1. INTRODUCTION

The twentieth century witnessed an unprecedented increase in environmental pollution, driven largely by rapid industrialization, urbanization, and agricultural intensification. These developments aimed at meeting the demands of a growing global population and advancing technological progress and contributed significantly to environmental degradation. Industrial activities have led to the release of a variety of pollutants, including heavy metals, hydrocarbons, pharmaceuticals, pesticides, and explosives, which pose serious risks to both human health and ecosystems. These pollutants are often persistent, bioaccumulative, and toxic, leading to long-lasting environmental damage and contributing to the destruction of biodiversity. As the scope of environmental contamination continues to expand, bioremediation has emerged as a promising solution to mitigate the adverse effects of pollution and restore ecosystems.

Bioremediation refers to the use of biological systems such as microorganisms and plants to degrade, transform, or sequester harmful pollutants. Over recent decades, bioremediation techniques have evolved significantly, increasing the efficiency of pollution removal and making these methods more adaptable to a wide range of environmental conditions. The key advantage of bioremediation lies in its ability to harness natural biological processes to detoxify and restore polluted environments, offering an eco-friendly and cost-effective alternative to traditional remediation methods. Recent advances in bioremediation technology have demonstrated its ability to address diverse environmental contaminants, including hydrocarbons, heavy metals, and pesticides, in soil, water, and air matrices. These developments highlight bioremediation potential as a scalable solution for large-scale environmental cleanup, offering a sustainable method for reducing pollution and preventing further ecological damage [1].

The types of pollutants that require remediation are diverse, but among the most concerning are heavy metals, hydrocarbons, pharmaceuticals, insecticides, and explosives. These substances pose significant threats to human health and environmental integrity. Heavy metals, such as arsenic, cadmium, lead, and mercury, are non-degradable and can accumulate in ecosystems, where they disrupt biological processes and adversely affect plants, animals, and humans. Many of these metals are carcinogenic and toxic to the nervous system, leading to long-term health risks upon exposure. Hydrocarbons, such as those found in oil spills, also present major environmental challenges. Their slow degradation, particularly in aquatic and soil environments, leads to the accumulation of toxic compounds that damage ecosystems and wildlife habitats. Pesticides and herbicides, although used extensively in agriculture, can leach into water supplies and affect biodiversity, posing risks to human and animal health. Explosives and other chemical compounds from industrial and military activities can contaminate soil and water, creating complex and hazardous environmental conditions [2].

Traditional physicochemical methods, such as adsorption, electrochemical treatment, precipitation, and electrocoagulation, have been widely used for pollution control. However, these methods often fall short of addressing the full spectrum of environmental contaminants. While they may be effective in certain contexts, these techniques are generally expensive, energy-intensive, and sometimes produce secondary waste, which requires additional treatment. In particular, traditional methods often struggle with low-concentration contaminants or mixed pollutant systems. For example, some pollutants are hydrophobic and may not be easily accessible to chemical agents or remediation technologies. This highlights the need for more innovative, effective, and environmentally friendly strategies to address these complex contamination issues. Bioremediation has thus emerged as an up-and-coming alternative, offering the potential to degrade pollutants in a more natural, cost-efficient manner, with fewer ecological impacts [3,4].

Bioremediation leverages microorganisms and plants to break down pollutants into less harmful compounds, restoring polluted environments to their natural state. The effectiveness of bioremediation depends on the presence of specific microorganisms that are capable of degrading the contaminants and the optimization of environmental conditions, such as temperature, pH, and nutrient availability. For instance, certain microbes are capable of metabolizing hydrocarbons, while others can transform heavy metals into less toxic forms. The ability to use a variety of microbial strains or their enzymes makes bioremediation a versatile tool for addressing a range of pollutants in different environmental settings. Furthermore, bioremediation is a relatively low-cost and low-tech approach, which makes it an attractive option for large-scale environmental cleanup operations. However, there are limitations to the widespread use of bioremediation, particularly in environments with low pollutant bioavailability or where microbial degradation rates are slow [5].

One of the most promising areas of bioremediation research in recent years is the integration of nanotechnology into environmental remediation strategies. Nanotechnology, which involves the manipulation of materials at the atomic and molecular scale, has opened new possibilities for enhancing pollutant degradation. Due to their small size and high surface-area-to-volume ratio, nanoparticles (NPs) exhibit unique properties that make them highly effective in environmental applications. These properties allow NPs to interact with pollutants at the molecular level, enabling more efficient degradation or removal of contaminants. In addition, NPs can be engineered to target specific pollutants, providing a more selective and precise remediation approach [6,7].

Nanotechnology has shown significant promise in addressing environmental contamination, particularly in water quality testing, pollutant detection, and the degradation of hazardous substances [Figure 1]. For example, carbon nanotubes (CNTs), quantum dots, and magnetic NPs have been used in water quality testing, particularly for the detection of toxins and harmful microbes [8]. Furthermore, the use of zero-valent metals in nanoscale forms, such as palladium, nickel, and iron, has proven effective in dehalogenating persistent organic pollutants and stabilizing heavy metals such as arsenic and chromium in contaminated environments. These metals have demonstrated their ability to break down hazardous chemicals into less toxic forms, offering a promising method for remediating polluted water and soil [9].

