We report a facile method to synthesize Fe3O4@polydopamine (PDA)-Ag core–shell microspheres. Ag nanoparticles (NPs) are deposited on PDA surfaces via in situ reduction by mussel-inspired PDA layers. High catalytic activity and fast adsorption of a model dye methylene blue (MB) at different pH values are achieved mainly due to the presence of monodisperse Ag NPs and electrostatic interactions between PDA and MB. The as-prepared Fe3O4@PDA-Ag microspheres also show high cyclic stability (>27 cycles), good acid stability, and fast regeneration ability, which can be achieved efficiently within several minutes by using NaBH4 as the desorption agent, showing great potentials in a wide range of applications.

Highly Regenerable Mussel-Inspired Fe3O4@Polydopamine-Ag Core–Shell Microspheres as Catalyst and Adsorbent for Methylene Blue Removal

Surface zwitterionization of graphene oxide (GO) was firstly conducted by grafting poly(sulfobetaine methacrylate) (PSBMA) onto the GO surface via reverse atom transfer radical polymerization (RATRP). Then, a novel type of GO-PSBMA/polyethersulfone (PES) loose nanofiltration membrane (NFM) was constructed by mixing with modified GO composites via phase inversion. FTIR, XRD, TEM, XPS and TGA were applied to analyze the chemical composition and morphology, confirming a favorable synthesis of GO-PSBMA composites. Besides, the effect of the embedded GO-PSBMA nanoplates on the morphology and overall performance of the hybrid membranes was systematically investigated based on the SEM images, water contact angle, zeta potential, and fouling parameters. It was found that the water flux of the hybrid membrane was greatly enhanced from 6.44 L m−2 h−1 bar−1 to 11.98 L m−2 h−1 bar−1 when the GO-PSBMA content increased from 0 to 0.22 wt%. The antifouling tests revealed that the GO-PSBMA embedded membranes had an excellent antifouling performance: a high flux recovery ratio (ca. 94.4%) and a low total flux decline ratio (ca. 0.18). Additionally, the hybrid membranes exhibited a distinct advance in the mechanical strength due to the addition of highly rigid GO. Notably, compared with unmodified membranes, the hybrid membranes had a higher retention of Reactive Black 5 (99.2%) and Reactive Red 49 (97.2%), and a lower rejection of bivalent salts (10% for Na2SO4) at an operational pressure of 0.4 MPa, rendering the membranes promising for dye/salt fractionation.

Surface zwitterionic functionalized graphene oxide for a novel loose nanofiltration membrane

Synergy of adsorption and visible-light photocatalytic degradation of methylene blue by a bifunctional Z-scheme heterojunction of WO 3 /g-C 3 N 4

Hybrid nanomaterials have received voluminous interest due to the combination of unique properties of organic and inorganic component in one material. In this class, magnetic polymer nanocomposites are of particular interest because of the combination of excellent magnetic properties, stability, and good biocompatibility. Organic–inorganic magnetic nanocomposites can be prepared by in situ, ex situ, microwave reflux, co-precipitation, melt blending, and ceramic–glass processing and plasma polymerization techniques. These nanocomposites have been exploited for in vivo imaging, as superparamagnetic or negative contrast agents, drug carriers, heavy metal adsorbents, and magnetically recoverable photocatalysts for degradation of organic pollutants. This review article is mainly focused on fabrication of magnetic polymer nanocomposites and their applications. Different types of magnetic nanoparticles, methods of their synthesis, properties, and applications have also been reviewed briefly. The review also provides detailed insight into various types of magnetic nanocomposites and their synthesis. Diverse applications of magnetic nanocomposites including environmental and biomedical uses have been discussed.

Magnetic polymer nanocomposites for environmental and biomedical applications

Polypyrrole-coated multiwalled carbon nanotubes (PPy-MWCNT) were used for the fabrication of activated carbon-coated MWCNT doped with nitrogen (N-AC-MWCNT). The conceptually new method for the fabrication of non-agglomerated PPy-MWCNT with good coating uniformity allowed the fabrication of uniform and well-dispersed N-AC-MWCNT with high surface area. The use of N-AC-MWCNT allowed the fabrication of supercapacitor electrodes with high mass loading in the range of 15–35 mg cm–2 and with a high active material to current collector mass ratio of 0.21–0.50. The N-AC-MWCNT electrodes showed excellent electrochemical performance in aqueous 0.5 M Na2SO4 electrolyte. The maximum specific capacitance of 3.6 F cm–2 (103.1 F g–1) was achieved for mass loading of 35 mg cm–2 at a scan rate of 2 mV s–1. The aqueous supercapacitor cells, based on N-AC-MWCNT electrodes, exhibited excellent performance with energy density of 16.1 mWh g–1, power density of 14.4 W g–1, and enlarged voltage window of 1.8 V. The individual ele...

