Industrial by-products-derived binders for in-situ remediation of high Pb content pyrite ash: Synergistic use of ground granulated blast furnace slag and steel slag to achieve efficient Pb retention and CO2 mitigation.

Ordinary Portland cement (OPC) is a cost-effective and conventional binder that is widely adopted in brownfield site remediation and redevelopment. However, the substantial carbon dioxide emission during OPC production and the concerns about its undesirable retention capacity for potentially toxic elements strain this strategy. To tackle this objective, we herein tailored four alternative binders (calcium aluminate cement, OPC-activated ground-granulated blast-furnace slag (GGBFS), white-steel-slag activated GGBFS, and alkaline-activated GGBFS) for facilitating immobilization of high Pb content pyrite ash, with the perspectives of enhancing Pb retention and mitigating anthropogenic carbon dioxide emissions. The characterizations revealed that the incorporation of white steel slag efficiently benefits the activity of GGBFS, herein facilitating the hydration products (mainly ettringite and calcium silicate hydrates) precipitation and Pb immobilization. Further, we quantified the cradle-to-gate carbon footprint and cost analysis attributed to each binder-Pb contaminants system, finding that the application of these alternative binders could be pivotal in the envisaged carbon-neutral world if the growth of the OPC-free roadmap continues. The findings suggest that the synergistic use of recycled white steel slag and GGBFS can be proposed as a profitable and sustainable OPC-free candidate to facilitate the management of lead-contaminated brownfield sites. The overall results underscore the potential immobilization mechanisms of Pb in multiple OPC-free/substitution binder systems and highlight the urgent need to bridge the zero-emission insights to sustainable in-situ solidification/stabilization technologies.

Mechanistic insights into Pb and sulfates retention in ordinary Portland cement and aluminous cement: Assessing the contributions from binders and solid waste.

Identifying immobilization mechanisms of potentially toxic elements (PTEs) is of paramount importance in the field application of solidification/stabilization. Traditionally, demanding and extensive experiments are required to better access the underlying retention mechanisms, which are usually challenging to quantify and clarify precisely. Herein, we present a geochemical model with parametric fitting techniques to reveal the solidification/stabilization of Pb-rich pyrite ash through conventional (ordinary Portland cement) and alternative (calcium aluminate cement) binders. We found that ettringite and calcium silicate hydrates exhibit strong affinities for Pb at alkaline conditions. When the hydration products are unable to stabilize all the soluble Pb in the system, part of the soluble Pb may be immobilized as Pb(OH)2. At acidic and neutral conditions, hematite from pyrite ash and newly-formed ferrihydrite are the main controlling factors of Pb, coupled with anglesite and cerussite precipitation. Thus, this work provides a much-needed complement to this widely-applied solid waste remediation technique for the development of more sustainable mixture formulations.

Environmental implications of one-century COPRs evolution in a single industrial site: From leaching impact to sustainable remediation of CrVI polluted groundwater.

The Stoppani factory manufactured chromium for more than one century, dumping millions of tons of Chromite Ore Processing Residues (COPRs) over decades. The massive presence of COPRs resulted in an intense CrVI leaching and consequent contamination of percolating groundwater. The site offers a unique opportunity to follow COPRs evolution from the primary roasting process to the aged Cr-bearing mineral phases. Herein, new insights on COPRs mineralogy evolution and their role in CrVI release are provided by a dry sample preparation protocol, coupled with in-depth multi-technique characterization. Besides typical COPRs mineral assemblages, highly soluble Na2CrO4 and the first evidence of crocoite (PbCrO4) in a COPR contaminated site are revealed. Selective extraction experiments confirmed a strong reactivity for Cr-bearing minerals as confirmed by concentrations as high as 375 mg L-1 of leached CrVI. The mineralogical approach was combined with a nanotechnological solution for CrVI wastewater remediation. The application of naked colloidal maghemite (γ-Fe2O3) nanoparticles (SAMNs) on the complex industrial wastewater, led to > 90% CrVI removal, either under acidic or in-situ conditions. The present case study of a highly polluted site, ranging from mineral characterization to wastewater remediation, highlights the use of multidisciplinary approaches to cope with complex environmental issues.

Enabling Circular Economy: The Overlooked Role of Inorganic Materials Chemistry.

Circular economy is considered a new chance to build a more sustainable world from both the social and the economic point of view. In this Essay, the possible contribution of inorganic chemistry towards a smooth transition to circularity in inorganic materials design and production is discussed by adopting an interdisciplinary approach.