Figure 1: Role of nano-bioremediation in environmental remediation (Created by the authors: BioRender). [Click here to view]

The application of nanotechnology in bioremediation offers a synergistic approach that combines the advantages of both fields. NPs can enhance microbial activity by improving the bioavailability of pollutants, protecting microorganisms, and catalyzing degradation reactions. For example, palladium-decorated NPs have been shown to accelerate microbial dechlorination processes in contaminated soils, while magnetic NPs can be used to immobilize microorganisms, facilitating pollutant removal and allowing for microbial recovery and reuse. The addition of NPs to bioremediation processes also aids in the solubilization of hydrophobic compounds, making them more accessible to microbial degradation [10,11].

Despite the substantial promise of nano-bioremediation, several challenges remain. One of the primary concerns is the potential toxicity of NPs to non-target organisms, including microorganisms, plants, and aquatic life. Although NPs may be effective in degrading pollutants, they may also pose risks to ecosystems if they are not carefully managed. The long-term stability and reactivity of NPs in environmental systems are also a concern. NPs tend to aggregate over time, reducing their surface area and reactivity, which can compromise their effectiveness. In addition, the interactions between NPs and natural organic matter in the environment can alter their behavior and impact their performance. Therefore, further research is required to develop environmentally benign and stable NPs for safe and effective environmental use [4].

2. NANO-BIOREMEDIATION

Relying solely on a single method for the remediation of environmental pollutants is often inadequate to address the complexity and scale of contamination. The integration of nanomaterials with bioremediation offers a highly promising approach, combining the strengths of both technologies to enhance the effectiveness and sustainability of pollutant removal. This combined approach, referred to as “nano-bioremediation,” utilizes the unique properties of nanotechnology to augment biological processes, leading to more efficient and faster degradation of contaminants. Specifically, nano-bioremediation involves the use of NPs, derived from plants, fungi, and microorganisms, to facilitate the removal of a diverse range of nanoparticle contaminants including heavy metals, organic pollutants, and inorganic toxins, by enhancing microbial activity [12,13]. Nanomaterials have already demonstrated significant utility in diverse fields, including medicine, industry, and environmental remediation, with their ability to interact at the molecular level offering precise and targeted pollutant removal [14,15]. In the context of phytoremediation, nanotechnology enhances the ability of plants to absorb, transform, and sequester pollutants from the environment. The incorporation of NPs can improve soil restoration, treat contaminated water, and remove both organic and inorganic pollutants. Applying nanomaterials in compound-based bioremediation allows complex environmental pollutants to be broken down into simpler, less harmful compounds. NPs, acting as catalysts, facilitate the breakdown of these complex molecules, which are then more readily degraded through the synergistic interaction of microorganisms and plants. This integration of biotechnology and nanotechnology offers an efficient and scalable method for addressing environmental pollution, particularly in contaminated sites where traditional bioremediation strategies may be less effective [16,17]. The combined use of NPs and biological agents holds great promise for advancing environmental remediation technologies, offering a more sustainable and effective solution to global contamination challenges.

3. BIOREMEDIATION AND NANOTECHNOLOGY: PIONEERING ENVIRONMENTAL SUSTAINABILITY

Bioremediation is a process that employs biological systems such as microbes and plants to degrade, transform, or stabilize environmental contaminants. Its eco-friendly and cost-effective nature makes it a key tool in environmental management. When integrated with nanotechnology, bioremediation transcends conventional limitations, offering innovative and scalable methods to tackle pollutants ranging from heavy metals to radioactive waste. This synergy not only enhances efficiency but also broadens the scope of applications in environmental restoration. Traditional remediation methods often rely on physical and chemical approaches, including precipitation, ion exchange, membrane filtration, chelate flushing, and reduction. These methods effectively improve metal solubility and facilitate the removal of contaminants but face significant challenges such as high costs, fouling, and sensitivity to operational conditions such as pH and temperature [Table 1].

Table 1: List of various treatment methods for bioremediation.

3.1. Physical Treatment Methods

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3.1.1. Precipitation

By adding an appropriate anion, the metal salts are precipitated in this manner. Manganese sulfate, copper sulfate, ammonium sulfate, alum, and ferric salts are the synthetic substances typically utilized in this technique. Low pH affects the efficiency of sludge and salt (ions) disposal, thus increasing the process’s cost [18]. Precipitation approaches on explicitness to eliminate low-concentration metal particles and it is not effective.

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3.1.2. Ion exchange

Heavy metals can be recovered from sector effluents using this method. This strategy is comprised of a strong stage particle trade material fit for trading cations or anions. The engineered particle trade tar is the generally utilized particle structure and interactions. It is moderately costly and, in any event, when a somewhat huge volume is dealt with, it can arrive at ppb levels. The issue with this technology is that it is unable to monitor high metal concentrations due to foul network arrangement. It is also highly susceptible to changes in the pH of the solution [19].

