Recycling of organocatalysts is an important aspect in green chemistry. Several techniques have been applied to address this issue ranging from traditional separation techniques (extraction, chromatography) to immobilization on solid supports. Magnetic separation, i.e. attraction of the catalyst by an external magnet and decantation of the supernatant appeared as a new way for separation of organocatalysts omitting problems connected to filtration when solid supported catalysts are used. In this publication, the state of the art of magnetic nanoparticle-supported organocatalysts is reviewed demonstrating a wide range of applications but at the same time hitherto unaddressed fields awaiting future exploration are discussed.

Magnetite nanoparticles are of great importance in nanotechnology and nanomedicine and have found manifold applications. Here, the effect of coating of magnetite nanoparticles with organic stabilizers, such as O-phosphoryl ethanolamine, glycerol phosphate, phospho-l-ascorbic acid, phospho-d,l-serine, glycolic acid, lactic acid, d,l-malic acid, and d,l-mandelic acid was studied. Remarkably, this procedure led to an improvement of saturation magnetization in three cases rather than to an unfavorable decrease as usually observed. Detailed X-ray powder diffraction investigations revealed that changes in the average crystallite occurred in the coating process. Surprisingly, changes of the average crystallite sizes in either direction were further observed, when the exposure time to the stabilizer was increased. These results imply a new mechanism for the well-known coating of magnetite nanoparticles with stabilizers. Instead of the hitherto accepted simple anchoring of the stabilizers to the magnetite nanoparticle surfaces, a more complex recrystallization mechanism is likely, wherein partial re-dispersion of magnetite moieties from the nanoparticles and re-deposition are involved. The results can help producers and users of magnetite nanoparticles to obtain optimal results in the production of core shell magnetite nanoparticles.

Synthetic dyes represent a significant class of contaminants released in the environment. Crystal violet is a triarylmethane dye used in several fields such as printing inks, the textile or paper industries, as well as in cell histology. Coating magnetic nanoparticles with functionalized polymers has been proved to improve their efficiency, offering unique properties for applications in wastewater treatment. The current paper focuses on preparing and characterising magnetic core-shell nanoparticles coated with poly(benzofuran-co-arylacetic acid) functionalized with folic acid as an organic shell. The new polymer-based magnetic nanostructures were applied for crystal violet extraction from aqueous solutions. The nanostructures were structurally and morphologically investigated by Fourier-transform infrared (FTIR) spectroscopy and transmission electron microscopy (TEM). While thermal and magnetic properties of the magnetic nanostructures were determined by thermogravimetric analysis (TGA) and magnetization measurements (VSM). At the same time, crystal violet concentrations were determined by UV-VIS spectroscopy. The influence of initial dye concentration and contact time on the removal efficiency has been studied to achieve the optimum adsorption conditions. The dye adsorbent neoteric magnetic nanostructure was easily desorbed and reused, the adsorption capacity decreasing from 100% to 97.63% in the first five cycles, reaching a minimum of 88.74% after the 10th recycling step.