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Petroleum spent catalysts may contain a significant amount of palladium (Pd) together with other major [aluminum (Al), nickel (Ni), and molybdenum (Mo)] and minor [iron (Fe), lead (Pb), and vanadium (V)] elements. Due to the high intrinsic value of Pd and its scarcity in natural ores, its recovery is highly desired. For this purpose, the ability of a strong basic anionic- resin, Purogold™ A194 resin, to remove Pd from the solution was assessed. Data from kinetic and equilibrium studies, performed under batch mode in 1 mol/L of NaCl and 1 mol/L of HNO

This study aimed at optimizing the one-step chemical activation and microwave pyrolysis of an agro-industrial waste to obtain a microporous activated carbon (AC) with superior textural and adsorptive properties by a fast, low-reagent and low-energy process. Spent brewery grains were used as precursor, and the antibiotics sulfamethoxazole (SMX), trimethoprim (TMP) and ciprofloxacin (CIP) were considered as target adsorbates. A fractional factorial design was applied to evaluate the effect of the main factors affecting the preparation of AC (activating agent, activating agent:precursor ratio, pyrolysis temperature and residence time) on relevant responses. Under optimized conditions (K2CO3 activation, pyrolysis at 800 °C during 20 min and a K2CO3:precursor ratio of 1:2), a microporous AC with specific surface area of 1405 m2 g-1 and large adsorption of target antibiotics (82-94%) was obtained and selected for further studies. Equilibrium times up to 60 min and maximum Langmuir adsorption capacities of 859 µmol g-1 (SMX), 790 µmol g-1 (TMP) and 621 µmol g-1 (CIP) were obtained. The excellent textural and adsorptive properties of the selected material were achieved with a very fast pyrolysis and low load of activating agent, highlighting the importance of optimization studies to decrease the environmental and economic impact of waste-based AC., This work was developed within the scope of the project CICECO - Aveiro Institute of Materials (UIDB/50011/2020 & UIDP/50011/2020). We acknowledge financial support to CESAM by FCT/MCTES (UIDP/50017/2020+UIDB/50017/2020+LA/P/0094/2020), through national funds. Érika M.L. Sousa thanks to Fundação para a Ciência e Tecnologia (FCT) for her PhD grant (2020.05390. BD). Paula Ferreira is thankful to FCT for the Investigator Program (IF/00300/2015). María V. Gil acknowledges support from a Ramón y Cajal grant (RYC-2017-21937) of the Spanish government and the Spanish State Research Agency, co-financed by the European Social Fund (ESF).

There is a growing interest in developing more environmentally friendly softeners for hardness reduction of water supplied for domestic consumption. This work focuses on exploring biopolymer-based softeners, through the surface modification of graphene oxide (GO) with the anionic biopolymer κ-carrageenan (GO-Si(κ)CRG). The performance of the modified GO to decrease the hardness of natural waters containing high levels of Ca2+ was assessed. The sorption efficiency was dependent on the initial Ca2+ concentration and on the sorbent dose, with 8–34% removal for GO and 21–100% for GO-Si(κ)CRG. The surface modification considerably improved the adsorptive efficiency and under certain experimental conditions, it was possible to convert very hard water (300 mg L−1 CaCO3) to soft water. Importantly, the performance was not affected by the presence of other ions typically found in natural bottled waters. The kinetics was well described by pseudo-first-order and diffusion models. The multi-linear nature observed in Boyd’s and Webber’s plots suggested that both film diffusion and pore diffusion controlled the sorption rate. The maximum Ca2+ sorption capacity at monolayer coverage of GO-Si(κ)CRG was 47.6 ± 3.2 mg g−1. The electrostatic attraction between sulfonate groups and calcium cations is likely to be the main mechanism involved in the sorption process of Ca2+ by GO-Si(κ)CRG. Overall, the results indicate good prospects for the development of a new class of softeners based on the GO modification described.

Nowadays, water is no longer regarded as an inexhaustible resource and the excessive release and proliferation of toxic metal(loid)s into aquatic environments has become a critical issue. Therefore, fast, accurate, simple, selective, sensitive and portable methodologies to detect multiple elements in natural waters is of paramount importance. Electrochemical stripping analysis is an efficient tool for trace metal(loid)s determinations and bring new prospects for answering the current environmental concerns. This review presents a survey of the advancements made between 2003 and 2016 on the development and application of non-toxic mercury free electrodes on the simultaneous analysis of metals and metalloids in waters and wastewaters by means of electroanalytical stripping techniques. The advantages, limitations, improvements and real applications of these "green" sensors are discussed from a critical point of view.