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3.1.3. Electrowinning and electrocoagulation

In modern metallurgical and mining techniques such as metal handling, corrosive mine seepage, hardware, and electrical businesses, and stack draining for weighty metal recovery and expulsion, electrowinning is conspicuously utilized. However, the electrocoagulation technique is used in the treatment of wastewater contaminants. In this, particles with the opposite electric charge undercut and accelerate the charged particles, assuming that the electrocoagulation framework kills them [19].

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3.1.4. Cementation

This technique is similar to precipitation, but it also involves an electrochemical system, in which metals enter the arrangement at a higher oxidation limit. Cementation is most commonly used to separate copper and also used to recover other metals such as gallium (Ga), lead (Pb), gold (Au), silver (Ag), antimony (Sb), cadmium (Cd), and tin (Sn). Several variables, including pH, surface energy, adsorbent surface area, and so on, affect how well metal particles are evacuated. The physisorption and chemisorption mechanisms in adsorption bind the adsorbent surface to the metal species. Activated alumina, carbon, KMnO₄, coated sand with iron oxide, granular ferric hydroxide, and copper-zinc granules are often used as adsorbents [19].

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3.1.5. Membrane filtration method

This method incorporates isolating metals from water through a semipermeable layer with a slope of pressure that goes about as the main impetus [20]. The essential disadvantage of this technique is fouling brought about by the coprecipitation of Fe^{2 +} and Mn^{2 +} particles in the water. In addition, this method is more expensive due to factors such as water pre-treatment and tracking pressure differences [19].

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3.1.6. Electrodialysis

Except for the primary thrust, this is nearly identical to the reverse osmosis (RO) process, which separates charged metal particles from debased water by passing a semipermeable screen across an electrical field. It is more viable in removing heavy metals from groundwater and is dependent on various variables, such as water content, surface tension, pH, porosity, and groundwater flow rate. To accomplish successful remediation goals, this treatment approach can be combined with other strategies such as bioaugmentation, penetrable receptive boundaries (PRBs), film filtration, surfactant flushing, responsive zonal treatment, and receptive zone treatment [20,21].

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3.2. Chemical Treatment Methods

Heavy metal contaminants are dispersed throughout groundwater, making conventional treatment methods extremely challenging. A portion of the accessible procedures of substance treatment and their impediments are examined beneath [Figure 2].

Figure 2: Methods and mechanisms involved in nano-bioremediation (Created by the authors: BioRender) [Click here to view]

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3.2.1. Reduction

In heavily contaminated areas where the soil has a higher soluble pH, reductants such as dithionite and vaporous hydrogen sulfide are injected. Pollutants are corrupted or immobilized in these contaminated regions. One instance of this is the colloidal zerovalent particle (ZVI), which may be introduced deep into the groundwater system for effective remediation purposes and swiftly degrade, producing toxic compounds in the process [22].

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3.2.2. Chemical washing

This is the immediate technique for eliminating metal pollutants through acids which act as powerful extractants. This process degrades the soil, which has negative effects on the surrounding area. It is perilous to treat contaminated soil in situ, and managing problems and handling hazardous waste is quite confusing.

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3.2.3. Chelate flushing

This is the technique for extricating a gigantic number of weighty metals, as it is feasible to restore and reuse the dynamic specialists utilized all the while. PRBs utilize solvent-charged resins, which are 100% regenerative and highly efficient. EDTA and DTPA are synthetic chelating agents widely used in industrial and agricultural applications. Although these compounds are generally regarded as non-carcinogenic, their excessive environmental accumulation may contribute to ecological toxicity and enhanced metal mobility, which could indirectly affect biological systems [23].

4. UTILIZING NANOTECHNOLOGY’S APPLICATIONS

NPs, also known as ultrafine solids, are made of extremely small particles (<100 nm), and their application is what defines nanotechnology. Atomic or sub-atomic totals are somewhere in the range of 1 and 100 nm long, and they can change their physicochemical attributes when contrasted with mass materials. NPs can be delivered from a scope of various components and can be viable with the variation’s substance synthesis, forms, and size. In essence, they are more agile and sensitive. NPs typically have two groups: Inorganic and natural NPs. Although inorganic NPs include attractive NPs, typical metal NPs (such as gold and silver), and semiconductive NPs (such as titanium and zinc oxide), natural NPs include carbon NPs (fullerenes). The synthesis of novel stable, affordable, and ecologically friendly NPs is important for use in agriculture, medicine, and electronics [70]. Even though NPs can be combined using a variety of conventional techniques, the biosynthetic pathway is advantageous because it can quickly combine regulated aspects, controlled harmfulness, low cost, and natural neighborliness. According to Okhovat et al. [71], biological contaminants such as bacteria and chemicals are frequently extracted using NPs, including organic pollutants.

