Ferromagnetic sorbents based on nickel nanowires for efficient uptake of mercury from water

In Vitro Hepatotoxic and Neurotoxic Effects of Titanium and Cerium Dioxide Nanoparticles, Arsenic and Mercury Co-Exposure

Considering the increasing emergence of new contaminants, such as nanomaterials, mixing with legacy contaminants, including metal(loid)s, it becomes imperative to understand the toxic profile resulting from these interactions. This work aimed at assessing and comparing the individual and combined hepatotoxic and neurotoxic potential of titanium dioxide nanoparticles (TiO₂NPs 0.75–75 mg/L), cerium oxide nanoparticles (CeO₂NPs 0.075–10 μg/L), arsenic (As 0.01–2.5 mg/L), and mercury (Hg 0.5–100 mg/L) on human hepatoma (HepG2) and neuroblastoma (SH-SY5Y) cells. Viability was assessed through WST-1 (24 h) and clonogenic (7 days) assays and it was affected in a dose-, time- and cell-dependent manner. Higher concentrations caused greater toxicity, while prolonged exposure caused inhibition of cell proliferation, even at low concentrations, for both cell lines. Cell cycle progression, explored by flow cytometry 24 h post-exposure, revealed that TiO₂NPs, As and Hg but not CeO₂NPs, changed the profiles of SH-SY5Y and HepG2 cells in a dose-dependent manner, and that the cell cycle was, overall, more affected by exposure to mixtures. Exposure to binary mixtures revealed either potentiation or antagonistic effects depending on the composition, cell type and time of exposure. These findings prove that joint toxicity of contaminants cannot be disregarded and must be further explored.

Template-Assisted Iron Nanowire Formation at Different Electrolyte Temperatures

We studied the morphology, structure, and magnetic properties of Fe nanowires that were electrodeposited as a function of the electrolyte temperature. The nucleation mechanism followed instantaneous growth. At low temperatures, we observed an increase of the total charge reduced into the templates, thus suggesting a significant increase in the degree of pore filling. Scanning electron microscopy images revealed smooth nanowires without any characteristic features that would differentiate their morphology as a function of the electrolyte temperature. X-ray photoelectron spectroscopy studies indicated the presence of a polycarbonate coating that covered the nanowires and protected them against oxidation. The X-ray diffraction measurements showed peaks coming from the polycrystalline Fe bcc structure without any traces of the oxide phases. The crystallite size decreased with an increasing electrolyte temperature. The transmission electron microscopy measurements proved the fine-crystalline structure and revealed elongated crystallite shapes with a columnar arrangement along the nanowire. Mössbauer studies indicated a deviation in the magnetization vector from the normal direction, which agrees with the SQUID measurements. An increase in the electrolyte temperature caused a rise in the out of the membrane plane coercivity. The studies showed the oxidation resistance of the Fe nanowires deposited at elevated electrolyte temperatures.

Evaluation of the toxicity of nickel nanowires to freshwater organisms at concentrations and short-term exposures compatible with their application in water treatment

In order to understand the potential impacts of nickel nanowires (Ni NWs) after reaching the aquatic environment, this research evaluated the toxicity of Ni NWs with different lengths (≤ 1.1, ≤11 and ≤ 80 μm) for several floating, planktonic and nektonic freshwater organisms. In this work, Ni NWs were synthesized by electrodeposition using anodized aluminum oxide (AAO) membranes. The toxicity of the NWs was assessed using a battery of aquatic species representative of key functions at the ecosystem level: the bacterium Aliivibrio fischeri, the algae Raphidocelis subcapitata, the macrophyte Lemna minor, the crustacean Daphnia magna and the zebrafish Danio rerio. Results indicated that for the concentrations tested (up to 2.5 mg L^-1) the synthesized Ni NWs showed low toxicity. And although no lethal toxicity was observed for D. magna, at a sublethal level the feeding activity of the freshwater cladoceran was severely affected after exposure to Ni NWs. These findings showed that NWs can be accumulated in the gut of D. magna, even during a short exposure (24 h) directly impairing Daphnia nutrition and eventually populations growth. Consequently, this can also contribute to trophic transfer of NWs along the food chain. According to our results the toxicity of Ni NW may be mainly attributed to physical effects rather than chemical effects of Ni ions, considering that the concentrations of Ni NWs tested in this study were well below the toxicity thresholds reported in the literature for Ni ions and for Ni NMs.

Can contaminated waters or wastewater be alternative sources for technology-critical elements? The case of removal and recovery of lanthanides

Technology critical elements (TCE) are considered the vitamins of nowadays technology. Factors such as high demand, limited sources and geopolitical pressures, mining exploitation and its negative impact, point these elements as new emerging contaminants and highlight the importance for removal and recycling TCE from contaminated waters. This paper reports the synthesis, characterization and application of hybrid nanostructures to remove and recover lanthanides from water, promoting the recycling of these high value elements. The nanocomposite combines the interesting properties of graphite nanoplatelets, with the magnetic properties of magnetite, and exhibits good sorption properties towards La(III), Eu(III) and Tb(III). The sorption process was very sensitive to solution pH, evidencing that electrostatic interactions are the main binding mechanism involved. Removal efficiencies up to 80% were achieved at pH 8, using only 50 mg/L of nanocomposite. In ternary solution, occurred a preferential removal of Eu(III) and Tb(III). The equilibrium evidenced a rare but interesting behaviour, and as a proof-of-concept the recoveries and reutilization rates, at consecutive cycles, highlight the recyclability of the composite without loss of efficiency. This study evidences that surface charge and the number of active sites of the composite controls the removal process, providing new insights on the interactions between lanthanoids and magnetic-graphite-nanoplatelets.

