollutants and greenhouse gases seems crucial. The use of nanomaterial-based technologies may be the answer. The dynamic development of nanoscience has led to the discovery of unique properties of nanomaterials, resulting primarily from quantum constraints, while the development of techniques for obtaining nanostructures has increased their availability. The ability to be used in filtration processes, as well as for adsorption, photocatalysis, and disinfection, predisposes nanomaterials to applications in environmental bioremediation and wastewater treatment. This article provides an overview of technologies currently in use or that may play a significant role in the fight for a healthier environment in the near future. The results of using nanomaterial-based technologies in air and water purification processes to date have been positive, promising further development of effective green technologies.

1. Introduction

Environmental pollution is believed to occur when harmful substances and pollutants are released into the air, soil, and water, generating negative impacts on the environment and human health. The source of most pollution is human activity (industrialization, transport, agriculture), but it can also arise as a result of natural processes [1]. According to the goals set by the UN, human actions should focus on ensuring the well-being of all people in the world, including reducing the number of diseases and deaths related to environmental pollution [2]. The World Health Organization (WHO) has released alarming data indicating that nearly 99% of the world’s population is exposed to air pollution at levels that may increase the risk of heart disease, stroke, chronic obstructive pulmonary disease, cancer, and pneumonia. Furthermore, ambient and household air pollution is estimated to be responsible for 6.7 million deaths annually. Contaminated water, which can be a carrier of disease-causing pathogens, also poses a threat to public health. Furthermore, access to water is a challenge for the world’s 2.2 billion people [1].

In recent years, global public discourse has repeatedly addressed the challenges posed by greenhouse gas emissions, rising temperatures, and the intensifying impacts of climate change. These discussions have led to agreements to reduce greenhouse gas emissions. However, it appears that these declarations have not been followed by sufficient action, and global greenhouse gas emissions continue to rise, remaining a significant environmental challenge.

It is certain that effective climate and pollution management requires coordinated international action [3]. Nanotechnologies can be incorporated into strategies to combat the climate crisis, environmental degradation, and pollution. This review addresses the potential use of nanomaterials in environmental remediation processes and greenhouse gas emission reduction.

2. Methodology

This research was based on a critical review of the literature [4]. The three-step literature selection process was conducted in the following order: selection of the primary database → selection of keywords → selection of exclusion and elimination criteria. To expand the scope of available articles, a complementary search was also conducted using the snowball sampling method. The Google Scholar database was used for this purpose. Both searches were based on four keywords: “nanomaterials,” “water treatment,” “remediation,” and “air purification.” The search yielded 64 articles (Scopus). Subsequently, the articles were filtered to include those published within the last 10 years (2016–2026), which reduced the number of articles to 59, with particular emphasis on the most recent works published within the last 5 years (2021–2026). Papers only indirectly related to the topics identified by the keywords were also excluded. During the analysis of the available materials, it was deemed appropriate to refine the search criteria to include air purification technologies (“photocatalysis,” “filtration,” “adsorption” and “disinfection”) and water treatment (“water desalination”). Therefore, due to their high substantive value, five earlier articles published between 2011 and 2014 were also included in the analysis. The stages of the literature selection process are illustrated in Scheme 1. The authors used GenAI (Canva AI 1.0) to generate the graphics presented in this paper.

Due to the general nature of the data obtained, it was decided to expand the previous analysis and conducted a separate search of the Scopus database using keywords specific to each section. The resulting data were exported to a CSV file(s) and analyzed using VOSviewer (version 1.6.20) software.

A second search of the Scopus database revealed a wider range of documents published between 2021 and 2026 in individual thematic sections, which were as follows:

• A total of 278 documents on “nanomaterials in air purification”;
• A total of 4969 documents on “nanomaterials in water treatment”;
• A total of 708 documents on “nanomaterials in soil remediation”.

The analysis conducted using both Scopus and VOSviewer (version 1.6.20) showed that the highest number of citations (385) in the field of “nanomaterials in air purification” was recorded for the article by Wei et al. [5]. In the field of “nanomaterials in water treatment”, the most frequently cited article was Mitra et al. [6], which received 1775 citations, while in the field of “nanomaterials in soil remediation”, the most frequently cited article was Osman et al. [7], which had 616 citations. The most frequently represented subject areas of the articles were “materials science” (197 articles in the scope of “nanomaterials in air purification) and “environmental science” (2810 articles in the scope of “ nanomaterials in water treatment” and 492 articles in the scope of “nanomaterials in soil remediation”).

The analysis of co-authorship by “authors” showed that in the scope of “nanomaterials in water treatment”, 28,004 authors were identified, of which 356 had published at least 5 papers. These authors were grouped into 21 interconnected clusters. The highest total link strength value was assigned to Wang, Xiangke. For “nanomaterials in air purification” and “nanomaterials in soil remediation”, 3 clusters of 26 interconnected authors (out of 1396 total) and 1 cluster of 12 interconnected authors (out of 71 total) were identified respectively. The highest total link strength value in the case of “nanomaterials in air purification” was assigned to Babapoor, Aziz and Chiang, and Wei-Hung. For “nanomaterials in soil remediation”, 12 authors with total link strength value were identified (they constituted a full cluster). In the analysis of co-authorship by “countries” in all three areas, the dominance of China and India was observed. Bibliometric maps of co-authorship analysis by “author” and “country” are presented in Figure 1, Figure 2, Figure 3, Figure 4, Figure 5 and Figure 6.

