Environmental implications and applications of engineered nanoscale magnetite and its hybrid nanocomposites: A review of recent literature

Nanofillers in Novel Food Packaging Systems and Their Toxicity Issues

Background: Environmental concerns about petroleum-based plastic packaging materials and the growing demand for food have inspired researchers and the food industry to develop food packaging with better food preservation and biodegradability. Nanocomposites consisting of nanofillers, and synthetic/biopolymers can be applied to improve the physiochemical and antimicrobial properties and sustainability of food packaging. Scope and approach: This review summarized the recent advances in nanofiller and their applications in improved food packaging systems (e.g., nanoclay, carbon nanotubes), active food packaging (e.g., silver nanoparticles (Ag NPs), zinc oxide nanoparticles (ZnO NPs)), intelligent food packaging, and degradable packaging (e.g., titanium dioxide nanoparticles (e.g., TiO2 NPs)). Additionally, the migration processes and related assessment methods for nanofillers were considered, as well as the use of nanofillers to reduce migration. The potential cytotoxicity and ecotoxicity of nanofillers were also reviewed. Key findings: The incorporation of nanofillers may increase Young's modulus (YM) while decreasing the elongation at break (EAB) (y = -1.55x + 1.38, R2 = 0.128, r = -0.358, p = 0.018) and decreasing the water vapor (WVP) and oxygen permeability (OP) (y = 0.30x - 0.57, R2 = 0.039, r = 0.197, p = 0.065). Meanwhile, the addition of metal-based NPs could also extend the shelf-life of food products by lowering lipid oxidation by an average of approx. 350.74% and weight loss by approx. 28.39% during the longest storage period, and significantly increasing antibacterial efficacy against S. aureus compared to the neat polymer films (p = 0.034). Moreover, the migration process of nanofillers may be negligible but still requires further research. Additionally, the ecotoxicity of nanofillers is unclear, as the final distribution of nanocomposites in the environment is unknown. Conclusions: Nanotechnology helps to overcome the challenges associated with traditional packaging materials. Strong regulatory frameworks and safety standards are needed to ensure the appropriate use of nanocomposites. There is also a need to explore how to realize the economic and technical requirements for large-scale implementation of nanocomposite technologies.

A partial oxidation-based approach to the synthesis of gold-magnetite hybrid nanostructures

Hybrid nanostructures composed of gold and magnetite are of singular interest because they allow the integration of plasmonic and magnetic properties in a single object. Due to this feature, their application has been proposed to perform various functions. The methods usually employed to prepare these particular kinds of nanostructures follow organic phase routes, whereas synthetic methodologies that employ more sustainable solvents have been much less explored. In this work, an environmentally friendly approach for the synthesis of gold-magnetite hybrid nanostructures in aqueous media is proposed. This approach relies on the partial oxidation of the Fe(II) precursor using hydrogen peroxide as the oxidizing agent in the presence of preformed gold nanoparticles dispersed in the reaction medium. The methodology used led to the formation of magnetite nanoparticles with a good stoichiometry and a median size of 30 nm. Furthermore, in the presence of gold nanoparticles in the reaction medium, the formation of gold-magnetite hybrid nanostructures is produced as a consequence of the heterogeneous nucleation of the iron oxide phase on the surface of the gold nanoparticles that act as seeds. The approach reported broadens the possibility of synthesizing hybrid nanostructures in aqueous media with integrated plasmonic and magnetic properties.

Recent advances in the application of magnetic materials for the management of perfluoroalkyl substances in aqueous phases

Perfluoroalkyl substances (PFASs) are a class of artificially synthesised organic compounds extensively used in both industrial and consumer products owing to their unique characteristics. However, their persistence in the environment and potential risk to health have raised serious global concerns. Therefore, developing effective techniques to identify, eliminate, and degrade these pollutants in water are crucial. Owing to their high surface area, magnetic responsiveness, redox sensitivity, and ease of separation, magnetic materials have been considered for the treatment of PFASs from water in recent years. This review provides a comprehensive overview of the recent use of magnetic materials for the detection, removal, and degradation of PFASs in aqueous solutions. First, the use of magnetic materials for sensitive and precise detection of PFASs is addressed. Second, the adsorption of PFASs using magnetic materials is discussed. Several magnetic materials, including iron oxides, ferrites, and magnetic carbon composites, have been explored as efficient adsorbents for PFASs removal from water. Surface modification, functionalization, and composite fabrication have been employed to improve the adsorption effectiveness and selectivity of magnetic materials for PFASs. The final section of this review focuses on the advanced oxidation for PFASs using magnetic materials. This review suggests that magnetic materials have demonstrated considerable potential for use in various environmental remediation applications, as well as in the treatment of PFASs-contaminated water.

Preparation of magnetic dialdehyde starch-immobilized phospholipase A1 and acyl transfer in reflection

In this paper, using a coprecipitation method to prepare Fe3O4 magnetic nanoparticles (Fe3O4 MNPS), magnetic dialdehyde starch nanoparticles with immobilized phospholipase A1 (MDSNIPLA) were successfully prepared by using green dialdehyde starch (DAS) instead of glutaraldehyde as the crosslinking agent. The Fe3O4 MNPS was characterized by infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), the Brunauer-Emmett-Teller (BET) surface area analysis method, thermogravimetric analysis (TGA), and transmission electron microscopy (TEM) et al. The results showed that the alkaline resistance and acid resistance of the enzyme were improved after the crosslinking of DAS. After repeated use (seven times), the relative activity of MDSNIPLA reached 56 %, and the magnetic dialdehyde starch nanoparticles (MDASN) had good carrier performance. MDSNIPLA was applied to enzymatic hydrolysis of phospholipids in the soybean oil degumming process. The results showed that the acyl transfer rate of sn-2-HPA was 14.01 %, and the content of free fatty acids was 1.144 g/100 g after 2 h reaction at 50 °C and pH 5.0 with appropriate boric acid. The immobilized enzyme has good thermal stability and storage stability, and its application of soybean oil improves the efficiency of the oil.

Pesticide Efficiency of Environment-Friendly Transition Metal-Doped Magnetite Nanoparticles

This study explored the potential of Fe3O4, SnFe2O4, and CoFe2O4 nanoparticles as larvicidal and adulticidal agents against Aedes aegypti (A. aegypti) larvae and adults, which are vectors for various diseases. This research involved the synthesis of these nanoparticles using the coprecipitate method. The results indicate that CoFe2O4 nanoparticles are the most effective in both larvicidal and adulticidal activities, with complete mortality achieved after 96 h of exposure. SnFe2O4 nanoparticles also showed some larvicidal and adulticidal efficacy, although to a lesser extent than the CoFe2O4 nanoparticles. Fe3O4 nanoparticles exhibited minimal larvicidal and adulticidal effects at low concentrations but showed increased efficacy at higher concentrations. The study also revealed the superparamagnetic nature of these nanoparticles, making them potentially suitable for applications in aquatic environments, where A. aegypti larvae often thrive. Additionally, the nanoparticles induced observable damage to the gut structure of the mosquitoes and larvae, which could contribute to their mortality. Overall, this research suggests that CoFe2O4 nanoparticles, in particular, hold promise as environment-friendly and effective agents for controlling A. aegypti mosquitoes, which are responsible for the transmission of diseases such as dengue fever, Zika virus, and Chikungunya. Further studies and field trials are needed to validate their practical use in mosquito control programs.