The main goal of this work was to produce an easily recoverable waste-based magnetic activated carbon (MAC) for an efficient removal of the antiepileptic pharmaceutical carbamazepine (CBZ) from wastewater. For this purpose, the synthesis procedure was optimized and a material (MAC4) providing immediate recuperation from solution, remarkable adsorptive performance and relevant properties (specific surface area of 551 m

The main goal of this work was to produce an easily recoverable waste-based magnetic activated carbon (MAC) for an efficient removal of the antiepileptic pharmaceutical carbamazepine (CBZ) from wastewater. For this purpose, the synthesis procedure was optimized and a material (MAC4) providing immediate recuperation from solution, remarkable adsorptive performance and relevant properties (specific surface area of 551 m g and saturation magnetization of 39.84 emu g) was selected for further CBZ kinetic and equilibrium adsorption studies. MAC4 presented fast CBZ adsorption rates and short equilibrium times (< 30–45 min) in both ultrapure water and wastewater. Equilibrium studies showed that MAC4 attained maximum adsorption capacities (q) of 68 ± 4 mg g in ultrapure water and 60 ± 3 mg g in wastewater, suggesting no significant interference of the aqueous matrix in the adsorption process. Overall, this work provides evidence of potential application of a waste-based MAC in the tertiary treatment of wastewaters. [Figure not available: see fulltext.]., This work is a contribution to the project WasteMAC (POCI-01-0145-FEDER-028598) funded by FCT – Fundação para a Ciência e a Tecnologia, I.P., through national funds, and the co-funding by the FEDER, within the PT2020 Partnership Agreement and Compete 2020. Thanks are also due for the financial support to CESAM (UID/AMB/50017/2019), to FCT/MCTES through national funds, and the co-funding by the FEDER, within the PT2020 Partnership Agreement and Compete 2020. Marta Otero and Diogo Pereira thank FCT funding through IF Program (IF/00314/2015). Vânia Calisto is thankful to FCT for the Scientific Employment Stimulus support (CEECIND/00007/2017). María V. Gil acknowledges support from a Ramón y Cajal grant (RYC-2017-21937) of the Spanish government, co-financed by the European Social Fund (ESF).

Mercury and cadmium are considered by the water framework directive priority hazardous substances. In this work, the capacity of crab carapace and clam shell wastes to remove mercury and cadmium from water was evaluated under batch conditions, for realistic contamination scenarios in monometallic and binary solutions. The results evidenced that in monometallic solutions and under studied operational conditions, both biosorbents can achieve Hg2+ removal efficiencies higher than 80% and the kinetic process is well described by two of the most widely used equations, the pseudo-second order and the Elovich model. In terms of biosorption equilibrium, crab carapace and clam shell wastes displayed very distinct behaviours. While clam shells achieve the complete monolayer coverage and the isotherm is well described by the Langmuir model, crab carapace powder display a more unusual behaviour, that is well described by the BET isotherm, and is characterized by an almost convex shape to the concentration axis, with an infinite slope for an Hg2+ concentration in solution around 25 mu g/L. In binary solutions, both wastes are able to uptake simultaneously Hg2+ and Cd2+, however the uptake of Hg2+ was inhibited in some extent, attributed to the high kinetic and equilibrium selectivities of the bio-wastes for cadmium. (C) 2016 Elsevier Ltd. All rights reserved.

This work aimed at the microwave-assisted production of activated carbon (AC) from primary paper mill sludge (PS) for the adsorption of antibiotics from water. Production conditions, namely pyrolysis temperature, pyrolysis time and activating agent (KOH):PS ratio, were optimized as a function of product yield, specific surface area (SBET), total organic carbon (TOC) content and adsorptive removal percentage of two target antibiotics (amoxicillin (AMX) and sulfamethoxazole (SMX)). Under the optimized conditions (pyrolysis at 800 °C during 20 min and a KOH:PS ratio of 1:5), a microporous AC (MW800-20-1:5, with SBET = 1196 m2 g-1, TOC = 56.2% and removal of AMX and SMX = 85% and 72%, respectively) was produced and selected for further kinetic and equilibrium adsorption studies. The obtained results were properly described by the Elovich reaction-based kinetic model and the Langmuir equilibrium isotherm, with maximum adsorption capacities of 204 ± 5 mg g-1 and 217 ± 8 mg g-1 for AMX and SMX, respectively. Considering the satisfactory comparison of these results with the performance of commercial and alternative AC produced by conventional pyrolysis, this work demonstrated the feasibility of the microwave-assisted production of environmentally and energetically sustainable waste-based AC to be applied in the efficient removal of antibiotics from water., This work is a contribution to the project WasteMAC (POCI-01-0145-FEDER-028598) funded by FCT – Fundação para a Ciência e a Tecnologia, I.P., through national funds, and the co-funding by the FEDER, within the PT2020 Partnership Agreement and Compete 2020. Thanks are also due for the financial support to CESAM (UIDB/50017/2020+UIDP/50017/2020), to FCT/MEC through national funds, and the co-funding by the FEDER, within the PT2020 Partnership Agreement and Compete 2020. Marta Otero, Vânia Calisto and Guilaine Jaria are thankful to FCT for the Investigator Program (IF/00314/2015), the Scientific Employment Stimulus (CEECIND/00007/2017) and a PhD grant (SFRH/BD/138388/2018), respectively. María V. Gil acknowledges support from a Ramón y Cajal grant (RYC-2017-21937) of the Spanish government, co-financed by the European Social Fund (ESF).

