Life Cycle Impact of Titanium Dioxide Nanoparticle Synthesis through Physical, Chemical, and Biological Routes

Green remediation of mercury-contaminated soil using iron sulfide nanoparticles: Immobilization performance and mechanisms, effects on soil properties, and life cycle assessment

Mercury (Hg) pollution in soil has grown into a severe environmental issue. Effective in situ immobilization techniques are crucially demanded. In this study, we explored the application of carboxymethyl cellulose stabilized iron sulfide nanoparticles (CMC-FeS) for in situ immobilization of Hg in soil. CMC-FeS (a CMC-to-FeS molar ratio of 0.0004) was prepared via the reaction between FeSO4 and Na2S using CMC as a stabilizer. Remedying the Hg-polluted soil using 0.03 % CMC-FeS via batch experiments effectively reduced the acid leachable Hg by 97.5 % upon equilibrium after 71 days. Column elution tests demonstrated that the addition of CMC-FeS decreased the peak Hg concentration by 89.9 % and the total Hg mass eluted by 94.9 % after 523 pore volumes. CMC-FeS immobilized Hg in soil via chemical precipitation, ion exchange, and surface complexation. After the CMC-FeS treatment, Hg was transformed from more available exchangeable, carbonate-bound, and organic material-bound forms into the less available residual fraction, reducing the environmental risk of soil Hg from medium to low. The application of CMC-FeS boosted the soil enzyme activities and enhanced the soil bacterial diversity whereas decreased the production of methylmercury. CMC-FeS also facilitated long-term immobilization of Hg in soil. The acid leachable Hg and relative Hg bioaccessibility was decreased. Lift cycle assessment indicated that the preparation and application of CMC-FeS for in situ Hg remediation in soil met green chemistry principles. The present study confirms that CMC-FeS can be applied as an efficient and "green" amending agent for long-term Hg immobilization in soil/sediment.

Comprehensive life cycle assessment of NH2-functionalized magnetic graphene oxide for mercury removal: Carbon emissions and economic evaluation

Heavy metals contamination critically affects human health and ecosystems, necessitating pioneering approaches to diminish their adverse impacts. Hence, this study synthesized aminated magnetic graphene oxide (mGO-NH2) for the removal of mercury (Hg) from aqueous solutions. Although functionalized GO is an emerging technology at the early stages of development, its synthesis and application require special attention to the eco-environmental assessment. Therefore, the life cycle assessment and life cycle cost of mGO-NH2 were investigated from the cradle-to-gate approach for the removal of 1 kg Hg. The adsorption process was optimized based on pH, Hg concentration, adsorbent dose, and contact time at 6.48, 40 mg/l, 150 mg/l, and 35 min, respectively, resulting in an adsorption capacity of 184.17 mg/g. Human carcinogenic toxicity with a 40.42% contribution was the main environmental impact, relating to electricity (35.76%) and ethylenediamine (31.07%) usage. The endpoint method also revealed the pivotal effect of the mGO-NH2 synthesis on human health (90.52%). The most energy demand was supplied by natural gas and crude oil accounting for 70.8% and 22.1%, respectively. A 99.02% CO2 emission originated from fossil fuels consumption based on the greenhouse gas protocol (GGP). The cost of mGO-NH2 was about $143.7/kg with a net present value of $21064.8 per kg Hg removal for a 20-year lifetime. Considering the significant role of material cost (>70%), the utilization of industrial-grade raw materials is recommended to achieve a low-cost adsorbent. This study demonstrated that besides the appropriate performance of mGO-NH2 for Hg removal, it is essential that further studies evaluate eco-friendly approaches to decrease the adverse impacts of this emerging product.

