Highly efficient Cu(II) capture by salicylaldoxime functionalized magnetic polydopamine core-shell hybrids: Behavior and mechanism.

Functionalized magnetic nanocomposites were considered as promising adsorbents owing to their abundant functional groups and ease of separation properties. Herein, we combined the solvothermal method with molecular copolymerization to synthesize a salicylaldoxime-grafted magnetic polydopamine (SMP) core-shell hybrid and exploited it for Cu(II) adsorption. The physicochemical properties of SMP were comprehensively studied by SEM, TEM, XRD, FT-IR, TGA, XPS, and VSM measurements. The results manifested that polydopamine acts as a bridge connecting magnetic iron oxide and salicylaldoxime to fabricated core-shell hybrids with rich functional groups. The batch experimental results showed that the Cu(II) adsorption was consumingly pH-reliant behavior, while adsorption data fitted the pseudo-second-order kinetic model and Langmuir isothermal model well, and the adsorption process achieved equilibrium within 60 min. Moreover, SMP exhibited remarkable anti-interference and can be recycled for 5 times with an inconspicuous decrease in adsorption performance. Importantly, salicylaldoxime functionalization endowed SMP with maximum Cu(II) adsorption capacity of 141.24 mg/g at pH 6.0 and 25 °C as compared with pure MP. Based on FT-IR and XPS study, the main adsorption mechanisms were proposed with a synergistic effect including a strong chemical chelation and partial Cu(II) reduction. Importantly, this strategy can be extended to multifunctional magnetic composites for Cu-contaminated wastewater cleanup.

Low-Frequency Evolution Mechanism of Customized HEAs-Based Electromagnetic Response Modes Manipulated by Carbothermal Shock.

An emerging carbothermal shock method is an ultra-convenient strategy for synthesizing high-entropy alloys (HEAs), in which the intelligent combination of carbon support and HEAs can be serve as a decisive factor for interpreting the trade-off relationship between conductive gene and dielectric gene. However, the feedback mechanism of HEAs ordering degree on electromagnetic (EM) response in 2-18 GHz has not been comprehensively demystified. Herein, while lignin-based carbon fiber paper (L-CFP) as carbon support, L-CFP/FeCoNiCuZn-X with is prepared by carbothermal shock method. The reflection loss of -82.6 dB with thickness of 1.31 mm is achieved by means of pointing electron enrichment within L-CFP/FeCoNiCuZn HEAs heterointerfaces verified by theoretical calculations. Simultaneously, low-frequency evolution with high-intensity and broadband EM response relies on a "sacrificing" strategy achieved by construction of polymorphic L-CFP/semi-disordered-HEAs heterointerfaces. The practicality of L-CFP/FeCoNiCuZn-X in complex environments is given prominence to thermal conductivity, hydrophobicity, and electrocatalytic property. This work is of great significance for insightful mechanism analysis of HEAs in the application of electromagnetic wave absorption.

PDMS/magnetic lignin sponge for oil/water separation.

Recyclable, non-toxic, and degradable biological substrates contribute significantly to super-wetting surfaces. In this work, we prepared magnetic micro-nano super-hydrophobic surfaces through a robust solution with magnetic modified lignin particles as the supporting structure. A novel PDMS (polydimethylsiloxane)/magnetic lignin particle (lignin@Fe3O4)/PDA sponge composite was fabricated. Through dopamine (DA) self-polymerization, covalent deposition of magnetic lignin (ML), and PDMS silane modification, the magnetic super-hydrophobic polyurethane sponge composite (Sponge-P) was synthesized so that the Fe3O4 nanoscale microspheres wrapped with microscale lignin magnetic particles adhered to the sponge surface tighter and were barely dislodged. The as-prepared Sponge-P displayed excellent flexibility and a water contact angle of up to 152.2°. The super-hydrophobic sponge prepared with the proposed method was acid-base stable (pH = 2-12), self-cleaning, and suitable for high-salinity seawater. The magnetic super-hydrophobic sponge has good oil-water separation ability and can absorb 43 times its own weight of oil. In the meantime, due to the introduction of magnetic materials into lignin, we not only constructed micro-nanostructures to improve the surface super-hydrophobicity, but also made Sponge-P have the function of magnetic recovery, which has a unique advantage in treating oily wastewater.

Mechanisms and degradation pathways of doxycycline hydrochloride by Fe3O4 nanoparticles anchored nitrogen-doped porous carbon microspheres activated peroxymonosulfate.

