جستجوی مقالات مرتبط با کلیدواژه « سرب » در نشریات گروه « شیمی »

In the present work, an efficient method was developed for the determination of lead in natural water samples. In this method, lead was extracted by octanoic acid reverse micelles (bulk phase) and measured by flame atomic absorption spectroscopy (FAAS). Ligand 1-(2-Pyridylazo)-2-naphthol was used as a chelating agent. In order to obtain the best extraction results, some experimental parameters (such as pH, ligand concentration, ionic strength, etc.) affecting the extraction efficiency were investigated and optimized. Under optimal conditions, the calibration curve was linear in the concentration range of 2.5-200.0 μgL-1 with a correlation coefficient of 0.9998. The detection limit was 0.8 μgL-1 and the preconcentration factor was 50. This method was successfully used to measure lead in natural water samples.

A ligandless on-line solid phase extraction method was developed for the preconcentration of lead prior to quantitation by inductively coupled plasma-optical emission spectrometry. In this method, the sample solution was passed through a syringe membrane filter coated with graphitic carbon nitride and Pb(II) ions were directly adsorbed on the surface of g-C3N4 particles. The adsorbed Pb(II) ions were subsequently eluted from the membrane and transferred directly into the ICP-OES nebulizer with nitric acid solution. Under the optimized conditions and preconcentration of 25 mL of sample, the enhancement factor of 110 and the detection limit of 0.12 μg L-1 were obtained. The proposed procedure was applied for the preconcentration and determination of lead in environmental water samples.

In the present research, the application of a functionalized ionic liquid with a specific role to simultaneous extraction and preconcentration of cadmium and lead ions in aqueous media by in-situ solvent formation microextraction (ISFME) technique was developed. The task-specific functionalized ionic liquid of 3-(2-(bis(2-(tert-butoxy)-2-oxoethyl)amino)ethyl)-1-methylimidazolium chloride ([Tamim][Cl]) as a complexing agent utilized for the formation of metal chelates with Cd(II) and Pb(II) ions in aqueous solutions. Finally, determination of concentrated or separated metal ions contents after dilution step was carried out by flame atomic absorption spectrometry (FAAS). To obtain optimum extraction conditions, analytical parameters including the various range of sample solution pH, chelating agent amount, ionic strength of solution, solution temperature and counter ion dosage were investigated. Furthermore, parameters represent figures of merit of the method such as limit of detection (LOD), relative standard deviation (RSD), linear dynamic range (LDR) and the enhancement factor (EF) were 0.64;0.76 µg L-1, 1.5;1.8%, 50-2500;50-2000 µg L-1 and 85;80 for cadmium and lead, respectively. The ability of the method for analyzing of real water and saline samples were evaluated and good results were obtained.

In this study, Magnetic Fe3O4-walnut sawdust nanocompositewas synthesized and used for removal of lead from aqueous solution. The size, structural, optical and morphological properties of nanoparticles have been analyzed by Scanning Electron Microscope )SEM) and Dynamic Light Scattering method. The effect of pH, contact time, adsorbent dose, initial concentration, ionic strength and the effect of temperature on the adsorption was checked out in a batch process mode. Using the equilibrium constants obtained at different temperatures, the thermodynamic results parameters were calculated as ∆G, ∆H and ∆S. The thermodynamic parameters showed that the uptake of lead is spontaneous and endothermic. The data were fitted with the Langmuir and Freundlich equations to describe the adsorption equilibrium. The maximum adsorption capacity by using Langmuir equation was calculated 12.99 mg/g. The kinetic data followed by Pseudo second. Owing to such outstanding features, Magnetic Fe3O4-walnut sawdust nanocompositeproved the great potential in adsorption lead removal from aqueous solutions.

Removal of Pb(II) and Zn(II) ions from aqueous solutions using naphthalene modified with 2-(3,4,5-trimethoxybenzylidene) malononitrile(TMBM) as synthetic adsorbent was investigated. It was characterized by FT-IR. Batch method was applied for testing of adsorption behavior. Adsorption experiments showed, the new sorbent has high selectivity and good adsorption for removal of lead and zinc ions from aqueous solutions. Equilibration time was 5 min for zinc and 15 min for lead. There was little effect of salt on removal of the ions. The maximum adsorption capacities for Pb(II) and Zn(II) were 88.5 and 38.9 mg g-1, respectively. The thermodynamic studies indicated that the adsorption was spontaneous, exothermic and endothermic process for lead and zinc, respectively.