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This study presents the use of the modified coffee husk and coffee lignin as sorbents in the heavy metal ions sorption of Pb(II), Cd(II), Cr(III), and Cu(II) in an aqueous solution. The modification of sorbents was carried out by the impregnation method, using silver nitrate (AgNO3) and sodium borohydride (NaBH4) as a nanoparticles’ (NPs) precursor, and reducing agent, respectively. The obtained nanocomposite material was morphologically characterized by electron microscopy. In addition, an evaluation of metal ions’ sorption, pseudo-first-order, and pseudo-second-order kinetics modeling was performed. Finally, antifungal activity was evaluated on different Candida species. Coffee and lignin modified with AgNPs increased the extraction capacity with the highest sorption for Pb ions with 2.56 mg/g and 1.44 mg/g, respectively.

13 pages, 4 figures, 3 tables, supplementary data https://doi.org/10.1016/j.envpol.2022.120230.-- Data availability: Data will be made available on request, Anthropogenic pollution is considered one of the main threats to the marine environment, and there is an imperious need to assess its potential impact on ecologically and economically relevant species. This study characterises plastic ingestion and tissue levels of potentially toxic metallic elements in Nephrops norvegicus and their simultaneous levels in abiotic compartments from three locations of the Catalan coast (NW Mediterranean Sea). A multidisciplinary assessment of the health condition of N. norvegicus through condition indices, enzymatic biomarkers and histological techniques is provided, and its relationship with anthropogenic pollutant levels explored. Plastic fibres were commonly found in stomachs of N. norvegicus (85% of the individuals), with higher abundances (13 ± 21 fibres · ind−1) in specimens captured close to Barcelona. The presence of long synthetic fibres in near-bottom waters, as well as the mirroring trends in abundance among locations for water and ingested plastics, suggest that uptake from water may be occurring potentially through suspension feeding. The spatial variability in the levels of metallic elements in N. norvegicus was poorly correlated to the variability in sediments. In any case, present levels in abdominal muscle are considered safe for human consumption. Levels of ingested plastics only showed significant, yet weak, correlations with glutathione S-transferase and catalase activities. However, no other health parameter analysed showed any trend potentially associated to anthropogenic pollutant levels. Neither the condition indices nor the histopathological assessment evidenced any signs of pathologic conditions affecting N. norvegicus. Thus, it was concluded that presently there is no evidence of a negative impact of the studied pollutants on the health condition of N. norvegicus in the studied grounds, This study was supported by the Spanish Ministry of Science, Innovation and Universities project ‘PLASMAR’ (RTI 2018-094806-B-100) and by the Catalan Department of Agriculture, Livestock, Fisheries and Food (European Maritime and Fisheries Fund (EMFF)) project ‘SOMPESCA’ (ARP059/19/00003). [...] ECC benefited from an FPU PhD student grant from the Spanish Ministry of Science, Innovation and Universities (FPU16/03430). MG and PZ acknowledge financial support from the i-plastic project (JPI-Oceans—Grant PCI 2020-112059). JC and MS acknowledge their institutional support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX 2019-000928-S) and CSIC Interdisciplinary Thematic Platform (PTI+) for Sustainable Plastics towards a Circular Economy+ (PTI-SusPlast+)

Water pollution is a global problem threatening the entire biosphere and affecting the life of many millions of people [...]

Water pollution is an environmental problem that affects the ecosystem and living beings. Adsorption is one of the best technologies for the removal of heavy metals. Since waste recovery is the basis of the Circular Economy, agro-industrial waste is emerging as low-cost adsorbents for these pollutants from wastewater. Residues of pine sawdust, sunflower seed hulls and corn residues mix were evaluated as adsorbents of synthetic aqueous solutions of Ni(II), Zn(II) and Cd(II). These residues were characterized to determine their structure and composition, and to understand the adsorption mechanism. Adsorption efficiencies and capacities for the adsorbents and adsorbates were determined and compared. From the obtained results, it is possible to affirm that all biomasses used are good alternatives to the synthetic materials, with adsorption efficiencies greater than 50%. The order of adsorption was Cd > Zn > Ni. At the concentration range checked, adsorption efficiencies decreased in sawdust when a mixture of all metals together was considered (as present in real sewage). Finally, the heavy metals were immobilized, with efficiencies over 88.5%, in clay ceramics (as brick’s precursors). This procedure would help to minimize the contamination that could be generated by the disposal of spent adsorbents, rarely explored in the literature.

Many carbon materials are well-known conductive materials, widely used in the fabrication of composite electrodes. In this work, diverse allotropic forms of carbon such as graphite, MWCNTs and rGO were tested. Furthermore, these materials allow the construction of cheaper, smaller, portable, reliable and easy-to-use devices, which can be easily modified. The above-mentioned composite electrodes were developed for metal analysis in water such as Cu, Cd and Pb that, at a high concentration, can have consequences on human health. SWASV is the selected technique. It would be ideal to exploit the potential properties of mercury for metal detection by tuning the electrode's surface. Due to mercury's hazardous properties and to reduce the amount of this substance used in polarography, the use of nanoparticles is a good option due to their properties. Mercury nanoparticles were used to modify the surface of the composite electrodes to improve electroanalytical sensor response. For this reason, using these modified composite electrodes can lower detection limits and widen the linear range that can be achieved for Cd (0.05-1 mg·L−1) and Pb (0.045-1 mg·L−1). However, for Cu (0.114-1.14 mg·L−1), meaningful variations were not observed compared to the bare electrode.