Role of carboxylic group pattern on protein surface in the recognition of iron oxide nanoparticles: A key for protein corona formation.

The knowledge of protein-nanoparticle interplay is of crucial importance to predict the fate of nanomaterials in biological environments. Indeed, protein corona on nanomaterials is responsible for the physiological response of the organism, influencing cell processes, from transport to accumulation and toxicity. Herein, a comparison using four different proteins reveals the existence of patterned regions of carboxylic groups acting as recognition sites for naked iron oxide nanoparticles. Readily interacting proteins display a distinctive surface distribution of carboxylic groups, recalling the geometric shape of an ellipse. This is morphologically complementary to nanoparticles curvature and compatible with the topography of exposed FeIII sites laying on the nanomaterial surface. The recognition site, absent in non-interacting proteins, promotes the nanoparticle harboring and allows the formation of functional protein coronas. The present work envisages the possibility of predicting the composition and the biological properties of protein corona on metal oxide nanoparticles.

Smart synthetic maghemite nanoparticles with unique surface properties encode binding specificity toward AsIII.

Pristine ɣ-Fe2O3 nanoparticles, called surface active maghemite nanoparticles (SAMNs) display unprecedented colloidal stability and specific binding properties. Herein, the interactions of SAMNs with AsV and AsIII as surface molecular probes were comparatively studied. Thermodynamic and kinetic characterizations, along with chemical and structural analysis of SAMN@As complexes, evidenced two distinct binding modalities. Arsenite, emerged as an elective and specific ligand for SAMNs, whereas arsenate adsorption was more labile, pH dependent and ruled by different binding possibilities. In particular, AsIII oxyacid exclusively interacts through inner-sphere coordination occupying available surface crystal positions resembling a key-lock fitting, while AsV leads to both outer-sphere and inner-sphere complexes. Noteworthy, discrimination between AsV and AsIII was never reported for nanostructured maghemite evidencing the importance of synthetic route on surface properties of the nanomaterial. The present report, besides enriching the chemistry of nanosized iron oxides, suggests SAMNs application for the remediation of water contaminated by AsIII, the most threatening As species in water.

Enzyme Immobilization on Maghemite Nanoparticles with Improved Catalytic Activity: An Electrochemical Study for Xanthine.

Generally, enzyme immobilization on nanoparticles leads to nano-conjugates presenting partially preserved, or even absent, biological properties. Notwithstanding, recent research demonstrated that the coupling to nanomaterials can improve the activity of immobilized enzymes. Herein, xanthine oxidase (XO) was immobilized by self-assembly on peculiar naked iron oxide nanoparticles (surface active maghemite nanoparticles, SAMNs). The catalytic activity of the nanostructured conjugate (SAMN@XO) was assessed by optical spectroscopy and compared to the parent enzyme. SAMN@XO revealed improved catalytic features with respect to the parent enzyme and was applied for the electrochemical studies of xanthine. The present example supports the nascent knowledge concerning protein conjugation to nanoparticle as a means for the modulation of biological activity.

Nano-immobilized flumequine with preserved antibacterial efficacy.

Flumequine was nano-immobilized by self-assembly on iron oxide nanoparticles, called surface active maghemite nanoparticles (SAMNs). The binding process was studied and the resulting core-shell nanocarrier (SAMN@FLU) was structurally characterized evidencing a firmly immobilized organic canopy on which the fluorine atom of the antibiotic was exposed to the solvent. The antibiotic efficacy of the SAMN@FLU nanocarrier was tested on a fish pathogenic bacterium (Aeromonas veronii), a flumequine sensitive strain, in comparison to soluble flumequine and the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) were assessed. Noteworthy, the MIC and MBC of soluble and nanoparticle bound drug were superimposable. Moreover, the interactions between SAMN@FLU nanocarrrier and microorganism were studied by transmission electron microscopy evidencing the ability of the complex to disrupt the bacterial wall. Finally, a preliminary in vivo test was provided using Daphnia magna as animal model. SAMN@FLU was able to protect the crustacean from the fatal consequences of a bacterial infection and showed no sign of toxicity. Thus, in contrast with the strength of the interaction, nano-immobilized FLU displayed a fully preserved antimicrobial activity suggesting the crucial role of fluorine in the drug mechanism of action. Besides the importance for potential applications in aquaculture, the present study contributes to the nascent field of nanoantibiotics.

Electrocatalytic nanostructured ferric tannate as platform for enzyme conjugation: Electrochemical determination of phenolic compounds.