3. Synthesis Routes for Nanomaterials

Nanomaterial synthesis can generally be achieved through three routes: physical, chemical, and biological. The most important examples of currently used methods are shown in Scheme 2. Conventional methods for obtaining nanomaterials, due to the use of high temperatures and pressures, toxic solvents, and reducing agents, are considered unsustainable and unecological. Furthermore, a comprehensive life-cycle assessment of these synthesis methods is often lacking, and economic costs are often underreported, further preventing a reliable assessment of the method in terms of cost-effectiveness and sustainability principles [8].

Microwave-assisted synthesis, sonochemical synthesis, synthesis using plant extracts, and biomolecule-assisted synthesis are considered green and environmentally friendly methods for obtaining nanomaterials. These methods are considered extremely beneficial due to reduced energy consumption, the elimination of harmful reagents, and the possibility of efficient production scalability. Literature reports indicate that materials obtained using these methods demonstrate improved properties, particularly important in medical applications, energy storage, catalysis, and environmental remediation. Microwave-assisted synthesis (MAS) ensures uniform and rapid heating of the reaction mixture thanks to the use of microwaves in the process. Obtaining nanomaterials dedicated to environmental remediation using the MAS method allows for the production of products with large surface areas and tailored physicochemical properties for pollutant capture and degradation [8]. Another method addressing the challenges of green chemistry is sonochemistry. This method typically does not require high temperatures, high pressure, an inert atmosphere, or long reaction times, making it less expensive than conventional nanoparticle synthesis methods. In sonochemistry, the product is formed through chemical reactions in solution, initiated by acoustic cavitation (the formation, growth, and implosion of bubbles). The use of ultrasound allows for the elimination of reducing and stabilizing substances, and the resulting products exhibit the same or even better properties. The products of sonochemical reactions are characterized by a relatively uniform size distribution, and the particle size can be controlled by modifying the reaction parameters [9,10]. In recent years, hydrodynamic cavitation (HC) has emerged as a promising sonochemical technology for industrial-scale applications, primarily due to its high efficiency, good scalability, and synergy with other physical and chemical methods. This method is also highly desirable due to its economic efficiency, which can be orders of magnitude higher than traditional methods. However, further development work is still required to improve the design of hydrodynamic cavitation reactors [11].

The biosynthesis of nanoparticles is also based on the concept of green chemistry. This method utilizes plants, microorganisms, and certain natural factors to produce nanoparticles. Biosynthetic methods are recognized to have numerous advantages over chemical and physical methods. The most frequently cited advantages are non-toxicity, environmental friendliness, and the process’s sustainability. However, the use of biosynthesis is associated with obstacles such as low yield, uneven particle size, complex extraction procedures, and seasonal and regional availability of raw materials [12].

Due to the extremely diverse parameters and mechanisms of nanomaterial synthesis, Scheme 3 presents a general comparison of selected criteria.

4. Nanomaterials in Air Purification Technologies

Compared to bulk materials, nanomaterials have a larger specific surface area and unique catalytic, magnetic, and electronic properties, making them highly desirable materials in adsorption, filtration, and photocatalysis processes. These processes are currently considered crucial in environmental remediation [13].

Air pollution is one of the most current problems due to its impact on increasing climate change and on public health and therefore human well-being. Currently, it is believed that the greatest threats are posed by nitrogen oxides (NO_x), sulfur oxides (SO_x), carbon monoxide (CO), and suspended particulate matter (PM10, PM2.5), as well as lead and ground-level ozone. Its presence in the ground-level ozone layer can be explained as a result of reactions between nitrogen oxides (NO_x) and volatile organic compounds (VOOs) [14]. Furthermore, the presence of nitrogen oxides, sulfur oxides, ammonia, and volatile organic compounds in the air is considered a secondary precursor to the formation of particulate matter. Air quality is also linked to the presence of carbon dioxide, which is not considered a pollutant, yet contributes to the greenhouse effect [15].

Air remediation processes based on the use of nanomaterials include filtration, adsorption, photocatalysis (also occurring at room temperature) and disinfection [13], as illustrated in Scheme 4.

4.1. Photocatalysis

The photocatalysis process can be defined as an advanced oxidation process in which irradiated semiconductors play a key role [13,16]. Adsorption of one photon of energy excites one electron from the valence band maximum to the conduction band minimum, generating a positive hole in the valence band. Electron–hole pairs undergo migration or diffusion. When these excited charge carriers reach the photocatalyst surface, they react with water and oxygen molecules, leading to the formation of reactive oxygen species (hydroxyl radicals, superoxide radicals). Due to the strong oxidation potential of these radicals, gaseous pollutants can be converted into products considered harmless. The efficiency of nanomaterials in photocatalysis is directly related to their light absorption efficiency. The most popular method for increasing light absorption and inhibiting photoinduced charge recombination is the deposition of plasmonic noble metals (Ag and Au) on the semiconductor. A method for extending the light absorption range of semiconductors is to dope them with metals or nonmetals [13]. Historically, nTiO₂ has been a widely used nanomaterial in photocatalysis due to its chemical and photonic stability [17]. One idea for counteracting air pollution in urban environments was to incorporate nTiO₂ into building materials. However, this eco-friendly and innovative idea encountered obstacles in reaching the laboratory scale, primarily related to photocatalytic efficiency. In recent years, numerous development studies have been conducted to improve the efficiency and stability of these materials [18]. It has been proven that one way to improve the efficiency of photocatalysts, including accelerating carrier separation, increasing spectral absorption, regulating the energy band, and providing adsorption sites, is to use quantum dots as modifiers. Furthermore, the role of quantum dots is not limited to modifying photocatalysts. It has been demonstrated that photocatalysts based on quantum dots can participate in the degradation of both inorganic and organic pollutants [19].