We presented a strategy for enhancing the sensitivity of terahertz glucose sensing with a hydrogel platform pre-embedded with Au nanoparticles. Physiological-level glucose solutions ranging from 0 to 0.8 mg/mL were measured and the extracted absorption coefficients can be clearly distinguished compared to traditional terahertz time domain spectroscopy performed directly on aqueous solutions. Further, Isotherm models were applied to successfully describe the relationship between the absorption coefficient and the glucose concentration (R2 = 0.9977). Finally, the origin of the sensitivity enhancement was investigated and verified to be the pH change induced by the catalysis of Au nanoparticles to glucose oxidation.

Human hair natural fiber is mainly considered a waste in our society and its disposal can cause a major environmental impact. Hence, its valorization as a biosorbent of pollutants such as heavy metals is an interesting route to explore since it can reduce the amount of waste and at the same time contributes to the circular economy strategy. In this work, the ability of two kinds of human hairs, used as biosorbents to remove Cr(III), Ni(II), Co(II), Mn(II), Cu(II), Zn(II), Cd(II) and Pb(II) ions from multiple-metal aqueous solutions, were examined and compared under different operating conditions. The influence of the time, pH and initial metal concentration on the metal uptake were studied. The biosorption kinetics and isotherm were also modeled observing that pseudo-second-order kinetic model and Langmuir model fitted successfully experimental data. Moreover, biosorption process did not significantly modify the morphology and the chemical structure of the hair samples, which was proved by SEM and FT-IR studies. These kinetic results underline the satisfactory capacity of human hair for the biosorption of Pb(II), Cu(II) and Cr(II) (values up to 95%), pointing up the high efficacy of human hair for the removal of heavy metal ions from aqueous media This work was financially supported by the CTM2012-30970 and CTM2015-65414-C2-1-R Spanish research projects and by the European project ORQUE-SUDOE SOE3-P2-F591. Helan Zhang thanks to the China Scholarship Council for the grant [2001]3005. The authors are grateful to the UAB Microscopy Service for the SEM analysis and the Service of Analytical Chemistry for the analysis of FTIR. Also, authors are grateful to M. Resina who helped performing the analysis of heavy metals by ICP-MS

Cytotoxic, chemical, biochemical, compositional, and morphometric responses were analyzed against heavy metal exposure in Ochrobactrum anthropi DE2010, an heterotrophic bacterium isolated from Ebro Delta microbial mats (Tarragona, NE Spain). Several parameters of effect and exposure were evaluated to determine tolerance to a range of cadmium (Cd), lead (Pb(II)), copper (Cu(II)), chromium (Cr(III)), and zinc (Zn) concentrations. Additionally, removal efficiency, polyphosphate production and metal localization patterns were also analyzed. O. anthropi DE2010 showed high resistance to the tested metals, supporting concentrations of up to 20 mM for Zn and 10 mM for the rest of the elements. The bacterium also demonstrated a high removal capacity of metals—up to 90 % and 40 % for Pb(II) and Cr(III), respectively. Moreover, polyphosphate production was strongly correlated with heavy metal concentration, and three clear cell localization patterns of metals were evidenced using compositional and imaging techniques: (i) extracellular in polyphosphate granules for Cu(II); (ii) in periplasmic space forming crystals with phosphorus for Pb(II); and (iii) intracytoplasmic in polyphosphate inclusions for Pb(II), Cr(III), and Zn. The high resistance and metal sequestration capacity of O. anthropi DE2010 both highlight its great potential for bioremediation strategies, especially in Pb and Cr polluted areas.

Human hair is considered a ubiquitous waste product and its accumulation can cause environmental problems. Hence, the search for alternatives that take advantage of this waste as a new raw material is of interest, and contributes to the idea of the circular economy. In this study, chemically modified human hair was used as a low cost biosorbent for the removal of heavy metal ions from aqueous solutions. The effect of the contact time, the pH, and the biosorbent concentration on the biosorption process were investigated. Kinetic modeling indicated that the pseudo-second order kinetic equation fitted well with R2 &gt, 0.999. Furthermore, the equilibrium data fitted the Langmuir adsorption isotherm at 295 K resulting in saturation concentrations of 9.47 &times, 10&minus, 5, 5.57 &times, 5, 3.77 &times, 5, and 3.61 &times, 5 mol/g for the sorption of Cr(III), Cu(II), Cd(II), and Pb(II), respectively. The biosorption process did not change the chemical structure and morphology of the hair, which was shown by FTIR and SEM. In addition, desorption experiments prove that 0.1 mol/L EDTA solution is an efficient eluent for the recovery of Pb(II) from the treated human hair. To summarize, treated human hair showed satisfactory biosorption capacity and can be considered as an effective biosorbent for the treatment of water with a low concentration of heavy metal ions.

This article reports a novel electrochemical recognition platform based on a nanocomposite carbon paste electrode containing carbon nanotubes modified with gold nanoparticles carrying a thiolated catechol for the fast amperometric determination of uranyl ion (UO22+) in water. Recognition of UO22+ is accomplished by supramolecular chemistry due to the formation of an inclusion complex between catechol and UO22+. The amperometric device operates at –0.40 V vs. Ag/AgCl, where the reduction of UO22+ takes place on the electrode surface, covering a linear range from 0.49 to 170 μg L−1 UO22+ in a 0.1 M boric acid buffer solution at pH 5.3. The developed sensing system presents good response towards UO22+ in aqueous environmental samples, with good selectivity over other browsed cations and can be easily reset by simple polishing. This platform has demonstrated to be a potential alternative regarding to the common standard bench-top analytical techniques for the development of in-field devices for in-situ monitoring., This work was supported by the Spanish project CTQ2012-36165 and CTQ2013-41161-R. Authors also want to thank the support of the Generalitat de Catalunya to GSB (2014-SGR-837), MERS (2014-SGR-1356) and GTS (2014-SGR-1152). Real samples from mine wells rich in uranyl ion were kindly supplied by Berkeley Energia and Consejo de Seguridad Nuclear (National Security Council, CSN-2015). Dr. J. Muñoz gratefully acknowledges the “Juan de la Cierva” programme.