The adsorption of pharmaceutical substances using carbonaceous materials, such as activated carbon (AC), biochar (BC) and hydrochar (HC), has received substantial attention by researchers working on water treatment, due to the simplicity, low-cost and high performance of this process. In order to widen the potentiality of these carbonaceous materials and to overcome some of their limitations, particularly the inefficient separation of powdered formulations from treated water, the incorporation of magnetic nanoparticles has been explored. The recovery of magnetic carbon materials (MCM) from the treated water can be attained by applying an external magnetic field, avoiding inefficient and costly filtration and centrifugation processes, typically applied in the case of non-magnetic carbonaceous adsorbents. In the last ten years, some work has been devoted to the preparation of MCM specifically from AC (MCACM), biochar (MCBCM) and hydrochar (MCHCM). This review aims to present the different aspects of using MCM in water treatment, namely in the removal of pharmaceutical compounds. The synthesis routes used to produce MCM, their physical, morphologic and chemical features, and their application in the removal of these micro-organic contaminants from water will be assessed. The advantages and disadvantages of using MCM in water treatment, and their comparative performance with the carbonaceous non-magnetic precursors will be also discussed in this review. published

Old reinforced concrete (RC) structures often exhibit unsatisfactory performances in terms of both residual serviceability and seismic behavior. The durability requirements were not considered at all at the age of design and construction, exposing such structures to severe decay in aggressive urban and/or industrial environment; in the meantime, the use of plain steel bars (with poor bond strength) was common at the age of construction and this jeopardizes the RC performance under cyclic load reversals like those induced by earthquakes. In this paper, the deep impregnation of cement-based mortars and concrete with a solution of ethyl silicate and with electrochemical treatments by means of a solution of sodium carbonate was investigated, with a twofold aim: (1) increasing the bond strength of the embedded plain steel bars in existing structures without any need for demolition and (2) increasing the durability and safety of the reinforced concrete elements. Both the treatments are already exploited in other fields: ethyl silicate solutions are widely used for stone consolidation (and only recently proposed for concrete surface protection), while migration of sodium carbonate under DC voltage is used for RC realkalization. In the present study these treatments are expected to penetrate inside mortar and concrete and to modify their microstructure, hence improving their properties. The effects of the treatments are investigated by comparing the characteristics of treated and untreated mortar and concrete samples reinforced with plain bars, in terms of penetration inside the samples, pull-out strength, water absorption, pore size distribution, carbonation resistance and corrosion resistance.

In the present work, the efficiency of rice husk to remove Hg(II) from river waters spiked with realistic environmental concentrations of this metal (μg L(-1) range) was evaluated. The residual levels of Hg(II) obtained after the remediation process were compared with the guideline values for effluents discharges and water for human consumption, and the ecotoxicological effects using organisms of different trophic levels were assessed. The rice husk sorbent proved to be useful in decreasing Hg(II) contamination in river waters, by reducing the levels of Hg(II) to values of ca. 8.0 and 34 μg L(-1), for an Hg(II) initial concentration of 50 and 500 μg L(-1), respectively. The remediation process with rice husk biowaste was extremely efficient in river waters spiked with lower levels of Hg(II), being able to eliminate the toxicity to the exposed organisms algae Pseudokirchneriella subcapitata and rotifer Brachionus calyciflorus and ensure the total survival of Daphnia magna species. For concentrations of Hg(II) tenfold higher (500 μg L(-1)), the remediation process was not adequate in the detoxification process, still, the rice husk material was able to reduce considerably the toxicity to the bacteria Vibrio fischeri, algae P. subcapitata and rotifer B. calyciflorus, whose responses where fully inhibited during its exposure to the non-remediated river water. The use of a battery of bioassays with organisms from different trophic levels and whose sensitivity revealed to be different and dependent on the levels of Hg(II) contamination proved to be much more accurate in predicting the ecotoxicological hazard assessment of the detoxification process by means of rice husk biowaste.