Treatment of landfill leachate using photocatalytic based advanced oxidation process - a critical review

Landfill leachate is a discrete volumetric component of municipal solid waste; hence, researchers and professionals are more concerned about it because of its obscurity. Innovative treatment and emerging technologies are being scrutinized to address the treatment of landfill leachate challenges. The leading target of this review was to examine the possibility of removing recalcitrant organic pollutants from landfill leachate by photocatalytic-based advanced oxidation processes. A summary of the systematic applicability of conventional treatment for landfill leachate is provided, with a focus on physico-chemical and biological processes. The biological treatment, such as aerobic and anaerobic digestion, is an excellent technique for treating highly concentrated organic pollutants in the wastewater. However, Leachate can scarcely be treated using conventional techniques since it is enriched with refractory organics and inorganic ions. It is clear from the literature review that none of the available combinations of physico-chemical and biological treatments are entirely relevant for the removal of recalcitrant organic pollutants from leachate. Recently, the photo-assisted TiO2/ZnO oxidation has shown an excessively potential and feasible way to treat landfill leachate. TiO2/ZnO photocatalysis is currently developing to treat recalcitrant organic pollutants from landfill leachate. The effect of operating parameters reveals that pH and temperature affect the reaction rate. The addition of oxidant H2O2 to the TiO2/ZnO suspension suggests that TiO2 leads to an increase in the rate of reaction when compared to ZnO. Photocatalytic remediation technique of landfill leachate would support the goal of environmental sustainability by greatly enhancing the effectiveness of treated leachate reutilization. In this review, the selection of the best photocatalytic treatment for leachate based on its systematic relevance and potential conditions, characteristics, cost-effectiveness, essential controlling, discharge limit, long-term environmental effects, and its future study perspectives are emphasized and discussed.

Biofabrication of Titanium Dioxide Nanoparticles Catalyzed by Solanum surattense: Characterization and Evaluation of their Antiepileptic and Cytotoxic Activities

The green synthesis of nanoparticles using plant extract is a new method that can be used in various biomedical applications. Therefore, the green approach was an aspect of ongoing research for the synthesis titanium dioxide nanoparticles (TiO₂ NP) using the Solanum surattense aqueous plant extract, which acts as a stabilizing and reducing agent. The synthesis of TiO₂ NPs was confirmed by energy dispersive X-ray (EDX), scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and UV-visible spectroscopy (UV-vis) analyses. The excitation energy to synthesize TiO₂ NPs was identified through the UV-vis spectrophotometric analysis at a wavelength of 244 nm. Further, the FT-IR spectroscopy visualized different biomolecules like OH, C=O, C-H, and C-O that were present in an aqueous extract of the plant and were responsible for the stabilization of TiO₂ NPs. The crystallinity and phase purity of TiO₂ NPs were illustrated by the sharp peaks of the XRD pattern. The spherical morphology with sizes ranging from 10 to 80 nm was examined using SEM images. The elemental composition of TiO₂ NPs was revealed by the intensity and narrow widths of titanium and oxygen using EDX analysis. This report also explains the antiepileptic activity of TiO₂ NPs in a maximal electroshock-induced epileptic (MESE) and pentylenetetrazol (PTZ) model. The synthesized TiO₂ NPs showed maximum antiepileptic activity in the PTZ model, significantly decreasing the convulsions (65.0 ± 5.50 s) at 180 mg/kg in contrast to standard drug phenytoin, whereas the MESE model was characterized by the appearance of extensor, clonus, and flexion. The results showed that synthesized TiO₂ NPs significantly reduced the time spent in each stage (15.3 ± 0.20, 16.8 ± 0.25, and 20.5 ± 0.14 s) at 180 mg/kg as compared to control groups. Furthermore, the cytotoxicity of synthesized produced TiO₂ NPs demonstrated that concentrations ≤80 μg/mL were biologically compatible.

UV-dependent freshwater effect factor of nanoscale titanium dioxide for future life cycle assessment application

Environmental impacts of nanoscale titanium dioxide (TiO₂ ) should be assessed throughout the lifetime of nanoparticles (NPs) to improve the state of knowledge of the overall sustainability. Life cycle assessment (LCA) has been previously recognized as a promising approach to systematically evaluating environmental impacts of NPs. As a result of their unique nanospecific properties, characterization factors (CF) were previously used for compensating the release and potential impacts of TiO₂ NPs. However, because TiO₂ NPs are known to generate reactive oxygen species and elicit toxicity to freshwater organisms, the lack of adequate UV-dependent effect factors (EFs) remains a major shortcoming when addressing their life cycle impacts. To complement the LCA of TiO₂ -NPs-enabled products under their specific applications, we recapitulated the freshwater toxicity of TiO₂ NPs and then modeled in USEtox to determine trophic level EF ranges under UV and non-UV exposure conditions. Results indicate that EFs derived for non-UV exposure were 52 (42.9-65) potentially affected fraction (PAF) m³ /kg, and combined toxicity data derived EFs were 70.1 (55.6-90.5) PAF m³ /kg. When considering only the UV-induced exposure condition, the modeled EF increased to 500 (333-712) PAF m³ /kg. Our work highlights that case-dependent EFs should be considered and applied to reflect more realistic ecological impacts and illustrate comprehensive life cycle environmental impacts for nanoenabled products. Integr Environ Assess Manag 2023;19:578-585. © 2022 SETAC.