The incorporation of nanomaterials on (bio)sensors based on composite materials has led to important advances in analytical chemistry field due to the extraordinary properties that these materials offer. Nanodiamonds (NDs) are a novel type of material that has raised much attention, as they have the possibility of being produced on large scale by using relatively inexpensive synthetic methodologies. Moreover, NDs present some other interesting features as suitability for fluorescence due to surface functionalization and a proved biocompatibility, which makes them well suited for biomedical applications. In addition, NDs can be modified with metallic nanoparticles (NP), such as silver or gold, in order to combine the special features of both. The aim of this research work is the nanostructuration of novel sensing devices using NDs combined with silver (Ag@NDs) and gold (Au@NDs) nanoparticles. A complete morphological and electrochemical characterization as function of the prepared nanocomposite composition have been performed in order to improve the electroanalytical properties of the developed (bio)sensors.

Three different types of feedstocks and their biochars were used to remove Cr(III), Cd(II), Cu(II) and Pb(II) ions from a mixture of multiple heavy metals. The effect of the initial concentration of heavy metals in solution has been analysed, and kinetics modelling and a comparison of the adsorption capacity of such materials have been performed to elucidate the possible adsorption mechanisms. The results show that the adsorption capacity is dependent on the type of feedstock and on the pyrolysis conditions. The adsorption capacity of the biomass types is ranked as follows: FO (from sewage sludge)>> LO > ZO (both from agriculture biomass waste)>> CO (from wood biomass waste). Biochars, which are the product of the pyrolysis of feedstocks, clearly improve the adsorption efficiency in the case of those derived from wood and agricultural biomasses. Complexation and cation exchange have been found to be the two main adsorption mechanisms in systems containing multiple heavy metals, with cation exchange being the most significant. The pore structure of biomass/biochar cannot be neglected when investigating the adsorption mechanism of each material. All the disposal biomasses presented here are good alternatives for heavy metal removal from wastewaters.

Pine biomass (Pine), pine gasification biochar (PG) and pine biomass loaded with TiO2 (Pine/TiO2) were used as sorbent materials to remove Cr(III) or Cr(VI) ions from aqueous solutions. Our results showed that Pine/TiO2 had an improved adsorption capacity respect to Pine being the adsorption capacity for Cr(VI), 12.8 mg/g, much larger than for Cr(III), 1.23 mg/g. On the other hand, PG showed much higher adsorption for Cr(III), 12.4 mg/g, than Pine/TiO2, and negligible adsorption for Cr(VI). To understand this species-dependent adsorption behavior, the adsorption mechanisms, sorbents morphology and functional sites were characterized using a multi-technique approach. The chemical state and local coordination structure of the adsorbed Cr species was studied by X-ray absorption spectroscopy (XAS). Our results show that the adsorption of Cr(III) occurred mainly through cation exchange with mineral elements in PG biochar, whereas the Cr(III) adsorption by functional groups (carboxyl and hydroxyl groups) dominate in the biomass sorbent. The enhancement of Cr(VI) adsorption in Pine/TiO2 can be explained by the presence of TiOH2+groups present in the surface of the TiO2 microparticles. X-ray absorption spectroscopy (XAS) results reveal that Cr(VI) reduces to Cr(III) after being adsorbed by the sorbent materials.

Four low-cost iron-bearing geo-adsorbents were tested for As(V) removal without pretreatment: Montanit300® (M), diatomite (D), pumice (P) and black sand (BS). The solids were carefully characterized by different analytical techniques (SEM-EDX, TPD-pyridine, N2 Physisorption, XRD and point of zero charge). The adsorption of As(V) was evaluated through isotherms and kinetic studies (bottled water matrix, pH0=8,25 g/L of solids), and experiments addressing pH effect (pH0=3.6,7.5,11) and the presence of interfering anions (Cl−, SO42−, NO3−, PO43−). Experimental results were fitted to the Freundlich and Langmuir sorption isotherms. Under the employed conditions, P showed negligible adsorption, M and D presented adsorption capacities around 0.02 mg/g and, in spite its lower surface area, BS displayed the highest value (0.045 mg/g), which relates to a higher density of Fe species, M and D samples were easily regenerated (80%–100% desorption) through a basic treatment (0.01 M NaOH) and presented fast adsorption kinetics (1 h for D and seconds for M). BS showed a slow adsorption kinetic (24 h) and poor regeneration (only 50% desorption). Sample M (natural zeolite) resulted a promising option due to its remarkably fast adsorption kinetic, easy regeneration and adsorption capacity suitable for systems with relatively low As concentrations. Fil: Inchaurrondo, Natalia Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentina Fil: Di Luca, Carla. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentina Fil: Haure, Patricia Monica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentina Fil: Zerjav, Gregor. Department For Environmental Sciences And Engineering; Eslovenia Fil: Pintar, Albin. Department For Environmental Sciences And Engineering; Eslovenia Fil: Palet, Cristina. Universidad Autónoma de Barcelona; España

International audience; In order to assess the effect of mixed pollutants, the influence of different concentration levels of a mixture of metals (Cr, Co, Pb, Mn, Ni, Cu, Zn) on the biodegradation of some PAHs (phenanthrene, fluoranthene, pyrene, benzo[b]fluoranthene and benzo[a]pyrene) in soil samples was evaluated. To do so, groups of microcosms of a natural soil from the region of Sabadell (Barcelona, Spain) were prepared as a reproduction of the native environment at laboratory scale, under controlled conditions. Mixtures of PAHs and metals were carefully selected, according to soil characterization and microbiological growth preliminary assays, and were added to microcosms. These microcosms were analyzed at various times, along two months, to obtain PAHs dissipation time-courses. A first-order kinetic modelling allowed obtaining different rate constants and DT50 values as a function of the metal levels introduced in microcosms. As a general observation, the higher the concentration of metals, the lower the biodegradation of PAHs of 3–4 rings (phenanthrene, fluoranthene and pyrene). On the other hand, no important effect on the biodegradation of higher molecular weight PAHs (benzo[b]fluoranthene and benzo[a]pyrene) was observed at the different concentration levels of metals tested.

