Improved Energy Storage Density and Efficiency of Nd and Mn Co-Doped Ba0.7Sr0.3TiO3 Ceramic Capacitors Via Defect Dipole Engineering.

In this paper, we investigate the structural, microstructural, dielectric, and energy storage properties of Nd and Mn co-doped Ba0.7Sr0.3TiO3 [(Ba0.7Sr0.3)1-xNdxTi1-yMnyO3 (BSNTM) ceramics (x = 0, 0.005, and y = 0, 0.0025, 0.005, and 0.01)] via a defect dipole engineering method. The complex defect dipoles (MnTi"-VO∙∙)∙ and (MnTi"-VO∙∙) between acceptor ions and oxygen vacancies capture electrons, enhancing the breakdown electric field and energy storage performances. XRD, Raman, spectroscopy, XPS, and microscopic investigations of BSNTM ceramics revealed the formation of a tetragonal phase, oxygen vacancies, and a reduction in grain size with Mn dopant. The BSNTM ceramics with x = 0.005 and y = 0 exhibit a relative dielectric constant of 2058 and a loss tangent of 0.026 at 1 kHz. These values gradually decreased to 1876 and 0.019 for x = 0.005 and y = 0.01 due to the Mn2+ ions at the Ti4+- site, which facilitates the formation of oxygen vacancies, and prevents a decrease in Ti4+. In addition, the defect dipoles act as a driving force for depolarization to tailor the domain formation energy and domain wall energy, which provides a high difference between the maximum polarization of Pmax and remnant polarization of Pr (ΔP = 10.39 µC/cm2). Moreover, the complex defect dipoles with optimum oxygen vacancies in BSNTM ceramics can provide not only a high ΔP but also reduce grain size, which together improve the breakdown strength from 60.4 to 110.6 kV/cm, giving rise to a high energy storage density of 0.41 J/cm3 and high efficiency of 84.6% for x = 0.005 and y = 0.01. These findings demonstrate that defect dipole engineering is an effective method to enhance the energy storage performance of dielectrics for capacitor applications.

Moldflow Simulation and Characterization of Pure Copper Fabricated via Metal Injection Molding.

Metal injection molding (MIM) is a representative near-net-shape manufacturing process that fabricates advanced geometrical components for automobile and device industries. As the mechanical performance of an MIM product is affected by green-part characteristics, this work investigated the green part of pure copper processed with MIM using the injection temperature of ~180 °C and injection pressure of ~5 MPa. A computational analysis based on the Moldflow program was proposed to simulate the effectivity of the process by evaluating the confidence of fill, quality prediction, and pressure drop of three distinctive regions in the green part. The results showed that the ring and edge regions of the green parts showed localized behavior, which was related to processing parameters including the position of the gate. A microstructural observation using scanning electron microscopy and a 3D X-ray revealed that both the surface and body matrix consisted of pores with some agglomeration of micro-pores on the edges and ring part, while any critical defects, such as a crack, were not found. A microhardness analysis showed that the three regions exhibited a reasonable uniformity with a slight difference in one specific part mainly due to the localized pore agglomeration. The simulation results showed a good agreement with the microstructures and microhardness data. Thus, the present results are useful for providing guidelines for the sound condition of MIM-treated pure copper with a complex shape.

Giant Energy Density via Mechanically Tailored Relaxor Ferroelectric Behavior of PZT Thick Film.

Relaxor ferroelectrics (RFEs) are being actively investigated for energy-storage applications due to their large electric-field-induced polarization with slim hysteresis and fast energy charging-discharging capability. Here, a novel nanograin engineering approach based upon high kinetic energy deposition is reported, for mechanically inducing the RFE behavior in a normal ferroelectric Pb(Zr0.52 Ti0.48 )O3 (PZT), which results in simultaneous enhancement in the dielectric breakdown strength (EDBS ) and polarization. Mechanically transformed relaxor thick films with 4 µm thickness exhibit an exceptional EDBS of 540 MV m-1 and reduced hysteresis with large unsaturated polarization (103.6 µC cm-2 ), resulting in a record high energy-storage density of 124.1 J cm-3 and a power density of 64.5 MW cm-3 . This fundamental advancement is correlated with the generalized nanostructure design that comprises nanocrystalline phases embedded within the amorphous matrix. Microstructure-tailored ferroelectric behavior overcomes the limitations imposed by traditional compositional design methods and provides a feasible pathway for realization of high-performance energy-storage materials.