Magnetic nanomaterials as an effective absorbent material for removal of fluoride concentration in water: a review

The rapid increases in industrialization and populations are significant sources of water contamination. The speed with which contamination of groundwater and surface water occurs is becoming a serious problem and poses a significant obstacle for water stakeholders. Heavy metals, organic, and inorganic contaminants in the form of suspended and dissolved materials are just a few of the contaminants that can be found in drinking water. One of the most common contaminants in the water is fluoride, which is responsible for numerous toxic diseases. Different traditional techniques, for example, coagulation, ion exchange, absorption, and membrane filtration are being used to dispose of fluoride from water. However, nanomaterials such as magnetic nanoparticles (NPs) are very efficient, reliable, cost-effective, and stable materials to replace traditional water treatment techniques. There has been an increase in interest in the application of nanomaterials to the purification of drinking water over the past few decades. The use of magnetic NPs, such as metal and metal oxide NPs, to remove fluoride ions and organic matter from water is highlighted in this review article. Also, this section also discusses the properties, benefits and drawbacks, and difficulties of utilizing magnetic NPs in the process of purifying drinking water.

Fluctuating redox conditions accelerate the electron storage and transfer in magnetite and production of dark hydroxyl radicals

Magnetite (Fe3O4), known as a geo-battery that can store and transfer electrons, often co-occurs with sulfide in subsurface environments with fluctuating redox conditions. However, little is known about how fluctuating redox conditions (e.g., sulfidation-oxidation) affect the electron storage and transfer in Fe3O4 that was associated with the production of dark hydroxyl radicals (⋅OH) and the oxidation of dissolved organic matter (DOM). This study revealed that Fe3O4 sulfidated by sulfide (S-Fe3O4) at neutral pH exhibited higher ⋅OH production upon oxygenation than Fe3O4, in which the cumulative ⋅OH concentration increased with increasing initial S/Fe ratio (≤ 0.50), sulfidation duration and number of sulfidation-oxidation cycle. X-ray photoelectron spectroscopy and wet-chemical analyses of Fe and S species of S-Fe3O4 showed that sulfidation enables electron storage in Fe3O4 by increasing both structural and surface Fe(II). Sulfide was converted into S0, acid volatile sulfur (AVS), and chromium-reducible sulfur (CRS) during Fe3O4 sulfidation. S-Fe3O4 with lower AVS/CRS ratio exhibited higher reactivity to produce ⋅OH, indicating the important role of CRS in transferring electrons from Fe(II) to O2. Based on quenching experiments and electron paramagnetic resonance analysis, a one-step two-electron transfer mechanism was proposed for O2 reduction during S-Fe3O4 oxygenation, and surface-bound rather than free ⋅OH were identified as the primary reactive oxygen species. The ⋅OH from S-Fe3O4 oxygenation was shown to be efficient in degradation of DOM. Overall, these results suggested that sulfidation-oxidation can accelerate the electron storage and transfer in Fe3O4 for dark ⋅OH production, having an important impact on the carbon cycling in subsurface environments.

Transition Metal Catalysts for Atmospheric Heavy Metal Removal: A Review of Current Innovations and Advances

Atmospheric heavy metal pollution presents a severe threat to public health and environmental stability. Transition metal catalysts have emerged as a potent solution for the selective capture and removal of these pollutants. This review provides a comprehensive summary of current advancements in the field, emphasizing the efficiency and specificity of nanostructured transition metals, including manganese, iron, cobalt, nickel, copper, and zinc. Looking forward, we delve into the prospective trajectory of catalyst development, underscoring the need for materials with enhanced stability, regenerability, and environmental compatibility. We project that advancements in computational materials science, nanotechnology, and green chemistry will be pivotal in discovering innovative catalysts that are economically and environmentally sustainable. The integration of smart technologies for real-time monitoring and adaptive control is anticipated to revolutionize heavy metal remediation, ensuring efficient and responsive pollution abatement strategies in the face of evolving industrial scenarios and regulatory landscapes.

Synthesis, characterization, and reusability of novel nanobiocomposite of endophytic fungus Aspergillus flavus and magnetic nanoparticles (Fe3O4) with dye bioremediation potential

The incorrect disposal of textile dyes, such as Reactive Black 5 (RB5), causes several problems for living beings and the quality of the environment. Nanobiocomposites (NBC) produced from endophytic fungi (potentially remediation dyes-agents) and magnetic nanoparticles have high biotechnological potential due to their superparamagnetic behavior, which would allow their recovery through the magnetic field after the bioremediation process. This work aimed to obtain a new nanobiocomposite from the interaction of magnetite nanoparticles (Fe3O4) with the endophyte Aspergillus flavus (Af-CL-7) to evaluate its bioremediation capacity and to reduce the toxicity of RB5 and its reuse. Before obtaining the NBC, Af-CL-7 showed discoloration of RB5 and it was tolerant to all tested concentrations of this dye. The discovery of the nanobiocomposite textile dye bioremediator product presents a significant environmental advantage by addressing the issue of water pollution caused by textile dyes. The NBC called Af-Fe3O4 was successfully obtained with the magnetized endophyte, and their magnetic properties were verified by VSM analysis and by action of magnetic fields generated by Nd-Fe-B magnets SEM analyzes showed that the nanoparticles did not cause any damage to the hypha morphology, and TEM analyzes confirmed the presence of nanoparticles in the fungus wall and also inside the cell. The NBC Af-Fe3O4 and Af-CL-7 showed, respectively, 96.1% and 92.2% of RB5 discoloration in the first use, 91.1% e 86.2% of discoloration in the validation test, and 89.0% in NBC reuse. In the toxicological bioassay with Lactuca sativa seeds, NBC showed a positive reduction in the toxicity of RB5 after treatment, allowing the hypocotyl growth to be statistically similar to the control with water. Thus, we highlight the promising obtaining process of NBC that could be applied in bioremediation of contaminated waters, wherein the industrial economic cost will depend on the fermentation efficiency, biomass production and nanoparticle synthesis.

Nanotechnologies for environmental remediation and their ecotoxicological impacts

Environmental nanoremediation is an emerging technology that aims to rapidly and efficiently remove contaminants from the polluted sites using engineered nanomaterials (ENMs). Inorganic nanoparticles which are generally metallic, silica-based, carbon-based, or polymeric in nature serve to remediate through chemical reactions, filtration, or adsorption. Their greater surface area per unit mass and high reactivity enable them to treat groundwater, wastewater, oilfields, and toxic industrial contaminants. Despite the growing interest in nanotechnological solutions for bioremediation, the environmental and human hazard associated with their use is raising concerns globally. Nanoremediation techniques when compared to conventional remediation solutions show increased effectivity in terms of cost and time; however, the main challenge is the ability of ENMs to remove contaminants from different environmental mediums by safeguarding the ecosystem. ENMs improving the accretion of the pollutant and increasing their bioavailability should be rectified along with the vigilant management of their transfer to the upper levels of the food chain which subsequently causes biomagnification. The ecosystem-centered approach will help monitor the ecotoxicological impacts of nanoremediation considering the safety, sustainability, and proper disposal of ENMs. The environment and human health risk assessment of each novel engineered nanomaterial along with the regulation of life cycle assessment (LCA) tools of ENMs for nanoremediation can help investigate the possible environmental hazard. This review focuses on the currently available nanotechnological methods used for environmental remediation and their potential toxicological impacts on the ecosystem.

