Can water remediated by manganese spinel ferrite nanoparticles be safe for marine bivalves?

Recent trends in magnetic spinel ferrites and their composites as heterogeneous Fenton-like catalysts: A review

In recent years, there has been a growing interest in utilizing spinel ferrite and their nanocomposites as Fenton-like catalysts. The use of these materials offers numerous advantages, including ability to efficiently degrade pollutants and potential for long-term and repeated use facilitated by their magnetic properties that make them easily recoverable. The remarkable catalytic properties, stability, and reusability of these materials make them highly attractive for researchers. This paper encompasses a comprehensive review of various aspects related to the Fenton process and the utilization of spinel ferrite and their composites in catalytic applications. Firstly, it provides an overview of the background, principles, mechanisms, and key parameters governing the Fenton reaction, along with the role of physical field assistance in enhancing the process. Secondly, it delves into the advantages and mechanisms of H2O2 activation induced by different spinel ferrite and their composites for the removal of organic pollutants, shedding light on their efficacy in environmental remediation. Thirdly, the paper explores the application of these materials in various Fenton-like processes, including Fenon-like, photo-Fenton-like, sono-Fenton-like, and electro-Fenton-like, for the effective removal of different types of contaminants. Furthermore, it addresses important considerations such as the toxicity, recovery, and reuse of these materials. Finally, the paper presents the challenges associated with H2O2 activation by these materials, along with proposed directions for future improvements.

An overview on dispersion procedures and testing methods for the ecotoxicity testing of nanomaterials in the marine environment

Considerable efforts have been devoted to develop or adapt existing guidelines and protocols, to obtain robust and reproducible results from (eco)toxicological assays on engineered nanomaterials (NMs). However, while many studies investigated adverse effects of NMs on freshwater species, less attention was posed to the marine environment, a major sink for these contaminants. This review discusses the procedures used to assess the ecotoxicity of NMs in the marine environment, focusing on the use of protocols and methods for preparing NMs dispersions and on the NMs physicochemical characterization in exposure media. To this purpose, a critical analysis of the literature since 2010 was carried out, based on the publication of the first NMs dispersion protocols. Among the 89 selected studies, only <5 % followed a standardized dispersion protocol combined with NMs characterization in ecotoxicological media, while more than half used a non-standardized dispersion method but performed NMs characterization. In the remaining studies, only partial or no information on dispersion procedures or on physicochemical characterization was provided. This literature review also highlighted that metal oxides NMs were the most studied (42 %), but with an increasing interest in last years towards nanoplastics (14 %) and multicomponent nanomaterials (MCNMs, 7 %), in line with the growing attention on these emerging contaminants. For all these NMs, primary producers as algae and bacteria were the most studied groups of marine species, in addition to mollusca, while organisms at higher trophic levels were less represented, likely due to challenges in evaluating adverse effects on more complex organisms. Thus, despite the wide use of NMs in different applications, standard dispersion protocols are not often used for ecotoxicity testing with marine species. However, the efforts to characterize NMs in ecotoxicological media recognize the importance of following conditions that are as standardized as possible to support the ecological hazard assessment of NMs.

Sulfadiazine's photodegradation using a novel magnetic and reusable carbon based photocatalyst: Photocatalytic efficiency and toxic impacts to marine bivalves

In the present study, waste-based biochar functionalized with titanium dioxide (TiO₂) and afterwards magnetized by an ex-situ approach, defined as synthetic photosensitizer (SPS), was explored for the photocatalytic degradation of sulfadiazine (SDZ), an antibiotic widely used in the aquaculture industry, under solar irradiation. The use of the SPS enhanced the photodegradation efficiency, with a half-life time (t_1/2) reduction from 12.2 ± 0.1 h (without SPS) to 5.6 ± 0.4 h. The applied magnetization procedure allowed to obtain a SPS with good reusability for SDZ photodegradation even after five consecutive cycles. To evaluate the effects on marine bivalves of SDZ, before and after photodegradation and in presence or absence of the SPS, a typical bioindicator species, the mussel Mytilus galloprovincialis, was used and different biochemical markers were analysed. Results obtained indicated that the exposure to SDZbefore irradiation, both in absence and presence of SPS, caused an increase in mussels' metabolism and defence mechanisms, evidencing great biochemical impacts. However, after irradiation (in the absence and presence of SPS), biochemical responses were similar to those observed in organisms exposed to control conditions, without SDZ. Therefore, this work provided a promising eco-friendly treatment for the removal of SDZ from aquaculture effluents.

