Chemically stable magnetic nanoparticles for metal adsorption and solid acid catalysis in aqueous media

Abstract

We have developed a magnetically collectable, reusable adsorbent and a catalyst for concentrating heavy metal ions in acidic aqueous solutions and solid acid catalysis in aqueous media. Chemically stable, magnetic rattle-type core-shell particles, comprising metallic cobalt nanoparticles in hollow silica microspheres, were prepared by the sol-gel reaction of alkylsilyl trichlorides around water droplets in a water-in-oil emulsion. Sulfonic groups were immobilized on the external surface of the core-shell particles through silylation with 3-mercaptopropyl(trimethoxysilane) and subsequent oxidization of the thiol groups by nitric acid. The sulfonic groups acted as adsorption sites for Zn and Pb ions under acidic conditions and as catalytically active sites for the hydrolysis of ethyl acetate in aqueous media. The enclosed Co was not eroded during the regeneration of the adsorbent/catalyst by 1 M HCl. The chemical stability arose from the dense non-porous shell, which prevents the passage of solvents.

An expedient ‘click’ approach for the synthetic evaluation of ester‐triazole‐tethered organosilica conjugates

“…The eradication of toxic transition metal ions accumulated in the biosphere and aqueous milieu is an important issue since long‐term exposure to them can lead to cardiovascular deficiency, lung neurological infection, bone lesion, hypertension and cancer, just to name a few. Consequently, many research groups have pioneered the introduction of advanced techniques such as ion exchange resins, coagulation, electro‐deposition, solvent extraction, hydrogels, biomimetic compounds, biopolymers, activated carbon and adsorbents for the removal of these toxic metal ions . Of all these methods, liquid–solid phase adsorption is indeed the most common method in practical use since the rest of them have severe drawbacks, such as complex working apparatus, non‐recyclability, low efficiency, sensitivity and selectivity, and cost .…”

Enhancement of Photo-Oxidation Activities Depending on Structural Distortion of Fe-Doped TiO2 Nanoparticles

“…The surface-sensitive S 2 p core level spectra were recorded using HRPES after 360 L of 2-ATP exposure in the presence of the same amount of oxygen under 365-nm UV light illumination. There are three distinct 2 p 3/2 peaks at 161.5, 162.9, and 168.6 eV, which correspond to the C-SH unbounded state (denoted S1), bounded state (denoted S2), and sulfonic acid (SO 3 H) (denoted S3), respectively [ 30 , 31 ]. Sulfonic acid was formed from the oxidation of thiol in 2-ATP.…”

Direct Crystallization of Layered Silicates on the Surface of Amorphous Silica

“…Hollow silica microspheres have potential applications in catalysis with molecular sieving, drug delivery, and magnetic fluid . We have studied encapsulation of a heteropoly compound and a magnetic substance through reverse emulsion template syntheses. The latter materials, in particular, have been available for adsorbent/catalyst supports with ability for facile recovery using magnets from aqueous media.…”