Life Cycle Impact Assessment of Solution Combustion Synthesis of Titanium Dioxide Nanoparticles and Its Comparison with More Conventional Strategies

This paper represents the first attempt to quantitatively and reliably assess the environmental sustainability of solution combustion synthesis (SCS) with respect to other soft chemistry strategies, which are more conventionally employed in the preparation of engineered oxide nanomaterials, namely hydrolytic and non-hydrolytic sol-gel syntheses (i. e., HSGS and NHSGS). Indeed, although SCS is well known to rely on significant reduction in the energy as well as time required for the obtainment of the desired nanocrystals, its quantitative environmental assessment and a detailed comparison with other existing synthetic pathways represents an absolute novelty of high scientific desirability in order to pursue a more sustainable development in the inorganic chemistry as well as materials science research fields. TiO₂ nanoparticles were selected as the material of choice, for the production of which three slightly modified literature procedures were experimentally reproduced and environmentally evaluated by the application of the comprehensive life cycle assessment (LCA) methodology. Particularly, SCS was compared from an environmental perspective with sol-gel approaches performed both in water and in benzyl alcohol. The results of the present study were also framed among those recently obtained in a systematic study assessing seven further chemical, physical, and biological routes for the synthesis of TiO₂ nanoparticles, comprising also flame spray pyrolysis (typically used in industrial productions), highlighting and quantifying the excellent environmental performances of SCS.

Environmental safety of nanotechnologies: The eco-design of manufactured nanomaterials for environmental remediation

Nanosafety is paramount considering the risks associated with manufactured nanomaterials (MNMs) whose implications could outweigh their advantages for environmental applications. Although nanotechnology-based solutions to implement pollution control, remediation and prevention are incremental with clear benefits for public health and Earth' natural ecosystems, nanoremediation is having a setback due to the risks associated with the safety of MNMs for humans and the environment. MNMs are diverse, work differently and bionano-interactions occurring upon environmental exposure will guide their fate and hazardous outcomes. Here we propose a new ecologically-based design strategy (eco-design) having its roots in green nanoscience and LCA that will ground on an Ecological Risk Assessment approach, which introduces the evaluation of MNMs' ecotoxicity along with their performances and efficacies at the design stage. As such, the proposed eco-design strategy will allow recognition and design-out since the very beginning of material synthesis, those hazardous peculiar features that can be hazardous to living beings and the natural environment. A more ecologically sound eco-design strategy in which nanosafety is conceptually included in MNMs design will sustain safer nanotechnologies including those for the environment as remediation by leveraging any risks for humans and natural ecosystems.

A perspective on the recovery mechanisms of spent lithium iron phosphate cathode materials in different oxidation environments

Oxidative extraction has become an economically viable option for recycling lithium (Li) from spent lithium iron phosphate (LiFePO₄) batteries. In this study, the releases behaviour of Li from spent LiFePO₄ batteries under different oxidizing conditions was investigated with sodium hypochlorite (NaClO) as the solid oxidant. We revealed that, due to the intervention of graphitic carbon, the generated species of Li in mechanochemical oxidation (NaClO:LiFePO₄ at a molar ratio of 2:1, 5 min, and 600 rpm) was lithium carbonate (Li₂CO₃). The graphite layer provided a channel for the conversion of Li species released by mechanochemical oxidation. While in hydrometallurgical oxidation (NaClO:LiFePO₄ at a molar ratio of 2:1 and 12.5 min), the presence of hydrogen species led to the formation of lithium chloride (LiCl). Moreover, life cycle assessment (LCA) demonstrated that for recycling 1.0 kg of spent LiFePO₄ batteries, mechanochemical and hydrometallurgical oxidation could reduce carbon footprints by 2.81 kg CO₂ eq and 2.88 kg CO₂ eq, respectively. Our results indicate that the oxidative environment determines the release pathway of Li from the spent LiFePO₄ cathode material, thereby regulating the product forms of Li and environmental impacts. This study can provide key technical guidance for Li recycling from spent LiFePO₄ batteries.