Iron oxide nanoparticles in the soil environment: Adsorption, transformation, and environmental risk

Iron oxide nanoparticles (IONPs) have great application potential due to their multifunctional excellence properties, leading to the possibility of their release into soil environments. IONPs exhibit different adsorption properties toward environmental pollutants (e.g., heavy metals and organic compounds), thus the adsorption performance for various contaminants and the molecular interactions at the IONPs-pollutants interface are discussed. After solute adsorption, the change in the environmental behavior of IONPs is an important transformation process in the natural environments. The aggregation, aging process, and chemical/biological transformation of IONPs can be altered by soil solution chemistry, as well as by the presence of dissolved organic matter and microorganisms. Upon exposure to soil environments, IONPs have both positive and negative impacts on soil organisms (e.g., bacteria, plants, nematodes, and earthworms). Moreover, we compared the toxicity of IONPs alone to combined toxicity with environmental pollutants and pristine IONPs to aged IONPs, and the mechanisms of IONPs toxicity at the cellular level are also reviewed. Given the unanswered questions, future research should include prediction and design of IONPs, new characterization technology for monitoring IONPs transformation in soil ecosystems, and further refinement the environmental risk assessment of IONPs. This review will greatly enhance our knowledge of the performance and impact of IONPs in soil systems.

Enhance antimony adsorption from aquatic environment by microwave-assisted prepared Fe3O4 nanospherolites

A novel hierarchically nanostructured magnetite (Fe3O4) was manufactured using microwave-assisted reflux method without surfactants. The nanostructured Fe3O4 is formed via the co-precipitation of Fe(III) and Fe(II), followed by a nanocrystal aggregation-based mechanism. Moreover, the effects of solution pH, contact time, initial Sb concentration, coexisting anions, and recycle numbers on the adsorption of nanostructured Fe3O4 toward Sb were extensively examined in the batch adsorption tests. The results demonstrated that the obtained Fe3O4 exhibited excellent adsorption ability toward Sb with the maximum adsorption capacities of 154.2 and 161.1 mg.g-1 for Sb(III) and Sb(V), respectively. The prepared Fe3O4 could be easily regenerated and reused for adsorption/desorption studies multiple times without compromising the Sb adsorption ability. Further exploration indicated that the oxidation or reduction reactions infrequently occurred during Sb adsorption processes. The proposed hierarchically nanostructured Fe3O4 thus could be potentially used for sustainable and efficient antimony removal.

Research progress on the magnetite nanoparticles in the fields of water pollution control and detection

Magnetite nanoparticles (MNPs) have shown increasing application in the fields of water pollution control and detection due to their perfect combination of interfacial functionalities and physicochemical properties, such as surface interface adsorption, (synergistic) reduction, catalytic oxidation, and electrical chemistry. This review presents the research advances in the synthesis and modification methods of MNPs in recent years, systematically summarizes the performances of MNPs and their modified materials in terms of three technical systems, including single decontamination system, coupled reaction system, and electrochemical system. In addition, the progress of the key roles played by MNPs in adsorption, reduction, catalytic oxidative degradation and their coupling with zero-valent iron for the reduction of pollutants are described. Moreover, the application prospect of MNPs-based electrochemical working electrodes for detecting micro-pollutants in water were also discussed in detail. This review addresses that the construction of MNPs-based systems for water pollution control and detection should be adapted to the natures of the target pollutants in water. Finally, the following research directions of MNPs and their remaining challenges are outlooked. In general, this review will inspire MNPs researchers in different fields for effective control and detection of a variety of contaminants in water.

Application of Functionalized Fe3O4 Magnetic Nanoparticles Using CTAB and SDS for Oil Separation from Oil-in-Water Nanoemulsions

Using magnetic nanoparticles (MNPs) for emulsified oil separation from wastewater is becoming increasingly widespread. This study aims to synthesize MNPs using amphiphilic coatings to stabilize the MNPs and prevent their agglomeration for efficiently breaking oil-in-water nanoemulsions. We coat two different sizes of Fe₃O₄ nanoparticles (15-20 and 50-100 nm) using cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS) with surfactant-to-MNP mass ratios of 0.4 and 0.8. We study the effect of various variables on the demulsification performance, including the MNP size and concentration, coating materials, and MNP loading. Based on the oil-water separation analysis, the smaller size MNPs (MNP-S) show a better demulsification performance than the larger ones (MNP-L ) for a 1000 ppm dodecane-in-water emulsion containing nanosized oil droplets (250-300 nm). For smaller MNPs (MNP-S) and at low dosage level of 0.5 g/L, functionalizing with surfactant-to-MNP mass ratio of 0.4, the functionalization increases the separation efficiency (SE) from 57.5% for bare MNP-S to 86.1% and 99.8 for the SDS and CTAB coatings, respectively. The highest SE for MNP-S@CTAB and the zeta potential measurements imply that electrostatic attraction between negatively charged oil droplets (-55.9 ± 2.44 mV) and positively charged MNP-S@CTAB (+35.8 ± 0.34 mV) is the major contributor to a high SE. Furthermore, the reusability tests for MNP-S@CTAB reveal that after 10 cycles, the amount of oil adsorption capacity decreases slightly, from 20 to 19 mg/g, indicating an excellent stability of synthesized nanoparticles. In conclusion, functionalized MNPs with tailored functional groups feature a high oil SE that could be effectively used for oil separation from emulsified oily wastewater streams.

A rationale for the rapid extraction of ultra-low-level uranyl ions in simulated bioassays regulated by Mn-dopants over magnetic nanoparticles

Although the sorption of uranyl ions and other heavy metal ions over magnetic nanoparticles is well reported, the parameters governing the sorption process over the magnetic nanoparticles have not been clearly enumerated. However, to increase the efficiency of the sorption over the surface of these magnetic nanoparticles, it is essential to understand the different structural parameters that are involved in the sorption process. The sorption of uranyl ions and other competitive ions in simulated urine samples at different pH was effectively accomplished over magnetic nanoparticles of Fe₃O₄ (MNPs) and Mn-doped Fe₃O₄ (Mn-MNPs). The MNPs and Mn-MNPs were synthesized using an easily modified co-precipitation method and were thoroughly characterised using several techniques, such as XRD, HRTEM, SEM, zeta potential, and XPS. The substitutional doping of Mn (1 to 5 at%) in the Fe₃O₄ lattice (Mn-MNPs) showed better sorption ability as compared to that of MNPs. The sorption properties of these nanoparticles were mainly correlated with the different structural parameters to understand the roles of surface charge and different morphological parameters. The interaction centres over the surface of MNPs with the uranyl ions were designated and the effects of ionic interactions with uranyl ions for these sites were calculated. Extensive XPS, ab initio calculations and zeta potential studies have provided deep insights into the different aspects that play key roles in the sorption process. These materials showed one of the best K_d values (∼3 × 10⁶ cm³) in a neutral medium with very low t_1/2 values (∼0.9 min). The fast sorption kinetics (very low t_1/2) makes them amongst the best sorption materials for uranyl ions and optimal for the quantification of ultra-low-level uranyl ions in simulated bioassays.

