Although macroalgae are promising biosorbents for the removal of various contaminants, their effectiveness in complex mixtures requires comprehensive comparative evaluation under multi-contaminant conditions. The ability of living and non-living Ulva lactuca and Gracilaria gracilis to simultaneously uptake Rare Earth Elements (REEs) (Y, La, Nd, Eu, Gd, Dy) and classical contaminants (Hg, Cd, Pb, As) from equimolar mixtures was compared. Batch sorption experiments were conducted for 72 h under optimised conditions of salinity (10) and pH (7.8), in which 5 g of living biomass and an equivalent non-living biomass (0.60–0.85 g) were exposed to contaminated seawater (1 L) under constant stirring (800 rpm). The living biomass exhibited high removal rates (> 80

Marine and freshwater ecosystems are not only exposed to metals but to increasing macronutrient enrichment, causing environmental and health consequences. Macroalgae can bind contaminants and use nutrients in their growth. The influence of nutrients in the biosorption of Rare Earth Elements (REEs) and Classical contaminants, in complex mixtures, has not been fully covered. Response Surface Methodology (RSM) with Box-Behnken Design was applied to study the influence of biosorbent mass, element concentration and nutrient concentration on the removal response. Batch sorption experiments were performed for 48h at salinity (10) and pH (6 and 8). Living biomass exhibited high removal rates (>80%) for REEs, Hg, and Pb, while As and Cd showed less affinity. Biosorbent dosage showed to be an influential parameter, while nutrients were not significant. Quadratic models exhibited the best fit after 48h of exposure for all elements, except Hg. Despite the negligible effect of nutrients, in different optimisation scenarios, it was possible to improve the removal response in their presence. To better understand the environmental impact of adding nutrients or the need for high doses of biosorbent, LCA methodology would give further insights into the cost and environmental impacts of a macroalgae cultivation step.

Nanoparticles functionalized with dithiocarbamate groups are well known for their high uptake efficiency of Hg(II) from water but where and how Hg coordinates is still an open question.In the present work, Perturbed Angular Correlations spectroscopy was combined with Density Functional Theory modelling to answer that question. Measuring the electric field gradient and comparing it with its calculated counterpart allows to determine the most probable local environment of Hg and its coordination, both for dithiocarbamate functionalized nanoparticles and for silica coated magnetite nanoparticles.The calculated bonding energy also answers why dithiocarbamate functionalized nanoparticles present such a high sorption efficiency.

This study explores the use of manganese ferrite nanoparticles (MnFe2O4) for the removal and recovery of neodymium (Nd) from aqueous solutions, focusing on their potential application in wastewater treatment and environmental remediation. Neodymium, a critical element for the high-technology and energy industries, is increasingly present in aquatic environments due to its widespread use in devices such as computers, electric vehicles, and wind turbines. Through a series of kinetic, equilibrium, and desorption tests, the study optimized key operational parameters using Response Surface Methodology. Equilibrium analyses revealed that the Nd removal at equilibrium (qe) reached 8 mg/g, while the maximum sorption capacity (qm) was determined to be 9.2 mg/g. The results demonstrated a high removal efficiency (up to 90 %) under optimal conditions, which included a nanoparticle dose of 1000 mg/L, an initial neodymium concentration of 20 mu mol/L, pH 6, and no salinity. The material showed great potential for neodymium recovery from synthetic magnet solutions, with removal rates exceeding 70 %. Desorption tests confirmed complete recyclability of the sorbent. These findings highlight manganese ferrite nanoparticles as a promising and sustainable approach for neodymium recovery.

Here, a thiourea-formaldehyde functionalized graphene oxide (G3DTF) is shown to effectively remove mercury (Hg) from various water sources, including ultrapure, bottled, and seawater. Over 99 % of the Hg in each water source is removed with only 10 mg/L of G3DTF resulting in a residual Hg concentration < 1 μg L−1. This concentration falls within the permissible limits established by the European drinking water guidelines. Notably, the presence of chlorocomplexes in seawater doesn’t reduce the sorption efficiency of G3DTF. The sorption process across all water matrices can be accurately described by pseudo-second-order kinetics, with an R2 > 0.99 suggesting chemical interactions between Hg ions and G3DTF functional groups. The equilibrium isotherms demonstrate a remarkably high maximum adsorption capacity (qm) of 1039 mg g−1, exceeding the values reported in literature for the sorption of Hg on carbon-based materials. Remarkably, G3DTF retains its performance in the presence of other metal ions such as Cu, Cd, and Pb. Incorporating G3DTF into commercially activated carbon (AC) at a concentration as low as 2 wt% significantly enhances the efficiency of Hg(II) removal in fixed bed adsorption. The breakthrough curve exhibits enhanced absorption, attaining a 99.7 % removal of Hg(II) within a span of 2 h, surpassing the efficiency of AC. This relevant result represents a substantial advancement towards the adoption of graphene-based nanocomposites as effective commercial remediation materials.