Life Cycle Assessment of UV-C based treatment systems for the removal of compounds of emerging concern from urban wastewater

In the last decades particular attention is being paid to the efficient and effective removal of compounds of emerging concern (CECs) present in wastewater before their eventual reuse or disposal. Several technologies have been developed for the degradation of CECs in aqueous matrix, in this regard advanced oxidation processes (AOPs) represent a nascent technological solution developed on a laboratory scale with applications on a prototype scale. The experimental evidences have shown that AOPs processes can oxidize numerous organic compounds in a much faster and more efficient way than that of the most common disinfection processes. The most common AOPs processes are those that involve the use of H₂O₂/UV, O₃/UV, H₂O₂/O₃, H₂O₂/O₃/UV, Fenton and photo-Fenton. The aim of this work is to illustrate the results of a comparative LCA study of a laboratory scale UV-C photoreactor for the tertiary treatment of urban wastewater of three treatment systems (UV-C, UV-C + H₂O₂ e UV-C + TiO₂). In particular, the specific objective is to evaluate, from an environmental point of view, an innovative advanced oxidation system based on nanostructures TiO₂ immobilized on a stainless steel mesh. Compared to the UV-C photolysis reference system, the addition of hydrogen peroxide reduces the total environmental impact of the system by almost 75 %, while the use of the stainless-steel mesh coated by the nanostructures titanium dioxide reduces the UV-C environmental impact by 30 %. These results are due to the lower energy consumption of these last treatments compared to photolysis alone. The main impacts of the three systems are related to the electric power consumption of the centrifugal pump (63-64 %) and of the UV-C lamp (32-33 %). The LCA applied to these systems has shown that TiO₂ assisted photocatalysis is not yet advantageous from an environmental point of view and that, therefore, the efficiency of the system needs to be improved.

Synthesis and application of titanium dioxide photocatalysis for energy, decontamination and viral disinfection: a review

Global pollution is calling for advanced methods to remove contaminants from water and wastewater, such as TiO₂-assisted photocatalysis.  The environmental applications of titanium dioxide have started after the initial TiO₂ application for water splitting by Fujishima and Honda in 1972. TiO₂ is now used for self-cleaning surfaces, air and water purification systems, microbial inactivation and selective organic conversion. The synthesis of titanium dioxide nanomaterials with high photocatalytic activity is actually a major challenge. Here we review titanium dioxide photocatalysis with focus on mechanims, synthesis, and applications. Synthetic methods include sol-gel, sonochemical, microwave, oxidation, deposition, hydro/solvothermal, and biological techniques. Applications comprise the production of energy, petroleum recovery, and the removal of microplastics, pharmaceuticals, metals, dyes, pesticides, and of viruses such as the severe acute respiratory syndrome coronavirus 2.

Advances in Hybrid Composites for Photocatalytic Applications: A Review

Heterogeneous photocatalysts have garnered extensive attention as a sustainable way for environmental remediation and energy storage process. Water splitting, solar energy conversion, and pollutant degradation are examples of nowadays applications where semiconductor-based photocatalysts represent a potentially disruptive technology. The exploitation of solar radiation for photocatalysis could generate a strong impact by decreasing the energy demand and simultaneously mitigating the impact of anthropogenic pollutants. However, most of the actual photocatalysts work only on energy radiation in the Near-UV region (<400 nm), and the studies and development of new photocatalysts with high efficiency in the visible range of the spectrum are required. In this regard, hybrid organic/inorganic photocatalysts have emerged as highly potential materials to drastically improve visible photocatalytic efficiency. In this review, we will analyze the state-of-art and the developments of hybrid photocatalysts for energy storage and energy conversion process as well as their application in pollutant degradation and water treatments.

