جستجوی مقالات مرتبط با کلیدواژه "chromium iii" در نشریات گروه "شیمی"

4-methylcoumarin-7-yloxy-N-4-nitrophenyl acetamide and 4-methylcoumarin-7-yloxy-N-phenyl acetamide were used as effective ionophores for preparation of chromium (III) and copper (II) selective liquid membrane electrodes, respectively. Optimization of the composition of the membranes and the conditions of the analysis was performed, and under the optimized conditions the chromium (III) liquid membrane electrode has a detections limit of 1.0×10-10 with response time 4-6 s and the concentration range 1.0×10-4 to 1.0×10-10 M chromium (III) with a Nernstian slope of 20.25±0.4 mV/decade over the pH range of 4.0–7.5 and copper (II) liquid membrane electrode has a detection limit of 3.0×10-5 with response time about 5 s and the concentration range 1.0×10-1 to 3.0×10-5 M copper (II) with a Nernstian slope of 31.08±0.5 mV/decade over the pH range of 4.5–8. The chromium (III) and copper (II) selective electrodes were stable for about 8 and 5 weeks, respectively. They exhibit good selectivity for two ions. They were successfully applied for the direct determination of chromium (III) and copper (II) in wastewater and as indicator electrodes for potentiometric titration of copper ions and chromium ions with EDTA.

The present study focuses on the synthesis of pillared bentonite materials prepared by intercalating solutions of aluminum, chromium, iron, and. cetyltrimethylammonium bromide (CTMAB) into natural bentonite. Six solids were obtained and applied as adsorbents to remove acid-yellow E-4G dye from aqueous solutions. Different characterization methods, such as chemical composition, X-ray diffraction, and specific surface area, were used for that purpose. The efficiency of dye removal was studied as a function of pH, initial dye concentrations, contact time, and temperature. The efficiency of dye removal by CTMA-Al intercalated bentonite was found higher than that of inorgano-bent, under similar conditions. The results obtained showed that the maximum adsorption capacity for dye by modified bentonite was reached within the pH range from 1 to 2. Indeed,  the maximum adsorption capacity was estimated to be 385 mg/g at room temperature. The results of the kinetic study regarding the removal of E-4G dye by modified bentonites was found to fit the pseudo-second-order model. Moreover, it turned out that the adsorption isotherm data obtained fit well the Freundlich model, which is not the case for the Langmuir and D-R models tested. Calculated thermodynamic parameters indicated that the adsorption process is spontaneous and endothermic with bentonite intercalated by aluminum and iron (B-AlFe) and is exothermic in the case of inserted bentonite by cetyltrimethylammonium and chromium (B-C-AlCr).

Exposure to hexavalent chromium (Cr VI) causes cancer in cells of the human body. So, the speciation and determination of the Cr (VI) and Cr (III) in water and human samples based on sensitive techniques are necessary. In this research, 2-mercapto-1-methylimidazole a novel Task-specific ionic liquid (C4H6N2S; HS-CH3-IM) was used with a new approach for speciation of Cr (III, VI) from water samples by ultra-assisted dispersive ionic liquid-liquid microextraction procedure (USA-D-ILLME). Due to the procedure, 100 mg of HS-CH3-IM and 0.2 mL of acetone were mixed and injected into 10 mL of water or standard Cr (III) and Cr (VI) solution in the conical tube. After stirringfor 5 min, the Cr (VI) and Cr (III) were extracted with a positive and negative charge of the thiol group (HS2+, HS-) in pH 2 or 8 and pH 5, respectively. The mixture of the HS-CH3-IM was collected at the bottom of the conical tube by centrifuging. The upper liquid phase was vacuumed with a peristaltic pump and the Cr (III, VI) loaded on the HS-CH3-IM was back-extracted in a liquid solution. Finally, the concentration of the Cr (III, VI) ions in a remained solution were measured with ET-AAS after dilution up to 0.5 mL with DW. The total chromium was determined in water samples by summarizing the Cr (VI) and Cr (III) contents. All parameters such as the amount of HS-CH3-IM, the sample volume, pH, and the shaking/centrifuging time were optimized. Under the optimal conditions, good linear range (LR), LOD, and enrichment factor (EF) were obtained 0.05–1.7 μg L−1, 15 ng L−1, and 19.82 respectively (RSD% < 1.45). The procedure was validated by spiking samples and good accuracy and precision results were achieved.

A new kinetic spectrophotometic method for the determination of trace amount Chromium (III) in Teareal samples has been described based on it s the catalytic effect on the oxidations of 1 - ( 2 –PyridylAzo ) - 2 - Naphthol, (PAN), by potassium bromated in sulfuric acid. The reaction is followedspec- trophotometrically by measuring the decrease in the absorbance at 469 nm. Under the optimumconditions of0.2 molL-1 sulfuric acid, 1.0 × 10-4 molL-1, 1- ( 2 -PyridylAzo ) - 2 - Naphthol, (PAN),0.01 molL-1 potassium bromate at 35oC, calibration graph in the rang of 0.001-0.06 ngL-1 Chromium(III). Concentration was obtained with detection limit of 0.2303 g mL-1 by the fixed-time method of5.5 min. The relative standard deviation for 0.05AngL-1 Chromium (III) is %90. No serious interferencewas identified. The applicability of the method was demonstrated by the determination of theChromium (III) in Water, Vegetables and blood samples.

A new poly(vinylchloride) membrane sensor for Cr3+ ions based on di (benzylamino)glyoxime asan ionophore was prepared. The electrode has a linear dynamic range 1×10-6-1×10-1 mol l-1,with aNernstian slope of 20.3 ± 0.5 mV per decade and a detection limit of 2×10-7. It has a fast responsetime of <15 s and can be used for at least 3 months without any considerable divergence inpotential. The proposed electrode revealed good sensitivity for Cr(III) over a wide variety of metalions and could be used in a pH range of 2-5.5. The proposed sensor was used for the determinationof Cr3+ ions in real samples such as tea leaves, coffee and cacao powder by direct potentiometry.