Influence of CoOx surface passivation and Sn/Zr-co-doping on the photocatalytic activity of Fe2O3 nanorod photocatalysts for bacterial inactivation and photo-Fenton degradation.

Hydrothermal and wet impregnation methods are presented in this study for synthesizing CoOx(1 wt%)/Sn/Zr-codoped Fe2O3 nanorod photocatalysts for the degradation of organic pollutants and deactivation of bacteria. A hydrothermal route was used to synthesize self-assembled rod-like hierarchical structures of Sn(0-6%) doped Zr-Fe2O3 NRs. Additionally, a wet impregnation method was used to load CoOx onto the surface of photocatalysts (Sn(0-6%)-doped Zr-Fe2O3 NRs). A series of 1 wt% CoOx modified Sn(0-6%)-doped Zr-Fe2O3 NRs were synthesized, characterized, and utilized for the photocatalytic decomposition of organic contaminants, along with the killing of E. coli and S. aureus. In comparison with 0, 2, and 6% Sn co-doped Zr-Fe2O3 NRs, the CoOx(1 wt%)/4%Sn/Zr-Fe2O3 NRs photocatalyst exhibited an E. coli and S. aureus inactivation efficiencies (90 and 98%). A bio-TEM study of treated and untreated bacterial cells revealed that the CoOx(1 wt%)/4%Sn/Zr-Fe2O3 NRs photocatalyst led to considerable changes in the bacterial cell membranes' morphology. The optimal CoOx(1 wt%)/Sn(4%) co-doped Zr-Fe2O3 NRs photocatalyst achieved degradation efficiencies of 98.5% and 94.6% for BPA and orange II dye, respectively. As a result, this work will provide a facile and effective method for developing visible light-active photocatalysts for bacterial inactivation and organic pollutants degradation.

Intense Pulsed Light Thermal Treatment of Pb(Zr,Ti)O3 /Metglas Heterostructured Films Resulting in Extreme Magnetoelectric Coupling of over 20 V cm-1 Oe-1.

Magnetoelectric (ME) film composites consisting of piezoelectric and magnetostrictive materials are promising candidates for application in magnetic field sensors, energy harvesters, and ME antennas. Conventionally, high-temperature annealing is required to crystallize piezoelectric films, restricting the use of heat-sensitive magnetostrictive substrates that enhance ME coupling. Herein, a synergetic approach is demonstrated for fabricating ME film composites that combines aerosol deposition and instantaneous thermal treatment based on intense pulsed light (IPL) radiation to form piezoelectric Pb(Zr,Ti)O3 (PZT) thick films on an amorphous Metglas substrate. IPL rapidly anneals PZT films within a few milliseconds without damaging the underlying Metglas. To optimize the IPL irradiation conditions, the temperature distribution inside the PZT/Metglas film is determined using transient photothermal computational simulation. The PZT/Metglas films are annealed using different IPL pulse durations to determine the structure-property relationship. IPL treatment results in an enhanced crystallinity of the PZT, thus improving the dielectric, piezoelectric, and ME properties of the composite films. An ultrahigh off-resonance ME coupling (≈20 V cm-1  Oe-1 ) is obtained for the PZT/Metglas film that is IPL annealed at a pulse width of 0.75 ms (an order of magnitude higher than that reported for other ME films), confirming the potential for next-generation, miniaturized, and high-performance ME devices.

Effect of Reduction Sequence during Rolling on Deformed Texture and Anisotropy of Ferritic Stainless Steel.