NPs have novel properties given their particular physical and synthetic qualities. For the past 10 years, NPs and nanomaterials have been the focal point of consideration. NPs have numerous unique mass-related features and are often very small, able to hold their iotas, and produce quantum effects. NPs, for example, gold in different fields, are usually used due to these particular elements. NPs have been used to produce nuclear materials such as uranium and to bioremediate radioactive waste from nuclear power plants. JG-A12 cells and S-layer proteins of Bacillus sphaericus are unique in their ability to clean wastewater [72]. Natural frameworks can arrange and integrate very receptive atoms. Various investigations on plants have demonstrated that specific NPs can prevent germination and revolutionary turn of events.

Customarily, just physical and compound strategies have produced NPs. The exorbitant expense of chemical and physical procedures has led to the necessity for NP biosynthesis. Microbes and subsequently grown crop specimens were employed for the analysis in search of simpler union cycles of NPs. Its synthesis is a granular perspective, wherein decrease/oxidation is the primary response. Microbial compounds or plant phytochemicals with cancer-prevention properties or decreased qualities are mostly responsible for the decline in the comparison of metal compound NPs. Nanomaterial yield is presently projected at a large number of tons all over the planet and is supposed to rise emphatically soon. The expression “nanomaterial” is typically used to portray textures with something like one aspect explicitly planned somewhere in the range of 1 and 100 nm. Yeasts, actinomycetes, green growth, tiny creatures, and parasites can all be used in the manufacture of NPs [73].

The progressive amalgamation of NPs with plants is fundamentally deducible from the one-step biosynthesis process, the toxins’ shortfall, and external coating materials [74]. The benefit of utilizing plants to combine NPs is that these particles are readily obtainable, safe to handle, and contain a wide range of metabolites that can aid in their degradation. Numerous types of plants are generally solicited for inclusion in the NP blend. Water-dissolvable phytochemicals considerably reduce the amount of time needed for growth and bacteria to hatch, while decreasing metal particles often takes a smaller amount of time. Consequently, crops are a better source of NPs than bacteria and fungi. Agricultural production of metallic and oxide NPs is possible if issues related to the metabolic state of the plant are adequately addressed by increasing plant tissue and additional processing. Based on the data collected, it is clear that the influence of NPs varies among plants and is dependent on their size, fixation, and mode of use [75]. Research has demonstrated that additional investigation is needed to fully understand the physiological, fundamental, and atomic components of yields related to the NPs. Facilitating research on NPs’ activities, interactions with biomolecules, and effects is standard. The study states that there is ongoing research on the relationship between NPs and plant life.

The bacteria and some other bioorganisms generate some NPs [Table 2]. Microscopic organisms are viewed as a planned “biofactory” for blending NPs such as Ag, Au, Pt, Pd, Ti, TiO₂, Cd, magnetite, and so on. Another approach can be employed in objective biosynthesis on catalysts, nutrients, polysaccharides, biodegradable polymers, and organic frameworks to engage the bacteria as a supply of proteins that can be equipped for accelerating explicit reactions that lead to an inorganic NP composite. Advantageously, the compound’s exceptionally high emission is accompanied by high measurements of 100–200 nm NPs in a rather unadulterated state, devoid of other cell proteins. By separating the NPs, the subsequent cleaning process is completed. The unique metal-holding capacities of bacterial cells and S-layers, as well as the tailored application of nanotechnology for bioremediation, need to be differentiated experimentally. Enhancing important limits that govern the stage of development of biological organisms, cell migration, and enzymatic processes (progressing reaction conditions and sequences of events) exemplifies the characteristics of NPs. More extensive work is expected to comprehend the exact reaction cycles of chemicals and proteins that contain NPs. The enormous combination of NPs with microbes is alluring because there is no requirement for risky, toxic, or exorbitant synthetic items in the amalgamation and solidness systems.

Table 2: Nanoparticles produced by various organisms and their applications in bioremediation.

Organisms can likewise be utilized to acquire NPs with clear-cut sizes notwithstanding monodispersed. Organisms could be utilized as a source to create more NPs than microbes. This results from the infectious release of more proteins, which directly causes an increase in the production of NPs [76]. Furthermore, unconnected proteins were effectively used in the assembly of NPs instead of parasite culture. It is also essential to understand the concept of NPs. Compared to plant selection, microbiological processes, the creation of NPs occurs more slowly. According to Oksanen et al. [77], proteins in metal NPs are made in a parasitic manner that reduces salt in places where the NPs are strongest through the action of the reactant. One of the main drawbacks of mixtures of natural NPs based on microorganisms is that they require adaptation to combat using various tactics. Certain features are necessary for fungi to be used in industrial settings. These features include higher levels of development, the ability to produce specific enzymes or metabolites more readily, ease of processing, and affordable production requirements. Parasites enjoy an upper hand over other natural frameworks, including a quick development rate, a wide assortment of proteins, insignificant supplement necessity, and simple to make due. This promotes a sustainable approach to the synthesis of NPs. Hereditary designing strategies can be utilized soon to further develop molecule highlights. Combining particular catalysts and quick improvement with the utilization of simple supplements, yeast species enjoy a few upper hands over microbes and blend with metal NPs [75].

