Degradation of tricyclic polyaromatic hydrocarbons in water, soil and river sediment with a novel TiO2 based heterogeneous nanocomposite

Fluorene-induced stress in the benthic oligochaete Tubifex tubifex: A multi-biomarker assessment of toxicological pathways and mechanisms under acute and subchronic exposures

This study examined the multifaceted impacts of fluorene exposure on Tubifex tubifex, encompassing acute (survival analysis and behavioral responses) and subchronic exposure regimens (antioxidant enzyme response and histopathology), molecular docking studies, and generalized read-across analysis. Survival analysis revealed concentration-dependent increases in toxicity over varying time intervals, with LC50 values decreasing from 30.072 mg/L at 24 h to 12.365 mg/L at 96 h, emphasizing the time-sensitive and concentration-responsive nature of the stressor. Behavioral responses were both concentration- and duration-dependent. While Erratic Movement and Clumping Tendency exhibited earlier responses (within 24 h) at lower concentrations, the wrinkling effect and mucus secretion) exhibited delayed onset, suggesting intricate regulatory mechanisms underlying adaptability to environmental challenges; moreover, the wrinkling effect was consistently induced at higher concentrations, indicating greater sensitivity to the toxic effects of fluorene. With sublethal environmentally relevant concentrations-1.24 mg/l and 2.47 mg/L i.e., 10% and 20% 96 h, respectively-the antioxidant enzyme response (i.e., upregulation of SOD, CAT, and GST) with increasing fluorene concentration, revealing a nonlinear, hormetic response, suggested adaptive protection at lower doses but inhibition at higher concentrations. Histopathological examination indicated that higher fluorene concentrations caused cellular proliferation, inflammation, and severe tissue damage in the digestive tract and body wall. Molecular docking studies demonstrated robust interactions between fluorene and major stress biomarker enzymes, disrupting their functions and inducing oxidative stress. Interactions with cytochrome c oxidase suggested interference with cellular energy production. Generalized Read-Across (GenRA) analysis unveiled shared toxicity mechanisms among fluorene and its analogs, involving the formation of reactive epoxides and the influence of cytochrome P450 enzymes. The diverse functional groups of these analogs, particularly chlorine-containing compounds, were implicated in toxicity through lipid peroxidation and membrane damage. Adverse outcome pathways and broader consequences for aquatic ecosystem health are discussed.

Photocatalytic degradation of fluoranthene in soil suspension by TiO2/α-FeOOH with enhanced charge transfer capacity

Polycyclic aromatic hydrocarbons (PAHs) in soil are potentially harmful to human health. However, the use of photocatalysis technology to treat soil contaminated with PAHs remains challenging. Therefore, TiO2/α-FeOOH composite photocatalyst has been synthesized by hydrothermal method and sol-gel method and applied to photocatalytic degradation of fluoranthene in soil. The morphology, elements, crystal structure, optical properties, electrochemical characteristics, and photocatalytic activity of TiO2/α-FeOOH have been characterized. Results showed that TiO2 is tightly fixed on the surface of α-FeOOH, and TiO2/α-FeOOH had higher photocatalytic activity on photocatalytic degradation of fluoranthene in soil under simulated sunlight. The degradation efficiency of TiO2/α-FeOOH is 3.0 and 4.8 times higher than that of TiO2 and α-FeOOH, respectively. This is attributed to enhanced photocatalytic ability by enhancing the transfer capacity of electrons and holes and broadening the spectrum absorption range. The highest degradation efficiency was achieved when the pH of the soil is neutral, the ratio of water/soil is 10:1, and the dosage of catalyst is 50 mg/g. In addition, it was proved that •O2-, h+, and 1O2 are the main active substances in the photocatalysis of TiO2/α-FeOOH. The possible mechanism of a Z-type electron transfer structure was also proposed. The degradation products of fluoranthene were detected, and the degradation pathway was deduced.