4.2. Filtration

Membrane technologies are desirable for use in air purification processes because they remove pollutants from the air without producing hazardous by-products. The nanofiltration process is considered to have several advantages, including ease of use, reliability, lack of additives, and scalability. Currently, nanofiltration utilizes carbon nanotube-based membranes, polymer membranes, inorganic membranes, and composite membranes. The mechanism of action of nanomembranes is based on physical and chemical adsorption processes. Due to the rapid development of nanotechnology, other solutions are also being considered [20]. It seems that one of the most important research streams concerning the practical application of nanofiltration is its use in vehicle exhaust purification. A breakthrough was the development of high-efficiency (>99.5%) polyimide nanofiber air filters for PM2.5 removal at high temperatures. The invention was characterized by high thermal stability within a temperature range of 25–370 °C and high airflow, and its effectiveness was confirmed in field tests [21]. The success of this solution has made nanofiltration and nanofiber technology an intensively developed field of materials engineering. Health problems caused by air pollution and the pathogens present in it have demonstrated in recent years the importance of personal protection. Ongoing research and emerging inventions focus on developing a high-efficiency air filter that provides a range of properties, including water vapor transfer while simultaneously absorbing gaseous pollutants, high dust removal efficiency, and biocidal activity against pathogens [22].

4.3. Adsorption

Adsorption, a process that is not insignificant, is also involved in air pollution removal. It is believed that both chemisorption and physisorption processes are useful in air remediation. However, there are a number of factors that can determine the effectiveness of the process, including: chemical structure, physical structure, pore size, porosity, and acidity [13]. In recent years, graphene-based materials have been successfully validated for gas adsorption and air pollution control. Two discoveries in particular are noteworthy. Nitrogen-doped graphene improves NO_x adsorption by up to 45%, and rGO–metal oxide composites have been shown to exhibit increased CO₂ selectivity in low-humidity conditions [23]. Carbon nanotubes, which are rolled graphene sheets, also demonstrate activity in air purification processes from heavy metals such as Pb(II), Hg(II), Cd(II), and As(III), emitted during industrial processes. This is due to their large specific surface area and numerous active sites. Therefore, it is not surprising that multi-walled carbon nanotubes (MWCNTs), due to their larger surface area, are particularly attractive for adsorption processes. This activity can also be enhanced through surface functionalization. An example of this is the production of functionalized MWCNTs, which have been proven to be 20 times more effective in removing metals from the air compared to their non-functionalized counterparts [24].

4.4. Disinfection

The mechanism of disinfection action of nanomaterials in air purification processes is associated with the generation of oxidative stress as a consequence of contact of nanoparticles with lipopolysaccharides of the outer cell wall. This leads to degradation of the lipid membrane, oxidation of membrane proteins, inhibition of respiratory enzyme activity, and DNA destruction, ultimately leading to cell death [16].

The above-mentioned activity of nanomaterials has been used in both passive and active air purification systems. A passive air purification strategy, used since the 1980s, involves adding nano-TiO₂ photocatalysts to cementitious materials and other building materials. This treatment aims to eliminate NO_x through photocatalysis activated by natural sunlight. Studies on cementitious materials (paving stones) placed in busy urban areas indicate that the effectiveness of NO_x reduction is dependent on UV light intensity [25]. Even higher NO_x pollution levels than in city centers are observed in tunnels, especially during rush hour. The Umberto I tunnel, built in 1900, located in the center of Rome, underwent renovation. The walls and ceilings were coated with cement-based photocatalytic paint, and new light sources were installed. A comparison of NO_x concentration levels before and after renovation indicated a 20% reduction in NO_x concentration [26]. Similarly promising results were obtained in an experiment in which a section of road was covered with a photocatalytic concrete surface [27]. Photocatalytic technologies are also considered extremely promising solutions for minimizing indoor pollution. The use of paint additives in the form of nano-oxides or nanocomposites has allowed the creation of coatings that improve indoor air quality and also control the activity of microorganisms on wall surfaces [28,29].

Constructing active air purification systems involves combining various techniques, often incorporating additional light sources and air fans [13]. Active air purification systems proposed in recent years address the problem from a multifaceted perspective, combining air purification technologies with renewable energy generation while mitigating climate change. An example of such a technology is solar chimneys, which have undergone numerous modifications over the years to improve energy harvesting and have been combined with other pro-environmental technologies, including those using nanotechnology. The latest concepts involve the use of photovoltaic cells to generate electricity that can power exhaust fans that increase airflow to the filters [30].

