A uniform decoration of hyphae by polyaniline nanoparticles (PANI NPs) was achieved here. This novel hybrid structure can be effectively assembled into a film by filtration and disassembled in water by shaking. This reversible process is very fast, which promises applications in nanomaterials including adsorption.

Magnetic Fe3O4@poly(m-phenylenediamine) particles (Fe3O4@PmPDs) with well-defined core–shell structure were first designed for high performance Cr(VI) removal by taking advantages of the easy separation property of magnetic nanoparticles (MNPs) and the satisfactory adsorption property of polymers. Through controlling the polymerization on MNPs, directly coating was realized without the complicated premodification procedures. The particle property and adsorption mechanism were analyzed in details. Fe3O4@PmPDs exhibited tunable PmPD shell thickness from 10 to 100 nm, high magnetic (∼150 to ∼73 emu g–1) and facile separation property by magnet. The coating of PmPD significantly enhanced Cr(VI) adsorption capacity from 46.79 (bare MNPs) to 246.09 mg g–1 (71.55% PmPD loading proportion), much higher than many reported composite adsorbents. The high Cr(VI) removal performance was attributed to the adsorption of Cr(VI) on protonated imino groups and the efficient reduction of Cr(VI) to Cr(III) by amine, followed by Cr(III) chelated on imino groups, which are spontaneous and endothermic. The Fe3O4@PmPDs have great potential in treating Cr(VI)-contaminated water.

Cu doped Fe3O4 (Fe3O4:Cu) particles were synthesized and applied for arsenic adsorption. As the copper ions increase, the adsorption capacity of Fe3O4:Cu towards As(V) and As(III) increases from 7.32 to 42.90 mg g−1 and from 8.12 to 37.97 mg g−1, respectively. The incorporation of copper decreased the particle size, increased the surface area, porosity and zeta potential, leading to the increase of the adsorption sites and affinity toward negative As(V) species. More importantly, the doped copper ions catalyzed the efficient oxidation of As(III) to As(V) by O2 followed by As(V) adsorption. The Fe3O4:Cu particles also exhibited good performance toward low level arsenic removal, excellent separation, and satisfactory regeneration property. The results indicate Fe3O4:Cu particles possess great potential for both As(III) and As(V) adsorption.

The mixing of graphene oxide and protonated poly(m-phenylenediamine) (PmPD) nanoparticles generates floccus that can be readily transformed into graphene@PmPD hybrid hydrogel through redox reaction. This macroscopic material can be directly applied as a monolith column adsorbent for water purification.

Hierarchical porous Fe3O4 particles with tunable grain size were synthesized based on a facile poly (diallyldimethylammonium chloride) (PDDA)-modulated solvothermal method. The products were characterized with scanning electron microscopy (SEM) and transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), N2 adsorption–desorption technique, vibrating sample magnetometer (VSM), and dynamic light scattering (DLS). The results show that increasing the PDDA dosage decrease the grain size and particle size, which increased the particle porosity and enhanced the surface area from 7.05 to 32.75 m2 g–1. Possible mechanism can be ascribed to the PDDA function on capping the crystal surface and promoting the viscosity of reaction medium to mediate the growth and assembly of grain. Furthermore, the arsenic adsorption application of the as-obtained Fe3O4 samples was investigated and the adsorption mechanism was proposed. High magnetic Fe3O4 particles with increased surface area display improved arsenic adsorption performance, superior efficiency in low-level arsenic removal, high desorption efficiency, and satisfactory magnetic recyclability, which are very promising compared with commercial Fe3O4 particles.Keywords: adsorption; Fe3O4; poly (diallyldimethylammonium chloride); solvothermal;

•Cu-OH-assistance satisfies clean synthesis of PmPD nanoparticle with yield 93.1%.•Polymerization mechanism was investigated.•PmPD nanoparticle possesses Ag+ adsorbance of ∼1767 mg g−1.Conventional chemically oxidative polymerization was successfully improved through the cooperative effect of Cu2+ and NaOH (Cu-OH-assistance method for short) to satisfy the high conversion synthesis of poly(m-phenylenediamine) (PmPD) nanoparticles. The highest yield calculated from the mass of de-protonated and de-doped PmPD can reach 93.1%, which obviously lowers the potential pollution caused by the organic side-products left inside the solution after the polymerization. The PmPD obtained via the conventional polymerization procedure that is gradual addition of oxidant, which can induce secondary growth, is the nanoparticles. The possible mechanism on the high yield was discussed based on in situ open-circuit potential, pH detections and Fourier transformed infrared (FTIR) spectroscopy. Moreover, the Ag+ adsorption performance of the PmPD nanoparticles synthesized with the highest yield was investigated. It was found that the adsorbance within 5 min reached up to 61% of the final value. The Ag+ adsorbance of PmPD nanoparticles can be as high as ∼1767 mg g−1, which is much higher than most of the adsorbents up to date.Poly(m-phenylenediamine) nanoparticles with the highest yield of 93.1% can be achieved with conventional chemically oxidative polymerization improved by Cu-OH-assistance method, which further displays superior performance for Ag+ adsorption.

A uniform decoration of hyphae by polyaniline nanoparticles (PANI NPs) was achieved here. This novel hybrid structure can be effectively assembled into a film by filtration and disassembled in water by shaking. This reversible process is very fast, which promises applications in nanomaterials including adsorption.

The mixing of graphene oxide and protonated poly(m-phenylenediamine) (PmPD) nanoparticles generates floccus that can be readily transformed into graphene@PmPD hybrid hydrogel through redox reaction. This macroscopic material can be directly applied as a monolith column adsorbent for water purification.