Solubility Constraints on Aquatic Ecotoxicity Testing of Anionic Surfactants

Towards a European sustainable beneficiation of rare earth elements bearing minerals: a review

This review explores the multifaceted aspects of sustainable extraction of rare earth elements (REEs) bearing minerals within Europe, stressing the exploitation of local deposits, that together with the integration of cleaner and greener approaches (including circular economy approaches) might help to reduce dependency on imports and contribute to a greener economy. The mineralogical characteristics and distribution of REEs in European deposits are examined, alongside current and emerging beneficiation techniques aimed at enhancing extraction efficiency and sustainability. Key challenges, such as the mineral extraction complexities (technological and economic limitations), radiochemical and environmental impacts, as well as social acceptance, are critically assessed. Innovative and new approaches that aim to be applied to mainly primary sources (mineral deposits) but also secondary sources (secondary raw materials) are presented and suggested for a sustainable mineral extraction. Finally, Europe's over-dependence on foreign countries and prospects for the mineral extraction of REEs are discussed, outlining a strategic roadmap for achieving sustainable and economically viable extraction practices in Europe. This comprehensive and holistic analysis stresses the importance of an integrated approach that combines developing unexploited mineral resources within Europe, boosting recycling initiatives, technological innovation, implementing environmental standards and community engagement to foster a sustainable REE supply chain within Europe.

Linear alkylbenzene sulfonate pollution investigation along the Capibaribe River Estuarine System (Northeast Brazil) using a digital imaging-based methodology

The Capibaribe Estuarine System (CES), in Recife-Brazil, is threatened by pollution from domestic effluents, including linear alkylbenzene sulfonate (LAS), a widely used and potentially toxic surfactant. This study uses an innovative in situ methodology: digital image-based (DIB) captured by smartphone, focused on environmental issues and analysis of LAS contamination in CES, assessing pollution sources and tidal influence. Triplicate water samples were collected over 4 consecutive weeks at 6 stations along the CES. The DIB method quantified LAS through color intensity by reaction with methylene blue. LAS concentrations ranged from 0.06 to 1.43 mg L-1, exceeding the limits allowed by CONAMA (National Environmental Council from Brazil) and USEPA (United States Environmental Protection Agency) (0.2 mg L-1). The highest concentrations were observed at the confluence of polluted rivers, and at stations close to the discharge of treated or irregularly discharged effluents, characterizing these locals as the main input sources of LAS for the CES. Higher concentrations were observed especially at ebb flow during spring tides, with lower contaminant dispersion, while areas with stronger marine influence had lower concentrations. The results showed critical levels of LAS in the CES, highlighting potential impacts on local biodiversity and human health, since several people use its water for various activities, including fishing. The DIB methodology has proven to be accurate, fast, cost-effective, and sustainable, making it a promising tool for environmental monitoring and/or improving effluent management.

Predicting aquatic toxicity of anionic hydrocarbon and perfluorinated surfactants using membrane-water partition coefficients from coarse-grained simulations

Anionic surfactants are widely used in commercial and industrial applications. For assessment of their environmental fate and effects, it is highly desirable to quantify the membrane-water partition/distribution coefficient (Kmw/Dmw). Here, we further develop a computational route to Dmw for anionic surfactants based on coarse-grained molecular dynamics simulations, validating it against new and existing experimental measurements. Having parameterised molecular fragments for the coarse-grained models, the simulations are used to predict Dmw for molecules where no experimental values are available. This expanded set of simulated Dmw values is then used to derive QSARs for acute toxicity of mono-constituent anionic surfactants in daphnids and fish, allowing for extrapolation to similar compounds without experimental Dmw values. For this study, we have selected hydrocarbon-based (HC) surfactants because of their widespread use, and perfluorinated (FC) surfactants as a challenging case study. Separate daphnid and fish QSARs demonstrate good fits, robustness and predictivity, and highlight differing toxicity relationships for HC and FC surfactants in daphnids. Overall, the combined use of simulated Dmw and derived QSARs is a promising approach for ecotoxicity screening of surfactants.