Can the recycling of europium from contaminated waters be achieved through living macroalgae? Study on accumulation and toxicological impacts under realistic concentrations

Europium (Eu) strategic importance for the manufacturing industry, high economic value and high supply risk, categorizes it as critical raw material. Due to anthropogenic contamination, Eu levels in ecosystems have been growing, which opens opportunities for innovation: its recovery and recycling from contaminated water as element source - circular economy. In this pioneering study, six widely available living marine macroalgae (Ulva intestinalis, Ulva lactuca, Gracilaria sp., Osmundea pinnatifida, Fucus vesiculosus and Fucus spiralis) were characterized (water content and specific surface area) and evaluated in the pre-concentration and recovery of Eu from contaminated seawater, under different relevant contamination scenarios (10, 152 and 500 μg L^-1). U. lactuca and Gracilaria sp. (3 g L^-1, fresh weight) proved to be the most effective in removing Eu, reaching up to 85% in 72 h, while the highest Eu enrichment was observed in U. intestinalis biomass, up to 827 μg g^-1 (bioconcentration factor of 1800), which is higher than Eu levels in common apatite ores. The effect of Eu exposure on macroalgae growth rate and organism biochemical performance (LPO, SOD, GPx and GSTs) was also evaluated for the first time, to the best of our knowledge. Although no cellular damage was recorded, findings revealed toxicity and defence mechanisms activation, emphasizing the need of further studies on the potential risks associated with the presence of this emerging contaminant in aquatic ecosystems.

Spinel ferrites (MFe2O4): Synthesis, improvement and catalytic application in environment and energy field

To develop efficient catalysts is one of the major ways to solve the energy and environmental problems. Spinel ferrites, with the general chemical formula of MFe₂O₄ (where M = Mg²⁺, Co²⁺, Ni²⁺, Zn²⁺, Fe²⁺, Mn²⁺, etc.), have attracted considerable attention in catalytic research. The flexible position and valence variability of metal cations endow spinel ferrites with diverse physicochemical properties, such as abundant surface active sites, high catalytic activity and easy to be modified. Meanwhile, their unique advantages in regenerating and recycling on account of the magnetic performances facilitate their practical application potential. Herein, the conventional as well as green chemistry synthesis of spinel ferrites is reviewed. Most importantly, the critical pathways to improve the catalytic performance are discussed in detail, mainly covering selective doping, site substitution, structure reversal, defect introduction and coupled composites. Furthermore, the catalytic applications of spinel ferrites and their derivative composites are exclusively reviewed, including Fenton-type catalysis, photocatalysis, electrocatalysis and photoelectro-chemical catalysis. In addition, some vital remarks, including toxicity, recovery and reuse, are also covered. Future applications of spinel ferrites are envisioned focusing on environmental and energy issues, which will be pushed by the development of precise synthesis, skilled modification and advanced characterization along with emerging theoretical calculation.

The Influence of Temperature Increase on the Toxicity of Mercury Remediated Seawater Using the Nanomaterial Graphene Oxide on the Mussel Mytilus galloprovincialis

Mercury (Hg) has been increasing in waters, sediments, soils and air, as a result of natural events and anthropogenic activities. In aquatic environments, especially marine systems (estuaries and lagoons), Hg is easily bioavailable and accumulated by aquatic wildlife, namely bivalves, due to their lifestyle characteristics (sedentary and filter-feeding behavior). In recent years, different approaches have been developed with the objective of removing metal(loid)s from the water, including the employment of nanomaterials. However, coastal systems and marine organisms are not exclusively challenged by pollutants but also by climate changes such as progressive temperature increment. Therefore, the present study aimed to (i) evaluate the toxicity of remediated seawater, previously contaminated by Hg (50 mg/L) and decontaminated by the use of graphene-based nanomaterials (graphene oxide (GO) functionalized with polyethyleneimine, 10 mg/L), towards the mussel Mytilus galloprovincialis; (ii) assess the influence of temperature on the toxicity of decontaminated seawater. For this, alterations observed in mussels’ metabolic capacity, oxidative and neurotoxic status, as well as histopathological injuries in gills and digestive tubules were measured. This study demonstrated that mussels exposed to Hg contaminated seawater presented higher impacts than organisms under remediated seawater. When comparing the impacts at 21 °C (present study) and 17 °C (previously published data), organisms exposed to remediated seawater at a higher temperature presented higher injuries than organisms at 17 °C. These results indicate that predicted warming conditions may negatively affect effective remediation processes, with the increasing of temperature being responsible for changes in organisms’ sensitivity to pollutants or increasing pollutants toxicity.