Potential Life-Cycle Environmental Impacts of the COVID-19 Nucleic Acid Test

Massive diagnostic testing has been performed for appropriate screening and identification of COVID-19 cases in the ongoing global pandemic. However, the environmental impacts of COVID-19 diagnostics have been least considered. In this paper, the environmental impacts of the COVID-19 nucleic acid diagnostics were assessed by following a full cradle-to-grave life-cycle approach. The corresponding life-cycle anthology was established to provide quantitative analysis. Moreover, three alternative scenarios, i.e., material substitution, improved waste treatment, and electric vehicle (EV)-based transportation, were further proposed to discuss the potential environmental mitigation and conservation strategies. It was estimated that the life cycle of a single COVID-19 nucleic acid diagnostic test in China would lead to the emission of 612.9 g CO2 equiv global warming potential. Waste treatment, as a step of life cycle, worsen the environmental impacts such as global warming potential, eutrophication, and ecotoxicity. Meanwhile, diesel-driven transportation was considered as the major contributor to particulate air. Even though COVID-19 diagnostics are of the greatest importance to end the pandemic, their environmental impacts should not be ignored. It is suggested that improved approaches for waste treatment, low-carbon transportation, and a reliable pool sampling strategy are critical for the achievement of sustainable and green diagnostics.

Ecological safety with multifunctional applications of biogenic mono and bimetallic (Au-Ag) alloy nanoparticles

Recently, the design and biosynthesis of metallic nanoparticles (NPs) have drawn immense interest, but their very specific function and secondary toxic effects are major concern towards commercial application of NPs. That's why environment-friendly (nontoxic) NPs having multiple functions are extremely important. Herein, we report the mechanism of biosynthesis of mono and bimetallic (Au-Ag) alloy NPs and study their multifunctional (antioxidant, antifungal and catalytic) activity and ecotoxicological property. AgNPs exhibit phytotoxicity (at 100 μg/ml) on morphological characteristics of Lentil (during germination), while alloy and AuNPs are non-toxic (up to 100 μg/ml). In-vitro antioxidant response using DPPH methods reveals that alloy NPs (IC₅₀ = 55.8 μg/ml) possesses better antioxidant activity compared to the monometallic NPs (IC₅₀ = 73.6-82.6 μg/ml). In addition, alloy NPs displayed appreciable antifungal efficacy against a plant pathogenic fungus Gloeosporium musarum by structural damage to hyphae and conidia of the fungus. The catalytic performance of NPs for degradation of chlorpyriphos (CP) pesticide reveals that alloy NPs is more efficient in terms of rate constant (k = 0.405 d^-1) and half-life (T₅₀ = 1.71 d) compared to the monometallic counterparts (k = 0.115-0.178 d^-1; T₅₀ = 3.89-6.04 d). Degradation products of CP (3,5,6-trichloropyridinol and diethyl thiophosphate) are confirmed using mass spectrometry and based on that a degradation pathway has been suggested. Thus, these sustainable and ecological safe biogenic (Au-Ag) alloy NPs promise multiple applications as an antioxidant in the pharmaceutical sector, as a fungicide for disease control in agriculture, as a catalyst for remediation of toxic pollutants and in other pertinent areas.

Phase-Selective Synthesis of Anatase and Rutile TiO2 Nanocrystals and Their Impacts on Grapevine Leaves: Accumulation of Mineral Nutrients and Triggering the Plant Defense

Titanium dioxide nanocrystals (TiO₂ NCs), through their photocatalytic activity, are able to generate charge carriers and induce the formation of various reactive oxygen species (ROS) in the presence of O₂ and H₂O. This special feature makes TiO₂ an important and promising material in several industrial applications. Under appropriate antioxidant balancing, the presence of ROS is crucial in plant growth and development, therefore, the regulated ROS production through the photocatalytic activity of TiO₂ NCs may be also exploited in the agricultural sector. However, the effects of TiO₂ NCs on plants are not fully understood and/or phase-pure TiO₂ NCs are rarely used in plant experiments. In this work, we present a phase-selective synthesis of TiO₂ NCs with anatase and rutile crystal phases. The nanomaterials obtained were characterized by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), diffuse reflectance UV-Vis spectroscopy, and electron paramagnetic resonance spectroscopy (EPR). In field experiments, Vitis vinifera cv. Cabernet Sauvignon leaves developed under natural sunlight were treated with aqueous dispersions of TiO₂ NCs at concentrations of 0.001, 0.01, 0.1, and 1 w/v%. The effect of the applied nanocrystals was characterized via leaf photochemistry, mineral nutrient contents, and pyridoxine levels. We found that stress responses of grapevine to anatase and rutile NCs treatments are different, which can be related to the different ROS profiles of the two polymorphs. Our results indicate that TiO₂ NCs may be utilized not only for direct pathogen inactivation but also for eliciting plant defense mechanisms.