Activated Carbon-Coated Carbon Nanotubes for Energy Storage in Supercapacitors and Capacitive Water Purification

Hierarchical WO3 hydrates have been synthesized via an ion exchange method using Na2WO4·2H2O as a precursor. The morphologies and phase structures of WO3 hydrates can be controlled by tuning the concentration of Na2WO4·2H2O solution. The as-synthesized urchin-like WO3·0.33H2O and flower-like WO3·H2O possess high specific surface area and numerous adsorption functional groups, such as WO and O–H bonds, on the surface. These characteristics result in excellent adsorption performance for both organic dyes and heavy metal ions from wastewater. The maximum uptake capacities of the urchin-like WO3·0.33H2O for methylene blue and Pb2+ are 247.3 and 248.9 mg g−1, respectively and those of the flower-like WO3·H2O are 117.8 and 315.0 mg g−1, respectively. The formation mechanism of such hierarchical mesoporous urchin-like WO3·0.33H2O and adsorption mechanism are studied in this paper.

Controlled fabrication of hierarchical WO3 hydrates with excellent adsorption performance

We report the design and synthesis of two hematite (α-Fe2O3)-based nanomaterials based on effective hydrothermal conversion of chemically metastable K1.33Mn8O16 nanowires (KWs) in Fe(NO3)3 aqueous solution. Insights are gained into the functions of sodium dodecyl benzene sulfonate (SDBS) and the mechanisms for generating large quantities of α-Fe2O3 hollow structures (FHSs) and K1.33Mn8O16@α-Fe2O3 heterostructured nanowires (KFHWs) in solution phase. The controllable growth dynamics allows convenient control over the morphology and production of the hematite-based nanostructures. Adsorption experiments indicate that the resulting hematite-based materials are powerful nanosorbents for swift removal of Congo red from wastewater at room temperature. The adsorption kinetics and adsorption isotherm are also investigated and the findings indicate that the as-prepared KFHW and FHS hold great potential as environmentally friendly filter materials for water purification and organic waste removal.

Designed synthesis of hematite-based nanosorbents for dye removal

Proton exchange growth to mesoporous WO3·0.33H2O structure with highly photochromic sensitivity

A new solid niobic acid phase, H2(H2O)Nb2O6, with fluorine (F) doping was crystallized using hydrothermal chemistry. F-doped H2(H2O)Nb2O6 octahedra could function as an efficient heterogeneous catalyst for the photodegradation of organic pollutants in water under UV light irradiation. The high photocatalytic activity of the F-doped H2(H2O)Nb2O6 materials is attributed to a synergistic effect of the specific surface area, the surface characteristics and the crystal structure. Our results suggest novel ways of controlling the crystallization of niobium oxides, further the fundamental understanding of their structure–property relationships, and may lead to their application in fields such as environmental protection and energy production.

New fluorine-doped H2(H2O)Nb2O6 photocatalyst for the degradation of organic dyes

Hollow mesoporous tungsten trioxide spheres (HMTTS) have been synthesized by spray drying method combined with proper calcination and Ag/HMTTS are prepared on the basis of a silver mirror reaction. HMTTS are composed of nanoparticles with diameter of 20-70 nm. The accumulation of nanoparticles generates pores with the mean pore size of about 45 nm. The formation mechanism of hollow mesoporous structure is studied in this work. Ag in WO3 narrows the band gap and derceases the recombination possibility of the photogenerated electron-hole pairs, which enhance photocatalytic activity of Ag/WO3 composites. The degradation rate of methylene blue is 98.16% under UV light illumination for 75 min and 49.07% under visible light irradiation for 150 min by Ag/WO3 composites.

Baixiong Liu

Papers

Controlled fabrication of hierarchical WO3 hydrates with excellent adsorption performance

Designed synthesis of hematite-based nanosorbents for dye removal

Proton exchange growth to mesoporous WO3·0.33H2O structure with highly photochromic sensitivity

New fluorine-doped H2(H2O)Nb2O6 photocatalyst for the degradation of organic dyes

Facile synthesis of hierarchical hollow mesoporous Ag/WO3 spheres with high photocatalytic performance.