Nano-bioremediation: an eco-friendly and effective step towards petroleum hydrocarbon removal from environment

Global concern about petroleum hydrocarbon pollution has intensified and gained scientific interest due to its noxious nature, high persistence in environmental matrices, and low degradability. One way to address this is by combining remediation techniques that could overcome the constraints of traditional physio-chemical and biological remediation strategies. The upgraded concept of bioremediation to nano-bioremediation in this direction offers an efficient, economical, and eco-friendly approach to mitigate petroleum contaminants. Here, we review the unique attributes of different types of nanoparticles and their synthesis procedures in remediating various petroleum pollutants. This review also highlights the microbial interaction with different metallic nanoparticles and their consequential alteration in microbial as well as enzymatic activity which expedites the remediating process. Besides, the latter part of the review explores the application of petroleum hydrocarbon degradation and the application of nano supports as immobilizing agents for microbes and enzymes. Further, the challenges and the future prospects of nano-bioremediation have also been discussed.

A Review on Photocatalysis Used For Wastewater Treatment: Dye Degradation

Water pollution is a global issue as a consequence of rapid industrialization and urbanization. Organic compounds which are generated from various industries produce problematic pollutants in water. Recently, metal oxide (TiO2, SnO2, CeO2, ZrO2, WO3, and ZnO)-based semiconductors have been explored as excellent photocatalysts in order to degrade organic pollutants in wastewater. However, their photocatalytic performance is limited due to their high band gap (UV range) and recombination time of photogenerated electron-hole pairs. Strategies for improving the performance of these metal oxides in the fields of photocatalysis are discussed. To improve their photocatalytic activity, researchers have investigated the concept of doping, formation of nanocomposites and core-shell nanostructures of metal oxides. Rare-earth doped metal oxides have the advantage of interacting with functional groups quickly because of the 4f empty orbitals. More precisely, in this review, in-depth procedures for synthesizing rare earth doped metal oxides and nonocomposites, their efficiency towards organic pollutants degradation and sources have been discussed. The major goal of this review article is to propose high-performing, cost-effective combined tactics with prospective benefits for future industrial applications solutions.

Titania nanoparticles for photocatalytic degradation of ethanol under simulated solar light

TiO₂ nanoparticles were synthesized by laser pyrolysis from TiCl₄ vapor in air in the presence of ethylene as sensitizer at different working pressures (250-850 mbar) with and without further calcination at 450 °C. The obtained powders were analyzed by energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, X-ray diffractometry, and transmission electron microscopy. Also, specific surface area and photoluminescence with optical absorbance were evaluated. By varying the synthesis parameters (especially the working pressure), different TiO₂ nanopowders were obtained, whose photodegradation properties were tested compared to a commercial Degussa P25 sample. Two series of samples were obtained. Series "a" includes thermally treated TiO₂ nanoparticles (to remove impurities) that have different proportions of the anatase phase (41.12-90.74%) mixed with rutile and small crystallite sizes of 11-22 nm. Series "b" series represents nanoparticles with high purity, which did not require thermal treatment after synthesis (ca. 1 atom % of impurities). These nanoparticles show an increased anatase phase content (77.33-87.42%) and crystallite sizes of 23-45 nm. The TEM images showed that in both series small crystallites form spheroidal nanoparticles with dimensions of 40-80 nm, whose number increases with increasing the working pressure. The photocatalytic properties have been investigated regarding the photodegradation of ethanol vapors in Ar with 0.3% O₂ using P25 powder as reference under simulated solar light. During the irradiation H₂ gas production has been detected for the samples from series "b", whereas the CO₂ evolution was observed for all samples from series "a".