A shell of nanostructured ferric tannates was spontaneously developed on the surface of naked maghemite nanoparticles (SAMNs, the core) by a simple wet reaction with tannic acid (TA). The as obtained core-shell nanomaterial (SAMN@TA) displays specific electrocatalytic and surface properties, which significantly differ from parent maghemite. Thanks to the known proclivity of TA to interact with proteins, SAMN@TA was proposed as a support for the direct immobilization of an enzyme. A ternary functional nanobioconjugate (SAMN@TA@TvL) was successfully self-assembled by incubating laccase from Trametes versicolor (TvL) and SAMN@TA. The SAMN@TA@TvL hybrid was kinetically characterized with respect to the native enzyme and applied for building an easy-to-use analytical device for the detection of polyphenols. The electrochemical biosensor allowed the determination of polyphenols by square wave voltammetry in mixed water-methanol solutions. The system sensitivity was 868.9 ±â€¯1.9nA µM-1, the LOD was 81 nM and the linearity range was comprised between 100 nM and 10 µM. The proposed approach was successfully applied to detect phenolics in blueberry extracts as real samples. Results suggest that SAMN@TA could be a promising, low cost and versatile tool for the creation of nano-bio-conjugates aimed at the development of new electrochemical sensing platforms.

Biologically safe colloidal suspensions of naked iron oxide nanoparticles for in situ antibiotic suppression.

A category of naked maghemite nanoparticles (γ-Fe2O3), named surface active maghemite nanoparticles (SAMNs), is characterized by biological safety, high water colloidal stability and a surface chemistry permitting the binding of ligands. In the present study, the interaction between SAMNs and an antibiotic displaying chelating properties (oxytetracycline, OxyTC) was extensively structurally and magnetically characterized. OxyTC emerged as an ideal probe for providing insights into the colloidal properties of SAMNs. At the same time, SAMNs turned out as an elective tool for water remediation from OxyTC. Therefore, a dilute colloidal suspension of SAMNs was used for the removal of OxyTC in large volume tanks where, to simulate a real in situ application, a population of zebrafish (Danio rerio) was introduced. Interestingly, SAMNs led to the complete removal of the drug without any sign of toxicity for the animal model. Moreover, OxyTC immobilized on SAMNs surface resulted safe for sensitive Escherichia coli bacteria strain. Thus, SAMNs were able to recover the drug and to suppress its antibiotic activity envisaging their feasibility as competitive option for water remediation from OxyTC in more nature related scenarios. The present contribution stimulates the use of novel smart colloidal materials to cope with complex environmental issues.

Metal transport and remobilisation in a basin affected by acid mine drainage: the role of ochreous amorphous precipitates.

Metal-polluted mine waters represent a major threat to the quality of waters and sediments in a downstream basin. At the confluence between acidic mine waters and the unpolluted waters of the Gromolo Torrent (Liguria, North-West Italy), the massive formation of an ochreous amorphous precipitate takes place. This precipitate forms a soft blanket that covers the torrent bed and can be observed down to its mouth in the sea. The aim of this work is to evaluate the dispersion of metals in the Gromolo Torrent basin from the abandoned Cu-Fe sulphide mine of Libiola to the Ligurian Sea and to assess the metal remobilisation from the amorphous precipitates. The mineralogy of the superficial sediments collected in the torrent bed and the concentrations of different elements of environmental concern (Cu, Zn, Cd, Co, Cr, Mn, Ni, Pb, As, and Sb) were therefore analysed. The results showed that the precipitates contain high concentration of Fe, Al, Cu, and Zn, significantly modifying the bulk chemistry of the Gromolo Torrent sediments. In order to evaluate the possible remobilisation of ecotoxic elements from the amorphous precipitates, bulk leaching tests were performed with both deionised and seawater. Bulk leaching tests with deionised water mobilised primarily high Pb amounts, but also relatively high concentrations of Fe, Al, Cu, and Zn are released in the leachate. In seawater tests, Fe, Al, Cu, and Zn were released in smaller amounts, while other elements like Mn, Cd, Co, and Ni increased in the released fraction. Pb was still strongly released as in deionised water experiments. The results show that the interaction of precipitates and seawater can remobilise high concentrations of metals, thus affecting the surrounding environment.

Colloidal Surface Active Maghemite Nanoparticles for Biologically Safe Cr(VI) Remediation: from Core-Shell Nanostructures to Pilot Plant Development.