5. UTILIZING NANOTECHNOLOGY IN ENVIRONMENTAL CLEANUP THROUGH BIOREMEDIATION

The science of NP bioremediation provides particular reasons for the use of bioremediation using discrete NMs. For example, an increase in surface area per unit mass occurs as a material approaches the nanoscale. If additional fabric comes into contact with nearby components, this could have an impact on the reactivity. Because of their quantum influence, NMs require less enactment energy to allow for synthetic replies. Surface plasma reverberation is another NP-shown feature that can be used to identify hazardous compounds. We can use different NMs in different structures and aspects to purify the climate concerning size and form. Because NPs are highly sensitive to redox pollutants and can disseminate a pollution area that microparticles cannot. It is observed that the oxide coating of FeO on NPs affects the reactivity of NPs with structures. A photoelectron reaction can contaminate pentachlorophenol (PCP) in a research center setting [85]. Single metal NPs can lessen dechlorination by acting as biocatalysts. In a bioreductive Pd (II) examination, palladium NPs can be deposited on the cell wall and within the cytoplasm of Shewanella oneidensis, further, it stacked with H⁺ water revolutionaries by coordinating various substrates, such as acetic acid and water derivation, and designing them as electron contributors. When the Pd(0) revolutionary H⁺ particle in these stacked S. oneidensis Pd(0)-stored cells comes into touch with chlorinated compounds, it can react chemically with PCP, causing the chlorinated compound atom to be evacuated [86]. Moreover, microbial organisms that can biorecover or degrade specific compounds might be rendered immobile by NPs. Pseudomonas delafieldii was exposed to magnetic NPs (Fe₃O₄) functionalized with ammonium oleate, as opposed to traditional fixed surface or micron-sized cell immobilization. Applying an outside attractive field to these microbial cells concentrates these attractive NP covered cells on a specific portion of the reactor wall, isolates them from the mass arrangement, and allows them to be reused for similar foundation treatment. After being exposed to a higher amount of biomass, these microbial cells desulfurized dibenzothiophene-like non-NP-coated cells [87]. They include soil and carbon remediation, wastewater treatment, heavy metal discharge remediation, and endless gas for hydrocarbons. In the upcoming centuries, the environment may see some of the biggest changes due to NM’s continuous efforts to reduce pollution output.

6. APPLICATION OF NPS IN WATER TREATMENT

Although water covers approximately 70% of Earth’s surface, less than 0.1% of the planet’s total water is readily accessible freshwater, posing a major global challenge. Water’s performance can be improved through the development of nanotechnology. A few strategies for extraction, filtration, bioremediation, and sterilization utilizing nanotechnology utilize responsive media. Remediation is a technique for eliminating, lessening, or killing water toxins that can influence biodiversity or biological systems. There are three distinct categories of remedial methods: (1) Warm, (2) physicochemical, and (3) organic. The most well-known methods of extraction, adsorption, and oxidation are cheap, exorbitant, and tedious, though more eco-accommodating organic crumbling is reasonable, even though tedious. Nanomaterials with upgraded nearness, capacity, and selectivity to weighty metals and different pollutants are trend-setting innovations that can be utilized. Zero-valent iron (ZVI), CNTs, and other NPs utilized in water remediation are just a few examples, and mesoporous support monolayers, biopolymers, and NPs containing a single enzyme that self-assemble. Rapid and crucial progress in wastewater treatment, including oxidation through photocatalysis, has been made to tackle the issue of water contamination [88-91].

According to Tratnyek and Johnson [92], a treatment and siphoning framework is a water remediation framework that has been developed over time. The strategy calls for siphoning, making do, and subsequently replenishing the floor with water from the earth to the top. Until 1998, the treatment and siphon system was still in use as a water solution. Another strategy to assist water is to employ a porous responsive border (PRB). Without requiring the water to be brought to the surface, PRB purifies and heals groundwater. Biphenyl polychlorinated (PCB) chemicals, chromate, fragrant nitro compounds, and insecticides can all be used to clear up poisons, such as hydrocarbons chlorinated using this treatment. Some disadvantages of the PRB technology are its high cost and ambiguous replacement time. The processes of treatment and siphoning should be replaced. Metal hydroxides and metal carbonates can occasionally reduce iron reactivity as a result of pollution. A few elective surgeries have overshadowed these deficiencies. Large amounts of dangerous water pollutants were handled or reduced in the early 1990s using various zero-valent metals, such as iron (ZVI), which were recommended as PRB filter material [93]. Nano-iron’s tiny size allows it to be applied to many different tasks, including cleanup, contaminant reduction, and groundwater remediation either through direct injection or through permeable reactive barriers (PRBs) [94,95]. ZVI is often arranged into two categories: (1) Nanoscale ZVI (nZVI) and (2) receptive nanoscale iron particle (RNIP) items. They are made using the main nanotechnology techniques. NZVI particles measure 100–200 nm iron (Fe) with zero valence, whereas RNIP particles have a weight distribution of 50/50 between Fe and Fe₃O₄. The future application of ZVI is strongly reactive with a large variety of contaminants, including Cr₂O₂, NO₃, Cu²⁺, and chlorinated hydrocarbons, as reported by Zhu et al. [96]. In addition to PRB, direct injection of nanoiron into soil, silt, or solid waste can be employed. The NPs are to be slurry tested. Once infused, the particles remain suspended, creating a healing environment. Although there is not much information on real applications, another strategy is to bind the NPs to a robust, effective matrix, such as ZVI’s activated carbonation. Different metals can supplant nanoiron. To corrupt trichloroethene and trichloroethane, two metal combinations, for example, endlessly iron nickel-copper were utilized [97].