A novel in situ method for linear alkylbenzene sulfonate quantification in environmental samples using a digital image-based method

Surfactants from detergents, when inadequately treated in sewage treatment plants, are carried away into estuaries, resulting in the contamination of aquatic environments. It is thus necessary to develop rapid and efficient techniques that are capable of effectively monitoring these pollutants. In this context, for the first time in the literature, this study reports the development and application of a digital image-based (DIB) method for the in situ quantification of the anionic surfactant linear alkylbenzene sulfonate (LAS) in water bodies using a smartphone. The DIB method is a highly effective modern detection method based on methylene blue, which is employed as a modified alternative technique to the spectrophotometric method and commonly used in environmental studies; in the DIB method, the images of interest are obtained using a smartphone and the analyses are carried out using free software Color grab. The results obtained from the application of the DIB method showed that the method possesses high precision and accuracy, with a linear calibration curve in the range of 0.15 to 4.5 mg L-1, R2 = 0.993, a limit of detection of 6.0 μg L-1, and recovery rates ranging from 82.7% to 114%. The efficacy of the proposed method was evaluated by comparing its results with those of spectrophotometry (used as a reference method) through the analysis of environmental samples obtained from the Capibaribe River Estuary using methylene blue. No statistically significant differences were observed between the results obtained from the DIB and the spectrophotometric method. The innovative method proposed in this study is fast, economical and environmentally friendly; the technique involves the use of only a few microliters of samples and generates little waste compared to spectrophotometry. In addition, the proposed method is applicable for in situ analyses, allowing real-time monitoring of LAS in different types of aquatic environments.

Research Priorities for the Environmental Risk Assessment of Per- and Polyfluorinated Substances

Per- and polyfluorinated substances (PFAS) are a group of thousands of ubiquitously applied persistent industrial chemicals. The field of PFAS environmental research is developing rapidly, but suffers from substantial biases toward specific compounds, environmental compartments, and organisms. The aim of our study was therefore to highlight current developments and to identify knowledge gaps and subsequent research needs that would contribute to a comprehensive environmental risk assessment for PFAS. To this end, we consulted the open literature and databases and found that knowledge of the environmental fate of PFAS is based on the analysis of <1% of the compounds categorized as PFAS. Moreover, soils and suspended particulate matter remain largely understudied. The bioavailability, bioaccumulation, and food web transfer studies of PFAS also focus on a very limited number of compounds and are biased toward aquatic biota, predominantly fish, and less frequently aquatic invertebrates and macrophytes. The available ecotoxicity data revealed that only a few PFAS have been well studied for their environmental hazards, and that PFAS ecotoxicity data are also strongly biased toward aquatic organisms. Ecotoxicity studies in the terrestrial environment are needed, as well as chronic, multigenerational, and community ecotoxicity research, in light of the persistency and bioaccumulation of PFAS. Finally, we identified an urgent need to unravel the relationships among sorption, bioaccumulation, and ecotoxicity on the one hand and molecular descriptors of PFAS chemical structures and physicochemical properties on the other, to allow predictions of exposure, bioaccumulation, and toxicity. Environ Toxicol Chem 2023;42:2302-2316. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Surfactants in water and wastewater (greywater): Environmental toxicity and treatment options

Surfactant, an emerging pollutant present in greywater, raises the toxicity levels in the water body. Soap, detergent, and personal care items add surfactant to greywater. Due to excessive washing and cleaning procedures brought on by the COVID-19 pandemic, the release of surfactants in greywater has also increased. Considering the environmental toxicity and problems it creates during the treatment, it's essential to remove surfactants from the wastewater. This review intends to explain and address the environmental toxicity of the surfactant released via greywater and current techniques for surfactant removal from wastewater. Various physical, chemical, and biological methods are reported. Modern adsorbents such as hydrophilic silica nanoparticles, chitosan, fly ash, and iron oxide remove surfactants by adsorption. Membrane filtration effectively removes surfactants but is not cost-effective. Coagulants (chemical and natural coagulants) neutralize surfactant charges and help remove them as bigger particles. Electrocoagulation/electroflotation causes surfactants to coagulate and float. Microorganisms break down surfactants in microbial fuel cells to generate power. Surfactants are removed by natural processes and plants in constructed wetlands where traditional aerobic and anaerobic approaches use microbes to break down surfactants. Constructed wetlands, natural coagulation-flocculation, and microbial fuel cells are environmentally beneficial methods to remove surfactants from wastewater.

