One-step synthesis of versatile magnetic nanoparticles for efficiently removing emulsified oil droplets and cationic and anionic heavy metal ions from the aqueous environment

Versatile polyethyleneimine (PEI)-coated Fe₃O₄ magnetic nanoparticles (MNPs) have been synthesized by a one-step solvothermal method. The morphologies, structures, and properties of MNPs prepared for different reaction times have been characterized through various techniques. The synthesized MNPs were then used to separate emulsified oil and cationic and anionic heavy metal ions from the aqueous environment; moreover, the effects of the temperature, pH, and ionic strength of aqueous media, the solvothermal reaction time, and the number of reuse cycles on the removal efficiency have been investigated in detail. The results showed that pseudo-second-order kinetics and the Langmuir isotherm well described the adsorption processes of Cu(II) and Cr(VI). The Langmuir model yielded maximum adsorption capacities of 66.6 mg g^-1 for Cu(II) and 54.5 mg g^-1 for Cr(VI) at pH 5.0 and 25 °C. The synthetic MNPs could also efficiently separate diesel oil or olive oil droplets stabilized by sodium dodecyl sulfate from aqueous media. Moreover, these MNPs could be recycled five times without showing significant loss in separation efficiency. Notably, the synthesized PEI-coated MNPs could simultaneously separate emulsified oil and cationic and anionic heavy metal ions from multicomponent wastewater. Such versatile PEI-coated MNPs displayed good affinity towards emulsified oil and cationic and anionic heavy metal ions, showing great potential for practical applications in the treatment of complicated industrial wastewater matrices. Graphical abstract Simultaneous separation of emulsified oil and cationic and anionic heavy metal ions from aqueous media by using polyethyleneimine-coated Fe₃O₄ magnetic nanoparticles.

Ionothermal synthesis of Fe3O4 magnetic nanoparticles as efficient heterogeneous Fenton-like catalysts for degradation of organic pollutants with H2O2

Fe₃O₄ magnetic nanoparticles (MNPs) are attractive heterogeneous Fenton-like catalysts for oxidative degradation of organic pollutants with H₂O₂. Herein highly efficient and stable Fe₃O₄ MNPs (Fe₃O₄-op-DES, ca. 10nm) were successfully prepared via a novel oxidative precipitation-combined ionothermal synthesis, which comprised oxidative precipitation of FeSO₄·7H₂O in choline chloride:2urea deep eutectic solvent. Among five different Fe₃O₄ particles tested, Fe₃O₄-op-DES MNPs exhibited the highest catalytic activity with the activation energy of 47.6kJmol^-1 for degradation of Rhodamine B (RhB) with H₂O₂ under the same conditions (Fe₃O₄ dosage of 0.50gL^-1, H₂O₂ concentration of 40mmolL^-1, pH 6.4, 55°C, 2h). Fe₃O₄-op-DES MNPs were magnetically recoverable, and had good catalytic stability and recyclability without the need of regeneration (>98% degradation efficiency of RhB in 2h and pseudo-first-order rate constant of 0.0376min^-1 after having been continuously running for 12h). The superior catalytic performance of Fe₃O₄-op-DES MNPs was attributed to the combination of multiple technologically important features, including the nanometer size, high Fe²⁺ content, large surface area, high density of surface active sites and stable crystal structure (no phase transformation, negligible iron leaching and particle aggregation after reaction). The wide applicability of Fe₃O₄-op-DES MNPs was also demonstrated by the degradation of four other organic pollutants.

Carbonized medlar-core particles as a new biosorbent for removal of Cu(2+) from aqueous solution and study of its surface morphology

The objective of this study was to investigate the use of carbonized medlar-core particles as a new biosorbent to remove Cu(2+) from aqueous solution. Fourier transform infrared spectroscopy and scanning electron microscopy were used to characterize the biosorbent. This paper reports the effects of adsorbent dose, pH, temperature and concentration of adsorbate. Batch isotherm studies were also performed to understand the ability of the adsorbent. The adsorption behavior of the Cu(2+) was studied using Langmuir and Freundlich adsorption isotherm models. The maximum adsorption capacity determined from the Langmuir adsorption equation has been found as 43.478 mg.g(-1) at 298.15 K. The adsorption of Cu(2+) by medlar core in carbonized form was spontaneous and endothermic. It was also found that the biosorption of Cu(2+) followed second-order kinetics. Carbonized medlar-core particles showed great potential in aqueous solution due to the high adsorption capacity.

Selective oxidation of benzyl alcohol to benzaldehyde with H2O2 in water on epichlorohydrin-modified Fe3O4 microspheres

The enhancing effect of modification by epichlorohydrin on the catalytic activity of Fe₃O₄ microspheres in the title reaction was theoretically and experimentally confirmed.