A Sandwich Structure of Fulvic Acid and PMIDA-Modified LDHs for the Simultaneous Removal of Cu2+ and Aniline in Multicomponent Solutions

The coexistence of organic and inorganic pollutants in industrial wastewater has emerged as a concerning environmental issue worldwide due to the critical levels of biological toxicity of these pollutants. In this context, the present study proposes a sandwich structure of fulvic acid and PMIDA-modified LDHs (FA/PMIDA-LDHs) for the simultaneous removal of Cu²⁺ and aniline from wastewater. The specific structure was synthesized using a combination of coprecipitation and impregnation methods. Abundant benzene rings and oxygen-containing functional groups greatly increased the number of sites for the adsorption of both Cu²⁺ and aniline. The maximum adsorption capacity of Cu²⁺ and aniline in solution with initial pH 5.0 at 25 °C could reach 221.24 and 132.28 mg/g, respectively. Cu²⁺ could be chelated by the functional groups in the FA/PMIDA-LDHs structure, and a coupled reduction-complexation mechanism was proposed for this process. The uptake of aniline on FA/PMIDA-LDHs was demonstrated to be a result of the combination of coordination forces, hydrophobic effects, π-π interactions, and hydrogen bonds. In a multicomponent solution, FA/PMIDA-LDHs exhibited excellent salt tolerance of up to 1000 mg/L of Na⁺ or Ca²⁺. The effects of Fe³⁺, Ni²⁺, Cl^-, Cr₂O₇^2-, SO₄^2-, and H₂PO₄^- on the uptakes of Cu²⁺ and aniline were also investigated.

Applications of functional nanoparticle-stabilized surfactant foam in petroleum-contaminated soil remediation

Surfactant foam (SF) can be used to remediate petroleum-contaminated soil because of its easy transfer to inhomogeneous and low-permeability formations. Nanoparticles (NPs) not only stabilize SF under extreme conditions but also impart various functions, aiding the removal of petroleum contaminants. This review discusses the stabilization mechanisms of nanoparticle-stabilized SF (NP-SF) as well as the effects of NP size, chargeability, wettability, and NP-to-surfactant ratio on foam stability. SF stabilized by inert SiO₂ NPs is most commonly used to remediate soil contaminated with crude oil and diesel. Low dose of SF stabilized by nano zero-valent iron is cost-effective for treating soil contaminated with chlorinated organics and heavy metal ions. The efficiency and recyclability of Al₂O₃/Fe₃O₄ NPs in the remediation of diesel and crude oil contamination could be enhanced by applying a magnetic field. This review provides a theoretical basis and practical guidelines for developing functional NP-SF to improve the remediation of petroleum-contaminated soils. Future research should focus on the structural design of photocatalytic NPs and the application of catalytic NP-SF in soil remediation.

Systematic and Bibliometric Analysis of Magnetite Nanoparticles and Their Applications in (Biomedical) Research

Recent reports show air pollutant magnetite nanoparticles (MNPs) in the brains of people with Alzheimer's disease (AD). Considering various field applications of MNPs because of developments in nanotechnology, the aim of this study is to identify major trends and data gaps in research on magnetite to allow for relevant environmental and health risk assessment. Herein, a bibliometric and systematic analysis of the published magnetite literature (n = 31 567) between 1990 to 2020 is completed. Following appraisal, publications (n = 244) are grouped into four time periods with the main research theme identified for each as 1990-1997 "oxides," 1998-2005 "ferric oxide," 2006-2013 "pathology," and 2014-2020 "animal model." Magnetite formation and catalytic activity dominate the first two time periods, with the last two focusing on the exploitation of nanoparticle engineering. Japan and China have the highest number of citations for articles published. Longitudinal analysis indicates that magnetite research for the past 30 years shifted from environmental and industrial applications, to biomedical and its potential toxic effects. Therefore, whilst this study presents the research profile of different countries, the development in research on MNPs, it also reveals that further studies on the effects of MNPs on human health is much needed.

Synthesis of TiO2, TiO2/PAni, TiO2/PAni/GO nanocomposites and photodegradation of anionic dyes Rose Bengal and thymol blue in visible light

Nowadays, fast-growing industrialization has resulted in the release of enormous amounts of contaminants such as toxic dyes into water bodies and leading to cause health and environmental risks. In this regard, we prepared inorganic nanocomposites for the treatment of toxic dyes. Hence, we synthesized TiO₂/PAni/GO nanocomposites and examined them by using XRD, SEM, TEM, UV-Vis spectroscopy, BET analysis, and a photoluminescence investigation. In addition, band gap energies of the nanocomposites were determined, and Total Organic Carbon (TOC) testing was used to determine dye degradation levels. The photocatalytic degradations of Thymol Blue and Rose Bengal dyes were investigated at different dye concentrations, illumination periods, solution pH values, and photocatalyst dosages. By using TiO₂/PAni/GO, TiO₂/PAni, and TiO₂ at neutral pH, a photocatalyst dose of 1600 mg/L, and exposure to visible light, Thymol Blue and Rose Bengal were photodegraded 85-99%, 60-97%, and 10-20%, respectively, at a concentration of 25 ppm (180 min). Reductions in the TOCs confirmed their photodegradation, and a kinetic study revealed photodegradation followed first-order kinetics. This study shows the coating of polyaniline (PAni) and graphene oxide (GO) on TiO₂ improved its ability to photodegrade Thymol Blue and Rose Bengal dye.

Engineering microbes for enhancing the degradation of environmental pollutants: A detailed review on synthetic biology

Anthropogenic activities resulted in the deposition of huge quantities of contaminants such as heavy metals, dyes, hydrocarbons, etc into an ecosystem. The serious ill effects caused by these pollutants to all living organisms forced in advancement of technology for degrading or removing these pollutants. This degrading activity is mostly depending on microorganisms owing to their ability to survive in harsh adverse conditions. Though native strains possess the capability to degrade these pollutants the development of genetic engineering and molecular biology resulted in engineering approaches that enhanced the efficiency of microbes in degrading pollutants at faster rate. Many bioinformatics tools have been developed for altering/modifying genetic content in microbes to increase their degrading potency. This review provides a detailed note on engineered microbes - their significant importance in degrading environmental contaminants and the approaches utilized for modifying microbes. The genes responsible for degrading the pollutants have been identified and modified fir increasing the potential for quick degradation. The methods for increasing the tolerance in engineered microbes have also been discussed. Thus engineered microbes prove to be effective alternate compared to native strains for degrading pollutants.