A protein that contains iron called ferritin, which is an iron-storing substance, has some influence over both plants and animals. It is generated when an included system is composed of 24 nearly similar polypeptides, according to Theil [98]. When the nook develops, the iron molecules may join the hole through the protein’s shell, where the mineralization activity converts iron particles into ferrihydrite NPs. Under conditions of daylight or light, ferritin has been observed to replenish hazardous metals and chlorocarbons [99]. Advantages of ferritin over conventional iron impetus include the following: Ferritin does not change under photoreduction, and it also becomes more stable. According to Watlington [100], the exploration community has demonstrated a reasonable use of ferritin, with the difference in chromium being Cr(VI) versus Cr(III). Cr(VI), a toxin that causes cancer and is commonly discovered in modern landfills, is different from Cr(III), which is usually referred to as a less harmful and water-insoluble Cr molecule.

Some polymers, such as iron (III), zinc oxide (ZnO), zinc sulfide (ZnS), and titanium dioxide (TiO₂), can be used as photocatalysts [Table 3]. There are countless uses for photocatalysts, such as the dark kind that tints paint and paper, light-immersion, protective antimicrobials, and altered cleansers for sunscreen. To remediate soil and air, photocatalysts can oxidize common toxins into harmless substances. Because of its low lethality, high photo stability, high photoconductivity, and better efficiency, TiO₂ is employed in state-of-the-art methods for photochemical oxidation in water remediation. Using a semiconductor’s properties, light may oxidize ordinary objects. The material will oxidize when the load transfers from the valence band to the conductive band at a high enough light level. Nanotechnology advances have allowed photocatalysts to be tailored to their reactivity and selectivity [100]. A photocatalyst is equipped for ousting pollutants of 1,1-dichloroethane, cis-1,2-dichloroethane, 1,1,1-trichloroethane, xylene, and toluene from groundwater. In a pilot scale, TiO₂ was likewise observed to be prepared to eliminate from groundwater benzene, toluene, ethylbenzene, and xylene (BTEX). According to Liang et al [101], using nanotubes to induce exterior impacts of TiO₂ is a strong point for progressively getting rid of the material. This is in line with the standard design of TiO₂ powder. Even though ZnO photocatalysts are being produced, TiO₂ has been deliberately used regularly in industry. ZnO is specifically used for two objectives in the identification and treatment of contaminants. In the early phases of the research, ZnO was a photocatalyst that worked well for identifying and removing 4-chlorocatechol [102].

Table 3: Some common photocatalysts used in bioremediation.

Nanotechnology is responsible for cleaning microorganisms in water, which is expected because of populace impacts, interest in clean water, and expanding contamination. Nanotechnology with antimicrobial properties is one option. According to Li et al. [103], several nanomaterials showed strong antimicrobial properties through a variety of techniques, including (1) substituting the bacterial cell envelope (e.g., peptides, chitosan, carboxyfullerene, CNTs, NPs ZnO, and silver); (2) producing oxygen-harming receptive organisms (e.g., ag and NPs of liquid fullerene); (3) imperativeness transduction interruption (e.g., ag and NPs of the liquid fullerene); and (4) compound activity weakness and DNA blend (e.g., chitosan). TiO₂ is the most effective opponent of all because it is simple, harmless when consumed, and stable in water [Figure 3].

Figure 3: Applications of nanomaterials in aquatic environments (Created by the authors: BioRender). [Click here to view]

Utilizing the weight-critical power, nanofiltration is a separating structure. More notable push or disposal of multivalent particles, pesticides, and heavy metals is provided by contracted nanofiltration layers and conventional treatment systems. These days, the most recent development in air treatment is this invention, which can be used in your household, business, or firm bureau. A couple of reports on nanofiltration film shows were circulated [104,105]. Depending on the needs, several manufacturers provide nanofiltration films that can target different particles based on their subatomic weight.

