Use of clinoptilolite loaded with 1-(2-pyridylazo)-2-naphthol as a sorbent for preconcentration of Pb(II), Ni(II), Cd(II) and Cu(II) prior to their determination by flame atomic absorption spectroscopy

A solid phase extraction system for separation and preconcentration of trace amounts of Pb(II), Ni(II), Cd(II) and Cu(II) is proposed. The procedure is based on the adsorption of Pb²⁺, Ni²⁺, Cd²⁺ and Cu²⁺ ions on a column of 1-(2-pyridylazo)-2-naphthol (PAN) immobilised on surfactant-coated clinoptilolite prior to their determinations by Flame Atomic Absorption Spectroscopy (FAAS). The effective parameters including pH, sample volume, sample flow rate and eluent flow rate were also studied. The analytes collected on the column were eluted with 5 mL of 1 mol L^?1 nitric acid. A concentration factor of 180 can be achieved by passing 900 mL of sample through the column. The detection limits (3 s) for Cd, Cu, Pb and Ni were found to be 0.28, 0.12, 0.44 and 0.46 µg L^?1, respectively. The relative SDs at 10 µg L^?1 (n = 10) for analytes were in the range of 1.2–1.4%. The method was applied to the determination of Pb, Ni, Cd and Cu in water samples.     

Determination of trace elements in hair of some local population in Iran by instrumental neutron activation analysis

Scalp hair samples from 100 individual residents in Isfahan, Iran were analyzed for Al, Br, Ca, Cu, Hg, I, K, Mg, Mn, Na, S, V, and Zn by instrumental neutron activation analysis. The results of this investigation show that the ranges of the concentration of trace elements in hair are somewhat wide, for example Mg has the range of 20 to 209 ppm for 100 subjects. The results are compared with the data reported in the literatures. A substantive correspondence between the present data and literature values from different countries, have been observed but they did not show any regular dependence. The level of iodine is significantly different from other countries and is strongly linked to local environmental factors. The correlation coefficient for Al–V, Mn–Al, Ca–Mg, and V–Mg pairs was 0.823, 0.821, 0.830 and 0.746, respectively.     

Adsorption of nitrogen from natural gas by clinoptilolite

Much of world’s natural gas reserves are impure, one of the principal contaminants being nitrogen which makes it unsuitable for application and, hence, its separation is important. In this research, clinoptilolite, the most abundant natural zeolite with an open aluminosilicate framework structure and high internal surface area, was modified by ion exchange process to highly exchanged forms of cations of Na⁺, K⁺ and H⁺. The adsorption of N₂, CH₄ and C₂H₆ on natural clinoptilolite (Cp) and on its cation-exchanged forms (Na-Cp, K-Cp and H-Cp) was studied at 25 °C. The influence of cation exchange on equilibrium adsorption of N₂ showed that selectivity decreased in the order of Cp > Na-Cp > K-Cp and H-Cp has no affinity to nitrogen.     

Study of natural radionuclides in Karun river region

In this study the concentration of natural radionuclides has been investigated in soil and water of Karun river by using a high resolution (HPGe detector, n-type) γ-spectrometry. The concentrations range in water sample was 47.6 ± 5.6–130.8 ± 6.3, 0.0–23.4 ± 0.5 and 0–6.4 ± 2.0 Bq L⁻¹ for ⁴⁰K, ²³²Th and ²²⁶Ra respectively. For soil samples the concentration range of 275.7 ± 8.6–458.6 ± 6.8, 19.2 ± 5.35–41.1 ± 3.95 and 29.9 ± 1.53–50 ± 1.54 Bq kg⁻¹ was obtained respectively for ⁴⁰K, ²³²Th and ²³⁸U. ¹³⁷Cs was also detected in some part of the region in soil samples. The mean concentration of ¹³⁷Cs was 5.5 ± 0.6 Bq kg⁻¹. The origin of this activity is unknown. The average absorbed dose rate in outdoor air at a height of 1 m above the ground was found to be 54.3 ± 3.7 nGy h⁻¹. The results of this study indicate that the area has standard background radiation level.     

Adsorption of 103Ru from aqueous solutions by clinoptilolite

The aim of this research is adsorption of ruthenium by natural zeolite, clinoptilolite. The experimental conditions were optimized in order to obtain higher adsorption capacity and the study was done under optimum conditions. Maximal adsorption capacity was obtained using ¹⁰³Ru as a tracer at 25 °C, pH 2.0 and contact time of 10 h and found to be 0.074 meq g^?1. Ruthenium measurments were done using inductively coupled plasma-optical emission spectrometry (ICP-OES) and gamma spectrometer methods. Break points were calculated from breakthrough curve at the 1%, 5% and 50%. The obtained results are respectively 2.8, 4.5 and 19.5 mL, which are equal to 2.5 × 10^?3, 1.35 × 10^?2 and 5.85 × 10^?2 meq g^?1. Desorption behavior of column packed zeolite using some eluents was also investigated. The highest recovery of 97.4 ± 0.2% was obtained using 2 mol L^?1 HCl solution as an eluent. The results of this study can be used for separation and preconcentration of ruthenium.     