A critical analysis of environmental sustainability metrics applied to green synthesis of nanomaterials and the assessment of environmental risks associated with the nanotechnology

Nanotechnology is one of the most relevant scientific areas today due to its multiple applications in fields such as medicine, environmental remediation, information technology and energy conversion. This importance has led to the need to advance in the development of environmentally sustainable and safe nanomaterials by incorporating the principles of green chemistry during their synthesis and in their applications. However, this qualitative framework of thought does not offer minimum criteria for the use of the term "green", and therefore, this adjective is commonly used to refer to bio-based or nanotechnological processes without taking into account their net ecological impact. In this context, environmental sustainability metrics can be applied to nanotechnology to compare, optimize and quantify the environmental sustainability of synthesis procedures. This review provides an overview of green chemistry and its application in nanotechnology, but also an analysis of the use of green chemistry principles in the development of bio-based nanobiotechnology and nanosynthesis, with special emphasis on the use of sustainability's metrics for the quantitative analysis of nanomaterial synthesis protocols. These include: Atom Economy, E-factor, Process Mass Intensity, Energy Intensity, and Life Cycle Analysis.

Exploring the impact of calcination parameters on the crystal structure, morphology, and optical properties of electrospun Fe2TiO5 nanofibers

Nanostructured Fe₂TiO₅ (pseudobrookite), a mixed metal oxide material holds significant promise for utilization in energy and environmental applications. However, its full application is still hindered due to the difficulty to synthesize monophasic Fe₂TiO₅ with high crystallinity and a large specific surface area. Herein, Fe₂TiO₅ nanofibers were synthesized via a versatile and low-cost electrospinning method, followed by a calcination process at different temperatures. We found a significant effect of the calcination process and its duration on the crystalline phase in the form of either pseudobrookite or pseudobrookite–hematite–rutile and the morphology of calcined nanofibers. The crystallite size increased whereas the specific surface area decreased with an increase in calcination temperature. At higher temperatures, the growth of Fe₂TiO₅ nanoparticles and simultaneous coalescence of small particles was noted. The highest specific surface area was obtained for the sample calcined at 500 °C for 6 h (S_BET = 64.4 m² g⁻¹). This work opens new opportunities in the synthesis of Fe₂TiO₅ nanostructures using the electrospinning method and a subsequent optimized calcination process for energy-related applications.

Nanostructured Fe₂TiO₅ (pseudobrookite), a mixed metal oxide material holds significant promise for utilization in energy and environmental applications.

Environmental Sustainability Evaluation of Iron Oxide Nanoparticles Synthesized via Green Synthesis and the Coprecipitation Method: A Comparative Life Cycle Assessment Study

Green synthesis, based on green chemistry, is replacing the traditional methods, aiming to contribute with an enhanced environmental sustainability, which can be achieved using nontoxic compounds from biological resources, such as natural extracts from plants. In this study, the life cycle assessment (LCA) of iron oxide nanoparticles prepared through the green synthesis and the coprecipitation method is reported by following a cradle-to-gate approach. The LCA allowed quantifying and normalized the environmental impacts produced by the green synthesis (1.0 × 10-9), which used a Cymbopogon citratus (C. citratus) extract and sodium carbonate (Na2CO3). The impacts were also determined for the coprecipitation method (1.4 × 10-8) using the iron(II) salt precursor and sodium hydroxide (NaOH). The contribution of C. citratus extract and Na2CO3 as the precursor and pH-stabilizing agents, respectively, was compared regarding the iron(II) and NaOH compounds. Environmental sustainability was evaluated in human toxicity, ecosystem quality, and resource depletion. The major environmental contribution was found in the marine aquatic ecotoxicity (7.6 × 10-10 and 1.22 × 10-8 for green synthesis and the coprecipitation method) due to the highest values for ethanol (3.5 × 10-10) and electricity (1.4 × 10-8) usage since fossil fuels and wastewater are involved in their production. The C. citratus extract (2.5 × 10-12) presented a better environmental performance, whereas Na2CO3 (4.3 × 10-11) showed a slight increase contribution compared to NaOH (4.1 × 10-11). This is related to their fabrication, involving toxic compounds, land occupation, and excessive water usage. In general, the total environmental impacts are lower for the green synthesis, suggesting the implementation of environmentally friendlier compounds based on natural sources for the production of nanomaterials.