Efficiency and mechanism on photocatalytic degradation of fluoranthene in soil by Z-scheme g-C3N4/α-Fe2O3 photocatalyst under simulated sunlight

Polycyclic aromatic hydrocarbons (PAHs) in soil have potential harm on human health. However, remediation of PAH-contaminated soils through photocatalytic technology remains a challenge. Therefore, the photocatalyst g-C₃N₄/α-Fe₂O₃ was synthesized and applied to photocatalytic degradation of fluoranthene in soil. The physicochemical properties of g-C₃N₄/α-Fe₂O₃ and various degradation parameters, such as catalyst dosage, the ratio of water/soil, and initial pH, were investigated in detail. In soil slurry reaction system (water/soil=10:1, w/w), the optimal degradation efficiency on fluoranthene was 88.7% after simulated sunlight irradiation for 12 h (contaminated soil=2 g, initial fluoranthene concentration=36 mg/kg, catalyst dosage=5%, and pH=6.8), and the photocatalytic degradation followed pseudo-first-order kinetics. The degradation efficiency of g-C₃N₄/α-Fe₂O₃ was higher compared with P25. Degradation mechanism analysis showed that •O₂^- and h⁺ are the main active species in photocatalytic degradation process of fluoranthene by g-C₃N₄/α-Fe₂O₃. Coupling g-C₃N₄ and α-Fe₂O₃ enhances the interfacial charge transport capacity via Z-scheme charge transfer route and inhibits the recombination of photogenerated electrons and holes of g-C₃N₄ and α-Fe₂O₃, then significantly improves the production of active species and photocatalytic activity. Results showed that photocatalytic treatment of soil by g-C₃N₄/α-Fe₂O₃ is an effective strategy for remediation of soils contaminated by PAHs.

An Overview on the Treatment of Oil Pollutants in Soil Using Synthetic and Biological Surfactant Foam and Nanoparticles

Oil-contaminated soil is one of the most concerning problems due to its potential damage to human, animals, and the environment. Nanoparticles have effectively been used to degrade oil pollution in soil in the lab and in the field for a long time. In recent years, surfactant foam and nanoparticles have shown high removal of oil pollutants from contaminated soil. This review provides an overview on the remediation of oil pollutants in soil using nanoparticles, surfactant foams, and nanoparticle-stabilized surfactant foams. In particular, the fate and transport of oil compounds in the soil, the interaction of nanoparticles and surfactant foam, the removal mechanisms of nanoparticles and various surfactant foams, the effect of some factors (e.g., soil characteristics and amount, nanoparticle properties, surfactant concentration) on remediation efficiency, and some advantages and disadvantages of these methods are evaluated. Different nanoparticles and surfactant foam can be effectively utilized for treating oil compounds in contaminated soil. The treatment efficiency is dependent on many factors. Thus, optimizing these factors in each scenario is required to achieve a high remediation rate while not causing negative effects on humans, animals, and the environment. In the future, more research on the soil types, operating cost, posttreatment process, and recycling and reuse of surfactants and nanoparticles need to be conducted.

Nanomaterials for Photocatalytic Degradations of Analgesic, Mucolytic and Anti-Biotic/Viral/Inflammatory Drugs Widely Used in Controlling SARS-CoV-2

The COVID-19 pandemic has been transformed into one of the main worldwide challenges, in recent years. For controlling symptoms that are caused by this disease (e.g., chills or fever, shortness of breath and/or difficulty in breathing, cough, sore throat, fatigue, headache, muscle aches, the new loss of tastes and/or smells, congestion or runny nose, nausea, vomiting and/or diarrhea), lots of medicines including analgesics, mucolytics, and anti-biotic/viral/inflammatory drugs have been frequently prescribed. As these medicines finally contaminate terrestrial and aquatic habitats by entering surface waterways through pharmaceutical production and excreting trace amounts of waste after human usage, they have negative impacts on wildlife’s health and ecosystem. Residual drugs in water have the potential to harm aquatic creatures and disrupt their food chain as well as the breeding cycle. Therefore, proper degradation of these broadly used medicines is highly crucial. In this work, the use of nanomaterials applicable in photocatalytic degradations of analgesics (e.g., acetaminophen, aspirin, ibuprofen, and naproxen), mucolytics (e.g., ambroxol), antibiotics (e.g., azithromycin and quinolones including hydroxychloroquine and chloroquine phosphate), anti-inflammatory glucocorticoids (e.g., dexamethasone and cortisone acetate), antihistamines (e.g., diphenhydramine), H2 blockers (e.g., famotidine), anthelmintics (e.g., praziquantel), and finally antivirals (e.g., ivermectin, acyclovir, lopinavir/ritonavir, favipiravir, nitazoxanide, and remdesivir) which widely used in controlling/treating the coronavirus have been reviewed and discussed.

