Extraction of trace amounts of silver on various amino-functionalized nanoporous silicas in real samples

Loading of Silver (I) Ion in L-Cysteine-Functionalized Silica Gel Material for Aquatic Purification

The L-cysteine-functionalized silica (SG-Cys-Na+) matrix was effectively loaded with silver (I) ions using the batch sorption technique. Optimal Ag(I) loading into SG-Cys-Na+ reached 98% at pHi = 6, 80 rpm, 1 mg L-1, and a temperature of 55 °C. The Langmuir isotherm was found to be suitable for Ag(I) binding onto SG-Cys-Na+ active sites, forming a homogeneous monolayer (R2 = 0.999), as confirmed by FTIR spectroscopy. XRD analysis indicated matrix stability and the absence of Ag2O and Ag(0) phases, observed from diffraction peaks. The pseudo-second-order model (R2 > 0.999) suggested chemisorption-controlled adsorption, involving chemical bonding between silver ions and SG-Cys-Na+ surface. Thermodynamic parameters were calculated, indicating higher initial concentrations leading to increased equilibrium constants, negative ΔG values, positive ΔS values, and negative ΔH. This study aimed to explore silver ion saturation on silica surfaces and the underlying association mechanisms. The capability to capture and load silver (I) ions onto functionalized silica gel materials holds promise for environmental and water purification applications.

A novel poly(2-mercaptobenzothiazole) coated magnetic nanoadsorbent derived from ZIF-8 for preconcentration/determination of palladium and silver

Herein, a novel poly(2-mercaptobenzothiazole) coated magnetic nanoadsorbent derived from zeolitic-imidazole framework-8 (ZIF-8) was synthesized and then employed for the extraction/preconcentration of trace amounts of palladium and silver in various real matrixes. In this way, magnetite was fabricated first, and then functionalized with tetraethyl orthosilicate. After that, the synthesized magnetite@silica was coated with the ZIF-8 to obtain magnetic ZIF-8. Afterward, the magnetic ZIF-8 was pyrolyzed under the protection of a nitrogen atmosphere to get a magnetic carbon nanoadsorbent. Finally, the magnetic carbon was functionalized with a conductive polymer (poly-2-mercaptobenzothiazole). Fabrication of the nanoadsorbent was affirmed with scanning and transmission electron microscopies, elemental analysis, X-ray diffraction, Fourier transform infrared spectroscopy, and vibrating sample magnetometry. The method is linear from 0.25 to 200 μg L^-1 for silver, and from 0.5 to 250 μg L^-1 for palladium. The detection limits are 0.07 and 0.15 μg L^-1 for Ag and Pd, respectively. The precision was evaluated at three concentration levels (1, 75, 200 μg L^-1, n = 5) and all the relative standard deviation (RSD) values were lower than 10.3%. In the end, the new method was utilized for the preconcentration/determination of trace amounts of palladium and silver in various real matrixes, satisfactorily (relative recovery: 86% to 104%; RSD%: 4.0-9.5%).

Fabrication of a novel magnetic metal-organic framework functionalized with 2-aminothiophenol for preconcentration of trace silver amounts in water and wastewater

Herein, a novel magnetic metal-organic framework functionalized (MMOF) with 2-aminothiophenol (2-ATP) was fabricated and employed for separation/preconcentration of trace silver amounts. At first magnetite nanoparticles (Fe3O4 NPs) were synthesized and then coated with SiO2. Thereafter, the Fe3O4@SiO2 nanoparticles were modified with 2-ATP. Finally, the functionalized MMOF was prepared by the fabrication of MIL-101(Cr) in the presence of Fe3O4@SiO2@2-ATP NPs. MIL-101(Cr)/Fe3O4@SiO2@2-ATP nanocomposite was characterized with FT-IR, SEM, elemental analysis, XRD and VSM and then utilized in the separation/determination of silver ions in various real samples. The effects of diverse experimental variables such as pH, uptake time, adsorbent amount, desorption time, eluent concentration and volume were studied comprehensively employing experimental design methodology. After optimization, LOD and linearity were 0.05 ng mL-1 and 0.2-200 ng mL-1, respectively. Repeatability of the new method was determined based on RSD value for 5, 50, 150 ng mL-1 (n = 5) concentrations which was 9.3%, 6.8% and 4.5%, respectively. Ultimately, the outlined method was utilized in the separation/determination of silver ions in various water and wastewater samples satisfactorily.