Peroxymonosulfate (PMS) based advanced oxidation processes have gained widespread attention in refractory antibiotics treatment. In this study, Fe3O4 nanoparticles anchored nitrogen-doped porous carbon microspheres (Fe3O4/NCMS) were synthesized and applied to PMS heterogeneous activation for doxycycline hydrochloride (DOX-H) degradation. Benefitting from synergy effects of porous carbon structure, nitrogen doping, and fine dispersion of Fe3O4 nanoparticles, Fe3O4/NCMS showed excellent DOX-H degradation efficiency within 20 min via PMS activation. Further reaction mechanisms revealed that the reactive oxygen species including hydroxyl radicals (•OH) and singlet oxygen (1O2) played the dominant role for DOX-H degradation. Moreover, Fe(II)/Fe(III) redox cycle also participated in the radical generation, and nitrogen-doped carbonaceous structures served as the highly active centers for non-radical pathways. The possible degradation pathways and intermediate products accompanying DOX-H degradation were also analyzed in detail. This study provides key insights into the further development of heterogeneous metallic oxides-carbon catalysts for antibiotic-containing wastewater treatment.

Interconnected hierarchical nickel-carbon hybrids assembled by porous nanosheets for Cr(VI) reduction with formic acid.

Magnetic carbon materials promise distinct advantages in the decontamination of heavy metal ions. In this work, a novel interconnected hierarchical nickel-carbon (Ni@IHC) hybrid was synthesized by combining the solvothermal method with a one-step pyrolysis under argon atmosphere. Benefitting from 3D flower-like morphology, interconnected porous nanosheets, large surface area, and abundant Ni nanoparticles, Ni@IHC hybrids can remove Cr(VI) within 25 min by using formic acid (FA) as a reductant at 25 ℃. Furthermore, the experimental parameters that can affect the material catalytic performance such as initial Cr(VI) concentration, catalyst dosage, FA concentration, and temperature were also investigated in detail. It was found that highly dispersed Ni nanoparticles contributed significantly to the reduction process. More importantly, the embedded Ni nanoparticles favor fast separation by a magnet and were helpful for the recycles use. This Ni@IHC hybrid was obtained by a facile and easy scale-up method, resulting in the fast transformation of Cr(VI) into Cr(III).

Solvent-Free Synthesized Monolithic Ultraporous Aluminas for Highly Efficient Removal of Remazol Brilliant Blue R: Equilibrium, Kinetic, and Thermodynamic Studies.

In this study, ultraporous aluminas (UPA) were synthesized as new effective adsorbents for Remazol Brilliant Blue R (RBBR) removal from aqueous solutions. The UPA monoliths were grown via facile oxidation process, followed by isochronous annealing treatment in air at different temperatures, through which γ, θ, and α phase polycrystalline fibrous grains of UPA can be accordingly obtained. The experimental factors that affect the material adsorption performances including initial pH, contact time, and temperature were comprehensively studied by batch experiments. The RBBR adsorption isotherms of UPA(γ) and UPA(θ) powders were found almost identical, while UPA(α) powders showed low effectiveness. To obtain the desirable mechanical stability of the UPA monolith with considerable RBBR adsorption capacity, UPA(θ) powders were further studied. The UPA(θ) powders exhibited maximum RBBR adsorption at pH 2 due to the positively charged surface under acidic conditions. Compared with the Lagergren pseudo-first-order model, the pseudo-second-order model was found to explain the adsorption kinetics better. Despite the film diffusion dominating the adsorption process, the contributions of the intraparticle diffusion and chemical reactions were also found significant. The adsorption equilibrium data at different temperatures were fitted by the Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich (D-R) isotherm models. The Langmuir model was found the most effective in the description of equilibrium data, and the maximum RBBR adsorption capacity retained by UPA(θ) powders was 122.55 mg·g-1 at 295 K. Thermodynamic parameters (ΔG0, ΔH0, and ΔS0) indicated the adsorption process was spontaneous and exothermic in nature.

Solvent-free engineering of Fe0/Fe3C nanoparticles encased in nitrogen-doped carbon nanoshell materials for highly efficient removal of uranyl ions from acidic solution.

In this work, nitrogen-doped carbon nanoshell structure with the encased Fe0/Fe3C nanoparticles (Fe@NC) was synthesized with a solvent-free method via direct carbonizing the ground mixture of dicyandiamide and ferric chloride hexahydrate. The morphology, structure, and surface properties of as-synthesized Fe@NC were characterized systematically, and the removal performance of Fe@NC towards U(VI) was studied in detail. The results manifested that the Fe@NC possessed large surface area (127.0 m2/g) with mesoporosity and the encapsulated Fe0/Fe3C nanoparticles were concentrated at the tip of N-doped carbon nanotubes. Moreover, the Fe@NC hybrid material exhibited the maximum removal capacities of 0.85 and 0.44 mg/m2 at pH 4.5 and 1.5, respectively. The mechanism of U(VI) removal by the Fe@NC was attributed to the synergistic effects of adsorption via nitrogen/oxygen-containing groups and redox reaction between Fe0/Fe2+ and U(VI).