Efficient removal of plastic additives by sunlight active titanium dioxide decorated Cd-Mg ferrite nanocomposite: Green synthesis, kinetics and photoactivity

Large use of flame retardants or additives in plastic industries have caused scientific attention as their leaching from consumer products is indicative of environmental concern. Moreover, plastic additives have proven features of endocrine disruptors, genotoxicity and persistence. Therefore, photodegradation of tetrabromobisphenol A (TBBPA) and bisphenol A (BPA) were explored in water. Seeing environmental safety, titanium dioxide decorated magnesium substituted cadmium ferrite (CdMgFe₂O₄@TiO₂) was synthesized by using plant extract of M. koenigii via co-precipitation. Sharp peaks obtained in PXRD ensured high crystallinity and purity of distorted spherical nanocomposite (5-25 nm). Subsequently, CdMgFe₂O₄@TiO₂ nanocatalyst was evaluated for the effective elimination of plastic additives at variable reaction parameters (pollutant: 2-10 mgL^-1; catalyst: 5-25 mg; pH: 3-7, dark-sunlight). With 20 mg of catalytic dose, CdMgFe₂O₄@TiO₂ showed maximum degradation of 2 mgL^-1 of TBBPA (91%) and BPA (94%) at neutral pH under sunlight. Considerable reduction in persistence of TBBPA (t_1/2:2.4 h) and BPA (t_1/2:2.1 h) indicated admirable photoactivity of CdMgFe₂O₄@TiO₂. Results were supported by BET, zeta potential, band reflectance and photoluminescence analysis that indicated for higher surface area (90 m²g^-1), larger particle stability (-20 mV), lower band gap (1.9 eV) and inhibited charge-pairs recombination in nanocomposite. Degradation consisted of initial Langmuir-adsorption followed by first order kinetics. Scavenger analysis revealed the role of hydroxyl radical in photodegradation studies. Nanocomposite was effective up to eight cycles without any significant loss of activity that advocated its high-sustainability and cost-effectiveness. Overall, with excellent surface characteristics, green synthesized CdMgFe₂O₄@TiO₂ nanocomposite is a promising and alternative photocatalyst for industrial applications.

Efficient degradation of organic pollutants by novel titanium dioxide coupled bismuth oxide nanocomposite: Green synthesis, kinetics and photoactivity

Herein, a green and facile methodology was used for the structural design of semiconductor nanomaterials and employed as efficient photocatalyst to resolve the environmental issues of water pollutants. Titanium oxide coupled with bismuth oxide (TiO₂@Bi₂O₃) nanocomposite was synthesized by employing the seed extract of Sapindus mukorossi (commonly found plant in India) and subsequently used for the elimination of toxic, and persistence industrial pollutants namely bisphenol A (BPA) and methylene blue (MB). Microscopic and spectroscopic techniques revealed particle size of synthesized nanocomposite found less than 50 nm along with high crystallinity. Appearance of stretching vibrations at 459 cm^-1 for Bi-O-Ti in the IR spectra of nanocomposite has established the coupling of TiO₂ with Bi₂O₃. The parameters of degradation were optimized by varying the pollutant concentration, catalytic amount and pH in the presence of natural sunlight. The nanocomposite TiO₂@Bi₂O₃ showed maximum degradation (MB: 94% and BPA: 91%) at a minimum concentration of pollutant (50 mgL^-1) with catalyst amount (35 mg), neutral pH and reduces half-life of pollutants (BPA: 1h, MB: 0.5h). Owing of higher surface area (80 m²g^-1), lower band gap (2.5 eV), and more negative zeta potential value (-40.3 mV) results into excellent photocatalytic properties. The breakage of S-N conjugated system in MB results into rapid degradation as compare to BPA. The degradation followed first-order kinetics and Langmuir adsorption in both the cases. Presence of active radicals during the photocatalysis process was responsible for quick degradation and strongly supported by scavenger analysis. GC-MS analysis revealed the degradation of toxic pollutants into safer metabolites and finally mineralized. Multiple times (n = 8) reusability of green photocatalyst advocated sustainability and appropriate for industrial applications.