Environmental contextStudying the mechanism of binding between metals and natural organic matter is fundamental to understanding the transport and availability of these contaminants in the environment. The influence of sample treatment on the purification of organic matter showed significant differences in the interaction with metals. The results will contribute to improved modelling of metal binding to organic matter in soils, thereby providing a basis for a more realistic risk assessment. AbstractWe studied the changes in metal binding characteristics of extracted humic acids induced by HF/HCl treatment followed by dialysis, i.e. the last step of the International Humic Substances Society (IHSS) extraction protocol. We performed metal binding experiments with both the alkaline-extracted material (AE) and the fully purified (FP) humic acid using the electrochemical stripping technique (AGNES) and modelled the results using the NICA-Donnan model. The results showed an increase of free Zn, Cd and Pb concentrations of similar to 1 order of magnitude for the AE compared with the FP. These differences may be mostly explained by the different carbon content (51.3% FP and 36.5% AE) associated with an AE/FP carboxyl ratio of 0.5. Simulations using the NICA-Donnan model showed that halving the amount of carboxylic groups (Q(max,1)) for the FP reduced this difference to 0.25 log units for Cd and Zn and to 0.15 log unit for Pb. There is a clear need for further research on the differences between purified v. less-disturbed natural organic material, which will contribute to improved modelling of metal binding to organic matter in soils, hence providing a basis for a more realistic risk assessment. Coordenadoria de Aperfeicoamento do Pessoal de Nivel Superior (CAPES CSF) [981313-6] Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq PVE) [400572/2013-3] French national research agency (ANR) [ANR-10-LABX-21-01/LABEX RESSOURCES 21] Portuguese national funding agency for science, research and technology [FCT-ANR/AAG-MAA/0065/2012] Region Lorraine

Six copolymers of styrenesulfonate-styrene (SS-S) of varying molecular weights were prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization and proven to give rise to micelles in aqueous solution. Three are diblock copolymers (PSS-b-PS), while the other three have a random distribution of the two monomers, probably forming a gradient (PSS-co-PS). The latter ones form micelles of smaller sizes and present lower critical micellar concentrations (CMC) than the former. The morphologic and dimensional features of the micelles were obtained by TEM analysis and their CMC were determined by fluorescence spectroscopy.The trace metal ion removal ability of these micelles was tested. Thus the complexation capacity of PSS-b-PS and PSS-co-PS micelles towards Cd and Pb was evaluated using an electro-analytical stripping technique (AGNES). Both micelles performed similarly yielding percentages of metal removal that varied between 85 and 97% and 95-99%, for Cd(II) and Pb(II) respectively. Both copolymers demonstrate a good potential for future application in metal removal from water, namely on Micellar Enhanced Ultrafiltration techniques. (C) 2016 Elsevier B.V. All rights reserved. Agence National de Recherché ANR- FCT, project N◦ 12-IS06-0001 − SPECIES: “Mesure in situ de la spéciation des métaux trace”

In this work, polyelectrolyte coatings assembled on glassy carbon/thin mercury film electrodes, as an adsorbed layer of poly(sodium 4-styrenesulfonate) (PSS), were studied. The goal was to search for the best conditions for the production of stable PSS-coated electrodes that could present high negative charge densities within the thin polymeric film, providing a fast and significant electrostatic cation accumulation. Square-wave anodic stripping voltammetry was applied to measure the amount of incorporated lead used as the reference cation. The influence of the composition of the PSS solution, the amount of deposited PSS, molecular weight and of the ionic strength of the electrolyte solution, on the features of the PSS coatings for ion-exchange voltammetry was studied. The PSS films morphology was assessed by SEM. The best PSS coating performance was found for the electrodes prepared from water solutions with a molecular weight of at least 70,000, and a mass loading of ca. 8 μg mm−2. In these conditions a three fold increase was observed in low ionic strength (0.0032 M) media. However, this improvement was not sufficient for the application of direct ion-exchange voltammetry, thus different strategies to obtain polymer films with higher charge densities have to be envisaged.

The efficiency of chitosan cross-linked with genipin (Chg) and cross-linked with genipin and grafted with caffeic acid (Ch(g+car)) to remove Hg(II) from waters was investigated. An optimal dose of 50 mg L-1 for both chitosan films was selected based on the equilibrium removal percentage and on the contact time required to attain the equilibrium. The sorption extent was dependent on the initial Hg(II) concentration (C-Hg,C-0), with removal efficiencies varying between 79% and 82% for C-Hg,C-0 = 0.05 mg L-1 and between 89% and 94% for C-Hg,C-0 = 0.50 mg L-1. Under ion competition, the Ch(g) and Ch(g+caf) films showed to be effective and selective for mercury in multimetallic solutions containing also cadmium and lead. In the case of natural river and seawaters, the mercury speciation played an important role in the overall sorption process, reducing the percentage removal of Hg. In terms of modeling, the kinetic data were well described by pseudo-first and pseudo-second order models, depending on the experimental conditions. The diffusion models suggested that the entire sorption process of Hg(II) by both Chg and Chg+caf films was essentially controlled by pore diffusion. The equilibrium data were well described by the Sips isotherm, and the estimated capacity was 2.2 and 4.0 mg g(-1) for Chg and Ch(g+caf) films, respectively. In the whole, the results showed that the sorption efficiency was improved by grafting caffeic acid to the polymeric chains of chitosan cross-linked with genipin. (C) 2016 Elsevier B.V. All rights reserved.