7. ROLE OF NANOMATERIALS IN THE TREATMENT OF SOIL

One of the most important environmental concerns of our time has been and continues to be the remediation of contaminated soils and water. This involves the removal of pollutants from soil and water through a variety of techniques, such as the use of fungi or myco-remediation, cultivated plants by phytoremediation, or soil microorganisms through bioremediation, or biosorbent materials such as biochar, fly ash and organic fertilizers, humic substances (nano-FeS coated humic acid complex), and nanomaterials through green remediation or combined remediation, nano-phytoremediation. Many strategies, including phytoextraction, bioaugmentation and bio-stimulation, immobilization, biodegradation, and, in the case of earthworms, vermi-accumulation, vermi-transformation, and vermi-degradation, could be used to accomplish the remediation. There are many NPs that can be used to remediate groundwater and soil through nano-Fe₃O₄, nano zero-valent iron (nZVI), nano-hydroxyapatite, nano zeolite, nZVI, ZnO-NPs, nano-TiO₂, stabilized NPs, and nano-silica [Tables 4 and 5].

Table 4: Different nanomaterials used in soil treatment.

Table 5: Nanomaterial-based techniques for the soil treatment.

Conventional remediation approaches may be used whether they are responsive or absorbent, in situ or ex situ. The extraordinary properties of nanomaterials are investigated such as their strong sorption and high reactivity (when mixed with pharmaceutical contaminants in water and wastewater systems) and collaboration. They can expand their invasion and handle water/wastewater in this way, which is often seen as unreasonable by conventional developments. Recently, oil spills have been smoothed with nanoscale calcium peroxide, and limitless soil cleanup has been achieved with nanoscale zero-valent iron [112]. Iron NPs with biopolymer adjustments suitably degrade lindane. Standard repairs include designed oxidation, the use of iron-responsive limitations, ex situ soil and siphon, and on-location warm treatment. NPs are used throughout the material to absorb a wide range of toxins, heavy metals, and pollutants. For water treatment and routine cleanup, iron oxide NMs are great because of their advantageous strong adsorption, simple parcels, and further developed security [113]. Groundwater can be treated and channeled through a siphon using photocatalysis. nZVI has been used in situ propels to remediate contaminated soils and groundwater by the following methods: (1) nZVI is inserted to produce a responsive limit; (2) adaptable nZVI is incorporated to form a nZVI crest; and (3) NP is incorporated into topsoil to adsorb or modify toxins. Iron oxide NPs (NMs) are excellent for mechanical wastewater treatment due to their strong adsorption, simple packaging, and enhanced security [114].

It has been demonstrated that poison significantly impairs structural flexibility and functional integrity and pace at which pollutants dissolve in polymeric materials, like polycyclic aromatic hydrocarbons, which can be bio-sanitized by designed polymer NPs. In addition, the sequestration of foreign materials by soil and package sorption in non-aqueous phase liquids (NAPLs) reduces bioavailability. To construct the polymer nanonetwork layers, the “upside” dissolvability of phenanthrene (PHEN), a designating hydrophobe regular infection, and PHEN’s presentation from debased spring material were demonstrated. In PHEN’s urethane acrylate (PMUA), the antecedent chain Poly(ethylene)glycol has been substituted. The union of valuable water stones was spurred by the rapidity of PHEN mineralization, and this has continued in PMUA NPs. After PHEN soaked in spring material, a NAPL model (hexadecane) was broken in PHEN’s presence. These results demonstrate that PMUA particles raise the mineralization level of sorbed and NAPL-got PHEN in addition to improving its presentation. In addition, subatomic usage may be a potent strategy for increasing the in situ biodegradation rate through trademark restrictions, given that PMUA foreign chemicals are accessible to microorganisms. For soil washing or siphon and treatment schemes, bioreactors can be used to repurpose removed particulate matter. When PHEN is attached to PMUA NPs and reduced by microscopic organisms, the characteristics of the particles are consistently settled and reusable in the presence of a diverse and potent bacterial population [115].

One example of a frequent contaminant that is hydrophobic and difficult to remove from the soil is polynuclear aromatic hydrocarbons or PAHs. Phenophilic polyurethane NPs (APU) have been coordinated in soil remedy with PAHs. In the same manner that surfactant micelles can advance PAH desorption and transportation, APU particles are unable to sorb individual cross-associated precursor chains on the surface of the soil, in contrast to the surface-specific sections of micelles. Thus, even with their fluid fixation, APU particles are stable. Preliminary results show how APU channels can be set up with hydrophobic outside regions that yield elevated phenanthrene (PHEN) and hydrophilic interior regions that increase atomic convey ability in soil. As an illustration, changing the size of the hydrophobic segment employed in the chain mix can lessen the partiality to APU particles for impurities. The transportability of colloidal dirt APU suspensions is limited by the heap thickness or the length of the swinging water-dissolvable chains on the outer layer of the particle. Because different mechanized NPs have the potential to control subatomic properties, they can change the kind of contamination and the conditions of the soil [115] [Table 6].

Table 6: Traditional versus nano-bioremediation pros and cons.