Hollow Iron Oxide Nanospheres Obtained through a Combination of Atomic Layer Deposition and Electrospraying Technologies

In the present study, we report on the successful synthesis of hollow iron oxide nanospheres. The hollow Fe₃O₄ nanospheres were synthesized following a four-step procedure: electrospraying spherical PVP particles, coating these particles with alumina (Al₂O₃) and hematite (Fe₂O₃) through atomic layer deposition and, finally, a thermal reduction process to degrade the polymer (PVP) and convert hematite (Fe₂O₃) into magnetite (Fe₃O₄). A structural analysis using X-ray diffraction (XRD) confirmed the effectiveness of the thermal reduction process. A morphological analysis confirmed that the four-step procedure allowed for the obtainment of hollow iron oxide nanospheres, even though the reduction process caused a contraction in the diameter of the particles of almost 300 nm, but did not affect the thickness of the walls of the hollow spheres that remained at approximately 15 nm. Magnetic properties of the hollow iron oxide nanospheres enable their use in applications where the agglomeration of magnetic nanostructures in liquid media is commonly not allowed, such as in drug encapsulation and delivery.

Adsorption of persistent organic pollutants (POPs) from the aqueous environment by nano-adsorbents: A review

The intensification of urbanisation and industrial activities significantly exacerbates the distribution of toxic contaminations into the aqueous environment. Persistent organic pollutants (POPs) have received considerable attention in the past few decades because of their persistence, long-distance migration, potential bioaccumulation, latent toxicity for humans and wildlife. There is no doubt that POPs cause serious effects on the global ecosystem. Therefore, it is necessary to develop a simple, safe and sustainable approach to remove POPs from water bodies. Among other conventional techniques, the adsorption process has proven to be a more effective method for eliminating POPs and to a larger extent meet discharge regulations. Nanomaterials can effectively adsorb POPs from aqueous solutions. For most POPs, a >70% adsorptive removal efficiency was achieved. The major mechanisms for POPS uptake by nano-adsorbents includes electrostatic interaction, hydrophobic (van der Waals, π-π and electron donor-acceptor) interaction and hydrogen bonding. Nano-adsorbent can sustain a >90% POPs adsorptive removal for about 3 cycles and reuseable for up to 10 cycles. Challenges around adsorbent ecotoxicity and safe disposal were also discussed. The present review evaluated recent research outcomes on nanomaterials that are employed to remove POPs in water systems.

Destructing surfactant network in nanoemulsions by positively charged magnetic nanorods to enhance oil-water separation

The separation of ultrafine oil droplets from wasted nanoemulsions stabilized with high concentration of surfactants is precondition for oil reuse and the safe discharge of effluent. However, the double barriers of the interfacial film and network structures formed by surfactants in nanoemulsions significantly impede the oil-water separation. To destroy these surfactant protective layers, we proposed a newly-developed polyethyleneimine micelle template approach to achieve simultaneous surface charge manipulation and morphology transformation of magnetic nanospheres to magnetic nanorods. The results revealed that positively charged magnetic nanospheres exhibited limited separation performance of nanoemulsions, with a maximum chemical oxygen demand (COD) removal of 50%, whereas magnetic nanorods achieved more than 95% COD removal in less than 30 s. The magnetic nanorods were also applicable to wasted nanoemulsions from different sources and exhibited excellent resistance to wide pH changes. Owing to their unique one-dimensional structure, the interfacial dispersion of magnetic nanorods was significantly promoted, leading to the efficient capture of surfactants and widespread destruction of both the interfacial film and network structure, which facilitated droplet merging into the oil phase. The easy-to-prepare and easy-to-tune strategy in this study paves a feasible avenue to simultaneously tailor surface charge and morphology of magnetic nanoparticles, and reveals the huge potential of morphology manipulation for producing high-performance nanomaterials to be applied in complex interfacial interaction process. We believe that the newly-developed magnetic-nanorods significantly contribute to hazardous oily waste remediation and advances technology evolution toward problematic oil-pollution control.

Converting wastes to resource: Utilization of dewatered municipal sludge for calcium-based biochar adsorbent preparation and land application as a fertilizer

Pyrolysis combined with land application for dewatered municipal sludge disposal revealed advantages in heavy metals solidification and resource utilization compared with other disposal technologies. In this study, utilizing dewatered municipal sludge for calcium-containing porous adsorbent preparation via pyrolysis was proposed and verified. After pyrolyzing at 900 ° C (Ca-900), the dewatered sludge obtained maximum adsorption capacity (83.95 mg P⋅ g^-1) and the adsorption process conformed to the pseudo-second-order model and double layer model. Characteristic analysis showed the predominant adsorption mechanism was precipitation. Continuous column bed experiment indicated 2 g adsorbent could remove 4.27 mg phosphorus from tail wastewater with the initial phosphorus concentration of 1.03 mg ⋅ L^-1. No heavy metals leaching was observed from Ca-900 adsorbent with pH value exceeding 1.0, and merely 1% addition of Ca-900 adsorbent (after actual water phosphorus adsorption) with soil could extremely promote the early growth of seedlings. Economic estimates demonstrated that this cost-effective modification could generate the most add-on value production. Based on these results, the strategy of 'one treatment but two uses' was proposed in this study, converting the wastes to resource and providing a native strategy for sludge disposal and resource recovery.

Transport and Retention of Poly(Acrylic Acid-co-Maleic Acid) Coated Magnetite Nanoparticles in Porous Media: Effect of Input Concentration, Ionic Strength and Grain Size

Understanding the physicochemical factors affecting nanoparticle transport in porous media is critical for their environmental application. Water-saturated column experiments were conducted to investigate the effects of input concentration (Co), ionic strength (IS), and sand grain size on the transport of poly(acrylic acid-co-maleic acid) coated magnetite nanoparticles (PAM@MNP). Mass recoveries in the column effluent ranged from 45.2 to 99.3%. The highest relative retention of PAM@MNP was observed for the lowest Co. Smaller Co also resulted in higher relative retention (39.8%) when IS increased to 10 mM. However, relative retention became much less sensitive to solution IS as Co increased. The high mobility is attributed to the PAM coating provoking steric stability of PAM@MNP against homoaggregation. PAM@MNP retention was about 10-fold higher for smaller grain sizes, i.e., 240 µm and 350 µm versus 607 µm. The simulated maximum retained concentration on the solid phase (Smax) and retention rate coefficient (k1) increased with decreasing Co and grain sizes, reflecting higher retention rates at these parameters. The study revealed under various IS for the first time the high mobility premise of polymer-coated magnetite nanoparticles at realistic (<10 mg L−1) environmental concentrations, thereby highlighting an untapped potential for novel environmental PAM@MNP application usage.

Treatment technologies for selenium contaminated water: A critical review

Selenium is an indispensable trace element for humans and other organisms; however, excessive selenium in water can jeopardize the aquatic environment. Investigations on the biogeochemical cycle of selenium have shown that anthropogenic activities such as mining, refinery, and coal combustion mainly contribute to aquatic selenium pollution, imposing tremendous risks on ecosystems and human beings. Various technologies thus have been developed recently to treat selenium contaminated water to reduce its environmental impacts. This work provides a critical review on the applications, characteristics, and latest developments of current treatment technologies for selenium polluted water. It first outlines the present status of the characteristics, sources, and toxicity of selenium in water. Selenium treatment technologies are then classified into three categories: 1) physicochemical separation including membrane filtration, adsorption, coagulation/precipitation, 2) redox decontamination including chemical reduction and catalysis, and 3) biological transformation including microbial treatment and constructed wetland. Details of these methods including their overall efficiencies, applicability, advantages and drawbacks, and latest developments are systematically analyzed and compared. Although all these methods are promising in treating selenium in water, further studies are still needed to develop sustainable strategies based on existing and new technologies. Perspectives on future research directions are laid out at the end.