The present study describes the pre-concentration of Uranium (VI) from nitric acid solutions (0.100 mg/L) by using bulk liquid membrane (BLM) and supported liquid membrane (SLM) systems. The transport of Uranium (VI) through both membrane systems was studied using low concentration of bis(2-ethyl hexyl) phosphoric acid (D2EHPA) as carrier in kerosene solvent which favors the removal of Uranium (VI) traces (0.001 or 0.004 mol/L). The stripping used was a mixture of phosphoric acid and citric acid, with concentrations ranging from 0.150 mol/L up to around 0.600 mol/L, which improves the removal of the Uranium (VI). In the case of SLM, the polymeric supports used were homemade Polysulfone membranes (PSf) and commercial Polyvinylidene Fluoride membranes from Millipore (PVDF). The kinetics of the uranyl ion transport system was studied for up to 24 h under fixed physical and chemical conditions. Maximum extraction values obtained were above 95%, and recovery yields were in the range 57–79% for the BLM and 90% for the SLM. Pre-concentration systems in both kinds of membrane systems are properly demonstrated and presented in this paper.

The objective of this study was the development and optimization of a method for the liquid–liquid extraction and recovery of Uranium (VI) traces (0.10 mg/L). A comparison was made of three different extracting agents at 0.10 mol/L: tri-n-butyl phosphate, methyltrioctylammonium chloride, and bis(2-ethylhexyl) phosphoric acid. As the optimized chemical conditions of the liquid–liquid systems are very important for the future applications for the extraction, recovery and pre-concentration of Uranium (VI) traces, whether in bulk liquid membranes or in supported liquid membranes systems, a response surface methodology was adopted. A Doehlert design is used to obtain a quadratic function relationship between the percentage of recovery of uranyl ion and the amount of bis(2-ethylhexyl) phosphoric acid in kerosene, as extracting agent (0.001–0.050 mol/L) and that of phosphoric (0.192–0.718 mol/L) and citric (0.206–0.698 mol/L) acids, mixed as recovery agents. From the results, the most important effects on the recovery are the concentration of bis(2-ethylhexyl) phosphoric acid in the organic phase and the concentration of phosphoric acid in the stripping solution, while the concentration of citric acid only favors the extraction of Uranium (VI) when the other compounds are at opposite levels of concentration. From the mathematical model, optimal conditions for the back-extraction of Uranium (VI) were found with predicted recoveries of 99%, which were later corroborated experimentally.

This paper describes a comparative study of activated composite (ACM) and hybrid membranes (HM), both incorporating the commercial anion exchanger Aliquat 336 as a carrier, for the transport of Pt(IV) ions in chloride media. The incorporation of the carrier molecules in the polymeric network of both types of membranes is one of the approaches to overcome supported liquid membrane (SLM) instability. ACM are membranes with a bilayer structure: a porous lower polymeric support prepared by phase inversion (polysulfone) and a dense upper layer made by interfacial polymerisation (polyamide). HM are plasticized membranes consisting of a polymeric matrix of cellulose triacetate with a plasticizer and modified by the incorporation of an inorganic material (silanes) prepared by a sol–gel route. The efficiency of both types of membrane for the transport of Pt(IV) ions has been investigated, and several parameters affecting metal transport have been evaluated, such as the composition of the stripping phase and the selectivity of the membranes in the presence of Pd(II) ions. Moreover, comparative studies for both ACM and HM systems have been made by contacting the same feed solution in a triple-compartment cell. Finally, the results of these membrane systems are compared with those previously reported using polymer inclusion membranes (PIM) and SLM for the transport of Pt(IV) under similar experimental conditions.

The industrial manufacture of membranes is well established at the present time. More than any other process, the production of ultrafiltration membranes by immersion or evaporation (phase inversion) precipitation techniques is one of the most common. In many cases, the macroscopic properties of the membranes are similar from one membrane to another and it is impossible to distinguish them, while they differ notably from the microscopic point of view. The aim of this work is to develop a method for the classification of polysulfone ultrafiltration membranes prepared either by immersion or evaporation. It also presents a classification of those membranes by thickness. For these purposes, near infrared spectroscopy (NIR) combined with chemometric techniques are attempted here for the first time in the area of membrane research. The NIR technique permits fast analytical measurement of membrane samples, together with the possibility of characterization in on-line mode, without destruction or invasion of the samples. This appears to be an excellent routine analysis for purposes of membrane classification. The membranes were prepared in our Universitat Autonoma de Barcelona (UAB) laboratory and, after obtaining the NIR spectra, principal component analysis (PCA) was used to describe the system. The second stage involved the application of a pattern recognition method: supervised independent modeling of class analogy (SIMCA) in order to classify unknown samples. Finally, the ultrafiltration membranes were classified in terms of the membrane preparation technique (immersion or evaporation). In addition, membranes prepared by immersion were classified by thickness.