In urban areas, proposed street lamps with an air purification module could potentially be more effective. Polluted air first enters a dust removal module, then a catalytic oxidation module. The catalytic module is based on a structure composed of activated carbon and a nanocomposite TiO₂ film. Conducted tests show very promising results in removal efficiency against PM2.5 (over 80%), O₃ (over 50%), and NO_x (over 50%) on sunny days [31].

5. Nanomaterials in Water Treatment

The UN reports that ensuring access to drinking water will become a fundamental global problem in the 21st century. The primary causes of water pollution stem from errors in sewage management, industrial and municipal waste management, and the use of agricultural chemicals. Wastewater treatment methods can be classified into four categories: preliminary, primary, secondary, and tertiary treatment [32]. Their mechanisms are related to the processes of flocculation or coagulation, sedimentation, filtration, disinfection, and adsorption [33]. Conventional approaches to wastewater treatment are highly effective, but this effectiveness decreases as new contaminants emerge. These challenges can be overcome by implementing nanotechnology solutions into wastewater treatment cycles. Nanotechnology applications offer a number of benefits, including improved operational efficiency, reusability, and low costs [34]. However, the success of nanomaterials in wastewater treatment processes stems primarily from their appropriate size, large surface area, mechanical stability, and reactivity [32,35].

Membrane-based technologies appear to act as a physical barrier against contaminants, but advances in nanotechnology have increased their selectivity and functionality. Currently, water and wastewater treatment and cleaning processes based on nanomembranes use:

• Nanofiltration membranes;
• Nanocomposite membranes;
• Self-assembly membranes;
• Nanofiber membranes;
• Aquaporin-based membranes;
• Graphene membranes;
• Cellulose membranes [36].

The dynamic development of nanoscience has led to the emergence of a multitude of techniques for obtaining nanomaterials, using both top-down and bottom-up methods. Therefore, the classification of nanomembranes found in the literature may be much broader than the one presented above [37]. Regardless of the nomenclature used, the characteristic feature of the nanofiltration process is the removal of contaminants with small dimensions corresponding to pore sizes of 0.5–1.5 nm [38]. Their mechanism of activity enables selective separation of ions by excluding size and charge effects [39]. From a water and wastewater treatment perspective, the use of nanomembranes for the removal of heavy metals such as copper, cobalt, zinc, cadmium, mercury, lead, iron, chromium, nickel, manganese, antimony, and arsenic seems promising [40]. Nanomembrane filtration offers a number of advantages, including simplicity, durability, energy efficiency, and reduced energy consumption in water and wastewater treatment. Despite this, the use of nanomembranes has certain drawbacks, the most significant of which is membrane fouling, which involves the accumulation of undesirable substances on the surface and in the pores, limiting the efficiency of the filtration process. Depending on whether membrane fouling is reversible or irreversible, various techniques are used to overcome these problems. Properly selecting the membrane material or modifying its surface can be a good way to combat membrane fouling, as well as improving the cost-effectiveness and rejection efficiency of nanofiltration [41].

Metal nanoparticles and metal oxide nanoparticles are extremely useful elements of bioremediation in aquatic systems due to their adsorption, rapid kinetics and ability to be modified [33]. Their use for the recovery of metal contaminants as substitutes for desorption materials is considered extremely effective [36]. In addition, nanostructured combined oxides and nanostructured materials are also used in nanoadsorption processes. They differ in their adsorption capacity and their use for specific types of contaminants [42]. In recent years, TiO₂ nanoparticles have exhibited enormous popularity, as evidenced by the number of publications investigating them. Interest in these nanoparticles stems from their thermal and chemical stability, light resistance, biological stability, and affordability. TiO₂ nanoparticles are useful in adsorption processes due to their high specific surface area and resistance to acidic and alkaline environments. The fact that the surface of these nanoparticles is rich in hydroxyl (-OH) groups, which are involved in the adsorption of contaminants from water through interactions, is also important in adsorption processes [43]. Obviously, the adsorption processes taking place in wastewater using TiO₂ take place according to the mechanism of chemisorption and physisorption, involving weak intermolecular interactions such as van der Waals–London forces, hydrogen bonds, covalent bonds, electrostatic interactions, dipole–dipole interactions, polarity and hydrophobicity [44]. The presence of TiO₂ in wastewater is beneficial due to not only its adsorption potential but also its potential for photocatalysis. Reactive oxygen species (ROS) are formed when TiO₂ is excited by ultraviolet radiation. Subsequently, the reaction of ROS with the contaminants leads to the gradual oxidation of CO₂, H₂O, and the anions NO₂⁻, PO₂⁻, and Cl₂. It was found that this process using TiO₂ nanoparticles enables the degradation of: pesticides, dyes, phenols, chlorinated organic compounds, polycyclic aromatic hydrocarbons and cyanides [45]. The photocatalytic effect exhibited by TiO₂ nanoparticles has implications for biocidal activity against microorganisms inhabiting wastewater. So far, antagonistic activity against herpes simplex virus, hepatitis B virus, poliovirus type 1, and MS2 bacteriophages has been confirmed [46]. Zinc oxide nanoparticles also exhibit similar properties and potential applications in wastewater and water treatment. These particles are environmentally friendly, exhibiting high UV absorption efficiency, oxidizing, and photocatalytic properties. Their advantage over TiO₂ nanoparticles is primarily related to price. ZnO nanoparticles are also known to have biocidal potential against pathogenic bacteria. Similarly to nano-TiO₂, the mechanism of this activity is likely related to the generation of ROS. Observations also indicate the possibility of disrupting cell membrane structures, which also has an inhibitory effect on bacteria [45,46].