This investigation studied the effect of reduction sequence during rolling of ferritic stainless steel on texture and anisotropy. A series of thermomechanical processes were performed on the present samples utilizing rolling deformation, with a total height reduction of 83% but with different reduction sequences, 67% + 50% (route A) and 50% + 67% (route B). Microstructural analysis showed that no significant difference was found in terms of the grain morphology between route A and route B. In terms of the texture, as compared to route A, route B developed a sharper texture on all components along the γ-fiber and a considerably higher fraction of boundaries that displayed 38°111 misorientations with respect to the surrounding deformed grains. In consequence, optimal deep drawing properties were achieved, where rm was maximized and Δr was minimized. Moreover, despite the similar morphology between the two processes, the resistance toward ridging was improved in the case of route B. This was explained in relation to the selective growth-controlled recrystallization, which favors the formation of microstructure with homogeneous distribution of the <111>//ND orientation.

Recent Advances in Triboelectric Nanogenerators: From Technological Progress to Commercial Applications.

Serious climate changes and energy-related environmental problems are currently critical issues in the world. In order to reduce carbon emissions and save our environment, renewable energy harvesting technologies will serve as a key solution in the near future. Among them, triboelectric nanogenerators (TENGs), which is one of the most promising mechanical energy harvesters by means of contact electrification phenomenon, are explosively developing due to abundant wasting mechanical energy sources and a number of superior advantages in a wide availability and selection of materials, relatively simple device configurations, and low-cost processing. Significant experimental and theoretical efforts have been achieved toward understanding fundamental behaviors and a wide range of demonstrations since its report in 2012. As a result, considerable technological advancement has been exhibited and it advances the timeline of achievement in the proposed roadmap. Now, the technology has reached the stage of prototype development with verification of performance beyond the lab scale environment toward its commercialization. In this review, distinguished authors in the world worked together to summarize the state of the art in theory, materials, devices, systems, circuits, and applications in TENG fields. The great research achievements of researchers in this field around the world over the past decade are expected to play a major role in coming to fruition of unexpectedly accelerated technological advances over the next decade.

Enhanced thermal stability by short-range ordered ferroelectricity in K0.5Na0.5NbO3-based piezoelectric oxides.

Industrial application of lead-free piezoelectric ceramics is prevented by intrinsic thermal instability. Herein, we propose a method to achieve outstanding thermal stability of converse piezoelectric constant () in lead-free potassium sodium niobate (KNN)-based ceramics by inducing a synergistic interaction between the grain size and polar configuration. Based on computational methods using phase-field simulations and first-principles calculations, the relationship between the grain size and polar configuration is demonstrated, and the possibility of achieving improved thermal stability in fine grains is suggested. A set of KNN systems is presented with meticulous dopant control near the chemical composition at which the grain size changes abnormally. Comparing the two representative samples with coarse and fine grains, significant enhancement in the thermal stability of is exhibited up to 300 °C in the fine grains. The origin of the thermal superiority in fine-grained ceramics is identified through an extensive study from a microstructural perspective. The thermal stability is realized in a device by successfully demonstrating the temperature dependence of piezoelectricity. It is notable that this is the first time that lead-free piezoelectric ceramics are able to achieve exceptionally stable piezoelectricity up to 300 °C, which actualizes their applicability as piezoelectric devices with high thermal stability.

Magnetically Driven Powerless Lighting Device with Kirigami Structured Magneto-Mechanoluminescence Composite.