In this work, the performance and applicability of the thin mercury film electrode (TMFE) in the heavy metal speciation, by stripping chronopotentiometry (SCP), were exploited. The TMFE thickness was optimized and a 7.6 nm mercury film was selected. This TMFE was mechanically stable and able to perform 60 SCP consecutive measurements, with no significant variation in the analytical signal of lead(II) (RSD less than 2%). Due to the small electrode thickness the measurements were performed under conditions of complete depletion over a wide oxidation current ( I s ) range, i.e., within the interval [75–500] × 10 −9 A. The limit of detection (3 σ ) for lead(II) was 2.4 × 10 −9 M for a deposition time of 40 s and an oxidation current of 75 × 10 −9 A. The TMFE was successfully applied to the construction of SSCP experimental waves, which were in conformity to those predicted by the theory. The stability constant calculated ( K ′) for the Pb(II)-carboxylated latex nanospheres system using a TMFE, agreed with the one obtained using the HMDE, for identical experimental conditions.

Ex-situ plated Bi film electrodes (Bi-FE) have been employed, for the first time, to measure the free concentration of Pb(II) in aqueous solutions using AGNES (Absence of Gradients and Nernstian Equilibrium Stripping) with Stripping Chronopotentiometry (SCP) quantification. The amount of deposited Pbº, below a certain threshold, follows a Nernstian relationship with the applied potential. This threshold can be interpreted as the frontier of transition from surface deposition to solid (bulk) formation of Pbº. AGNES with Bi-FE yielded a very good detection limit (3σ) for Pb(II) of 6.0×10-9 M with an applied gain of 398 and a deposition time of 400 s. The ability of the Bi film electrode to perform speciation measurements was demonstrated for Pb(II)-PSS and Pb(II)-IDA systems. The measured values with the Bi-FE were in good agreement with the values obtained using the Hg film electrode and/or the values reported in the literature. The authors thank Nuno G. Alves, Ana M. Rosa da Costa, and José A. Moreira for the synthesis of polystyrenesulfonate polymer. This work is supported by Portuguese funding through Fundação para a Ciência e a Tecnologia (Grant FCTANR/AAG-MAA/0065/2012), Faculdade de Ciências e Tecnologia (Grants Pest-OE/EQB/LA0023/2013 and PEst- OE/QUI/UI4023/2014), and by the Spanish Ministry of Science (Projects CTM2012-39183 and CTM2013-48967). L.S. Rocha also thanks FCT Project FCTANR/AAG-MAA/ 0065/2012 for her grant.

The incorporation/exclusion features of dopamine (DA), ascorbic acid (AA) and uric acid (UA) are evaluated for Nafion (NA)-coated glassy carbon electrodes (GCE) of different thicknesses. The ion-exchange partition of DA(+) between the NA film and the sodium phosphate electrolyte is evaluated by determining the partition coefficient (k(D)) and the apparent diffusion coefficient (D(app)) in thick NA films which were 401 and 1.5 x 10(-9) cm(2) s(-1), respectively. The solution diffusion coefficient was found to be 6.0 x 10(-6) cm(2) s(-1). Also, the effect of NA loading and of the voltammetric timescale on DA voltammetry in the presence of excess AA is assessed, at physiologic like conditions. It is demonstrated that, although AA is excluded at the NA coating, a catalytic regeneration of DA, induced by AA, occurs at the interface NA film/electrolyte resulting from the diffusion of the o-quinone product of DA oxidation from the electrode surface to that interface. The interference of AA in the voltammetric signal of DA is eliminated using 18 microg mm(-2) NA films and v> or =0.5 V s(-1). Therefore, fast, selective and sensitive voltammetric analysis of DA at concentrations

This work aimed to produce improved polymer coatings for the modification of thin mercury film electrodes (TMFEs). The goal is to obtain sensitive, reproducible, mechanically stable and antifouling devices suitable for the determination of trace metal cations in complex media. Therefore, novel mixed coatings of two sulfonated cation-exchange polymers of dissimilar characteristics-Nafion (NA) and poly(sodium 4-styrenesulfonate) (PSS)-were produced by solvent evaporation onto glassy carbon electrodes. The effect of the mass ratio (NA:PSS) on the film morphology was studied by scanning electron microscopy, revealing the formation of biphasic polymer systems, where PSS bead-shaped clusters appeared randomly dispersed into a uniform and compact NA environment. The permselectivity/ion-exchange features of the mixed films onto glassy carbon were evaluated using cathecol, urate, and dopamine. To allow trace metal analysis, thin mercury films were plated through the NA/PSS coatings, being the reproducibility and ion-exchange features of the mixed coatings-TMFE evaluated using lead ions. The best NA/PSS coating was found for the mass ratio of 5.3. Analytical performance of the NA/PSS-TMFE yielded a detection limit of 5.5 nM (3sigma), and the application of this modified electrode to an untreated polluted estuarine water sample produced significant improvements in the quality of the signal compared with that for a bare TMFE.