The crucial role of Rare Earth Elements (REEs) in the development of hi-tech in addition to their limited availability have urged countries to develop sustainable alternatives to their conventional primary sources (ore mining). Sorption technologies using magnetic materials such as spinel ferrite nanoparticles provide efficient removal of REEs from contaminated solutions and ease of separation through application of an external magnetic field. However, there is still limited knowledge available regarding the optimal operational conditions in which to use these materials, especially in complex aqueous mixtures with different REEs. In this study, we have used Surface Response Methodology (SRM) applied to MnFe2O4 nanosorbents to identify their ideal sorption conditions of pH (4-8), REEs concentration (1-5 mu M) and sorbent mass (20-180 mg L-1) in a mixture of nine REEs in water samples of distinct salinity (NaCl: 0-30 g L-1). Our results indicated that high pH favored REEs sorption because of the material's surface charge, which promoted interactions with REEs ions at pH 6-8. Yttrium was the least removed element, but total removal was achieved for lowest REEs concentration using 151 mg L-1 of sorbent. High removals were also obtained for the concentration of 5 mu M (100 % removal, except for Y and La). Salinity did not impair sorption significantly (<10 %), which was owed to the high sorbent mass used in those assays. An increase in sorbent mass and initial REEs concentration also promoted faster kinetics. The spinel type MnFe2O4 nanoparticles showed great promise in a realistic application, which is the next proposed step in this line of research.

Given the significant industrial applications of rare earth elements (REEs), supply chain constraints, and negative environmental impacts associated with their extraction, finding alternative sources has become a critical challenge. Previously, we highlighted the potential of living Ulva sp. in the removal and pre-concentration of Y from a solution obtained by sequential acid leaching of spent fluorescent lamps (SFLs). Here, we extended that study to other REEs extracted from SFLs and evaluated the effect of pH (4.5-9.0), light exposure (absence, natural and supplemented with artificial light), and Hg (presence and absence). The results showed small differences in the removal of Y (23-30%) and other REEs at the different pH values, opening the scope of the methodology. However, Ulva sp. relative growth rate (RGR) was negatively affected in the higher acidity condition, without any visible signs of decay. In the absence of light, the RGR also decreased, which was accompanied by a halving of the removal efficiency compared to that with artificial light supplementation (40% for Y). Although Hg had minimal influence on the removal and concentration of REEs by Ulva sp., its presence in the enriched biomass is undesirable. Therefore, this contaminant was selectively removed from the solution using Fe3O4@SiO2/SiDTC nanoparticles before contact with the macroalgae (70% removal in 30 min; 99% in 72 h). In addition to easy solubilization, macroalgae enriched with REEs have a simpler composition compared to SFLs. Calcination of the biomass allowed the REEs to be further concentrated, with concentrations (130 mg/g for Y) up to 240 times higher than in typical apatite ore. This highlights enriched biomass as a sustainable alternative to traditional mining for obtaining these critical raw materials.

This study investigates the impact of three key variables on the performance of nanoporous AM-3 and layered AM-4 titanosilicates in removing nine REEs (Y, La, Ce, Pr, Nd, Eu, Gd, Tb, and Dy) from natural mineral water and identifies optimal operational conditions using Response Surface Methodology (RSM). The experimental conditions were determined by a Box-Behnken Design of 3 factors-3 levels (pH 4, 6, and 8; sorbent dose 20, 100, and 180 mg/L; and element concentration 1, 3, and 5 μmol/L). Three-dimensional response surfaces were used to assess the linear, quadratic, and interaction influences of each factor on the REEs’ removal percentage. The pH was the most significant factor in the removal process using AM-3, while the sorbent dose was more important for AM-4. The results highlighted the sorbents’ strong capacity for REE removal. The optimal operating conditions obtained by RSM were applied to aqueous solutions with salinity 10 (common in coastal and transitional systems) and 30 (average seawater salinity). The results showed that AM-3 has a strong potential for removing REEs in solutions with salinity 10 and 30, while AM-4 was less efficient due to competition between REEs and other ions present in the solution.