The target of agricultural biomass waste recovery from hydrolysis treatment is presented by comparing the performance of two different types of enzymatic polymeric membranes that were previously developed and characterized, based on a polysulfone derivative or monolithic polymers. Our aim was to achieve in one single step both enzymatic catalyzed hydrolysis of the xylan polysaccharide and the separation of the released products for the recovery of the short chain xylooligosaccharides. We present the behaviour of two different membrane modules operating in different procedure settings. The possible reuse of the membranes has also been evaluated. Xylooligosaccharides products have been characterized using Matrix Assisted Laser Desorption Ionization-Time of Flight-Mass Spectrometry (MALDI-TOF-MS). The application of such enzymatic membranes enables the recovery of short chain xylooligosaccharides from biomass waste treatment, which has many potential applications in the food and pharmaceutical industries as well in the production of renewable energy.

A macrovoid structure is formed in polysulfone (PSf) polymeric membranes prepared by the immersion technique using N-dimethylformamide (DMF)/water as a solvent/non-solvent pair. It is actually important controlling the macrovoid formation process, because macrovoids can cause unwanted mechanical failure during high-pressure applications. In order to control the formation of these structures, the influence of different parameters like membrane thickness, solvent additives (isopropyl myristate, IPM or N-hexadecyl- l -hydroxypriline, HHP), temperature of the coagulation bath, and solvent/non-solvent pair has been studied for chiral activated membranes. With the same purpose, corresponding membranes where physically characterized by scanning electron microscopy (SEM) measurements of their cross-section images. Those SEM images have been treated by the software IFME®, which provides the parameters of asymmetry and irregularity of the membranes. The surface of the membranes has been analyzed by atomic force microscopy (AFM) and brightness analysis in order to calculate their roughness. A comparison of the same PSf membranes, but prepared by evaporation precipitation, or by using chloroform/methanol as solvent/non-solvent pair during the immersion precipitation step, has been also checked. That paper helps us to understand and predict which will be the best conditions to prepare the optimum membranes.

We report on a new enzyme/support system to immobilize proteins such as enzymes through a covalent bond on polysulfone membranes. In the present case the enzyme endo-1,4-β-xylanase (E.C.3.2.1.8) is attached to polysulfone previously derivatized by introducing an acrylate group. Membranes are properly prepared from this polysulfone acrylate. Afterwards the enzyme is immobilized though the amino groups of side chains of the amino acids of the enzyme and the acrylate group of the derivatized polysulfone. Such immobilization of the enzyme is confirmed by microelemental analysis as well as by amino acid analysis by HPLC. Moreover, the enzymatic activity of the membranes was evaluated and compared with that corresponding to the free enzyme. Certain physical parameters (asymmetry, irregularity, pore size and surface roughness) of the corresponding enzymatic membranes were obtained from SEM and AFM image interpretation.

The characterization of new synthesized chiral polymeric membranes, based in polysulfone polymer is here reported. Polysulfone was derivatized to chiral polysulfone, by bonding covalently the chiral carrier, N-dodecyl-4(R)-hydroxy- l -proline, to the polymer matrix. Two different chiral polysulfones, referred to as CPSA and CPSB, have been synthesized and used in the preparation of chiral polymeric membranes. However, as a consequence of the limited CPSB solubility, only CPSA resulted adequate to obtain useful membranes. Therefore, various chiral polysulfone membranes containing different amounts of CPSA in unmodified polysulfone (PS) were prepared and properly characterized by scanning electron microscopy (SEM) and by enantioselective transport experiments of racemic propranolol. Dialysis transport experiments allowed us to determine the influence of the carrier content in the membrane on the transport rate and on enantiomer separation. Membranes containing a CPSA/PS ratio of 1:3 showed an alpha value of 1.1 at 96 h of performance. Modelling of the propranolol transport rate is also performed.

Activated composite membranes (ACMs) containing the chiral carrier N-hexadecyl-l-hydroxyproline have been characterized by scanning electron microscopy (SEM). SEM membrane images have been further ...

In this work, chiral activated membranes have been tested for the enantioseparation of the racemic drug propranolol. Polysulfone (PS)‐based membranes have been prepared for this purpose, using N‐he...

A supported liquid membrane (SLM) containing the chiral selector N‐hexadecyl‐L‐hydroxyproline (HHP) was characterized for the enantioseparation of a β‐blocking drug. SR‐propranolol was the target racemic mixture to be resolved by the membrane separation system. The different affinity shown by the selected carrier, HHP, for the two propranolol enantiomers produced a discrimination of their transport through this SLM. We investigated the influence of various chemical parameters involved in that system, such as the acidity of feed and receiving phases, as well as the carrier concentration in the membrane. Valuable knowledge on the transport mechanisms within this system was thus attained.

Dense (homogeneous) membranes were prepared from poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) by using 1,1,2-trichloroethylene as a solvent at 25, 35, 45, 55 and 65 °C evaporation temperature. The effect of temperature used for evaporation of solvent on the characteristics of the membrane was studied by using electron spin resonance, atomic force microscopy and gas permeation rate. The ESR signal from the spin probe in the membrane, the membrane surface morphology and the gas permeation through the membrane were all affected by evaporation temperature. The membrane becomes denser according to the ESR study; the surface becomes rough according to atomic force microscopy and, the permeation of CO 2 , CH 4 , O 2 and N 2 decreases according to gas permeation experiments as the evaporation temperature increases. However, no significant change was observed on the permeability ratio for gas pairs CO 2 /CH 4 and O 2 /N 2 . A possible mechanism has been discussed.

