Hollow Polyaniline Microsphere/MnO2/Fe3O4 Nanocomposites in Adsorptive Removal of Toxic Dyes from Contaminated Water

Dyes are considered as recalcitrant compounds and are not easily removed through conventional water treatment processes. The present study demonstrated the fabrication of polyaniline hollow microsphere (PNHM)/MnO₂/Fe₃O₄ composites by in situ deposition of MnO₂ and Fe₃O₄ nanoparticles on the surface of PNHM. The physicochemical characteristics and adsorption behavior of the prepared PNHM/MnO₂/Fe₃O₄ composites towards the removal of toxic methyl green (MG) and Congo red (CR) dyes have been investigated. The characterization study revealed the successful synthesis of the prepared PNHM/MnO₂/Fe₃O₄ adsorbent with a high Brunauer-Emmett-Teller (BET) surface area of 191.79 m²/g. The batch adsorption study showed about 88 and 98% adsorption efficiencies for MG and CR dyes, respectively, at an optimum dose of 1 g/L of PNHM/MnO₂/Fe₃O₄ at pH ∼6.75 at room temperature (303 ± 3 K). The adsorption phenomena of MG and CR dyes were well described by the Elovich and pseudo-second-order kinetics, respectively, and Freundlich isotherm model. The thermodynamics study shows that the adsorption reactions were endothermic and spontaneous in nature. The maximum adsorption capacity (Q_max) for MG and CR dyes was observed as 1142.13 and 599.49 mg/g, respectively. The responsible adsorption mechanisms involved in dye removal were electrostatic interaction, ion exchange, and the formation of the covalent bonds. The coexisting ion study revealed that the presence of phosphate co-ion considerably reduced the CR dye removal efficiency. However, the desorption-regeneration study demonstrated the successful reuse of the spent PNHM/MnO₂/Fe₃O₄ material for the adsorption of MG and CR dyes for several cycles. Given the aforementioned findings, the PNHM/MnO₂/Fe₃O₄ nanocomposites could be considered as a promising adsorbent for the remediation of dye-contaminated water.

Hollow Polyaniline Microsphere/Fe3O4 Nanocomposite as an Effective Adsorbent for Removal of Arsenic from Water

Polyaniline hollow microsphere (PNHM)/Fe₃O₄ magnetic nanocomposites have been synthesized by a novel strategy and characterized. Subsequently, PNHM/Fe₃O₄-40 (Fe₃O₄ content: 40 wt.%) was used as an adsorbent for the removal of arsenic (As) from the contaminated water. Our investigations showed 98–99% removal of As(III) and As(V) in the presence of PNHM/Fe₃O₄-40 following pseudo-second-order kinetics (R² > 0.97) and equilibrium isotherm data fitting well with Freundlich isotherm (R² > 0.98). The maximum adsorption capacity of As(III) and As(V) correspond to 28.27 and 83.08 mg g⁻¹, respectively. A probable adsorption mechanism based on X-ray photoelectron spectroscopy analysis was also proposed involving monodentate-mononuclear/bidentate-binuclear As-Fe complex formation via legend exchange. In contrast to NO₃⁻ and SO₄²⁻ ions, the presence of PO₄³⁻ and CO₃²⁻ co-ions in contaminated water showed decrease in the adsorption capacity of As(III) due to the competitive adsorption. The regeneration and reusability studies of spent PNHM/Fe₃O₄-40 adsorbent showed ~83% of As(III) removal in the third adsorption cycle. PNHM/Fe₃O₄-40 was also found to be very effective in the removal of arsenic (<10 μg L⁻¹) from naturally arsenic-contaminated groundwater sample.

Construction of polyporous polymer microspheres with a tailored mesoporous wall

Polymer microspheres with a novel hierarchically porous structure (inner macropores and a mesoporous wall) were fabricated by taking advantage of γ-ray-radiation-initiated dispersion polymerization.

A facile method of synthesizing size-controlled hollow cyanoacrylate nanoparticles for transparent superhydrophobic/oleophobic surfaces

A novel method to synthesize size-controllable hollow polymeric nanoparticles is reported. The synthesis process completes in a moment with tunable particle diameters. Coated surfaces show superhydrophobicity/oleophobicity with high transparency.

Poly(N-acryloyl ciprofloxacin-co-acrylic acid) grafted magnetite nanoparticles for microbial decontamination of collagen solution: have we conquered the problem of antimicrobial residues?

A strategy to avoid antimicrobial residues in decontaminated collagen solution is provided.