Metal-Based Nanocomposite Materials for Efficient Photocatalytic Degradation of Phenanthrene from Aqueous Solutions

Polycyclic aromatic hydrocarbons (PAHs) are a class of naturally occurring chemicals resulting from the insufficient combustion of fossil fuels. Among the PAHs, phenanthrene is one of the most studied compounds in the marine ecosystems. The damaging effects of phenanthrene on the environment are increasing day by day globally. To lessen its effect on the environment, it is essential to remove phenanthrene from the water resources in particular and the environment in general through advanced treatment methods such as photocatalytic degradation with high-performance characteristics and low cost. Therefore, the combination of metals or amalgamation of bimetallic oxides as an efficient photocatalyst demonstrated its propitiousness for the degradation of phenanthrene from aqueous solutions. Here, we reviewed the different nanocomposite materials as a photocatalyst, the mechanism and reactions to the treatment of phenanthrene, as well as the influence of other variables on the rate of phenanthrene degradation.

Effect of nanomaterials on remediation of polycyclic aromatic hydrocarbons-contaminated soils: A review

The remediation of toxic polycyclic aromatic hydrocarbons (PAHs) in the soil is always an important topic since exposure to contaminated soil with carcinogenic, mutagenic, and teratogenic potential can result in serious health effects. With respect to the remediation of PAHs contaminated soil, nanomaterials (NMs) have recently received a great deal of attention due to the special characteristics arising from their nanoscale sizes. However, the usefulness and potency of these NMs depend on their adaption to specific site conditions and soil properties. Since there is no comprehensive review of the applications of NMs, it is of great importance to analyze, discuss, and interpret the latest progress in the application of NMs for the remediation of contaminated soils containing PAHs. This overview essentially captures the novel advances made in nano zero valent-iron (nZVI), metal oxides, carbon-based NMs, and polymer-based materials. Each characteristic of NMs that contributes to the enhancement of the process is highlighted. Moreover, operational conditions in which the best-obtained results are achieved qualitatively summarize. This review is also given special attention to the type of soil and pollutant, which are major influential factors to affect the performance of the process. Furthermore, the potential implication of NMs and PAHs on soil properties is reviewed in terms of the changes in migration behavior of pollutants, plant phytotoxicity, and soil microbial community composition. Discussion on future perspectives is presented on the use and prospects for the application of NMs in contaminated soils.

Insight in to sunlight-driven rapid photocatalytic degradation of organic dyes by hexacyanoferrate-based nanoparticles

Release of colouring agents into the environment alarms the need to design a cheap, quick and safe process. Owing to environmental safety concern, synthesis of two metal hexacyanoferrates (MHCFs) based on cadmium (CdHCF) and manganese (MnHCF) was carried out using natural plant extract of Azadirachta indica and water as a solvent. Synthesized MHCFs were utilized for the removal of an acid dye (fuchsin acid, FA) and a xanthenes dye (rhodamine B, RB). The reactions were optimized at various conditions of dye concentration, catalyst dose, reaction pH, time and source of light. The MHCFs showed excellent results with both the dyes within very limited span of time (2 h). Consequently, 98% of FA and 97% of RB were degraded with 10 mg of CdHCF, at neutral pH and under sunlight. The degradation process followed the first-order reaction kinetics having t_1/2 around 0.3 min. The MHCFs exhibited difference of only little percentage in degradation owing to a very slight difference between their surface areas (CdHCF: 54.1 m² g^-1; MnHCF: 49.7 m² g^-1). The synthesised nanocatalysts were stable as indicated by their higher negative zeta potential values. The adsorption of dyes was found to be maximum with CdHCF having X_m value 19.69 mg g^-1 and 18.15 mg g^-1 for FA and RB, respectively. Photocatalytic degradation involved the main role of hydroxyl radical as indicated by decline in activity of nanocatalyst in the presence of scavengers. All in all, this study presents highly active nanomaterials with higher surface area, stability and semiconducting properties under natural conditions.