Metabolomics screening of serum biomarkers for occupational exposure of titanium dioxide nanoparticles

Although nanotoxicology studies have shown that respiratory exposure of titanium dioxide nanoparticles (TiO₂ NPs) could induce adverse health effects, limited biomarkers associated with occupational exposure of TiO₂ NPs were reported. The purpose of this study is to screen serum biomarkers among workers occupationally exposed to TiO₂ NPs using metabolomics. Compared with the control group, a total of 296 serum metabolites were differentially expressed in the TiO₂ NPs-exposed group, of which the relative expression of 265 metabolites increased, and the remaining 31 decreased. Three machine learning methods including random forest (RF), support vector machines (SVM), and boruta screened eight potential biomarkers and simultaneously selected a metabolite, Liquoric acid. Through multiple linear regression analysis to adjust the influence of confounding factors such as gender, age, BMI, smoking and drinking, occupational exposure to TiO₂ NPs was significantly related to the relative expression of the eight potential biomarkers. Meanwhile, the receiver operating characteristic curves (ROCs) of these potential biomarkers had good sensitivity and specificity. These potential biomarkers were related to lipid peroxidation, and had biological basis for occupational exposure to TiO₂ NPs. Therefore, it was demonstrated that the serum metabolites represented by Liquoric acid were good biomarkers of occupational exposure to TiO₂ NPs.

Exploring urine biomarkers of early health effects for occupational exposure to titanium dioxide nanoparticles using metabolomics

Many experimental studies have demonstrated that titanium dioxide nanoparticles (TiO2 NPs) could induce adverse health effects in vivo and in vitro. But epidemiological evidence and biomarkers related to early health effects are still lacking. This study aimed to explore biomarkers in the urine samples of workers occupationally exposed to a relatively low concentration of TiO2 NPs. A cross-sectional study was conducted in Jinan, China, involving 132 employees of a TiO2 NP manufacturing plant, among which the exposed group and control group were 1 : 1 matched by confounding factors such as gender, age, BMI, smoking and drinking. Untargeted metabolomics was performed in urine samples using high performance liquid chromatography-mass spectrometry (HPLC-MS) technology. The differential metabolites between the TiO2 NP exposed group and the control group were analyzed and then screened for potential biomarkers using bioinformatics methods. Metabolomics found a total of 1760 differentially expressed metabolites in the TiO2 NP exposed group, of which 60 differential metabolites were simultaneously confirmed by one-dimensional and multi-dimensional statistical analysis. Among these 60 differential metabolites, the relative expression of 27 metabolites increased, and the remaining 33 decreased. Pathway enrichment analysis further found that the metabolic pathway of long chain acyl-coa dehydrogenase deficiency (Lcad) was significantly enriched. Ten differential metabolites were selected as potential biomarkers of occupational exposure to TiO2 NPs using machine learning methods, including dibenzyl ether, quassimarin, tryptophan, etc. The receiver operating characteristic curves (ROCs) of these potential biomarkers showed good sensitivity and specificity. These potential biomarkers also had biological basis for occupational exposure to TiO2 NPs. Therefore, urine metabolites represented by dibenzyl ether are considered as good biomarkers of early health effects for occupational exposure to TiO2 NPs.

Carbon Gels-Modified TiO2: Promising Materials for Photocatalysis Applications

Carbon gels are a kind of porous organic polymer, which play pivotal roles in electrode, supercapacitor, hydrogen storage, and catalysis. Carbon gels are commonly prepared by the condensation of resorcinol and formaldehyde. The as-prepared polymers are further aged and sintered at a high temperature in an inert atmosphere to form cross-linked and intertwined porous structures. Owing to its large specific area and narrow pore size distribution, this kind of material is very appropriate for mass transfer, substrate absorption, and product desorption from the pores. In recent years, carbon gels have been discovered to function as effective hybrid materials with TiO₂ for photocatalytic applications. They could act as efficient deep-traps for photo-induced holes, which decreases the recombination probability of photo-induced carriers and lengthens their lifetime. In this mini-review, we will discuss the state-of-the-art paragon examples of carbon gels/TiO₂ composite materials applied in photo(electro)catalysis. The major challenges and gaps of its application in this field will also be emphasized.