The metal ion affinity concept is used to effect facilitated and selective transport of amino acids through liquid membranes. A palladium organometallic complex, trans-benzyl chloride bis-triphenylphosphinepalladium(II) [BPP-Pd(II)], has been checked for various amino acids, i.e. glycine (Gly), alanine (Ala), valine (Val), leucine (Leu), methionine (Met), histidine (His), phenylalanine (Phe), tyrosine (Tyr), and tryptophan (Trp). The interaction of the different amino acids with the membrane and the carrier has been evaluated in terms of their lipophilicity and polarity. Their liquid-liquid distribution in a solvent containing the palladium organometallic complex correlate with such amino acid properties, except in the case of Phe and Trp which show an interaction exceeding that predicted because of their aromatic structure. The behavior of the amino acids in liquid-liquid distribution can be used to predict their transport through supported liquid membranes (SLM) containing the same carrier. The greater the distribution in the liquid-liquid system, the higher the flux in SLM.

Activated composite membranes (ACM) containing bis-(2-ethyl-hexyl) phosphoric acid (DEHPA) have been found to facilitate the transport and separation of aromatic amino acids. The ACM, prepared according to a previously established procedure, were used to experimentally determine their behavior for the transport of phenylalanine (Phe), that was used as target amino acid. A general characterization of the Phe transport through DEHPA-ACM membranes including: the existence of facilitated counter transport, reproducibility and the effect of buffering the feed solution has been performed prior to a systematic study of the influence of some chemical transport parameters. In this concern, the initial Phe concentration, the nature and concentration of the stripping agent and the pH of the feed solution have been optimized (the feed phase was 0.5 mM of Phe in a 2 M NaCl solution at pH 3 and a 2 M HCl solution was used as stripping phase). Also, the influence of the DEHPA concentration in the casting solution used to prepare the membrane is established. It is found that the membrane phase controls the rate transport up to a DEHPA concentration of 1200 mM. Finally, although the affinity of the aromatic amino acids phenylalanine, tryptophan (Trp) and tyrosine (Tyr) for DEHPA is in the order Phe>Trp>Tyr, the selectivity of the DEHPA-ACM was found to be Trp>Phe>Tyr.

A new supported liquid membrane system based on a palladium carrier (trans-benzylchloride bis-triphenylfosfine palladium(II) (BPP-Pd (II))) for the transport and pre-concentration of amino acids has been characterised. The amino acid tryptophan (Trp) has been used as a target for the membrane transport. The affinity of the anionic form of Trp for the metallic centre (Pd(II)) is the power that maintains the extraction of the amino acids. The lower pH in the receiving phase changes the speciation of the amino acid leading to its release in the receiving phase. Various parameters that characterise the Trp transport by this liquid membrane have been studied, i.e. carrier concentration, stripping agent, concentration of the stripping agent, pH in the donor phase and pre-concentration time. A valuable pre-concentration factor of 45 was achieved with an initial Trp concentration of 0.1 mM at pH 9 of the donor solution and after 40 h of running the transport experiment.

This paper describes an approach to the chemical characterisation of the facilitated transport of lead(II) and cadmium(II) by an activated composite membrane (ACM) containing immobilised di-(2-ethyl-hexyl)phosphoric acid (DEHPA). Such membranes were prepared, by interfacial polymerisation and characterised physically and chemically. The ACMs were used to experimentally determine their transport behaviour for Pb(II) and Cd(II). So, the influence of some chemical parameters (i.e. DEHPA concentration on the ACM, the feed solution composition, the concentration of nitric acid in the stripping solution, and the ionic strength of the feed and stripping aqueous solutions) was assayed for each metal ion. A correlation of the chemical behaviour of those ACM systems with the physical characterisation of those membranes, prior to and after their use, is reported. The optimum chemical conditions for Pb(II) and Cd(II) transport enhance the lifetime of the ACMs, giving higher DEHPA immobilisation on the polymeric phase of the composite membrane.

The immobilized metal affinity chromatography (IMAC) technique principles applied to the facilitated transport of anions across liquid membranes (LM) is shown. Two approaches have been developed for preparing the LM carrier: either the formation of a metallic complex, by the appropriate metal extraction, or the use of a commercial water insoluble organometallic complex. The characteristics of such a metallic complex to transport anions, being stable enough to avoid the leaching of the metal, are established. Once the metallic complex was prepared, it was used as carrier for anions in the corresponding LM (by the interactions of the anions with this specific metal properly immobilised). Pd(II) metal complexes in organic diluent have been studied for the transport of NO2− as specific target system for LM. For this purpose, different types of reagents were used as Pd(II) extractants to get the proper immobilisation of this metal and thus, to accomplish for the best transport of NO2−. Among them, tri-isobutylfosfine sulphide (Cyanex 471) was found to provide best characteristics as anion carrier for the organic Pd(II)–Cyanex 471 complex. On the other hand, the organometallic complex trans-benzylchloride bis-triphenylfosfine palladium(II) (BPP–Pd(II)) has been studied as nitrite carrier, providing a higher rate of transport than the Pd(II) extracted complex. Different parameters have been investigated to contribute to NO2− transport, including the nature of stripping solutions, pH of feed solution and membrane modifiers. Selectivity of the liquid membrane transport has been also determined as well as the influence of membrane modifiers in the selectivity of anion transport. The results have been compared to the behaviour of the BPP–Pd(II) complex as ISE carrier for anions.