Applications, Surface Modification and Functionalization of Nickel Nanorods

The growing number of nanoparticle applications in science and industry is leading to increasingly complex nanostructures that fulfill certain tasks in a specific environment. Nickel nanorods already possess promising properties due to their magnetic behavior and their elongated shape. The relevance of this kind of nanorod in a complex measurement setting can be further improved by suitable surface modification and functionalization procedures, so that customized nanostructures for a specific application become available. In this review, we focus on nickel nanorods that are synthesized by electrodeposition into porous templates, as this is the most common type of nickel nanorod fabrication method. Moreover, it is a facile synthesis approach that can be easily established in a laboratory environment. Firstly, we will discuss possible applications of nickel nanorods ranging from data storage to catalysis, biosensing and cancer treatment. Secondly, we will focus on nickel nanorod surface modification strategies, which represent a crucial step for the successful application of nanorods in all medical and biological settings. Here, the immobilization of antibodies or peptides onto the nanorod surface adds another functionality in order to yield highly promising nanostructures.

Magnetic Hybrid Nanosorbents for the Uptake of Paraquat from Water

Although paraquat has been banned in European countries, this herbicide is still used all over the world, thanks to its low-cost, high-efficiency, and fast action. Because paraquat is highly toxic to humans and animals, there is interest in mitigating the consequences of its use, namely by implementing removal procedures capable of curbing its environmental and health risks. This research describes new magnetic nanosorbents composed of magnetite cores functionalized with bio-hybrid siliceous shells, that can be used to uptake paraquat from water using magnetically-assisted procedures. The biopolymers κ-carrageenan and starch were introduced into the siliceous shells, resulting in two hybrid materials, Fe₃O₄@SiO₂/SiCRG and Fe₃O₄@SiO₂/SiStarch, respectively, that exhibit a distinct surface chemistry. The Fe₃O₄@SiO₂/SiCRG biosorbents displayed a superior paraquat removal performance, with a good fitting to the Langmuir and Toth isotherm models. The maximum adsorption capacity of paraquat for Fe₃O₄@SiO₂/SiCRG biosorbents was 257 mg·g-1, which places this sorbent among the best systems for the removal of this herbicide from water. The interesting performance of the κ-carrageenan hybrid, along with its magnetic properties and good regeneration capacity, presents a very efficient way for the remediation of water contaminated with paraquat.

Amino organosilane grafted ordered mesoporous alumina with enhanced adsorption performance towards Cr(vi)

Amino organosilane N-(β-aminoethyl)-γ-aminopropylmethylbimethoxysilane (2N) functionalized ordered mesoporous aluminas (MA–2N) with enhanced adsorption performance towards Cr(vi) were successfully prepare by a facile grafting method.

Electrochemical pore filling strategy for controlled growth of magnetic and metallic nanowire arrays with large area uniformity

While a variety of template-based strategies have been developed in the fabrication of nanowires (NWs), a uniform pore filling across the template still poses a major challenge. Here, we present a large area controlled pore filling strategy in the reproducible fabrication of various magnetic and metallic NW arrays, embedded inside anodic aluminum oxide templates. Using a diffusive pulsed electrodeposition (DPED) technique, this versatile strategy relies on the optimized filling of branched nanopores at the bottom of templates with Cu. Serving the Cu filled nanopores as appropriate nucleation sites, the DPED is followed by a uniform and homogeneous deposition of magnetic (Ni and Fe) and metallic (Cu and Zn) NWs at a current density of 50 mA cm^-2 for an optimal thickness of alumina barrier layer (∼18 nm). Our strategy provides large area uniformity (exceeding 400 μm²) in the fabrication of 16 μm long free-standing NW arrays. Using hysteresis loop measurements and scanning electron microscopy images, the electrodeposition efficiency (EE) and pore filling percentage (F _p) are evaluated, leading to maximum EE and F _p values of 91% and 95% for Ni and Zn, respectively. Moreover, the resulting NW arrays are found to be highly crystalline. Accordingly, the DPED technique is capable of cheaply and efficiently controlling NW growth over a large area, providing a tool for various nanoscale applications including biomedical devices, electronics, photonics, magnetic storage medium and nanomagnet computing.

Surface-Functionalized Porous Lignin for Fast and Efficient Lead Removal from Aqueous Solution

The development of ecofriendly sorbents for fast and efficient removal of heavy metals from aqueous media still remains a significant challenge. Here, we report that this task can be addressed by creating a porous naturally occurring polymer, as illustrated by functionalizing lignin with large numbers of mesopores and functional groups. We show that surface-functionalized porous lignin (SFPL), obtained by a two-step process, has a large surface area of 22.3 m2/g, 12 times that of lignin, and a high density of dithiocarbamate groups (2.8 mmol/g). SFPL was found to exhibit an excellent adsorption performance toward lead ions dissolved in water. For example, 99% of the lead ions from 50 mL of a solution containing 20 mg/L lead ions was removed in just 30 min by 0.01 g of SFPL. The saturated adsorption capacity of SFPL for lead ions was found to be 188 mg/g, which is 13 times that of the original lignin and 7 times that of activated carbon. The adsorption process is endothermic and involves intraparticle diffusion and chemical adsorption between lead ions and the functional groups of SFPL. The cost effectiveness and environmental friendliness of SFPL make it a promising material for removing lead and other heavy metals from wastewater.