Evaporation of Metals during the Thermal Treatment of Oxide Nanomaterials in Cellulose-Based Matrices

Like conventional material products, waste is the last stage of the life cycle of engineered nanomaterials, which are then incinerated or stabilized before disposal. However, because of their special physical characteristics, the fate of the thermally treated nanomaterials may differ or not from the conventional ones. In this study the thermal release of metals from three nanomaterials, namely CuO, ZnO, and TiO₂, embedded in matrices containing organic and inorganic compounds was investigated by using an in-house developed setup. The latter, which combines a TGA (Thermogravimetric Analyzer) and an ICP-OES (Inductively Coupled Plasma Optical Emission Spectrometer), offers the possibility to gain simultaneously thermogravimetric and elemental information. It is shown that the matrix composition, such as chlorine and silicon, plays a key role in the evaporation of Cu and Zn at temperatures above 700 °C, while at relatively low temperatures (250 to 450 °C) the nanomaterials are most probably entrained in the flue gas independently of their chemical properties. Incineration experiments using a tubular furnace and subsequent ICP-MS (ICP Mass Spectrometry) analysis of the obtained residues allowed for quantification of the metal evaporation from the three nanomaterials.

Life Cycle Assessment of the Sustainability of Enhancing the Photodegradation Activity of TiO2 with Metal-Doping

While TiO2 nanoparticles have shown potential as photocatalysts in the degradation of organic contaminants, their inability to absorb efficiently visible light has limited their industrial application. One strategy for solving this problem is monodoping TiO2 photocatalysts with transition metals, which has worked in the degradation of several pollutants. However, it is not clear if this improvement is enough to offset the potential environmental impacts of adding metal ions to the synthesis of TiO2. Herein, we have used Life Cycle Assessment (LCA) to determine the sustainability of monodoping TiO2 with transition metals (Fe, Co, Mn and Ni, with a 1% weight ratio) to enhance the photocatalytic properties of the photocatalyst toward the degradation of Carbamazepine and Methyl Orange, under UV-A and visible light irradiation. We found that the addition of transition-metals has no significant effect on the environmental impacts associated with the synthesis of TiO2, when a weight-based functional unit was considered. However, when photocatalytic activity was considered, major differences were found. Thus, our results demonstrate that the sustainability of monodoping with different transition metals is solely determined by their ability to enhance (or not) the photocatalytic activity of TiO2. Our data also demonstrated that isopropyl alcohol constitutes a critical point in the synthesis of TiO2 photocatalysts, with ethanol being a potential substitute.

Controlling the growth of nanosized titania via polymer gelation for photocatalytic applications

Nanocrystalline titania was synthesized by a simple, innovative and eco-friendly gelation method by using biopolymers (polysaccharides).

Irrigation Water Quality—A Contemporary Perspective

In the race to enhance agricultural productivity, irrigation will become more dependent on poorly characterized and virtually unmonitored sources of water. Increased use of irrigation water has led to impaired water and soil quality in many areas. Historically, soil salinization and reduced crop productivity have been the primary focus of irrigation water quality. Recently, there is increasing evidence for the occurrence of geogenic contaminants in water. The appearance of trace elements and an increase in the use of wastewater has highlighted the vulnerability and complexities of the composition of irrigation water and its role in ensuring proper crop growth, and long-term food quality. Analytical capabilities of measuring vanishingly small concentrations of biologically-active organic contaminants, including steroid hormones, plasticizers, pharmaceuticals, and personal care products, in a variety of irrigation water sources provide the means to evaluate uptake and occurrence in crops but do not resolve questions related to food safety or human health effects. Natural and synthetic nanoparticles are now known to occur in many water sources, potentially altering plant growth and food standard. The rapidly changing quality of irrigation water urgently needs closer attention to understand and predict long-term effects on soils and food crops in an increasingly fresh-water stressed world.