The energy crisis and global shift toward sustainability drive the need for sustainable technologies that utilize often-wasted forms of energy. A multipurpose lighting device with a simplistic design that does not need electricity sources or conversions can be one such futuristic device. This study investigates the novel concept of a powerless lighting device driven by stray magnetic fields induced by power infrastructure for obstruction warning light systems. The device consists of mechanoluminescence (ML) composites of a Kirigami-shaped polydimethylsiloxane (PDMS) elastomer, ZnS:Cu particles, and a magneto-mechano-vibration (MMV) cantilever beam. Finite element analysis and luminescence characterization of the Kirigami structured ML composites are discussed, including the stress-strain distribution map and comparisons between different Kirigami structures based on stretchability and ML characteristic trade-offs. By coupling a Kirigami-structured ML material and an MMV cantilever structure, a device that can generate visible light as luminescence from a magnetic field can be created. Significant factors that contribute to luminescence generation and intensity are identified and optimized. Furthermore, the feasibility of the device is demonstrated by placing it in a practical environment. This further proves the functionality of the device in harvesting weak magnetic fields into luminescence or light, without complicated electrical energy conversion steps.

Characterization of Green Part of Steel from Metal Injection Molding: An Analysis Using Moldflow.

Metal injection molding (MIM) is a quick manufacturing method that produces elaborate and complex items accurately and repeatably. The success of MIM is highly impacted by green part characteristics. This work characterized the green part of steel produced using MIM from feedstock with a powder/binder ratio of 93:7. Several parameters were used, such as dual gates position, injection temperature of ~150 °C, and injection pressure of ~180 MPa. Analysis using Moldflow revealed that the aformentioned parameters were expected to produce a green part with decent value of confidence to fill. However, particular regions exhibited high pressure drop and low-quality prediction, which may lead to the formation of defects. Scanning electron microscopy, as well as three-dimensional examination using X-ray computed tomography, revealed that only small amounts of pores were formed, and critical defects such as crack, surface wrinkle, and binder separation were absent. Hardness analysis revealed that the green part exhibited decent homogeneity. Therefore, the observed results could be useful to establish guidelines for MIM of steel in order to obtain a high quality green part.

Efficient removal of Cs ion by electrochemical adsorption and desorption reaction using NiFe Prussian blue deposited carbon nanofiber electrode.

Prussian blue (PB) analog (NiFe, CoFe, FeFe, and commercial(cPB)) decorated carbon nanofiber (CNF) electrodes were synthesized by the drop casting method in this study to investigate the interaction between PB and CNF for the electrochemical adsorption (EA) and electrochemical desorption (ED) of Cs ion (Cs+). The adhesion of PB on the electrode and the EA and ED of Cs+ were substantially higher when the CNF electrode was used, compared with the fluorine-doped tin oxide supporting electrode. The use of CNF led to the smooth occurrence of EA and ED of Cs+, where the reported efficiency was: NiFe > FeFe > cPB. The EA and ED of Cs+ on NiFe decorated CNF (C-NiFe) were strongly affected by the loading amount of NiFe. Although the strongest EA capacity was identified when 1 mg of NiFe was used, it decreased as the loading amount of NiFe increased. Thus, the EA of Cs+ occurs under the reduction of NiFe with some Fe(III) reduced to Fe(II) of NiFe, thus inducing more adsorption of Cs+. Overall, we confirmed that the C-NiFe electrode with appropriate thickness of NiFe layer is potentially an excellent adsorbent for Cs removal.

Adsorption of potentially harmful elements by metal-biochar prepared via Co-pyrolysis of coffee grounds and Nano Fe(III) oxides.

Nano Fe(III) oxide (FO) was used as an amendment material in CO2-assisted pyrolysis of spent coffee grounds (SCG) and its impacts on the syngas (H2 & CO) generation and biochar adsorptive properties were investigated. Amendment of FO led to 153 and 682% increase of H2 and CO in pyrolytic process of SCG, respectively, which is deemed to arise from enhanced thermal cracking of hydrocarbons and oxygen transfer reaction mediated by FO. Incorporation of FO successfully created porous structure in the produced biochar. The adsorption tests revealed that the biochar exhibited bi-functional capability to remove both positively charged Cd(II) and Ni(II), and negatively charged Sb(V). The adsorption of Cd(II) and Ni(II) was hardly deteriorated in the multiple adsorption cycles, and the adsorption of Sb(V) was further enhanced through formation of surface ternary complexes. The overall results demonstrated nano Fe(III) oxide is a promising amendment material in CO2-assisted pyrolysis of lignocellulosic biomass for enhancing syngas generation and producing functional biochar.