The present study is aimed at the exploration of achievable improvements for Cr(VI) ex situ and in situ water remediation by using novel naked colloidal maghemite (γ-Fe2 O3 ) nanoparticles (surface active maghemite nanoparticles, SAMNs). The reliability of SAMNs for Cr(VI) binding and removal was demonstrated, and SAMN@Cr(VI) complex was characterized, as well as the covalent nature of the absorption was unequivocally proved. SAMNs were structurally and magnetically well conserved after Cr(VI) binding. Thus, in consideration of their affinity for Cr(VI) , SAMNs were exploited in a biological model system, mimicking a real in situ application. The assay evidenced a progressive reduction of revertant colonies of Salmonella typhimurium TA100 strain, as maghemite nanoparticles concentration increased, till the complete suppression of Cr(VI) mutagen effect. Finally, an automatic modular pilot system for continuous magnetic removal and recovery of Cr(VI) from water is proposed. SAMNs, thanks to their colloidal, binding, and catalytic properties, represent a promising tool as a reliable nanomaterial for water remediation by Cr(VI) .

Ternary Hybrid γ-Fe2 O3 /Cr(VI) /Amine Oxidase Nanostructure for Electrochemical Sensing: Application for Polyamine Detection in Tumor Tissue.

Dichromate binds to surface-active maghemite nanoparticles (SAMNs) to form a stable core-shell nanostructures (SAMN@Cr(VI) ). The hybrid was characterized by Mössbauer spectroscopy, high-angle annular dark-field imaging, electron energy-loss spectroscopy, and electrochemical techniques, which revealed a strong interaction of dichromate with the nanoparticle surface. Electrochemical characterization showed lower charge-transfer resistance, better electrochemical performance, and more reversible electrochemical behavior with respect to naked SAMNs. Moreover, SAMN@Cr(VI) is an excellent electrocatalyst for hydrogen peroxide reduction. Furthermore, an enzyme, namely, bovine serum amine oxidase (BSAO: EC 1.4.3.6), was immobilized on SAMN@Cr(VI) by self-assembly to give a ternary hybrid nanostructured catalyst for polyamine oxidation (SAMN@Cr(VI) -BSAO). SAMN@Cr(VI) -BSAO was applied for the development of a reagentless, fast, inexpensive, and interference-free polyamine biosensor, which was successfully exploited for the discrimination of tumorous tissue from healthy tissue in human crude liver extracts.

Core-shell hybrid nanomaterial based on prussian blue and surface active maghemite nanoparticles as stable electrocatalyst.

A novel core-shell nanomaterial based on prussian blue (PB) coating on peculiar surface active maghemite nanoparticles (SAMNs), was developed. The synthetic process involves the direct crystallization of Fe(II)(CN)6(4-) onto the surface of SAMNs by simple incubation in water at controlled pH, demonstrating the presence of under-coordinated Fe(III) on nanoparticle surface. The coating reaction occurs in a narrow pH range and the synthetic procedure was optimized. The resulting SAMN@PB hybrid nanostructures were characterized by transmission and scanning electron microscopy, Mössbauer, UV-vis and FTIR spectroscopy and X-ray powder diffraction. The nanomaterial, characterized by high stability in alkaline media, behave as excellent electro-catalyst for hydrogen peroxide reduction. The stability of SAMN@PB hybrid has been investigated as a function of pH, showing excellent stability up to pH 9.0 and demonstrating the feasibility of SAMNs, superficially derivatized with prussian blue, to produce an efficient and extremely stable nanostructured material. This maghemite supported nanostructured prussian blue was applied to develop a sensor, based on a simple carbon paste electrode, which was able to catalyze the electro-reduction of hydrogen peroxide, in aqueous solutions, buffered at pH 7.0, at low applied potentials (0.0 V vs. SCE).

A glucose biosensor based on surface active maghemite nanoparticles.