A simple, rapid procedure for the determination of organic mercury in sediments, plants and fish tissues has been developed and validated. Extraction and separation of organic mercury compounds from the sample matrix was achieved by an established procedure based on an acid leaching of the sample (H2SO4/KBr/CuSO4), followed by extraction of the organic mercury halide with toluene and back-extraction with an aqueous solution of thiosulphate. Detection and quantification of mercury, in the liquid extracts, was made by atomic absorption spectrometry (AAS), following thermal decomposition of the sample. The method was evaluated using Certified Reference Material (CRM) BCR 463 (tuna fish), BCR 580 (estuarine sediment), IAEA-140TM (sea plant homogenate) and NRCC TORT-2 (lobster hepathopancreas). The recovery factors for organic mercury in all tested CRM were between 81–107%. The precision of the method has relative standard deviations of less than 10% for sediments and fish tissues and of less than 16% for plant material. The method was successfully applied to natural samples of sediments, plants, macroalgae and fish tissues collected from an estuarine ecosystem and could, therefore, be used for routine analyses.

In the present work the anodic stripping voltammetric (ASV) methodology using a thin mercury film electrode in situ plated in thiocyanate media was re-assessed in order to allow the simultaneous determination of copper and lead in seawater. Under previously suggested conditions [6], i.e. using a concentration of thiocyanate of 5mM, the ASV peaks of copper and lead overlapped due to the formation of a stable copper(I)-thiocyanate species, limiting the analytical determinations. Therefore, the best value for the thiocyanate concentration was re-evaluated: for 0.05mM a trade-off between good resolution of the copper and lead peaks and high reproducibility of the mercury film formation/removing processes was achieved. In this media, the ASV peaks for Pb and Cu occurred, separated by 140mV. Also, the in situ thin mercury film electrode was produced and removed with good repeatability, which was confirmed by the relative standard deviation values for the ASV determinations: 0.5% for Pb and 2.0% for Cu (10 replicate determinations in a solution with metal concentrations 1.5x10(-8)M for lead and 2.2x10(-8)M for copper). The optimised methodology was successfully applied to the determination of copper in the presence of lead, in certified seawater (NASS-5).

This study aimed to assess and explore the bioaccumulation capabilities of three different macroalgae species, Ulva lactuca (green), Gracilaria gracilis (red) and Fucus vesiculosus (brown), very common on temperate coasts and estuaries, for the removal of mercury (Hg) from contaminated waters (with high salinity), using environmentally realistic concentrations of metal (10–100 μg L −1 ). Levels of Hg accumulated by all seaweeds ranged between 20.8 and 208 μg g −1 , corresponding to bioconcentration factors of c.a. 2000. A comparative evaluation of bioaccumulation (living biomass) and biosorption (dried biomass) was performed for U. lactuca , which had displayed the best performance in accumulating Hg. The removal conducted by the living seaweed ( m macroalgae / V solution ≈ 500 mg L −1 ), although slower, was more promising since all Hg levels were reduced by about 99%, fulfilling the European criteria for drinking water quality. Pseudo-second-order and Elovich models described quite well the experimental data, assuming a process essentially of chemical nature. Determination of total Hg content in algal biomass over time, allowed to confirm and to follow the uptake of this metal by the living organism. Volatilization of Hg or its conversion to organo-metallic forms (0.02–0.05%) was negligible during the decontamination process. Overall, the results are a contribution for the development of an efficient and cost-effective water remediation biotechnology, based on the use of living macroalgae to promote the removal of Hg.

We report on an international proficiency test (PT) scheme for mercury (Hg) determination in soil, sediment, fish and human-hair samples (ILAE-Hg-02). For total-Hg determination, 74% of participants had a satisfactory performance (|z-score| ≤ 2), 8% had a questionable performance and 18% required action (|z-score| > 3). The best results were obtained for soil, while fish yielded the most-biased results, reflecting the analytical problems of quantifying Hg at low concentrations. Proficiency in the extraction of organometallic and available metal fractions was an important goal of the ILAE-Hg-02 and it was concluded that most laboratories are still not acquainted with the procedures for Hg fractionation; we therefore discuss their importance and highlight the need for more PT schemes dedicated to this matter, as they are an important tools in the standardization of procedures and for the development of adequate quality control/quality analysis protocols and certified reference materials.

The present study aims to establish unambiguously the conditions required for the validity of the average diffusion (D¯) approximation in fully labile systems with significant ligand size polydispersity. The average diffusion coefficient is a key parameter in mass transfer that affects signal interpretation in dynamic electroanalytical techniques. To achieve this goal, the binding of Cd(II) and Pb(II) to binary and ternary mixtures containing chemically homogenous (PSS)n-COOH polymers (ligand excess conditions were required) of different sizes (4, 10 and 30 KDa) was evaluated. It was experimentally evidenced that the average diffusion coefficient (D¯), can indeed be computed as the weighted average of several metal-polymer complexes of diverse sizes.