Ball-milled magnetite for efficient arsenic decontamination: Insights into oxidation-adsorption mechanism

Conventional adsorbents for decontaminating arsenic exhibit low efficacy for the removal of arsenite (As(III)). This study aims to develop a robust As adsorbent from natural magnetite (M₀) via a facile ball milling process, and evaluate their performance for decontaminating As(III) and As(V) in water and soil systems. The ball milling process decreased the particle size and crystallinity of M₀, resulting in pronounced As removal by the ball-milled magnetite (M_m). Ball milling under air facilitated the formation of Fe-OH and Fe-COOH functional groups on M_m interface, contributing to effective elimination of As(III) and As(V) via hydrogen bonding and complexation mechanisms. Synergistic oxidation effects of hydroxyl and carboxyl groups, and reactive oxygen species (O₂^·-, and ·OH) on the transformation of As(III) to As(V) during the adsorption were proposed to explain the enhanced As(III) removal by M_m. A short-term soil incubation experiment indicated that the addition of M_m (10 wt%) induced a decrease in the concentration of exchangeable As by 30.25%, and facilitated the transformation of water-soluble As into residual fraction. Ball milling thus is considered as an eco-friendly (chemical-free) and inexpensive (scalable, one-stage process) method for upgrading the performance of natural magnetite towards remediating As, particularly for tackling the highly mobile As(III).

Removal of As(V) from wastewaters using magnetic iron oxides formed by zero-valent iron electrocoagulation

Electrocoagulation of zero-valent iron has been widely applied to the removal of dissolved arsenic, but the solid-liquid separation of arsenic-containing precipitates remains technically challenging. In this work, zero-valent iron was electrochemically oxidized to magnetic iron oxides for the removal of As(Ⅴ) from simulated and actual mining wastewaters. The results indicated that lepidocrocite was formed when zero-valent iron was oxidized by dissolved oxygen, but ferrihydrite and green rust were first formed and then transformed to magnetic iron oxides (mainly magnetite and maghemite) in the electrochemical oxidation from 0 to 0.9 V (vs. SCE), which facilitates the adsorption of As(V) and subsequent solid-liquid separation under a magnetic field. In simulated As(V)-containing solution with initial pH 7.0, zero-valent iron was electrochemically oxidized to magnetite and maghemite at 0.6 V (vs. SCE) for 2 h. The As(V) concentration first decreased from 5127.5 to 26.8 μg L^-1 with a removal ratio of 99.5%. In actual mining wastewaters, zero-valent iron was electrochemically oxidized to maghemite at 0.6 V (vs. SCE) for 24 h, and the As(V) concentration decreased from 5486.4 to 3.6 μg L^-1 with a removal ratio of 99.9%. The removal ratio of As(V) increased slightly with increasing potential, and increased first and then decreased with increasing initial pH. Compared with that of SO₄^2- and NO₃^-, the presence of Cl^- significantly enhanced the removal of As(V). This work provides a highly efficient, facile and low-cost technique for the treatment of arsenic-containing wastewaters.

Layered Double Hydroxide Catalysts Preparation, Characterization and Applications for Process Development: An Environmentally Green Approach

The adage of new generation of fine chemicals process is the best process applied in the absence of conventional methods. However, many methods use different reaction parameters, such as basic and acidic catalysts, for example oxidation, reduction, bromination, water splitting, cyanohydrin, ethoxylation, syngas, aldol condensation, Michael addition, asymmetric ring opening of epoxides, epoxidation, Wittig and Heck reaction, asymmetric ester epoxidation of fatty acids, combustion of methane, NOx reduction, biodiesel synthesis, propylene oxide polymerization. Layered Double Hydroxides (LDHs) have received considerable attention due their potential applications in flame retardant and has excellent medicinal property for reducing acidity. These catalysts are characterized using analytical techniques, such as: X-ray diffraction (XRD), Fourier-transform infrared (FT-IR), Raman spectroscopy, Thermogravimetric-Differential Thermal Analyzer (TG-DTA), Scanning electron microscope (SEM), Transmission electron microscopes (TEM), Brunauer-Emmett-Teller (BET) surface area, N2 Adsorption-desorption, Temperature programmed reduction (TPR), X-ray photoelectrons spectroscopy (XPS), which gives its overall picture of its structure, porosity, morphology, thermal stability, reusability, and activity of catalysts. LDHs catalysts have proven to be economic and environmentally friendly. The above discussed applications make these catalysts unique from Green Chemistry point of view since they are reusable, and eco-friendly catalysts. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0). 

Preparation, characterization, and applications of Fe-based catalysts in advanced oxidation processes for organics removal: A review

Fe-based catalysts as low-cost, high-efficiency, and non-toxic materials display superior catalytic performances in activating hydrogen peroxide, persulfate (PS), peracetic acid (PAA), percarbonate (PC), and ozone to degrade organic contaminants in aqueous solutions. They mainly include ferrous salts, zero-valent iron, iron-metal composites, iron sulfides, iron oxyhydroxides, iron oxides, and supported iron-based catalysts, which have been widely applied in advanced oxidation processes (AOPs). However, there is lack of a comprehensive review systematically reporting their synthesis, characterization, and applications. It is imperative to evaluate the catalytic performances of various Fe-based catalysts in diverse AOPs systems and reveal the activation mechanisms of different oxidants by Fe-based catalysts. This work detailedly summarizes the synthesis methods and characterization technologies of Fe-based catalysts. This paper critically evaluates the catalytic performances of Fe-based catalysts in diverse AOPs systems. The effects of solution pH, reaction temperature, coexisting ions, oxidant concentration, catalyst dosage, and external energy on the degradation of organic contaminants in the Fe-based catalyst/oxidant systems and the stability of Fe-based catalysts are also discussed. The activation mechanisms of various oxidants and the degradation pathways of organic contaminants in the Fe-based catalyst/oxidant systems are revealed by a series of novel detection methods and characterization technologies. Future research prospects on the potential preparation means of Fe-based catalysts, practical applications, assistive technologies, and impact in AOPs are proposed.

Superior elimination of Cr(VI) using polydopamine functionalized attapulgite supported nZVI composite: Behavior and mechanism

In this study, a polydopamine (PDA) modified attapulgite (ATP) supported nano sized zero-valent iron (nZVI) composite (PDA/ATP-nZVI) was rapidly synthesized under acidic conditions, and employed to alleviate Cr(VI) toxicity from an aqueous solution. Kinetic studies revealed that Cr(VI) adsorption process followed the pseudo-second order model, suggesting chemisorption was the dominant adsorption mechanism. Liu isotherm adsorption model was able to better describe the Cr(VI) adsorption isotherm with the maximum adsorption capacity of 134.05 mg/g. The thermodynamic study demonstrated that the adsorption process occurred spontaneously, accompanied by the increase in entropy and endothermic reaction. Low concentrations of coexisting ions had negligible effects on the removal of Cr(VI), while high concentrations of interfering ions were able to facilitate the removal of Cr(VI). Reactive species test revealed that Fe²⁺ played a key role in Cr(VI) reduction by PDA/ATP-nZVI. PDA enhanced the elimination of Cr(VI) via donation of electrons to Cr(VI) and acceleration of Fe³⁺ transformation to Fe²⁺. Furthermore, PDA was able to effectively inhibit the leaching of iron species and generation of ferric hydroxide sludge. Mechanistic study revealed that 72% of Cr(VI) elimination was attributed to reduction/precipitation, while 28% of Cr(VI) elimination was due to the surface adsorption.