Effects of temperature on caffeine and carbon nanotubes co-exposure in Ruditapes philippinarum

In the marine environment, organisms are exposed to a high and increasing number of different contaminants that can interact among them. In addition, abiotic factors can change the dynamics between contaminants and organisms, thus increasing or even decreasing the toxic effect of a particular compound. In this study, the effects of caffeine (CAF) and functionalized multi-walled carbon nanotubes (f-MWCNTs) induced in the clam Ruditapes philippinarum were evaluated, acting alone and in combination (MIX), under two temperature levels (18 and 21 °C). To assess the impact of such compounds, their interaction and the possible influence of temperature, biochemical and histopathological markers were investigated. The effects of f-MWCNTs and caffeine appear to be clearly negative at the control temperature, with lower protein content in contaminated clams and a significant decrease in their metabolism when both pollutants were acting in combination. Also, at control temperature, clams exposed to pollutants showed increased antioxidant capacity, especially when caffeine was acting alone, although cellular damages were still observed at CAF and f-MWCNTs treatments. Increased biotransformation capacity at 18 °C and MIX treatment may explain lower caffeine concentration observed. At increased temperature differences among treatments were not so evident as at 18 °C, with a similar biological pattern among contaminated and control clams. Higher caffeine accumulation at MIX treatment under warming conditions may result from clams' inefficient biotransformation capacity when exposed to increased temperatures.

Mesoporous ferromagnetic manganese ferrite nanoparticles for enhanced visible light mineralization of azoic dye into nontoxic by-products

In this study, a one pot facile synthesis of ferromagnetic manganese ferrite nanoparticles (MnFe₂O₄) was carried out using chemical co-precipitation method for mineralization of azo dye (Congo red (CR)) in aqueous solution under visible light irradiation. The synthesized MnFe₂O₄ nanoparticles were highly crystalline and showed face-centred cubic (FCC) structure with average particle size of 58 ± 4 nm. The BET analysis of the MnFe₂O₄ nanoparticles revealed the mesoporous distribution of material with high surface area can provide large electro active sites and short diffusion paths for the transport of ions which plays a vital role in the photocatalytic degradation of CR. The point of zero charge (pH_PZC) was observed to be 6.7 indicating favourable condition for material-anionic dye interaction. The XPS studies revealed that the large amounts of oxygen vacancies were produced due to the defects in the lattice oxygen. The MnFe₂O₄ nanoparticles mineralised 98.3 ± 0.2% of 50 mg/L CR within 30 min when tested in photocatalytic reactor under 565 nm. The particles were recoverable under the influence of an external magnet after the photocatalytic reaction and were reusable. The recovered nanoparticles showed 96% of CR degradation efficiency even after five cycles of reuse. The by-product analysis with GC-MS indicated mineralization of CR into simple alcohols and acids. The aqueous solution containing mineralised CR was nontoxic to Trigonella foenumgraecum and Vigna mungo seeds and favoured increased germination, plumule and radicle length when compared to untreated CR.

High affinity of 3D spongin scaffold towards Hg(II) in real waters

This study focuses on the ability of commercial natural bath sponges, which are made from the skeletons of marine sponges, to sorb Hg from natural waters. The main component of these bath sponges is spongin, which is a protein-based material, closely related to collagen, offering a plenitude of reactive sites from the great variety of amino acids in the protein chains, where the Hg ions can sorb. For a dose of 40 mg L^-1 and initial concentration of 50 μg L^-1 of Hg(II), marine spongin (MS) removed ~90% of Hg from 3 water matrixes (ultrapure, bottled, and seawater), corresponding to a residual concentration of ~5 μg L^-1, which tends to the recommend value for drinking water of 1 μg L^-1. This value was maintained even by increasing the MS dosage, suggesting the existence of a gradient concentration threshold below which the Hg sorption mechanism halts. Kinetic modelling showed that the Pseudo Second-Order equation was the best fit for all the water matrixes, which indicates that the sorption mechanism relies most probably on chemical interactions between the functional groups of spongin and the Hg ions. This material can also be regenerated in HNO₃ and reused for Hg sorption, with marginal losses in efficiency, at least for 3 consecutive cycles.

The Era of Nanomaterials: A Safe Solution or a Risk for Marine Environmental Pollution?

In recent years, the application of engineered nanomaterials (ENMs) in environmental remediation gained increasing attention. Due to their large surface area and high reactivity, ENMs offer the potential for the efficient removal of pollutants from environmental matrices with better performances compared to conventional techniques. However, their fate and safety upon environmental application, which can be associated with their release into the environment, are largely unknown. It is essential to develop systems that can predict ENM interactions with biological systems, their overall environmental and human health impact. Until now, Life-Cycle Assessment (LCA) tools have been employed to investigate ENMs potential environmental impact, from raw material production, design and to their final disposal. However, LCA studies focused on the environmental impact of the production phase lacking information on their environmental impact deriving from in situ employment. A recently developed eco-design framework aimed to fill this knowledge gap by using ecotoxicological tools that allow the assessment of potential hazards posed by ENMs to natural ecosystems and wildlife. In the present review, we illustrate the development of the eco-design framework and review the application of ecotoxicology as a valuable strategy to develop ecosafe ENMs for environmental remediation. Furthermore, we critically describe the currently available ENMs for marine environment remediation and discuss their pros and cons in safe environmental applications together with the need to balance benefits and risks promoting an environmentally safe nanoremediation (ecosafe) for the future.