An overview on surfactants as pollutants of concern: Occurrence, impacts and persulfate-based remediation technologies

Surfactants are molecules that reduce interfacial energy and increase solubility of other pollutants in water. These properties make them suitable for various domestic and industrial applications, soil remediation, pesticide formulation, among others. The increase in their use and the lack of strict regulations regarding their disposal and management is a matter of concern and requires more attention since the release and distribution of these compounds into the environment can modify important water quality parameters. As a result of these changes, different toxicological effects to aquatic organisms are discussed and exposed herein. On this basis, we provide an overview of the classes of surfactants, as well as their occurrence in different aqueous matrices. In addition, existing regulations around the world regarding their concentration limit for different environments are discussed. Current research focuses on the application of conventional treatments, such as biological treatments; notwithstanding, more toxic and bioaccumulative products can be generated. Advanced Oxidation Processes are promising alternatives and have also been widely applied for the removal of surfactants. This study provides, for the first time, an overview of the application of persulfate-based processes for surfactants degradation based on recent literature findings, as well as the various factors related to the activation of the persulfate anions. This review also highlights the challenges and opportunities for future research to overcome the obstacles to the practical application of this process.

Critical Review on the Presence of Phthalates in Food and Evidence of Their Biological Impact

Phthalates are a huge class of chemicals with a wide spectrum of industrial uses, from the manufacture of plastics to food contact applications, children's toys, and medical devices. People and animals can be exposed through different routes (i.e., ingestion, inhalation, dermal, or iatrogenic exposure), as these compounds can be easily released from plastics to water, food, soil, air, making them ubiquitous environmental contaminants. In the last decades, phthalates and their metabolites have proven to be of concern, particularly in products for pregnant women or children. Moreover, many authors reported high concentrations of phthalates in soft drinks, mineral waters, wine, oil, ready-to-eat meals, and other products, as a possible consequence of their accumulation along the food production chain and their accidental release from packaging materials. However, due to their different physical and chemical properties, phthalates do not have the same human and environmental impacts and their association to several human diseases is still under debate. In this review we provide an overview of phthalate toxicity, pointing out the health and legal issues related to their occurrence in several types of food and beverage.

Quantitative structure-activity relationship between the toxicity of amine surfactant and its molecular structure

With the extensive applications and ongoing world demand, more and more amine surfactants are discharged into natural environment. However, the database about toxicity of amine surfactants is incomplete, which is not beneficial to environmental protection process. In this paper, the toxicity of 20 amine surfactants on Daphnia magna were tested to extend the toxicity data of amine surfactants. Besides, 35 molecular structure descriptors including quantum parameters, physicochemical parameters and topological indices were chosen and calculated as independent variables to develop the quantitative structure-activity relationship (QSAR) model between the toxicity of amine surfactants and their molecular structure by genetic function approximation (GFA) algorithm. According to statistical analysis, a robust model was built with the determination coefficient of (R²) was 0.962 and coefficient determinations of cross-validation (R_cv²) was 0.794. Meanwhile, external validation was implemented to evaluate the QSAR model. The result of coefficient determinations of cross-validation (R_ext²) for external validation was calculated as 0.942, illustrating the model has great goodness-of-fit and good prediction ability.

Membrane-Water Partition Coefficients to Aid Risk Assessment of Perfluoroalkyl Anions and Alkyl Sulfates

This study determined the sorption affinity to artificial phospholipid membranes ( K_MW) for series of perfluorinated carboxylates (PFCAs), perfluorinated sulfonates (PFSAs), alkyl sulfates (C _xSO₄), and 1-alkanesulfonates (C _xSO₃). A sorbent dilution assay with solid supported lipid membranes (SSLM) showed consistent CF₂ unit increments of 0.59, and CH₂ unit increments of 0.53, for the log K_MW of perfluorinated and hydrogenated anions, respectively. PFSAs sorbed 0.90 log units stronger than analogue PFCAs; C _xSO₄ sorbed 0.75 log units stronger than analogue C _xSO₃ anions. The log K_MW values for the octyl analogues increase in the order H(CH₂)₈SO₃^- (1.74) < H(CH₂)₈SO₄^- (2.58) < F(CF₂)₈CO₂^- (PFNA, 4.04) < F(CF₂)₈SO₃^- (PFOS, 4.88). Intrinsic partition ratios determined on a phospholipid coated HPLC column (IAM-HPLC) closely aligned with SSLM K_MW values. COSMO-RS based molecular calculations of K_MW aligned with SSLM K_MW values for hydrogenated anions with C₈-C₁₄ alkyl chains but strongly underestimated CF₂ and CH₂ unit increments for C₄-C₈ based anions. Dividing the critical narcotic membrane burden of 100 mmol/kg by the experimental K_MW predicts lethal baseline toxicity concentrations (LC_50,narc). The LC_50,narc coincides with the lowest reported acute LC₅₀ values for several anionic surfactants but were on average about an order of magnitude lower.