Magneto-Mechano-Electric (MME) Composite Devices for Energy Harvesting and Magnetic Field Sensing Applications.

Magneto-mechano-electric (MME) composite devices have been used in energy harvesting and magnetic field sensing applications due to their advantages including their high-performance, simple structure, and stable properties. Recently developed MME devices can convert stray magnetic fields into electric signals, thus generating an output power of over 50 mW and detecting ultra-tiny magnetic fields below pT. These inherent outstanding properties of MME devices can enable the development of not only self-powered energy harvesters for internet of thing (IoT) systems but also ultra-sensitive magnetic field sensors for diagnosis of human bio-magnetism or others. This manuscript provides a brief overview of recently reported high-performance MME devices for energy harvesting and magnetic sensing applications.

Microbial mediated reaction of dimethylarsinic acid in wetland water and sediments.

The biogeochemical reactions of dimethylarsinic acid (DMAs(V)) were investigated using simulated wetland systems in a laboratory. DMAs(V) was injected into the wetland water, and the As concentrations in the water, plants, and sediments were monitored. Aqueous and solid-phase As speciation was evaluated, and the results revealed that the DMAs(V) was completely transported to the sediments and plants. X-ray absorption spectroscopic measurement of the As in the sediment revealed that approximately 85-95% of As existed as inorganic As species, demonstrating the important role of microorganisms in the biogeochemical reaction of DMAs(V). The influences of microbes were further investigated in smaller batches under aerobic and anaerobic conditions. The microbial batch results showed that DMAs(V) demethylation reduced the total aqueous As concentration, demonstrating that As(V) has higher affinity to wetland sediment than DMAs(V). The redox conditions were also revealed as an important controlling factor of the As reaction and, under anaerobic conditions, we observed the presence of the most toxic form of inorganic As(III) in the aqueous phase. Although this study reports one example from a specific wetland, the important roles of the redox conditions and microbial influences were identified from the comprehensive analysis of As speciation and mass balance.

Iron oxide (Fe3O4)-laden titanium carbide (Ti3C2Tx) MXene stacks for the efficient sequestration of cationic dyes from aqueous solution.

We prepared two-dimensional (2D) stack-structured magnetic iron oxide (Fe3O4) nanoparticle anchored titanium carbide (Ti3C2Tx) MXene material (Ti3C2Tx/Fe3O4). It was used as a potential adsorbent to remove carcinogenic cationic dyes, such as methylene blue (MB) and rhodamine B (Rh B), from aqueous solutions. Ti3C2Tx/Fe3O4 exhibited maximum adsorption capacities of 153 and 86 mg g-1 for MB and Rh B dyes, respectively. Batch adsorption experimental data fits the Langmuir model well, revealing monolayer adsorption of MB and Rh B onto the adsorption sites of Ti3C2Tx/Fe3O4. Additionally, Ti3C2Tx/Fe3O4 showed rapid MB/Rh B adsorption kinetics and attained equilibrium within 45 min. Moreover, Ti3C2Tx/Fe3O4 demonstrated recyclability over four cycles with high stability due to the presence of magnetic Fe3O4 nanoparticles. Furthermore, it exhibited remarkable selectivities of 91% and 88% in the presence of co-existing cationic and anionic dyes, respectively. Given the extraordinary adsorption capacities, Ti3C2Tx/Fe3O4 may be a promising material for the effective removal of cationic dyes from aqueous media.

Cr(VI) immobilization by FeS-coated alumina and silica: Effects of pH and surface coating density.