A solvent impregnated hollow fibre (SIHF) module has been developed for the preconcentration of lead by using bis(2-ethylhexyl) phosphoric acid (DEHPA) dissolved in kerosene as extractant. The module has been designed for an on-line determination of trace amounts of lead(II) at mg l −1 (ppm) level by flame atomic absorption spectrometry (FAAS). The SIHF system is based on the metal liquid–liquid distribution between aqueous solutions of different acidity and the mentioned organic solution. The highest enrichment factor of Pb(II) was determined at pH=4.0 using a formic acid/formiate buffer solution. Preconcentration experiments were carried out at low lead(II) concentration (mg l −1 level) by using the SIHF module. This study includes the influence of hydrodynamic and chemical conditions on the loading and elution of Pb(II) on the SIHF, i.e., flow rate through the fibres, acidity of the eluent (as nitric acid concentration) and the chemical nature of the acid used in the elution. Breakthrough curves were determined for different sampling flow rates, 0.54 ml min −1 was selected to minimise the loading volume of Pb(II) sample. 0.1 M nitric acid was chosen as eluent solution, and perchloric acid also shows appropriate elution characteristics. The degree of concentration obtained for Pb(II) are of 10 fold the original concentration. The quantification limit for Pb(II) achieved with this preconcentration system is 0.17 mg l −1 . The results obtained indicate that the SIHF system can be applied for on-line determination of trace amounts of lead(II) by FAAS.

A method for the determination of the total metal ion concentration in samples of unknown composition after separation on a chelating resin was applied to the determination of aluminium(III) concentration in real freshwater samples, using Chelex 100 as a sorbing resin. The method, called chelating resin titration, was previously tested on synthetic samples, and allows also the evaluation of the side reaction coefficient [αM(I)] of the metal ion in the presence of the resin, which is useful for the study of metal speciation. To obtain this information, the sorption equilibria of aluminium(III) on Chelex 100 under the experimental conditions must be exactly known. These equilibria were investigated according to a previously reported method, based on the determination of the sorption curves of aluminium on Chelex 100 from solutions of known composition, sometimes containing chelating substances. It was found that the sorption of aluminium on Chelex 100 takes place by formation of three species, AlL, AlL(OH) and Al(OH)3. The corresponding exchange coefficients were determined. Despite the fact that Chelex 100 sorbs aluminium(III) strongly, it was found that the sorption from fresh waters was not quantitative, which was ascribed to the strong complexation of aluminium in the samples considered. The values of αM(I) of aluminium in some freshwater samples at natural pH and acidified up to pH 3 were determined. They were found to be much higher than those ascribable to hydrolysis or to inorganic and organic ligands present in natural waters, being for instance 1012.1 at pH 7.48 and 107.5 at pH 4.88. A similar determination carried out in a 10–3 mol kg–1 sodium chloride solution containing a known amount of aluminium at pH ≈ 8 gave log αM(I) = 14, completely ascribable to hydrolysis, showing that an accurate evaluation can be obtained by the proposed method.

Separation membranes systems for the trans-port of Pt(IV) and Pd(II) from aqueous feedchloride solutions have been developed andcharacterised by using tricaprilylmethylammo-nium chloride, Aliquat 336, as carrier. Thisextracting agent has previously demonstratedits effectiveness to transport Pt(IV) and Pd(II)across SLM [1]. Activated composite membranes (ACM) andhybrid membranes (HM) have been developedwith the main purpose of improving SLMsphysical and chemical properties, to get itsdiffusion facilities but with major chemical andphysical stability. These are metals of high interest due totheir extensive anthropogenic uses such as inautomotive catalysts, as catalysts in thesynthesis of pharmaceuticals as well as injewellery. The large demand of these metalsnext to their high prices has lead to a furtherimpetus for techniques to allow its separationand recovery.

The complex formation between Se(IV) and Na(DDTC) has been exploited to carry out the transport of selenite through an SSLM. The differences of solubilities of the related complex in aqueous and in organic kerosene solution along with the additional effect of H 2 O 2 have provided the conditions for such transport. In this case, the study reveals that transport of selenite is effectively facilitated by DDTC. It has been determined that the concentration of HCl in the stripping solution has an optimum value around 2.0 M. The presence of H 2 O 2 in the stripping solution is necessary to accomplish the mass transfer of selenite. The role of this reagent has been investigated. The transport has shown to be selective for Se(IV) and Cu 2+ in the presence of Mg 2+ , Fe 3+ and Ca 2+

A hollow fiber supported liquid membrane (HFSLM) system for the separation and concentration of vanadium (V) has been developed and characterized by using tricaprylylmethylammonium chloride (Aliquat 336®) dissolved in dodecane as carrier. The transport of vanadium through the liquid membrane is based on a pH gradient between feed and stripping solutions to provide an appropriate change on the chemical species of aqueous vanadate, i.e., aqueous metavanadate, VO2(OH)2−1 (4.0 8.0) is not extracted. Selective separation and concentration experiments were carried out at low vanadium(V) concentration (mg 1−1 level). The study of the HFSLM includes the influence of hydrodynamic, physical and chemical conditions, i.e., flow rate of feed solution through the fibers, number and length of fibers, lifetime of the system, initial vanadium concentration in the feed solution, and pH of aqueous phases. Transport of V(V) increases with the flow rate of the feed solution through the fibers until a ‘plateau’ is reached (> 0.2 ml min−1 in a single fiber). It has been shown that in a HFSLM module, the membrane area increases with the number of fibers but also there is an increase of the sterical hindrance between the fibers which reduces the expected increase of vanadium transport. On the other hand, the length of the fibers has a scarce influence on the transport process. The effect of the acidity of the feed solution on the vanadium transport shows a similar behavior to that obtained previously for liquid-liquid distribution and laminar SLM studies. The results obtained indicate that vanadium(V) can be effectively concentrated and selectively separated by hollow fiber SLM containing Aliquat 336® as carrier.