Colloidal Stability of Silica-Modified Magnetite Nanoparticles: Comparison of Various Dispersion Techniques

The production of stable and homogeneous batches during nanoparticle fabrication is challenging. Surface charging, as a stability determinant, was estimated for 3-aminopropyltriethoxysilane (APTES) coated pre-formed magnetite nanoparticles (MNPs). An important consideration for preparing stable and homogenous MNPs colloidal systems is the dispersion stage of pre-formed samples, which makes it feasible to increase the MNP reactive binding sites, to enhance functionality. The results gave evidence that the samples that had undergone stirring had a higher loading capacity towards polyanions, in terms of filler content, compared to the sonicated ones. These later results were likely due to the harsh effects of sonication (extremely high temperature and pressure in the cavities formed at the interfaces), which induced the destruction of the MNPs.

Conversion of biomass to N, S co-doped porous graphene as an adsorbent for mercury vapor removal: optimization and DFT study

This study is devoted to optimization synthesis conditions of the N, S co-doped porous graphene via a single step thermal chemical activation process from agricultural wastes such as cabbage waste. To this end, the response surface method (RSM) was considered, and the synthesis parameters were varied in specific ranges. By doing so, the optimum conditions in terms of the best performance in mercury removal was determined which was characterized by TEM, SEM, BET, XRD, XPS, and FTIR techniques. The chosen key process parameters were Activation agent to carbon precursor ratio (A: KOH/C), Reaction time (B: Time), Activation temperature (C: Temperature), and (Dopant to carbon precursor ratio (D: Dopant/C). Each parameter was investigated in 3 levels with lower and upper bounds being A: 2-6; B:30-90 min.; C: 600-800 ˚C; D:2-10. The optimum conditions of the process were determined to be as: A: 2; B: 30 min.; C: 600 ˚C and D: 2. The optimized sample was prepared in repeated runs with reproducible results with Hg vapor adsorption capacity of 2100 µg/g at 40 ˚C and 2266 µg/g at 90 ˚C. In addition to the experiments, DFT calculations were also carried out which elucidated the positive role of N and S co-doping in improving the mercury adsorption intensity.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s40201-021-00712-y.

Colorimetric determination of trace orthophosphate in water by using C18-functionalized silica coated magnetite

In this study, we customized magnetic sorbents by functionalizing silica coated magnetite with octadecyl(C₁₈)silane (Fe₃O₄@SiO₂@C₁₈). This sorbent was intended for the determination of trace orthophosphate (o-PO₄³⁻) in unpolluted freshwater samples. The o-PO₄³⁻ was transformed to phosphomolybdenum blue (PMB), a known polyoxometalate ion. Then the PMB were coupled with cetyl trimethyl ammonium bromide (CTAB), cationic surfactant, in order to hydrophobically bound with the Fe₃O₄@SiO₂@C₁₈ particles through dispersive magnetic solid-phase extraction (d-MSPE) as part of sample preconcentration. The PMB–CTAB–magnetic particles are simply separated from the aqueous solution by the external magnet. The acidified ethanol 0.5 mL was used as PMB-CTAB eluent to produce an intense blue solution, which the absorbance was measured using a UV–Vis spectrophotometer at 800 nm. The proposed method (employing 2 mg of Fe₃O₄@SiO₂@C₁₈) yielded an enhancement factor of 32 with a linear range of 1.0–30.0 µg P L⁻¹. Precision at 6.0 µg P L⁻¹ and 25.0 µg P L⁻¹ were 3.70 and 2.49% (RSD, n = 6) respectively. The lower detection limit of 0.3 µg P L⁻¹ and quantification limit of 1.0 µg P L⁻¹ allowed trace levels analysis of o-PO₄³⁻ in samples. The reliability and accuracy of the proposed method were confirmed by using a certified reference material. Our method offers highly sensitive detection of o-PO₄³⁻ with simple procedures that can be operated at room temperature and short analysis time.

Ce-Mn ferrite nanocomposite promoted the photosynthesis, fortification of total yield, and elongation of wheat (Triticum aestivum L.)

Recent advances in nano-enabled agriculture raised hope in the efficient delivery of bioactive minerals to crops. Nanocomposites (NCPs) are promising technologies in soil fertilizing without compromising environmental contamination. NCPs have shown positive impacts on plant growth and nanofortification of crop yield. Here, we have synthesized a nanocomposite that could induce the positive impacts of the Mn, Fe, and Ce nanoparticles for the crops. The NCPs were extensively characterized and applied at three levels 100, 250, and 500 ppm on T. aestivum L. seeds for 10 days. The germination, biomass, and elongation have been measured as the main physiological parameters of the plant. The total content of chlorophyll, carotenoids, and enzymatic and non-enzymatic antioxidant in response to NCPs was quantified. The concentration of essential minerals (iron and manganese) and the non-essential element of cerium in roots and shoots were quantified using inductively coupled plasma mass spectrometry (ICP-MS). Briefly, the germination rate increased by 15%; total chlorophyll and carotenoid were augmented by 61% and 38%, respectively, in exposure to 100 ppm. Higher uptake of micronutrient Fe and Mn in shoots and led to higher yield production by 14% and 18%, respectively. A positive correlation between the increasing dose of NCPs and the total content of the superoxide dismutase (SOD), and peroxidase (POD) were quantified. Overall, the results indicate the high potential of NCPs applications in agricultural practice.

Modification of Magnetite Nanoparticles with Triazine-Based Dendrons and Their Application as Drug-Transporting Systems

The following research aims at the synthesis of magnetite nanoparticles functionalized with triazine-based dendrons and the application of the obtained materials as effective sorptive materials dedicated to acidic bioactive compounds. The adopted synthetic approach involved: (1) the synthesis of nanosized Fe₃O₄ particles via classic co-precipitation method, (2) the introduction of amine groups on their surface leading to materials’ precursor, and (3) the final synthesis of branched triazine-based dendrons on the support surface by an iterative reaction between cyanuric chloride (CC) and piperazine (p) or diethylenetriamine (DETA) via nucleophilic substitution. The characterized materials were tested for their adsorptive properties towards folic acid, 18β–glycyrrhetinic acid, and vancomycin, showing high adsorption capacities varying in the ranges of 53.33–401.61, 75.82–223.71, and 68.17–132.45 mg g⁻¹, respectively. The formed material–drug complexes were also characterized for the drug-delivery potential, performed as in vitro release studies at pH 2.0 and 7.4, which mimics the physiological conditions. The release profiles showed that the proposed materials are able to deliver up to 95.2% of the drugs within 48 h, which makes them efficient candidates for further biomedical applications.