Carbon nanotubes have attracted considerable attention in recent years due to their unique physical and mechanical properties. These nanostructures are also attracting attention in the field of water and wastewater treatment. This is due to their high adsorption capacity for a wide range of pollutants, selectivity towards aromatic compounds, rapid kinetics, and large specific surface area [47]. The basic structure of a carbon nanotube can be considered a rolled-up sheet of graphene. In addition to single-walled (SWCNT) structures, nanotubes can also form more complex multi-walled (MWCNT) systems, which should be considered to be centrically oriented, multilayered nanotube systems. Therefore, in more complex nanotube systems, there are four possible adsorption sites: the outer surface, the peripheral groove, the inner site, and the interstitial channel. Contaminants adsorb on both the inner and outer surfaces of the carbon nanotubes. It seems that the application potential of nanotubes in water and wastewater treatment processes is very large, which is confirmed by reports on the effectiveness of removing 1,2-dichlorobenzene (DCB), cadmium and lead from water [48].

Water Desalination

Industrial and domestic factors related to the intensive exploitation of freshwater sources, as well as lower groundwater levels, have led to the search for alternative water sources. The fact that 97% of water resources are found in the oceans makes desalination processes extremely important in obtaining potable water. In recent years, reverse osmosis has been used in seawater desalination plants, with process efficiency ranging from 35 to 85%. Higher process efficiency can be achieved by using high pressure; however, this increases energy consumption. High pressure and temperature also increase membrane wear. Electrodialysis, on the other hand, is a low-energy, pressure-free process limited to desalination of water with a low total dissolved salt concentration. These problems can be overcome by using nanofiltration. The elimination of salts in the nanofiltration process is due to steric, Gibbs–Donnan and dielectric effects [49].

The concept of using graphene in water desalination was first presented by Cohen-Tanugi and Grossman. This idea involved creating pores in the impermeable structure of graphene [50]. The efficiency of graphene use in the desalination process is correlated with the pores’ size and functionalization. Creating pores of a specific size in a graphene monolayer simultaneously ensures water permeability and the retention of ions, particles, and bacteria. Research indicates that the pore diameter for effective Na⁺ and Cl⁻ retention should be less than 5.5 Å. However, the presence of charged groups within the pores will increase water flow. Therefore, for hydrophilic pores with anionic hydroxyl groups, the water flow will be greater than for pores of the same size but with hydrogenated groups. Technically, creating porous graphene with a large surface area and uniform pore size remains a matter of further development. Techniques based on ion bombardment (e.g., gallium) [51], oxidative etching, oxygen plasma etching, hydroxyl radical etching and electron beam exposure are helpful in creating pores [49]. Another approach to graphene membrane design involves the use of porous multilayer graphene. This approach can improve salt removal efficiency by up to 94.54%, but requires appropriate selection of pore diameter and appropriately distributed electrical charge [52].

The use of graphene oxide also enables the creation of membranes for water purification and desalination applications. In layered graphene oxide membranes, water moves through nanochannels formed in the spaces between the nanoplatelets. Rapid water flow due to low friction values is observed in the unoxidized areas of graphene oxide. In desalination processes, it is advisable to use membranes in which the distance between the graphene oxide platelets is less than 0.7 nm, which allows for the separation of sodium cations from water. This reduced distance can be achieved by partial reduction of GO and by covalently binding the arranged graphene oxide nanoplatelets to small-sized particles [53].

Other applications utilizing nanotechnology advances in desalination processes are inspired by the photothermal effect as a driving force in the natural hydrological cycle and atmospheric circulation. The weaknesses of conventional seawater evaporation systems used to date include low light absorption efficiency and rapid heat dissipation. The solar desalination system consists of three structures: a photothermal material, a heat management element, and an element that supplies the water to be desalinized. Carbon nanotubes, graphene, and graphene oxide, due to their ability to absorb portions of the photoelectromagnetic spectrum of visible and near-infrared light, are used to construct the photothermal element [54]. Li and colleagues developed a desalination device in which the water path is limited to two dimensions. This two-dimensionality is intended to reduce heat loss and ensure efficient water supply. Graphene oxide, positioned at the top of the device so that it does not contact the water reservoir, serves as the absorber. The adsorber rests on an insulating layer made of polystyrene foam. The insulator is surrounded by a cellulose layer, which contacts the water in the reservoir, simultaneously creating a two-dimensional water path to the adsorber. Capillary forces are responsible for water movement within the cellulose. Evaporation occurs in the upper part of the device [55].

Research to overcome the freshwater crisis draws inspiration from nature. Tian et al. proposed a lotus-like nanostructure as a solar vapor generation system. The evaporation technology they proposed is characterized by an evaporation rate of 1.33 kg m⁻² h⁻¹ and a solar energy conversion of ~90% under normal solar illumination. The nanostructure has a T-shaped geometry. Vertically arranged graphene fragments obtained by plasma-based methods are oriented on a horizontal, leaf-like plane. This spatial arrangement ensures improved light absorption. The stem-like element, on the other hand, provides a one-dimensional water flow path and ultrafast water transport thanks to interconnected channels and superhydrophilicity [56].