A synthetic receptor that can discriminate dicarboxylic acids based on host-guest principles has been prepared. This compound incorporates two amidopyridine units as hydrogen-bonding centers that are capable of binding the carboxylic acid functional group. The receptor was dissolved in a kerosene/dodecanol mixture and used as a carrier in supported liquid membranes. Facilitated transport based on the liquid-liquid distribution of dicarboxylic acids between aqueous feed and stripping solutions and an organic phase containing the carrier was accomplished. This transport was driven by a pH gradient that assures the predominance of the protonated neutral form of the carboxylic acids in the feed solution and the corresponding deprotonated form in the stripping solution. Selective transport of dicarboxylic acids was observed allowing for an efficient separation of different carboxylic acids.

Hydroxylated polycyclic aromatic hydrocarbons (OH-PAHs), a group of metabolites produced during the biodegradation of PAHs by microorganisms, are known to be difficult to analyze from complex environmental or biological matrices. In the field of contaminated soils, where OH-PAHs are less studied, a new method was compared to a common method for the analysis of monohydroxylated PAH metabolites: 2-naphthol, 2-hydroxyfluorene, 9-phenanthrol and 1-hydroxypyrene. After optimizing the microwave assisted extraction (MAE) step, the obtained extracts, containing the OH-PAHs together with the corresponding PAHs, were purified by molecularly imprinted polymers (MIPs). MIPs showed an effective selectivity for the hydroxylated derivatives studied (and not for native PAHs), which allowed their identification and quantification by HPLC/FLD. By this method, good limits of detection (0.003–0.014 μg g−1) and limits of quantification (0.010–0.044 μg g−1) were achieved. On the other hand, following the common method, the sample extract was concentrated by evaporation, silylated, and analyzed by GC/MS. The new method was more sensitive for all OH-PAHs and the analysis showed fewer matrix effects due to the use of MIP clean-up. In the present work the advantages and disadvantages of the new method are shown, as well as the possible application to soil biodegradation studies.

A liquid membrane system for vanadium transport has been designed by using tricaprylylmethylammonium chloride (Aliquat 336®) dissolved in isopropylbenzene (cumene) or dodecane as carrier. The work has been undertaken by first determining the liquid-liquid distribution of vanadium(V) between aqueous solutions of different acidity and an organic solution containing the carrier. Optimum conditions for both extraction (4 Transport experiments were carried out at low vanadium(V) concentration (ppm level). The study of the liquid membrane included the influence of hydrodynamic and chemical conditions, i.e., stirring speed, organic solvent, carrier concentration, ionic strength and pH of the aqueous phases. Dodecane membranes provided higher transport of vanadium(V) than cumene membranes. Dodecanol, ranging from 0 to 10% (v/v), was added to the dodecane solution of Aliquat 336® to enhance its solubility. The effect of acidity of the feed solution on vanadium transport showed a similar behaviour to that obtained for the liquid-liquid distribution studies. On the contrary, selectivity properties of the liquid membrane showed clear differences with the corresponding data of solvent extraction, i.e., molybdate extracted by Aliquat 336® was not transported through the liquid membrane. The results obtained in both batch distribution experiments and dynamic membrane transport indicated that vanadium(V) was extracted by means of metavanadate chemical species.

Supported liquid membranes (SLMs) have demonstrated all along the years every high selectivity in facilitated transport of metal ions, however, they have some well known limitations, such as the gradual loss of the organic phase to the aqueous solutions. This paper describes two different types of novel membranes developed for the general purpose of separating and concentrating metal ions of interest in order to improve SLM physical and chemical characteristics. Both hybrid (organic—inorganic) membranes and activated composite membranes have been tested for the selective transport of Zn/Cd and Pt/Pd mixtures. For this purpose, different carriers have been used: 2-ethylhexyldithiophosphoric acid and 2-ethylhexylphosphoric acid for the separation of Zn and Cd whereas Aliquat 336 for Pt/Pd mixtures. The choice of these metal couples is related to environmental detoxification and catalyst recovery, respectively.

The present work studies the mass transfer and separation of Ag+ through a liquid membrane immobilized in a micro porous laminar membrane from some base metals, e. g. Cu, Zn, Pb. Fe. The transport of silver from aqueous nitrate colutions to ammonia aqueous solutions have been studied. The active liquid membrane consist of a solution of triisobutyl phosphine sulphide, Cyanex 471, dissolved in isopropylbenzene absorbed in a micro porous film of polyvinildene fluoride. The results have been analyzed by a linear diffusion model which interprets closely the experimental transport data. Diffusion coefficient of the permeating species and the thickness of the aqueous diffusion layer were determined. The selectivity of silver transport through the liquid membrane provides an effective silver separation from solutions containing the base metals Cu, Fe, Pb and Zn. Such results have been applied to a treatment of the sulfide mineral spharelite.

The aim of this work was the development and optimization of enzymatic monolithic membranes with high catalytic activity for the degradation of xylan into xylooligosaccharides. The chemometric tool design of experiments has been utilized here for the first time for the optimization of the enzymatic activity of the monolithic membranes based on their constituents. The effect of three process variables, including the amount of various monomer contents and the porogenic solvents ratio, has been studied on the enzymatic activity of the resulted membranes. The experimental design chosen was a central face centred with six central points in order to obtain an orthogonal model, with the precision of the results being independent of the range of values considered for each parameter. The software Modde(c) 6.0 from Umetrics(c) was used to build and analyze the results of the experimental design using partial least squares regression. The optimization of the suggested model provided the best membrane composition to achieve maximum enzymatic activity, which can be related to the amount of enzyme immobilized on the monolithic membrane. The predictive capacity of the model was evaluated performing additional experiments.