8. NP TOXICITY, ECOLOGICAL RISKS, AND MITIGATION STRATEGIES

While nanobioremediation offers transformative potential for environmental cleanup, concerns regarding NP toxicity and ecological risks remain critical obstacles for its practical deployment. Engineered NPs such as silver, zinc oxide, and TiO₂ are known to exert cytotoxic effects on beneficial microbial consortia by generating reactive oxygen species, damaging cell membranes, and interfering with enzymatic functions, ultimately reducing microbial viability and bioremediation efficiency [133]. Beyond microbial systems, NPs can persist in soil and aquatic environments, where they may bioaccumulate and cause adverse effects on plants, invertebrates, and higher trophic organisms. Such uncontrolled release can disrupt microbial community structures and alter ecological balances, raising long-term biosafety concerns [134].

To address these challenges, innovative solutions are emerging. Coating NPs with biodegradable polymers has been shown to minimize microbial toxicity while retaining their catalytic and adsorptive functions, offering a safer route for environmental applications. Similarly, surface functionalization and green synthesis approaches such as using plant extracts or microbial metabolites enhance NP stability, biocompatibility, and eco-safety [135]. Recent studies also emphasize the importance of biosafety frameworks and standardized risk assessments to ensure safe field-level translation of nanobioremediation. These strategies demonstrate that thoughtful material engineering, combined with regulatory oversight, can significantly reduce risks and make nanobioremediation a sustainable and scalable technology for environmental restoration [136].

9. CHALLENGES OF NPS

The industrialization of nanotechnologies for field application is still in the testing stages, and their use for eliminating ecological pollutants is yet limited to the lab. While NPs have shown encouraging results in the removal of pollutants, their application in contaminated sites is constrained by their effect on microorganisms, loss of reactivity with time, transportation, and other factors [137]. For instance, some metal NPs lose their reactivity after a specific time of treatment because of limiting the section of liquids by obstructing the impact of soil. To conquer the issue, the utilization of stabilizers, for example, lactate, builds the versatility of iron NPs in soil. The lack of information regarding how NPs affect the development of microbial communities is another major issue with NPs. While several controlled tests on the effects of NPs on microbial populations have been conducted, the results are yet unconnected [138]. Some tests have a significant impact on microorganisms such as Escherichia coli and Staphylococcus aureus [139]. However, a few studies demonstrated that NPs as electron donors have a stimulatory effect on microorganisms such as bacteria and methanogens [140]. Notably, microorganisms are a significant piece of the regular pattern of supplements in the biological system and they assume a significant part in the evacuation of natural and inorganic impurities from the climate. Subsequently, the decrease of the microbial populace will prompt a diminishing in the obstruction of soil to impurities. Several mechanisms are responsible for NP toxicity. For example, NPs may disrupt cell membranes through the generation of reactive oxygen species and inhibit microbial growth by interfering with nutrient uptake across the cell membrane. Just a few investigations have displayed no evidence of any effect of NPs on the growth of parasitic provinces [141]. Certain microbes release tailored compounds and polysaccharides to shield themselves from the detrimental effects of NPs. One potential solution to this problem is to reduce the toxic effects of NPs by coating NP for specific natural polymers.

10. CONCLUSION

The integration of nanotechnology with bioremediation represents a forward-looking strategy to address persistent environmental challenges. While bioremediation offers eco-friendly, cost-effective, and sustainable solutions for pollutant degradation, its limitations such as slow kinetics and restricted pollutant range can be significantly overcome by the unique physicochemical properties of NPs. Engineered nanomaterials enhance microbial activity, improve pollutant bioavailability, and provide catalytic support for complex degradation pathways, thereby creating a synergistic remediation framework. However, careful attention must be given to NP toxicity, ecological impacts, and long-term sustainability to ensure that solutions do not generate secondary risks. Future research should emphasize the design of biocompatible and biodegradable nanomaterials, coupled with optimized microbial systems, to maximize remediation efficiency while minimizing environmental hazards. Overall, this synergistic approach offers a promising pathway toward cleaner ecosystems, advancing global efforts in sustainable development and environmental protection.

11. AUTHORS’ CONTRIBUTIONS

All authors made substantial contributions to conception and design, acquisition of data, or analysis and interpretation of data; took part in drafting the article or revising it critically for important intellectual content; agreed to submit to the current journal; gave final approval of the version to be published; and agree to be accountable for all aspects of the work. All the authors are eligible to be author as per the International Committee of Medical Journal Editors (ICMJE) requirements/guidelines.

12. FUNDING

There is no funding to report.

13. CONFLICTS OF INTEREST

The authors report no financial or any other conflicts of interest in this work.

14. ETHICAL APPROVALS

This study does not involve experiments on animals or human subjects.

15. DATA AVAILABILITY

All the data is available with the authors and shall be provided upon request.

16. PUBLISHER’S NOTE

All claims expressed in this article are solely those of the authors and do not necessarily represent those of the publisher, the editors and the reviewers. This journal remains neutral with regard to jurisdictional claims in published institutional affiliation.

17. USE OF ARTIFICIAL INTELLIGENCE (AI)-ASSISTED TECHNOLOGY

The authors declare that they have not used artificial intelligence (AI)-tools for writing and editing of the manuscript, and no images were manipulated using AI.

REFERENCES