Construction of novel graphene-based materials GO@SiO2@C@Ni for Cr(VI) removal from aqueous solution.

A series of novel sandwich-like GO@SiO2@C@Ni composites were developed. The morphologies and adsorption capacities of the materials sintered at different carbonization temperatures were investigated. The formed GO@SiO2@C@Ni-400 possessed of wonderful dispersion, large surface area (229.88 m2/g) and high saturation magnetization. Batch experimental results revealed that maximum adsorption capacities of these materials towards Cr(VI) were as follows: GO@SiO2@C@Ni-400 (299.20 mg/g) > GO@SiO2@C@Ni-500 (244.05 mg/g) > GO (202.39 mg/g) > Graphene@C@Ni (188.80 mg/g) > GO@SiO2@C@Ni-600 (165.51 mg/g) > GO@SiO2@C@Ni-700 (93.36 mg/g). Moreover, the influence of hydrochemistry, such as contact time, pH, co-existing ions and solution temperature, on Cr(VI) adsorption was researched as well. It was demonstrated that GO@SiO2@C@Ni-400 had remarkable adsorption capacity for Cr(VI) removal under the acidic condition, hardly disturbed by other anions, and showed better adsorption performance at 328 K. Besides, On the base of X-ray photoelectron spectroscopy analysis, mechanisms of adsorption could be explained that Cr(VI) was reduced to Cr(III) by nitrogen dopant, and the complexation was existed between Cr(VI) and oxygen-containing functional groups. Additionally, GO@SiO2@C@Ni-400 could be easily separated under the external magnetic field and displayed outstanding reusability. Herein, GO@SiO2@C@Ni-400 opens up the possibility of future practical applications.

Gamma-ferric oxide nanoparticles decoration onto porous layered double oxide belts for efficient removal of uranyl.

Layered double oxides (LDO) and γ-Fe2O3 have been demonstrated to be promising adsorbents to remove radioactive elements from aqueous media. Herein, magnetic γ-Fe2O3 nanoparticles decoration onto porous layered double oxides belts (γ-Fe2O3/LDO) were fabricated by in situ solid-state thermolysis technique combined with Fe(III)-loaded layered double hydroxides as a precursor. The microstructure, chemical composition, and magnetic properties of γ-Fe2O3/LDO were characterized in detail. The as-obtained γ-Fe2O3/LDO was employed as an adsorbent for the elimination of U(VI) from water. The adsorption process followed the Langmuir model with the maximal adsorption capacity of U(VI) onto γ-Fe2O3/LDO being 526.32 mg·g-1 at 303 K and pH 5, which surpassed pristine LDO and many other materials. The Fourier transformed infrared spectra and the X-ray photoelectron spectra analysis suggested that the interaction mechanism was mainly controlled by the surface complexation and electrostatic interactions. All in all, the γ-Fe2O3/LDO with remarkable adsorption capacity, excellent regeneration, and easy magnetic separation opens a new expectation as a suitable material for the cleanup of U(VI) from contaminated water.

Influence of carbonate on sequestration of U(VI) on perovskite.

Cubic perovskite (CaTiO3) was successfully synthesized by a facile solvothermal method and was utilized to sequestrate U(VI) from aqueous solutions. The batch experiments revealed that carbonate inhibited U(VI) sequestration at pH > 6.0 due to the formation of uranyl-carbonate complexes. The maximum sequestration capacity of U(VI) on perovskite was 119.3 mg/g (pH 5.5). The sequestration mechanism of U(VI) on perovskite were investigated by XPS and EXAFS techniques. According to XPS analysis, the presence of U(IV) and U(VI) oxidation states revealed the photocatalytic reduction of U(VI) by perovskite under UV-vis irradiation. In addition, photocatalytic reduction performance significantly decreased in the presence of carbonate. Based on EXAFS analysis, the occurrence of U-Ti and U-U shells revealed the inner-sphere surface complexation and reductive precipitation of U(VI) on perovskite. These findings herein are crucial for the application of perovskite-based composites in the decontamination of U(VI) in aquatic environmental cleanup.

Investigation of the adsorption mechanisms of Pb(II) and 1-naphthol by ß-cyclodextrin modified graphene oxide nanosheets from aqueous solution.