The technical feasibility of using stopper-derived cork as an effective biosorbent towards bivalent mercury at environmentally relevant concentrations and conditions was evaluated in this study. Only 25 mg/L of cork powder was able to achieve 94 % of mercury removal for an initial mercury concentration of 500 mu g/L. It was found that under the conditions tested, the efficiency of mercury removal expressed as equilibrium removal percentage does not depend on the amount of cork or its particle size, but is very sensitive to initial metal concentration, with higher removal efficiencies at higher initial concentrations. Ion exchange was identified as one of the mechanisms involved in the sorption of Hg onto cork in the absence of ionic competition. Under ionic competition, stopper-derived cork showed to be extremely effective and selective for mercury in binary mixtures, while in complex matrices like seawater, moderate inhibition of the sorption process was observed, attributed to a change in mercury speciation. The loadings achieved are similar to the majority of literature values found for other biosorbents and for other metals, suggesting that cork stoppers can be recycled as an effective biosorbent for water treatment. However, the most interesting result is that equilibrium data show a very rare behaviour, with the isotherm presenting an almost square convex shape to the concentration axis, with an infinite slope for an Hg concentration in solution around 25 mu g/L.

In this work, the efficiency of a local and highly, available agricultural waste, the raw rice husk, was used to remove mercury (Hg) from synthetic and natural waters, spiked with concentrations that reflect the contamination problems found in the environment. Different operating conditions were tested, including initial pH, ionic strength, the presence of co-ions (cadmium) and organic matter. The sorption efficiency of rice husk was slightly affected by the presence H+ ions (pH range between 3 and 9), but in the presence of NaNO3 and NaCl electrolytes and in binary solutions containing Cd2+ and H2+, the sorption efficiency was dependent on the nature and levels of the interfering ion and on the initial concentration of Hg+ used. Nevertheless, in a situation of equilibrium the effect of those ions was negligible and the removal efficiency ranged between 82% and 94% and between 90% and 96% for an initial Hg2+ concentration of 0.05 mg L(-1) and 0.50 mg L(-1), respectively. In more complex matrices, i.e. in the presence ofhumic substances and in natural river waters, the speciation and dynamics of Hg was changed and a fraction of the metal becomes unavailable in solution. Even then, the values obtained for Hg removal were satisfactory, i.e. between 59% and 76% and 81% and 85% for an initial concentration of Hg2+ of 0.05 and 0.50 mg L(-1), respectively.

A microporous material denoted ETS-4 was used as the decontaminant agent to treat water with a low level of Hg contamination. The effectiveness of the treatment was evaluated by assessment of the efficiency of Hg removal and ecotoxicological responses. The results showed that under highly competitive conditions the removal of Hg ranged between 58 % and 73 % depending upon the initial Hg concentration, and that Hg removal was reflected in decreased toxicity to some organisms. The ecotoxicological data indicated that the bacterium Vibrio fischeri was the least sensitive organism tested, as no toxicity was observed in either pre- or post-treatment waters. Daphnia magna was highly sensitive to Hg. Mercury removal by ETS-4 was not sufficient to completely remove the toxicity of Hg to D. magna. However, it was effective in the complete reduction of toxicity for the green alga, Pseudokirchneriella subcapitata.

In the present work the removal of mercury from aqueous solutions media and for realistic concentrations of this metal was evaluated, by using an inexpensive and highly available agricultural waste, rice husk. An economical method was developed based on the use of the natural/unmodified form of rice husk and on the amount of material required, which was minimized to produce the lowest amount of biological slurry. In order to study the kinetics of the process, batch stirred experiments were performed for initial concentrations of Hg 2+ of: 50 μg L -1 , representing the actual maximum value for Hg discharges from industrial sectors, and 500 μg L -1 , to simulate a situation of an accidental spill. The kinetic curves were described by a rapid removal of Hg 2+ by rice husk, in the first hours of contact, followed by a slower removal of Hg 2+ , until it reaches equilibrium. The removal of Hg 2+ using a rice husk dose of 0.50 g L -1 was ca. 83% for an initial concentration of 50 μg L -1 and 92% for 500 μg L -1 . Furthermore, the results show that is possible the reuse the rice husk in additional cleaning treatments, maintaining the efficiency of the removal process.