"In-situ synthesized" iron-based bimetal promotes efficient removal of Cr(VI) in by zero-valent iron-loaded hydroxyapatite

Anionic Cr(VI) and cationic heavy metals generally co-exist in industrial effluents and threaten the public health. Zero-valent iron (ZVI) particles tent to passivate rapidly, which results in a gradual drop in its reactivity. In this work, a strategy of "in-situ synthesized" iron-based bimetal was first developed to stimulate the self-activation of passivated ZVI. During this process, ZVI-loaded hydroxyapatite (ZVI/HAP) was prepared to enhance the affinity for co-existing Cu²⁺, which promoted the in-situ Cu⁰ deposition on ZVI/HAP to form a Fe-Cu bimetal. The deposited Cu⁰ significantly decreased the activation energy (E_a) of Cr(VI) reduction by 24.9%, and its corresponding Cr(VI) removal (96.53%) was much higher that of single Cr(VI) system (68.67%) within 9 h. More importantly, the removal of Cr(VI) and Cu²⁺ were synchronously achieved. Systematical electrochemical characterizations were first introduced to explore the galvanic behaviors of iron-based bimetal. The charge transfer resistance and the negative open circuit potential of ZVI/HAP significantly decreased with the Cu⁰ deposition, thereby accelerating the electron transfer from Fe⁰ to Cu²⁺. The enhanced electron transfer further facilitated the Fe(II) release to promote Cr(VI) reduction. This "in-situ synthesized" iron-based bimetal strategy provides a novel pattern for ZVI activation and exhibits practical application in remediation of combined contaminant.

Green synthesis of AgNP-ligand complexes and their toxicological effects on Nilaparvata lugens

BACKGROUND

Despite developments in nanotechnology for use in the pharmaceutical field, there is still a need for implementation of this technology in agrochemistry. In this study, silver nanoparticles (AgNPs) were successfully prepared by a facile and an eco-friendly route using two different ligands, 2'-amino-1,1':4',1″-terphenyl-3,3″,5,5″-tetracarboxylic acid (H4L) and 1,3,6,8-tetrakis (p-benzoic acid)-pyrene (TBAPy), as reducing agents. The physiochemical properties of the as-obtained AgNPs were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The toxicity of H4L-AgNP and TBAPy-AgNP against the brown planthopper (BPH, Nilaparvata lugens) was also measured.

RESULTS

SEM and TEM analyses demonstrated the formation of quasi-spherical AgNP structures in the presence of H4L and TBAPy. Insecticidal assays showed that TBAPy is less effective against N. lugens, with a median lethal concentration (LC50) of 810 mg/L, while the toxicity of H4L increased and their LC50 reached 786 mg/L 168 h posttreatment at a high concentration of 2000 mg/L. H4L-AgNPs were also highly toxic at a low concentration of 20 mg/L, with LC50 =  ~ 3.9 mg/L 168 h posttreatment, while TBAPy-AgNPs exhibited less toxicity at the same concentration, with LC50 =  ~ 4.6 mg/L.

CONCLUSIONS

These results suggest that the synthesized AgNPs using the two ligands may be a safe and cheaper method compared with chemical insecticides for protection of rice plants from pests and has potential as an effective insecticide in the N. lugens pest management program.

Exceptionally high saturation magnetisation in Eu-doped magnetite stabilised by spin-orbit interaction

The significance of the spin-orbit interaction is very well known in compounds containing heavier elements such as the rare-earth Eu ion. Here, through density functional calculations, we investigated the effect of the spin-orbit interaction on the magnetic ground state of Eu doped magnetite (Fe₃O₄:Eu_Fe). By examining all possible spin alignments between Eu and magnetite's Fe, we demonstrate that Eu, which is most stable when doped at the tetrahedral site, adapts a spin almost opposite the substituted Fe. Consequently, because of smaller spin cancellation between the cations on the tetrahedral site (Fe_Tet and Eu_Tet) and the cations on the octahedral sites (Fe_Oct), Fe₃O₄:Eu_Fe exhibits a maximum saturation magnetisation of 9.451 μ_B per f.u. which is significantly larger than that of undoped magnetite (calculated to be 3.929 μ_B per f.u.). We further show that this large magnetisation persists through additional electron doping. However, additional hole doping, which may unintentionally occur in Fe deficient magnetite, can reduce the magnetisation to values smaller than that of the undoped magnetite. The results presented here can aid in designing highly efficient magnetically recoverable catalysts for which both magnetite and rare earth dopants are common materials.

Fouling Release Coatings Based on Acrylate-MQ Silicone Copolymers Incorporated with Non-Reactive Phenylmethylsilicone Oil

Copolymers containing MQ silicone and acrylate were synthesized by controlling the additive amount of compositions. Subsequently, fouling release coatings based on the copolymer with the incorporation of non-reactive phenylmethylsilicone oil were prepared. The surface properties of the coating (CAMQ₄₀) were consistent with that of the polydimethylsiloxane (PDMS) elastomer, which ensured good hydrophobicity. Moreover, the seawater volume swelling rate of all prepared coatings was less than 5%, especially for CAMQ₄₀ with only 1.37%. Copolymers enhanced the mechanical properties of the coatings, while the enhancement was proportional to the molar content of structural units from acrylate in the copolymer. More importantly, the adhesion performance between the prepared coatings and substrates indicated that pull-off strength values were more than 1.6 MPa, meaning a high adhesion strength. The phenylmethylsilicone oil leaching observation determined that the oil leaching efficiency increased with the increase in the structural unit’s molar content from MQ silicone in the copolymer, which was mainly owing to the decrease in compatibility between oil and the cured coating, as well as the decrease in mechanical properties. High oil leaching efficiency could make up for the decrease in the biofouling removal rate due to the enhancement of the elastic modulus. For CAMQ₄₀, it had an excellent antifouling performance at 30 days of exposure time with more than 92% of biofouling removal rate, which was confirmed by biofilm adhesion assay.

Amidoximated wooden solar evaporator for high-efficiency nuclear wastewater treatment

The efficient removal of uranium (VI) (UO₂²⁺) is of great significance to the ecological environment. However, there is still a lack of efficient adsorption materials to remove UO₂²⁺ in wastewater economically. Because natural basswood has high porosity, natural hydrophilicity, and abundant surface functional groups, wood as a support material has a good application prospect in water treatment. In the present work, the amidoxime functional group (AO) is grafted to the hydroxyl group of the wood fiber (AO-wood). A carbon layer is formed on the surface of the basswood by heating, and some Ag nanoparticles with good optothermal effect are added to the wood tunnel (Ag-C-AO-wood). Ag-C-AO-wood is used for efficient wastewater treatment under light conditions. The adsorption kinetic of Ag-C-AO-wood is 4.6 h under one irradiation, which is 7 times faster than AO-wood. It has approached or even surpassed some traditional carbon materials with stirring. This method is expected to break the traditional stirring method. Ag-C-AO-wood can not only remove uranium up to 82% but also have a good removal efficiency (27%) on iodide ions. More importantly, due to basswood characteristics, it is possible to large-scale preparation and explore its potential application value in wastewater.