Nanotechnology in soil remediation - applications vs. implications

Engineered nanomaterials (ENMs) and nanotechnology have shown great potential in addressing complex problems and creating innovative approaches in soil remediation due to their unique features of high reactivity, selectivity and versatility. Meanwhile, valid concerns exist with regard to their implications towards the terrestrial environment and the ecosystem. This review summarizes: (i) the applications and the corresponding mechanisms of various types of ENMs for soil remediation; (ii) the environmental behavior of ENMs in soils and their interactions with the soil content; (iii) the environmental implications of ENMs during remedial applications. The overall objective is to promote responsible innovations so as to take optimal advantage of ENMs and nanotechnology while minimizing their adverse effects to the ecological system. It is critical to establish sustainable remediation methods that ensure a healthy and safe environment without bringing additional risk.

Impact of Titanium Dioxide (TiO2) Modification on Its Application to Pollution Treatment—A Review

A high-efficiency method to deal with pollutants must be found because environmental problems are becoming more serious. Photocatalytic oxidation technology as the environmentally-friendly treatment method can completely oxidate organic pollutants into pollution-free small-molecule inorganic substances without causing secondary pollution. As a widely used photocatalyst, titanium dioxide (TiO2) can greatly improve the degradation efficiency of pollutants, but several problems are noted in its practical application. TiO2 modified by different materials has received extensive attention in the field of photocatalysis because of its excellent physical and chemical properties compared with pure TiO2. In this review, we discuss the use of different materials for TiO2 modification, highlighting recent developments in the synthesis and application of TiO2 composites using different materials. Materials discussed in the article can be divided into nonmetallic and metallic. Mechanisms of how to improve catalytic performance of TiO2 after modification are discussed, and the future development of modified TiO2 is prospected.

Mineralization of carcinogenic anthracene and phenanthrene by sunlight active bimetallic oxides nanocomposites

Polycyclic aromatic hydrocarbons (PAHs) are causing environmental concerns due to their persistent nature and carcinogenicity. Hence, their removal through advanced nanomaterials with characteristics of low-cost and high efficiency is essential. In view of this, bimetallic oxides (BMOs) nanocomposites of NiO-ZnO, ZnCo₂O_4, MnCo₂O₄ and CoFe₂O₄ were synthesized via green route using leaf extract of Aegle marmelos. Subsequently, these BMOs were investigated for photocatalytic removal of selected PAHs like anthracene (ANTH) and phenanthrene (PHEN) from water. Nanospheres of NiO-ZnO, ZnCo₂O_4, and CoFe₂O₄ and nanosheets of MnCo₂O₄ with particle size range of 10-30 nm were confirmed by transmission electron microscopy. At neutral pH, nanocomposites showed excellent ability in degrading 2 mg L^-1 of PAHs (ANTH: 98%; PHEN: 93%) within 12 h under the exposure of sunlight. Among the synthesized BMOs, NiO-ZnO was found best followed by ZnCo₂O_4, MnCo₂O₄ and CoFe₂O_4. This fact is attributed to the highest surface area (129 m² g^-1) and particles stability (zeta potential: -30 eV) of NiO-ZnO. Photodegradation of PAHs by nanocomposites followed first order kinetics and fitted in Langmuir model for adsorption. Higher degradation under sunlight and lower removal efficiency with scavenger confirmed the photodegradation activity of nanocomposites. Overall, reusable (n = 10) nanocomposites with no loss of activity have high photocatalytic potential in the removal of carcinogenic PAHs.