ß-cyclodextrin decorated graphene oxides (ß-CD-GO) was prepared by using an in-situ aggregation treatment, and used to remove inorganic (Pb(II)) and organic pollutants (1-naphthol) from water environment. The batch adsorption experiments of as-prepared ß-CD-GO were carried out as a function of pH values, initial Pb(II) and 1-naphthol concentration, ionic strength, contact time and temperature. ß-CD-GO kinetic results indicated that the adsorption was dominated by chemisorptions and followed a pseudo-second order model. The maximum adsorption capacities of ß-CD-GO toward Pb(II) and 1-naphtholon the base of the Langmuir model were 149.56 and 207.6 mg·g-1 at 293 K, respectively. The thermodynamic experiments revealed that the adsorption of Pb(II) and 1-naphthol was spontaneous and endothermic. The surface compexation, hydrogen bonds and π-π interactions contributed to Pb(II) and 1-naphthol adsorption by means of the hydroxy and carboxyl functional groups on the surface of the ß-CD-GO. The experimental results indicate that the ß-CD-GO is an excellent composite for the elimination of Pb(II) and 1-naphthol from wastewater.

Synthesis of Ag nanoparticles decoration on magnetic carbonized polydopamine nanospheres for effective catalytic reduction of Cr(VI).

More discrete and active Ag nanoparticles (Ag NPs) were fabricated by decorating them on the surface of magnetic nanoparticles encapsulated in carbonized polydopamine nanospheres (M/C-PDA/Ag) via in-situ solid-state decomposition process. The morphology, structure, surface compositions and textural properties of the M/C-PDA and M/C-PDA/Ag catalyst were characterized. The results revealed a dispersion of Ag NPs with average particle size of less than 50 nm on C-PDA nanospheres uniformly embedded with Fe3C NPs of only 3-5 nm in size. With the synergistic effect of Ag NPs, nitrogen doping, and hierarchical mesopores, M/C-PDA/Ag displayed a superior catalytic capability for catalytic reduction of toxic Cr(VI) to less-toxic Cr(III) by formic acid as a reductant. Moreover, M/C-PDA/Ag maintained good physicochemical structure and stable activity even after several cycles of reactions. According to the results, the simple synthetic strategy, good stability, highly catalytic activity, and easy magnetic separation property of M/C-PDA/Ag hybrid make it serve as a promising environmentally friendly catalyst for the elimination of Cr(VI).

Impact of water chemistry on surface charge and aggregation of polystyrene microspheres suspensions.

The discharge of microplastics into aquatic environment poses the potential threat to the hydrocoles and human health. The fate and transport of microplastics in aqueous solutions are significantly influenced by water chemistry. In this study, the effect of water chemistry (i.e., pH, foreign salts and humic acid) on the surface charge and aggregation of polystyrene microsphere in aqueous solutions was conducted by batch, zeta potentials, hydrodynamic diameters, FT-IR and XPS analysis. Compared to Na+ and K+, the lower negative zeta potentials and larger hydrodynamic diameters of polystyrene microspheres after introduction of Mg2+ were observed within a wide range of pH (2.0-11.0) and ionic strength (IS, 0.01-500mmol/L). No effect of Cl-, HCO3- and SO42- on the zeta potentials and hydrodynamic diameters of polystyrene microspheres was observed at low IS concentrations (<5mmol/L), whereas the zeta potentials and hydrodynamic diameters of polystyrene microspheres after addition of SO42- were higher than that of Cl- and HCO3- at high IS concentrations (>10mmol/L). The zeta potentials of polystyrene microspheres after HA addition were decreased at pH2.0-11.0, whereas the lower hydrodynamic diameters were observed at pH<4.0. According to FT-IR and XPS analysis, the change in surface properties of polystyrene microspheres after addition of hydrated Mg2+ and HA was attributed to surface electrostatic and/or steric repulsions. These investigations are crucial for understanding the effect of water chemistry on colloidal stability of microplastics in aquatic environment.

Polyaniline-modified 3D-flower-like molybdenum disulfide composite for efficient adsorption/photocatalytic reduction of Cr(VI).

Polyaniline (PANI) was modified onto 3D flower-like molybdenum disulfide (MoS2) to prepare a novel organic-inorganic hybrid material, PANI@MoS2. PANI@MoS2 was characterized by scanning and transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction and thermogravimetric analysis. The results indicate that PANI was modified onto MoS2. PANI@MoS2 was applied as an adsorbent to remove Cr(VI) from aqueous solutions, and the adsorption isotherms fit well to the Langmuir model; the maximum removal capacity of Cr(VI) by PANI@MoS2 was 526.3 and 623.2mg/g at pH 3.0 and 1.5, respectively. PANI@MoS2 exhibited an enhanced removal capacity of Cr(VI) in comparison with bare MoS2 and other adsorbents. The adsorption of Cr(VI) on PANI@MoS2 might be attributed to the complexation between the amine and imine groups on the surface of PANI@MoS2 with Cr(VI). This study implies that the hybrid material PANI@MoS2 is a potential adsorbent for Cr(VI) removal from large volumes of aqueous solutions.