The present work explores the sorption capacity of an inexpensive and highly available agricultural waste, rice husk, to remove mercury using realistic concentrations of this metal. The efficiency of the process was evaluated for two initial Hg(II) concentrations, one representing the maximum value for Hg discharges from industrial sectors (0.05 mg L-1), and the other ten times higher. A very small amount of rice husk (0.25 and 0.50 g L-1) was able to reduce the Hg(II) levels in more than 80 % for an initial concentration of 0.05 mg L-1 and in more than 90 % for 0.50 mg L-1, corresponding to residual concentrations of Hg(II) of 0.048 and 0.009 mg L-1, respectively. The biosorvent was reused in further cleaning treatments, maintaining the efficiency and high performance. The sorption kinetics of the Hg-rice husk system is well fitted by the Elovich model and the diffusion models suggested that, depending on the initial Hg(II) concentrations, the sorption process can be controlled by intraparticle diffusion or by both film and intraparticle diffusion. The equilibrium data are well described by the linear isotherm and the distribution coefficient found was 36.1 L g-1. published

To better understand the impacts posed by soil contamination to aquatic ecosystems it is crucial to characterise the links between ecotoxicity, chemical availability and geochemical reactivity of potentially toxic elements (PTE's) in soils. We evaluated the adverse effects of water extracts obtained from soils contaminated by chemical industry and mining, using a test battery including organisms from different trophic levels (bacteria, algae and daphnids). These tests provided a quick assessment of the ecotoxicity of soils with respect to possible adverse effects on aquatic organisms although the ecotoxicological responses could be related to the solubility of PTE's only to a limited extent. The analysis of results of bioassays together with the chemical characterisation of water extracts provided additional relevant insight into the role of conductivity, pH, Al, Fe, and Mn of soil extracts on toxicity to organisms. Furthermore, an important conclusion of this study was that the toxicity of extracts to the aquatic organisms could also be related to the soil properties (pH, Org C and Fe(ox)) and to the reactivity of PTE's in soils which in fact control the soluble fraction of the contaminants. The combined assessment of ecotoxicity in water fractions, solubility and geochemical reactivity of PTE's in soils provided a more comprehensive understanding of the bioavailability of inorganic contaminants than ecotoxicological or chemical studies alone and can therefore be most useful for environmental risks assessment of contaminated soils. (C) 2011 Elsevier Ltd. All rights reserved.

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The adsorptive stripping voltammetric behaviour of trimethoprim (TMP) was studied at pH 3.8 and 7.0 by linear-sweep (LS) and cyclic voltammetry at the hanging mercury drop electrode. The charges and surface concentrations of the protonated TMP species were determined at both pH values. Taking advantage of the adsorption features of TMP fast voltammetric techniques (LS and square-wave (SW) voltammetry) were applied to the determination of TMP at the 10(-7)mol dm(-3) concentration level (pH 3.8). For these concentrations the relative standard deviations were2% (N=8) and the detection limit was 10nM (3 ng/mL) for the SW-AdCSV (3s; accumulation time 10s, frequency 100 Hz). The use of SW-adsorptive cathodic stripping voltammetry originated a very fast and sensitive method for the direct analysis of TMP in pharmaceutical suspensions without any matrix effects or interference from sulfamethoxazole. No sample pre-treatments or solvent extraction procedures were needed. The quantitative results were in agreement with the data supplied by the manufacturer.

Environmental context Electroanalytical methods have found wide application in trace metal speciation analysis in environmental systems. The need to find functional alternatives to mercury electrodes for in situ speciation studies has encouraged the use of bismuth as a solid-state electrode substrate. We demonstrate the utility of bismuth electrodes for quantitative dynamic speciation analysis. Abstract Bismuth film electrodes are employed for dynamic metal speciation analysis of PbII complexes by stripping chronopotentiometry at scanned deposition potential (SSCP). Their performance is found to be comparable to that of mercury-film electrodes. The quantitative SSCP expressions that describe the thermodynamic and kinetic complexation parameters are straightforwardly applicable to this solid electrode.

In the present work, the applicability of thin mercury film on a rotating disk electrode (TMF-RDE), to assess the free metal ion concentration by the absence of gradients and Nernstian equilibrium stripping (AGNES), is evaluated. The thickness of the mercury film and several AGNES parameters has been optimized. A nominal 16 nm film is chosen due to the higher signal (faradaic current) relative to the value of the noise (capacitive current). Due to the smaller volume to area ratio, the deposition time needed to reach a certain preconcentration factor ( Y ) is much shorter than in larger electrodes, like the HMDE. The limit of detection (3 σ ) for lead(II) is 7.4 × 10 −9 M and 7.2 × 10 −8 M for a Y of 5000 (deposition time of 150 s) and 1000 (deposition time of 100 s), respectively. A specific mathematical treatment is developed in order to subtract a corrected blank taking into account the degradation of the thin film (presumably, falling down of drops). The couple TMF-RDE/AGNES is successfully applied for speciation purposes in the systems Pb(II)–latex nanospheres and Pb(II)–IDA (iminodiacetic acid), where the stability constants calculated for both systems agree with values reported in the literature.