The release of hazardous elements by industrial effluents to aquatic ecosystems is a potential threat to the environment. Chromium (Cr) is one of the elements whose levels in several freshwater ecosystems should be reduced to promote water reuse. In recent years, magnetic materials have gained increasing interest as sorbents because of their easy removal from treated water through magnetic separation. In this study, colloidal cobalt ferrite (CoFe2O4) particles were investigated as magnetic sorbents for chromium-aqueous chemical species. The oxidative stress responses of Mytilus galloprovincialis mussels exposed to 200 μg/L of Cr, resembling remediated water, were evaluated. More than 95

Rare Earth Elements (REE) are nearly irreplaceable in many technologies, but their supply is limited by geopolitical factors. Additionally, their exploration and refinement bring serious environmental consequences. Therefore, alternative sourcing of these elements through methods such as sorption has recently been attempted. Nanoparticles are exceptional REE sorbents, however, difficulties in material separation post-sorption have fueled an interest in the use of magnetic nanoparticles, which can be easily separated from the solution by applying an external magnetic field. In this study, we explore the influence of sorbent dosage, pH and matrix complexity in the removal of trivalent cations of nine REE (Y, La, Ce, Pr, Nd, Eu, Gd, Tb and Dy) using manganese ferrite nanoparticles (MnFe2O4); herein the abbreviation REE is employed to indicate such elements including the trivalent cations. The REE removal increased for higher sorbent dosages and pH. More than 90% of REE in mono-elemental solutions were removed from water at pH 6 and 8. Removal below 10% was observed for pH < 4, due to the positive surface charge of the sorbent, which did not favor interaction with cationic REE species. Increasing the complexity of the matrix, the removal of REE from water decreased considerably, which can be attributed to an increase of total REE concentration and the limited number of sorption sites in the sorbent. Further sorption inhibition was reported in increased ionic strength scenarios (mineral and saline water), possibly due to competition with Na+, which may limit the application of this material in complex matrices.

In this study, response surface methodology (RSM) was applied with a Box–Behnken design to optimize the biosorption (removal and bioconcentration) of rare earth elements (REEs) (Y, La, Ce Eu, Gd, Tb) by living Ulva sp. from diluted industrial wastewaters (also containing Pt and the classic contaminants Hg, Pb, Zn, Cu, Co, and Cd). Element concentration (A: 10–190 μg/L), wastewater salinity (B: 15–35), and Ulva sp. dosage (C: 1.0–5.0 g/L) were the operating parameters chosen for optimization. Analysis of the Box–Behnken central point confirmed the reproducibility of the methodology and p- values below 0.0001 validated the developed mathematical models. The largest inter-element differences were observed at 24 h, with most REEs, Cu, Pb and Hg showing removals ≥ 50 %. The factor with the greatest impact (positive) on element removal was the initial seaweed dosage (ANOVA, p < 0.05). The optimal conditions for REEs removal were an initial REEs concentration of 10 μg/L, at a wastewater salinity of 15, and an Ulva sp. dosage of 5.0 g/L, attaining removals up to 88 % in 24 h. Extending the time to 96 h allowed seaweed dosage to be reduced to 4.2 g/L while achieving removals ≥ 90 %. The high concentrations in REE-enriched biomass (∑REEs of 3222 μg/g), which are up to 3000 times higher than those originally found in water and exceed those in common ores, support their use as an alternative source of these critical raw materials.

