Induced rapid magnetic sedimentation of stabilized-Fe3O4 nanoparticles by bridging and depletion flocculation

Fe3O4-Nanoparticle-Doped Epoxy Resin as a Detachable Adhesive by Electromagnetic Heating for GFRP Single-Lap Joints

An adhesive based on a Fe3O4-nanoparticle (MNP)-doped epoxy resin was proposed for the development of detachable adhesive joints with GFRP substrates. The analysis of cryofractures showed that the increasing MNP content promotes a higher presence of larger aggregates and a lower sedimentation of nanoparticles due to the higher viscosity of the mixture. In this regard, the inclusion of expandable microspheres (MS) induces a more uniform dispersion of MNPs, reducing their sedimentation. The capability of the proposed adhesives for electromagnetic (EM) heating was also evaluated, with increases in temperature of around 100 °C at 750 A, enough to reach the Tg of the polymer required to facilitate the adhesive detachment, which is around 80 °C. Finally, the lap shear strength (LSS) of 14 and 20 wt.% MNP samples was evaluated in a single-lap shear joint with simultaneous EM heating. The LSS values were reduced by 60-80% at 750 A, thus promoting successful adhesive joint detachment under EM heating.

Biocompatibility of magnetic nanoparticles coating with polycations using A549 cells

Fe₃O₄ nanoparticles were obtained by chemical coprecipitation of iron chloride and sodium hydroxide. The morphology and sizes of the obtained nanoparticles were characterized using laser Doppler velocimetry, transmission electron and atomic force microscopy. Then the nanoparticles were stabilized by three polycations (polyethylenimine (PEI), poly(allylamine hydrochloride) (PAH), poly(diallyldimethylammonium chloride) (PDADMAC)) to increase their biocompatibility. The cytotoxicity of the obtained polymer-stabilized nanoparticles was studied using a human lung carcinoma cell line (A549). The biodistribution of nanoparticles stabilized by polycations in human lung carcinoma cells was analyzed by transmission electron microscopy, and the toxicity of nanomaterials was evaluated using toxicity tests and flow cytometry. As a result, the most biocompatible nanoparticle-biopolymer complex was identified. PAH stabilized magnetic nanoparticles demonstrated the best biocompatibility, and the PEI-magnetic nanoparticle complex was the most toxic.

Synthesis of Fe3O4 nanocomposites for efficient separation of ultra-small oil droplets from hexadecane-water emulsions

Eco-friendliness and low cost are critical when investigating new oil–water separation agents with high separation efficiencies for the treatment of emulsified oily wastewater in industrial applications, including crude oil exploitation. Treatment methods specifically suited to wastewater containing ultra-small oil droplets are lacking and urgently required. This study investigated the one-pot synthesis of humic acid and polydimethyldiallylammonium chloride coated Fe₃O₄ nanoparticles. A low dosage of the nanoparticles (375 μg mL⁻¹) exhibited excellent separation efficiency (nearly 100%) and reusability when applied to hexadecane–water emulsions containing ultra-small droplets (200–300 nm). Electrostatic interactions and the strong interfacial activity of the nanoparticles played essential roles in achieving oil–water separation. This study provided an efficient extraction material synthesized by a facile and cheap method for separating ultra-small oil droplets from emulsions.

A facile one-pot synthesis of Fe₃O₄ nanoparticles exhibited excellent separation efficiency with a low dosage and reusability when applied to hexadecane–water emulsions containing ultra-small droplets.

Magnetic separation of phosphate contaminants from starch wastewater using magnetic seeding

Traditional chemical precipitation of phosphates from wastewater is somewhat inefficient because it produces some ultrafine hydroxyapatite particles that are difficult to settle. In this study, magnetic seeds with a core-shell structure were prepared by sulfation roasting for magnetic flocculation of those fine particles. Zeta potential measurements show that the hydroxyapatite particles are positively charged at pH 10, whereas the magnetic seeds are negatively charged. The Derjaguin-Landau-Verwey-Overbeek calculation indicates that the van der Waals force between the magnetic seeds and hydroxyapatite particles is always attractive. Moreover, the electrostatic attraction also contributes to aggregation of the magnetic seeds and hydroxyapatite particles. Orthogonal experiments show that the main factor affecting the magnetic flocculation is the dosage of magnetic seeds, and polymeric ferric sulfate also plays an important role. Under the optimal magnetic flocculation experimental conditions, the turbidity of wastewater after magnetic separation was only 16.388 NTU, contributing to the removal of phosphate contaminants. Therefore, magnetic flocculation and magnetic separation may provide an alternative solution for efficient purification of phosphate-containing wastewater.