6. Nanomaterials in Soil Remediation

Intensive exploitation of soil as part of agricultural practices, as well as industrial and mining activities and improper waste disposal, put soil at risk of contamination [57,58]. The presence of heavy metals, petroleum hydrocarbons, polycyclic aromatic hydrocarbons (PAHs), and persistent organic pollutants (POPs) has reduced soil fertility, degraded soil structure, and disrupted biodiversity. Furthermore, these pollutants can pose a threat to humans and animals through the food chain. Previously used soil remediation techniques—washing, solidification, bioremediation, and thermal desorption—have exhibited a number of limitations, typically related to cost-effectiveness, specificity, and environmental sustainability. It is believed that the use of nanomaterials in soil remediation processes will help overcome these challenges [59]. The potential of nanomaterials to remove contaminants from soil relies on immobilization. The immobilization mechanism typically involves three processes: adsorption, reduction, and degradation. The activity of nanomaterials in adsorption processes is possible due to their large surface area and reactive sites, and can be modified by pH, temperature, and the presence of competing ions [60]. The reduction process, in simple terms, involves the transfer of an electron to contaminants, leading to the formation of less toxic or insoluble compounds. This phenomenon is particularly important in the immobilization of heavy metals and chlorinated organic compounds [61]. Some nanomaterials can facilitate the degradation of contaminants through photocatalytic and oxidative processes [62].

Immobilization is used in soil remediation processes due to the environmental friendliness, cost-effectiveness and efficiency of the process. Literature reports indicate its potential for use in removing organic and inorganic soil contaminants using carbon nanoparticles, metal nano-oxides, and nanocomposites. The activity of metal oxide nanoparticles and nanocomposites is due to their ability to complex surfaces. In turn, carbon-derived nanoparticles immobilize organic contaminants through molecular bonds. Carbon nanotubes exhibit particularly high affinity for organic contaminants [63]. Despite this, the most commonly used soil remediation method is currently the use of zero-valent iron particles. It appears that in the near future, iron macroparticles will be completely replaced by nanometric particles, because zero-valent iron nanoparticles are more effective in remediation processes. Zero-valent iron (NZVI) nanoparticles, due to their high reactivity towards various types of contaminants, make them very useful in soil remediation processes. Furthermore, their size allows them to penetrate porous substrates. Remediation technologies based on zero-valent iron nanoparticles typically consist of several stages, including transport to the contaminated area and a series of reactions with the contaminant. The use of these nanoparticles in soil remediation processes is also beneficial because it reduces the need for soil excavation and groundwater pumping. Literature reports confirm the effectiveness of these nanoparticles in removing heavy metals and metalloids, as well as pesticides, polychlorinated hydrocarbons, chlorobenzenes, and dyes [64]. The use of zero-valent iron (NZVI) nanoparticles, while very promising, requires monitoring of their impact on soil microbial communities. Reports indicate a negative impact of these particles on the microbiological quality of contaminated soil, likely due to a “stress on stress” effect. At the same time, no negative impact on microorganisms inhabiting uncontaminated soil was observed in the control sample [65].

It appears that the use of nanosilica in soil remediation may be a potentially safe solution for ecosystems. The use of these nanoparticles is particularly promising in heavy metal removal processes [66]. In situations where soil has been contaminated with metals, it is also important to limit their mobility to protect groundwater. Tests conducted in field-like conditions confirmed that carbon nanotubes have the potential to minimize the mobility of heavy metals in contaminated soils [67]. Graphene oxide nanoparticles (nGOx) also demonstrate the ability to eliminate metals from soil, and literature reports also indicate the possibility of combining them with other techniques, such as phytoremediation [68]. Carbon nanotubes, interpreted as rolled-up graphene sheets, have been shown in experimental studies to be active in immobilizing soil contaminants, similarly to graphene itself. Studies conducted by Correia and colleagues demonstrated that the addition of small amounts of nanotubes improved the immobilization of heavy metals (Pb, Cu, Ni, Zn) in the soil matrix [69]. Studies conducted by Chandran and colleagues demonstrated that the use of nanotubes improved the removal of copper and zinc in electrokinetic soil remediation processes. The use of carbon nanotubes increased copper removal from approximately 28% to approximately 95% and zinc removal from approximately 20% to approximately 92% [70].

The above examples of the use of nanomaterials as well as the use of hybrid materials show promising results in future applications on a larger scale [71,72]. One of the most recently developed soil remediation techniques is nano-phytoremediation. This approach combines phytoremediation and nanotechnology to remove pollutants from the environment. Plants play a role in this process by absorbing and accumulating pollutants, while the use of nanomaterials aims to improve pollutant bioavailability, reduce plant stress, and accelerate pollutant degradation [73,74]. The literature highlights the development potential of nano-phytoremediation as a technology that counteracts environmental pollution while simultaneously supporting a circular economy [73].

Table 1. Review of available information on technological limitations and application conditions of selected nanomaterials.