Mercury (Hg) is a global and top priority contaminant, toxic at low concentrations. Although it has been progressively eliminated from processes, this metal continues to circulate in the atmosphere, soil, and water. In this work, the Response Surface Methodology (RSM) combined with a Box-Behnken Design (3 factors - 3 levels) was used to optimize key operational conditions that influence the removal and uptake of Hg by living macroalga Ulva sp. in a complex mixture containing several elements used in industry (potentially toxic elements, rare earth elements, and platinum-group elements) (initial concentration 10, 100 and 190 µg/L, salinity 15, 25 and 35, seaweed stock density 1.0, 3.0 and 5.0 g/L). Results evidenced the great capability of Ulva sp. to remove Hg, with removal efficiencies between 69 % and 97 %. 3-D surfaces showed that the most impactful variable was seaweed stock density, with higher densities leading to higher removal. Regarding the uptake, a positive correlation between initial concentration and qt values was observed. The appliance of RSM made possible to obtain optimal operating conditions for removing virtually 100 % of Hg from waters with high ionic strength, which is a pivotal step in the direction of the application of this remediation biotechnology at large scale.

A seasonal characterization of mercury (Hg) accumulation in three different estuaries along the Portuguese coast (i.e. Ria de Aveiro, Tagus estuary and Ria Formosa) was done. For that, it was evaluated: (1) Hg concentrations in abiotic (water) and biotic matrices (flora and fauna); (2) the risk of consumption of local seafood species (e.g. bivalves) to human health; and (3) the environmental risk to Hg exposure. During 1 year, water and biological samples were collected during low tide, in each system for Hg quantification. Our findings revealed that total Hg concentrations in surface waters were higher in Ria de Aveiro and Tagus estuary than in Ria Formosa. In Ria de Aveiro, a particular attention should be given in autumn periods, where Hg levels (≈ 100 µg L−1) were considered quite high according to European quality parameters. The same was observed for the Tagus estuary during spring time. Regarding macrofauna Hg levels, no clear seasonal trend was observed. Also, total Hg concentrations in edible species (< 0.5 µg. g−1 ww) represent no risk for consumption. However, considering the environmental risk, in Ria de Aveiro, there is a moderate risk (RQ > 0.1) in autumn periods, which can be a matter of concern.

To routinely assess whether consumed food meets international guidelines, a single analytical method able to quantify minerals and potentially toxic elements (PTEs) in real food matrices is required. This work validated a simple and efficient method to quantify nine elements in different food matrices by ICP-MS. Samples from local markets (chicken, mussels, fish, rice, and seaweed) and certified reference materials were digested with HNO3 68 % and H2O2 30 %. All performance criteria (working range, linearity, LOD, LOQ, selectivity, repeatability, and trueness) met the requirements of the Portuguese Association of Accredited Laboratories. Comparison between raw and cooked food showed significant changes in most element levels, and PTEs contents complied with the maximum permissible values (EC N° 1881/2006). The minimum and maximum amounts of the foods studied, alone or in combination, raw or cooked, that can be daily consumed to meet EFSA and WHO nutritional and safety requirements were analysed.

The mining of Rare-Earth Elements (REE) is an unsustainable practice that raises environmental, economic, and societal concerns. As a result, there is a need to develop suitable technologies for the removal of these elements from contaminated waters. Sorption is a clean and efficient method for decontaminating water, and microporous titanosilicates have shown promise for REE removal. However, the influence of solution parameters on this process remains poorly understood. In this study, the effect of pH (4-8), concentration (1-5 mu M), and sorbent amount (20-180 mg L-1) on the removal of a mixture of REE3+ (Y, La, Ce, Pr, Nd, Eu, Gd, Tb, Dy) from water by the microporous titanosilicate ETS-4 (Na9Ti5Si12O38(OH)center dot 12H(2)O) was assessed. A Box-Behnken design was used to investigate the experimental conditions, and the results were presented as three-dimensional response surfaces. The removal mechanism involves the ion exchange of Na+ by REE3+, with pH being the main variable in the process due to competition with H+. Increasing pH resulted in higher removal, with 100% removal achieved at ETS-4 amounts of 180 mg L-1 and REE concentrations of 1 mu M. Most REE3+ removal occurs within the first 15 min, with little difference between metals (except for Y, which exhibits lower removal). At ETS-4 amounts of 20 mg L-1, REE are highly concentrated in the sorbent, reaching 145 mg g(-1) (15% of the sorbent's mass, postsorption). These results demonstrate that even low amounts of ETS-4 have the potential to remove high concentrations of REE3+ from aqueous solutions with pH levels similar to those found in natural systems.