A simple carbon paste (CP) electrode, modified with novel maghemite (γ-Fe2O3) nanoparticles, called SAMNs (surface active maghemite nanoparticles) and characterized by a mean diameter of about 10nm, has been developed. The electrode catalyzes the electro-reduction of hydrogen peroxide at low applied potentials (-0.1 V vs SCE). In order to improve the electrocatalytic properties of the modified electrode an ionic liquid, namely 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF6), was introduced. At -0.1 V, the sensitivity of the SAMN-BMIM-PF6-CP electrode was 206.51 nA µM(-1)cm(-2), with a detection limit (S/N=3) of 0.8 µM, in the 0-1.5mM H2O2 concentration range. Furthermore, glucose oxidase was immobilized on the surface of maghemite nanoparticles as a monomolecular layer, by a bridge constituted of rhodamine B isothiocyanate, leading to a fluorescent, magnetic drivable nanocatalyst, containing 10 ± 2 enzyme molecules per nanoparticle. The resulting enzyme electrode presents a linear calibration curve toward glucose in solution in the concentration range of 0-1.5mM glucose, characterized by a sensitivity of 45.85 nA µM(-1)cm(-2) and a detection limit (S/N=3) of 0.9 µM. The storage stability of the system was evaluated and a half-life of 2 months was calculated, if the electrode is stored at 4°C in buffer. The present work demonstrates the feasibility of these surface active maghemite nanoparticles as efficient hydrogen peroxide electro-catalyst, which can be easily coupled to hydrogen peroxide producing enzymes in order to develop oxidase based reagentless biosensor devices.

Avidin functionalized maghemite nanoparticles and their application for recombinant human biotinyl-SERCA purification.

We report on the surface characterization, functionalization, and application of stable water suspensions of novel surface active maghemite nanoparticles (SAMNs), characterized by a diameter of 11 ± 2 nm and possessing peculiar colloidal properties and surface interactions. These features permitted the acquisition of titration curves and aqueous UV-vis spectra and suggested a role played by surface under-coordinated iron atoms. This new class of nanoparticles was obtained through an easy, inexpensive, one-step, green procedure and functionalized with ligands of high biotechnological interest, such as biotin and avidin, by simple incubation in aqueous solution. Bound avidin was determined by measuring the disappearance of free avidin absorbance at 280 nm, as a function of increasing nanoparticle concentration, showing the presence of 10 ± 3 avidin molecules per nanoparticle. The biological activity of the SAMN@avidin complex was evaluated and the number of available biotin binding sites was determined, using biotinyl-fluorescein as a probe, showing that each bound avidin molecule is able to bind 2.8 ± 0.8 biotin molecules, confirming the maintenance of biological activity and excellent binding capacity of the SAMN@avidin complex. Furthermore a Langmuir isotherm model was used to describe the biomolecule specific monolayer adsorption onto the particle surface, and in the case of avidin, the maximum adsorption capacity was 100 ± 27 µg avidin/mg SAMN, whereas the binding constant is 45.18 µL µg(-1). The SAMN@avidin complex was characterized by UV-vis spectroscopy, quartz crystal microbalance, FTIR spectroscopy, and transmission electron microscopy. Finally, SAMN@avidin was applied for the large scale purification of recombinant biotinylated human sarco/endoplasmic reticulum Ca(2+)-ATPase (hSERCA-2a), expressed by Saccharomyces cerevisiae. The protein was magnetically purified, and about 500 µg of a 70% pure hSERCA-2a were recovered from 4 L of yeast culture, with a purification yield of 64%.

Charge binding of rhodamine derivative to OH- stabilized nanomaghemite: universal nanocarrier for construction of magnetofluorescent biosensors.

Superparamagnetic nanoparticles (20-40 nm) of maghemite, γ-Fe(2)O(3), with well-defined stoichiometric structure, are synthesized by the borohydride reduction of ferric chloride at an elevated temperature (100°C) followed by thermal treatment of the reaction product. Prepared maghemite nanoparticles reveal excellent colloidal stability for a long time without the necessity for any additional surface modification. These colloidal features are due to surface stabilizing OH(-) groups, which act as charge barriers preventing a particle aggregation and enabling a reversible binding of various oppositely charged organic substances. Such binding with rhodamine B isothiocyanate results in the fluorescent magnetic nanocarrier providing, at the same time, a spacer arm for covalent immobilization of other biosubstances including enzymes. In this work, we exploit this general applicability of the developed nanocarrier for covalent immobilization of glucose oxidase. This is the first reported example of magnetically drivable fluorescent nanocatalyst. The immobilized enzyme creates a 3-5 nm thick layer on the nanoparticle surface as proved by high-resolution transmission electron microscopy. This layer corresponds to 10 enzyme molecules, which are bound to the nanoparticle surface as found by the fluorimetric determination of flavin adenine dinucleotide. The developed magnetic fluorescent nanocatalyst, showing a rate constant of 32.7s(-1) toward glucose oxidation, can be used as a biosensor in various biochemical, biotechnological, and food chemistry applications. The presence of the nanocatalyst can be simply monitored by its fluorescence; moreover, it can be easily separated from the solution by an external magnetic field and repeatedly used without a loss of catalytic efficiency.