Nanomaterial	Performance Metrics/Efficiencies	Application Conditions	Technological Limitations	Ref
Air purification
Photocatalysis
TiO2	Reaction rate constant (k, pseudo-first-order kinetics)—typically 10−3–10−2 min−1 for VOCs VOC degradation efficiency (e.g., formaldehyde, toluene): typically 60–95% (under laboratory conditions)	UV (λ ≤ 387 nm)—necessary for excitation (Eg approx. 3.2 eV) Relative humidity (RH)—moderate RH improves •OH generation, but excess RH inhibits VOC adsorption Light intensity and airflow—key parameters influencing the reaction rate	Low activity in visible light Fast recombination of e−/h+ pairs Surface deactivation (adsorption of intermediate products) Difference between laboratory results and actual installations	[18,75,76,77,78]
ZnO	Not found	UV (Eg ≈ 3.2–3.3 eV) Requires structure control	Photocorrosion Humidity sensitivity Potentially higher environmental toxicity (in the form of free NPs)	[79]
WO3	Wide absorption range of visible light (Eg approx. 2.1–2.8 eV) Dye and VOC degradation efficiency up to approx. 90–97% in optimal systems	Visible light Often requires the formation of heterojunctions (e.g., with g-C3N4)	Limited •OH generation capacity Needs modification	[80]
Heterogeneous systems (e.g., TiO2/ZnO, TiO2/g-C3N4, WO3/g-C3N4)	Degradation efficiency > 90–97%	UV-VIS (broadened absorption spectrum) Control of component ratio and phase interface (key performance factor)	Complexity of synthesis and scaling Difficulty maintaining interface stability High material cost	[79,81]
Filtration
Nanofibers (electrospun nanofibers, e.g., PAN, PVDF, NPs composites)	Filtration efficiency (η): 97–99.6% for PM2.5 Pressure reduction (ΔP): 80–120 Pa Particle capture range: 9–300 nm (aerosol nanoparticles)	Airflow 0.1–1 m/s (typical for HVAC and personal filters) Ability to operate at higher temperatures (e.g., up to 450 °C for composites) High porosity and small pore size Dominant mechanisms: diffusion, interception, electrostatic interactions	Pore clogging (fouling), decreased permeability Electrostatic degradation Limited mechanical durability (for ultra-thin layers)	[82,83]
Carbon nanomaterials	Not found	Operation based primarily on: Adsorption (π–π interactions, van der Waals) Electrostatic interactions Often used as membrane modifiers (not standalone filters) Significant role of electrostatic charge of the material	Efficiency decreases after electrostatic charge loss by up to approx. 7–12% for various PM fractions Potential toxicity of nanoparticles (environmental issues) Production costs (especially for high-purity CNTs)	[84,85]
Metal/oxide nanoparticle composites (TiO2, ZnO, Ag in filters)	Filtration efficiency close to 100% for nanoaerosols Additional benefits: Antibacterial (Ag, TiO2) Biological degradation (bioaerosols)	Often integrated with nanofibers (hybrid membranes) Combined action: mechanical filtration and biocidal effect Light activation possible	Nanoparticle aggregation Possibility of secondary nanoparticle emission Compromise between activity and structural stability	[83]
Adsorption
Activated carbon and carbon nanomaterials (CNT, graphene, aerogel)	Adsorption energy for CNTs: −0.5 to −1.3 eV (chemisorption of VOCs)	Passive process Dominant mechanisms: Van der Waals interactions π–π interactions (graphene, CNTs) Chemisorption (after surface modification)	Secondary emission (desorption when conditions change)	[86,87]
MOF	Gas adsorption capacity (e.g., CO2): 3.8–3.9 mmol/g	Effective for: VOCs (e.g., formaldehyde, benzene), greenhouse gases Effective at low pollutant concentrations and under ambient conditions	Moisture sensitivity (structure degradation) Difficulty in regeneration and long-term stability Cost and scalability Necessity of integration with catalysis	[88,89]
Aerogels (e.g., SiO2, graphene, cellulose)	Not found	Effectiveness for: organic molecules, gaseous pollutants, CNTS, graphene, metals	Low mechanical strength High hygroscopicity (affected by humidity) Difficulty in industrial scaling	[90]
Polymer nanomaterials and bioadsorbents (nanocellulose, biochar)	Not found	Low-energy processes Suitable for indoor filters and hybrid systems	Biological degradation Low selectivity	[91]
Disinfection
AgNPs	Minimum inhibitory concentration (MIC): approx. 0.85–17 μg/mL for AgNPs against pathogens	Mechanisms: release of metal ions (Ag+), denaturation of proteins and DNA, disruption of the cell membrane	Cytotoxicity and environmental impact Deactivation by aggregation High cost (e.g., AgNPs)	[92,93]
Water treatment
Carbon nanoparticles (CNT, Graphene)	Adsorption capacity (q): up to 215 mg/g for Pb(II) Contaminant removal efficiency: up to 98% for heavy metals and organic compounds	Key parameters: pH (determining surface charge), solution ionic strength Often require functionalization (–COOH, –OH)	Aggregation (available surface area) Difficulty in separation (without magnetic modification) Potential environmental toxicity	[79,94]
TiO2	>90% degradation of organic pollutants; high stability	Exposure time (UV), Oxygen availability	UV source required (high operating costs) Limited effectiveness in turbid waters Necessity of immobilization in continuous systems	[95]
MOFs	Not found	Chemical stability Pore design	Low stability in water (some)	[96]
Zero-valent iron nanoparticles	Not found	Redox conditions pH	Oxidation Passivation Aggregation Limited use in surface waters Better for in situ (soils/groundwater) Difficulty controlling the reaction	[97]
Soil remediation
Zero-valent iron nanoparticles	Heavy metal removal efficiency (Cd, Pb): 60–80% after a single application	Mechanisms: reduction (redox), precipitation and immobilization, co-precipitation Applied in situ (no soil removal required) Effectiveness dependent on soil pH, oxygen availability, and moisture	Rapid surface passivation (Fe0 oxidation) Particle agglomeration Limited mobility in soil (dispersion)	[98,99]
Carbon nanoparticles (CNT, Graphene)	Removal efficiency: 90% for many pollutants (typical values for nanoremediation)	Dominant mechanisms: adsorption, complexation of metal ions Effectiveness depends on: pH (impact on surface charge) and organic matter content in the soil	Strong aggregation Difficulty in even distribution in soil Potential toxicity to soil microorganisms	[63,100]
TiO2	Adsorption of heavy metals up to 143–385 mg/g Removal of organic compounds up to 98.6%	Mechanisms: photocatalysis (UV/VIS), surface adsorption Key parameters: pH, presence of organic matter, soil microbiological activity	Aggregation and sedimentation at a specific pH Light dependence (for photocatalysis) Effect on soil microorganisms	[101]
Nanocomposites (e.g., biochar–nZVI)	Not found	Proportions of composite components Soil properties	Possible changes in soil properties (e.g., alkalinity) Dependence on soil type (mineral composition, organic matter) The formulation must be adapted to local conditions	[102]
MOFs	Not found	pH Moisture Structural stability	Low stability in the water and soil environment High implementation costs Lack of in situ application technologies	[103]
Metal nanoparticles (e.g., AgNPs)	Not found	Redox conditions Access to oxygen and microorganisms	Possible ecosystem toxicity Regulatory constraints (agriculture) Impact on soil microbiome	[103,104]