We investigated the feasibility of using FeS-coated alumina and silica for permeable reactive barrier (PRB) applications. By both coated materials, Cr(VI) was reduced to Cr(III), which was immobilized via surface complexation/precipitation at acidic pH, and bulk precipitation at neutral to basic pH. Both pH and surface coating density (the amount of FeS deposits per unit surface area of a supporting matrix) controlled Cr(VI) reduction capacity and [Cr,Fe](OH)3 composition. The reduction was higher at acidic pH due to lower passivation, as evidenced by the increased production of Fe(III) (oxyhydr)oxides over Fe(II)-Fe(III) phases. The coated alumina, despite the lower amount of FeS deposits than the coated silica, showed greater reduction capacities due to its higher surface coating density, which made Fe(III) closer together to favor Fe(III) (oxyhydr)oxide formation. Since Cr(III) was preferentially substituted for Fe(III) in Fe(III) (oxyhydr)oxides, lower pH and higher surface coating density led to lower Cr fractions in [Cr,Fe](OH)3 because of the increased production of Fe(III) (oxyhydr)oxides. Given that Cr-poor [Cr,Fe](OH)3 is more resistant to re-oxidation, FeS-coated alumina is better for PRB applications. This study reveals the significance of the surface coating density when evaluating the effectiveness of coated materials in redox-based treatments.

Recent Progress in Devices Based on Magnetoelectric Composite Thin Films.

The strain-driven interfacial coupling between the ferromagnetic and ferroelectric constituents of magnetoelectric (ME) composites makes them potential candidates for novel multifunctional devices. ME composites in the form of thin-film heterostructures show promising applications in miniaturized ME devices. This article reports the recent advancement in ME thin-film devices, such as highly sensitive magnetic field sensors, ME antennas, integrated tunable ME inductors, and ME band-pass filters, is discussed. (Pb1-xZrx)TiO3 (PZT), Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT), Aluminium nitride (AlN), and Al1-xScxN are the most commonly used piezoelectric constituents, whereas FeGa, FeGaB, FeCo, FeCoB, and Metglas (FeCoSiB alloy) are the most commonly used magnetostrictive constituents in the thin film ME devices. The ME field sensors offer a limit of detection in the fT/Hz1/2 range at the mechanical resonance frequency. However, below resonance, different frequency conversion techniques with AC magnetic or electric fields or the delta-E effect are used. Noise floors of 1-100 pT/Hz1/2 at 1 Hz were obtained. Acoustically actuated nanomechanical ME antennas operating at a very-high frequency as well as ultra-high frequency (0.1-3 GHz) range, were introduced. The ME antennas were successfully miniaturized by a few orders smaller in size compared to the state-of-the-art conventional antennas. The designed antennas exhibit potential application in biomedical devices and wearable antennas. Integrated tunable inductors and band-pass filters tuned by electric and magnetic field with a wide operating frequency range are also discussed along with miniaturized ME energy harvesters.

Visible-Light-Active CuO x -Loaded Mo-BiVO4 Photocatalyst for Inactivation of Harmful Bacteria (Escherichia coli and Staphylococcus aureus) and Degradation of Orange II Dye.

In the present study, Mo-BiVO4-loaded and metal oxide (MO: Ag2Ox, CoOx, and CuOx)-loaded Mo-BiVO4 photocatalysts were synthesized using a wet impregnation method and applied for microbial inactivation (Escherichia coli and Staphylococcus aureus) and orange II dye degradation under visible-light (VL) conditions (λ ≥ 420 nm). The amount of MO cocatalysts loaded onto the surface of the Mo-BiVO4 photocatalysts was effectively controlled by varying their weight percentages (i.e., 1-3 wt %). Among the pure Mo-BiVO4, Ag2Ox-, CoOx-, and CuOx-loaded Mo-BiVO4 photocatalysts used in bacterial E. coli and S. aureus inactivation under VL irradiation, the 2 wt % CuOx-loaded Mo-BiVO4 photocatalyst showed the highest degradation efficiency of E. coli (97%) and S. aureus (99%). Additionally, the maximum orange II dye degradation efficiency (80.2%) was achieved over the CuOx (2 wt %)-loaded Mo-BiVO4 photocatalysts after 5 h of radiation. The bacterial inactivation results also suggested that the CuO x -loaded Mo-BiVO4 nanostructure has significantly improved antimicrobial ability as compared to CuOx/BiVO4. The enhancement of the inactivation performance of CuOx-loaded Mo-BiVO4 can be attributed to the synergistic effect of Mo doping and Cu2+ ions in CuOx, which further acted as an electron trap on the surface of Mo-BiVO4 and promoted fast transfer and separation of the photoelectron (e-)/hole (h+) pairs for growth of reactive oxygen species (ROS). Furthermore, during the bacterial inactivation process, the ROS can disrupt the plasma membrane and destroy metabolic pathways, leading to bacterial cell death. Therefore, we provide a novel idea for visible-light-activated photocatalytic antibacterial approach for future disinfection applications.

