Synthesis/characterization of a new chelating resin and on-line solid phase extraction for the determination of Ag(I) and Pd(II) from water, cream, anode slime and converter samples by flow injection flame atomic absorption spectrometry

In-situ formation of the adsorbent based on octadecylamine for the extraction of Ag+ ions from aqueous solutions and its determination by microinjection flame atomic absorption spectrometry

In this research, a dispersive solid phase extraction procedure based on changing the solubility of octadecylamine with pH was proposed to determine Ag+ ions in different water samples. For this purpose, first, the pH of sample solution containing the analyte was adjusted to 10.5. Then desired volume of the octadecylamine dissolved in acidic solution was injected into the solution. Because of the low solubility of octadecylamine in alkaline solution, a cloudy state was formed. The produced octadecylamine particles acted as a complexing agent for Ag+ ions and adsorbent for the formed complex. The obtained cloudy solution was centrifuged and the sedimented particles were removed and dissolved in a diluted nitric acid solution. It was injected into a flame atomic absorption spectrometry to determine the extracted amounts of the analyte. The effect of important parameters such as the amount of octadecylamine, volume of nitric acid, and centrifugation and vortexing conditions on the extraction efficiency of the procedure was studied and optimized. In optimal conditions, the developed method showed a linear range of 0.50-200 µg L-1. The limits of detection and quantification were 0.18 and 0.50 µg L-1, respectively. Extraction recovery was 93.6%. The relative standard deviations were less than 4%. The effectiveness of the method was investigated by determination of Ag+ ions in water and wastewater samples.

An Ethyl-Thioglycolate-Functionalized Fe3O4@ZnS Magnetic Fluorescent Nanoprobe for the Detection of Ag+ and Its Applications in Real Water Solutions

Ethyl-thioglycolate-modified Fe₃O₄@ZnS nanoparticles (Fe₃O₄@ZnS-SH) were successfully prepared using a simple chemical precipitation method. The introduction of ethyl thioglycolate better regulated the surface distribution of ZnS, which can act as a recognition group and can cause a considerable quenching of the fluorescence intensity of the magnetic fluorescent nanoprobe, Fe₃O₄@ZnS-SH. Benefiting from stable fluorescence emission, the magnetic fluorescent nanoprobe showed a highly selective fluorescent response to Ag+ in the range of 0-400 μM, with a low detection limit of 0.20 μM. The magnetic fluorescent nanoprobe was used to determine the content of Ag⁺ in real samples. A simple and environmentally friendly approach was proposed to simultaneously achieve the enrichment, detection, and separation of Ag⁺ and the magnetic fluorescent nanoprobe from an aqueous solution. These results may lead to a wider range of application prospects of Fe₃O₄ nanomaterials as base materials for fluorescence detection in the environment.

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.

Comparative study on a kilowatt-MPT-MS-based method with two ion polarity modes for the inert palladium metal

Inert metals are of much importance and play a key role in modern industrial manufacturing. The analytical techniques of inert metals remain challenging. In particular, the mass spectrometry of inert metal elements is yet to be further developed, which also limits the contemporary conceptual in situ analysis of inert metals. As the representative element, the mass spectral detection of palladium is critical and of far-reaching significance. Herein, we developed a mass spectrometry method, which can be used for the high-speed and in situ analysis of palladium, and even for other inert metals. Combining the line ion trap mass spectrometer with the versatile ambient ionization source, a novel kilowatt microwave plasma torch (MPT) can be used to obtain the fully characteristic MPT mass spectra of palladium. Detailed multistage tandem mass spectra show that the general form of target ions is [M(O2)x(NO)mNy(NO2)n]- for the negative ion mode and [M(H2O)x(NO2)y(N2)m]+ for the positive ion mode. Moreover, the formation and evolution of these palladium complex ions were reasonably derived based on the analysis of MPT background mass spectra. This mass spectrometric technique is also suitable for the determination of the palladium-containing solution in the sub-trace level. Semi-quantitative results showed that the detecting ability for palladium in the negative mode is better than that of the positive mode. Under the negative ion mode, the limit of detection (LOD) for m/z 259 were evaluated to be 0.5 μg L-1 under the optimized conditions of the negative mode, with the linear range of 1-100 μg·L-1 (R2 ≥ 0.9985) and the relative standard deviation (RSD, n = 11) being in the range of 1.20%-5.98% (refer to Table S3). Our experimental data showed that MPT-MS was a promising technique for providing another alternative in the on-site analysis of liquid samples and other intimate relevant fields, as the supplement of ICP-MS for the detection of inert metal elements. On the other hand, this work will also certainly promote the more broad applications of platinum-group elements (PGE) in modern science and industry.

Removal of oxytetracycline and determining its biosorption properties on aerobic granular sludge

This study investigates biosorption of Oxytetracycline, a broad-spectrum antibiotic, using aerobic granular sludge as an adsorbent in aqueous solutions. A sequencing batch reactor fed by a synthetic wastewater was operated to create aerobic granular sludge. Primarily, the pore structure and surface area of granular sludge, the chemical structure and the molecular sizes of the pharmaceutical, operating conditions, such as pH, stirring rate, initial concentration of Oxytetracycline, during adsorption process was verified. Subsequently, thermodynamic and kinetic aspects of the adsorption were examined and adsorption isotherm studies were carried out. It was shown that the aerobic granular sludge was a good alternative for biosorption of this pharmaceutical. The pharmaceutical was adsorbed better at pH values of 6-8. The adsorption efficiency increased with rising ionic strength. Also, it was seen that the adsorption process was an exothermic process in terms of thermodynamics. The adsorption can be well explained by Langmuir isotherm model.

Application of l-cystine modified zeolite for preconcentration and determination of ultra-trace levels of cadmium by flame atomic absorption spectrometry

A very convenient, sensitive and precise solid phase extraction (SPE) system was developed for enrichment and determination of ultra-trace of cadmium ion in water and plant samples. This method was based on the retention of cadmium(II) ions by l-cystine adsorbed in Y-zeolite and carry out in a packed mini-column. The retained cadmium ions then were eluted and determined by flame atomic absorption spectrometry. The scanning electron microscopy (SEM), powder X-ray diffraction (XRD) and Fourier Transform Infrared (FT-IR) spectroscopy techniques were applied for the characterization of cystine modified zeolite (CMZ). Some experimental conditions affecting the analytical performance such as pH, eluent type, concentration of sample, eluent flow rate and also the presence of interfering ions were investigated. The calibration graph was linear within the range of 0.1-7.5ngmL(-1) and limit of detection was obtained 0.04ngmL(-1) with the preconcentration factor of 400. The relative standard deviation (RSD) was obtained 1.4%, indicating the excellent reproducibility of this method. The proposed method was successfully applied for the extraction and determination of cadmium(II) ion in black tea, cigarette's tobacco and also various water samples.

Preconcentration of Ag and Pd ions using graphite oxide and 2,6-diaminopyridyne from water, anode slime and catalytic converter samples

In this work, graphite oxide was used for the first time as an effective adsorbent for the separation/preconcentration of Ag and Pd ions in various samples prior to flame atomic absorption detection.