presents a summary of nanoparticles frequently discussed in the literature, along with their technological limitations and application conditions.

7. Challenges Associated with the Use of Nanomaterials

There is currently an ongoing debate regarding the safety and consequences of using nanotechnology-based materials. The use of nanomaterials has increased over the years and appears set to continue, particularly due to their use in so-called new technologies. At this point, the ultimate consequences of nanomaterial use are difficult to predict. All analyses aimed at predicting the fate of nanomaterials in the environment and the resulting consequences for the environment and humans must consider the sources of nanoparticles, their transformation under the influence of environmental conditions, their durability, and their adaptability.

Few of the nanomaterial applications discussed in this article are already in widespread use. Most operate at pilot or laboratory scales, making risk assessment (RA) and life-cycle analysis (LCA) difficult to perform because the available data does not cover the full market scale. It appears that only ex ante analyses are possible at this time. Furthermore, nanotechnologies, being complex technologies, require a broader supply chain and a more complex infrastructure than traditional technologies, although it should be remembered that LCA databases are designed primarily with traditional technologies in mind [105].

However, there is no doubt that these technologies will be commercially exploited in the coming years, so it is crucial to develop detailed strategies for managing waste generated after remediation processes now. European Union legislation is also insufficient, as it insufficiently addresses how to handle nanomaterials at every stage of their life cycle.

That is why it is so important to use nanomaterials obtained in a sustainable, environmentally safe manner. Developments in nanoscience have led to at least several nanomaterial synthesis methods fulfilling the ideals of green chemistry. However, challenges arise related to scaling the process. Success is possible if limitations in mass transfer, heat and mass management, safety considerations, and process control complexities are overcome [106].

It appears that once the aforementioned challenges related to environmental safety, legal regulations, and the scalability of production processes are overcome, it will be possible to integrate existing conventional remediation systems with nanotechnology remediation on a large scale.

8. Conclusions

A review of the available literature indicates significant potential for using nanostructures in processes related to improving the quality of air, water, and soil. Environmental remediation processes rely on nanomaterials’ photocatalytic, adsorption, and biocidal potential. Membranes composed of nanomaterials also offer functional potential; in addition to separating even monovalent ions, they are also believed to reduce energy consumption in filtration processes. Due to the rapid development of nanomaterial-obtaining methods, including microbiological methods, an increasing number of nanostructures are aligned with the concept of sustainable production.

To date, numerous studies have been conducted on the use of nanomaterials, and most technologies based on them are in the pilot or development phase. If these technologies successfully pass environmental safety tests and the economic balance of these processes is satisfactory, it seems likely that nanofiltration and adsorption using nanosorbents will play a key role in environmental pollution management in the future.

Recent trends in the field of remediation emphasize that the presence of PFAS, pharmaceuticals, and microplastics in the environment is an increasingly serious problem that society will have to face in the near future. It is no surprise, then, that the most current research and inventions are focused on developing the next generation of nanomaterials—hybrid nanomaterials capable of removing these contaminants [107]. Another interesting and promising topic is the design of nanomaterials capable of both detecting and degrading contaminants [108].