Synthesis of Copper Nanoparticles from Cu2+-Spiked Wastewater via Adsorptive Separation and Subsequent Chemical Reduction.

Copper in ionic form (Cu2+) should be removed from wastewater because of its harmful effects on human health. Meanwhile, Cu-metal nanoparticles (Cu0 NPs) are widely used in various applications such as catalysts, optical materials, sensors, and antibacterial agents. Here, we demonstrated the recovery of Cu2+ from wastewater and its subsequent transformation into Cu0 NPs, a value-added product, via continuous adsorption followed by chemical reduction by hydrazine. To separate and enrich Cu2+ from wastewater, a biosorbent that exhibits excellent selectivity and adsorption capacity toward Cu2+, i.e., polyethyleneimine-grafted cellulose nanofibril aerogel (PEI@CNF), was packed into a column and used to treat 20 mg/L Cu2+ wastewater at a flow rate of 5 mL/min. The Cu2+ adsorption reached equilibrium at 72 h, and the Cu2+-saturated column was eluted using 0.1 M of HCl. After five consecutive elutions of Cu2+ from the adsorbent column, a Cu2+-enriched solution with a concentration of 3212 mg/L was obtained. The recovered Cu2+ concentrate was chemically reduced to obtain Cu0 NPs by reaction with hydrazine as a reductant in the presence of sodium dodecyl sulfate (SDS) as a stabilizer. The solution pH and hydrazine/Cu2+ ratio strongly affected the reduction efficiency of Cu2+ ions. When 0.1 M of SDS was used, spherical 50-100 nm Cu0 NPs were obtained. The results demonstrate that Cu2+-spiked wastewater can be converted into Cu0 NPs as a value-added product via adsorption followed by chemical reduction.

Simultaneous removal of radioactive cesium and strontium from seawater using a highly efficient Prussian blue-embedded alginate aerogel.

Radioactive cesium (137Cs) and strontium (90Sr) contaminants in seawater have been a serious problem since the Fukushima accident in 2011 due to their long-term health risks. For the effective and simultaneous removal of radioactive cesium (137Cs) and strontium (90Sr) from seawater, a Prussian blue (PB)-immobilized alginate aerogel (PB-alginate aerogel) was fabricated and its adsorption performance was evaluated. PB nanoparticles were homogeneously dispersed in the three-dimensional porous alginate aerogel matrix, which enabled facile contact with seawater. The PB-alginate aerogel exhibited Cs+ and Sr2+ adsorption capacities of 19.88 and 20.10 mg/g, respectively, without substantial interference because Cs+ and Sr2+ adsorption occurred at different adsorption sites on the composite. The Cs+ and Sr2+ adsorption onto the PB-alginate aerogel was completed within 3 h due to the highly porous morphology of the aerogel. The Cs+ and Sr2+ adsorption behaviors on the PB-alginate aerogel were systematically investigated under various conditions. Compared with Cs+ adsorption, Sr2+ adsorption onto the PB-alginate aerogel was more strongly influenced by competing cations (Na+, Mg2+, Ca2+, and K+) in seawater. 137Cs and 90Sr removal tests in real seawater demonstrated the practical feasibility of the PB-alginate aerogel as an adsorbent.