Synthesis and Characterization of Mesoporous Titanosilicate as an Adsorbent for Toxic Metal Ions

Hexagonal mesoporous titanosilicates (Ti‐MCM‐41) have been prepared using cetyltrimethylammonium bromide (CTAB) as the structure directing agent under the mild alkaline conditions. Powder X‐ray diffraction, nitrogen gas sorption, FTIR spectroscopy and thermogravimetry analysis of samples have confirmed that well ordered MCM‐41 type mesoporous materials were prepared. The potential of removing toxic metal ions from waste waters using mesoporous titanosilicates was evaluated. Separation of Co^II‐U^VI, Cs^I‐U^VI and Sm^III‐U^VI has been developed on columns of this adsorbent.     

Iranian clinoptilolite-rich tuffs for radionuclide removal from water

Three Iranian natural zeolites were characterized and evaluated for their abilities to take up Ba⁺², Ca⁺², K⁺ and Na⁺ from radioactive waste waters. The distribution coefficient values (K _d ) of the cations were measured and investigated as a function of pH. Four different cationic forms (Na, K, NH₄, and Ca) were also prepared and theirK _d values were determined. Some cations such as potassium presented highK _d values both in natural and exchanged zeolites. In sodium and ammonium exchanged forms theK _d values increased between 7 to 100 times with respect to the untreated zeolite.     

Selective Solid‐phase Extraction of Cu2+ by a Novel Cu(II)‐imprinted Silica Gel

A new Cu(II)‐imprinted salen functionalized silica gel adsorbent was synthesized by surface imprinting technique and was employed as a selective solid phase extraction material for Cu²⁺ removal from aqueous solutions. The samples were characterized by FT‐IR, ¹HNMR, ¹³CNMR, CHNS and DTG techniques. The BET surface area of the silica gel was also determined. The adsorbent was then used for removal of Cu²⁺ from aqueous solutions under different experimental conditions. It was concluded that the synthesized imprinted silica gel had higher selectivity and capacity compared to the non‐imprinted silica gel and the maximal adsorption capacity of 67.3 and 56.5 mg.g^?1 was obtained respectively for ion‐imprinted and non‐imprinted adsorbents. The relative selectivity factor (β) of 50.32 and 31.94 was obtained respectively for Cu²⁺/Ni²⁺ and Cu²⁺/Zn²⁺ pairs. The dynamic adsorption capacity of the imprinted adsorbent was close to the static adsorption capacity due to the fast kinetic of adsorption. Furthermore, the ion‐imprinted adsorbent was recovered and repeatedly used and satisfactory adsorption capacity with acceptable precision was obtained. Each experiment was repeated at least for three times and the mean and the standard deviation for each measurement were calculated. The applicability of the method was examined for Zayandehrood water as real sample. Acceptabe standard deviation was obtained.     

N-butyl-pyridinium tetrafluoroborate as a highly efficient ionic liquid for removal of dibenzothiophene from organic solutions

In this research,1-butyl-pyridinium tetrafluoroborate([C4Py][BF4]-)was prepared by ion exchange method and was characterized by1H-NM R,13C-NM R,and FT-IR techniques.The synthesized ionic liquid w as used for removal of dibenzothiophene as a typical organosulfur pollutant from organic medium.The effect of different parameters on the extraction efficiency w as studied and optimized.At the optimized conditions,97.68%of dibenzothiophene w as extracted from 1 000 mg/L n-hexane solution.The extraction efficiency obtained in this w ork w as higher than the previous reported values.The desulfurization reaction w as kinetically follow ed the second order mechanism.The ionic liquid w as reusable and after four regeneration cycles 97%of its original extraction efficiency w as retained.     

Adsorption isotherm for uranyl biosorption by Saccharomyces cerevisiae biomass

Biosorption of uranyl ions from aqueous solution by Saccharomyces cerevisiae was studied in a batch system. The influence of contact time, initial pH, temperature and initial concentration was investigated. The optimal conditions were found to be 3.5?h of contact time and pH?=?4.5. Temperature had no significant effect on adsorption. The uptake of uranyl ions was relatively fast and 85?% of the sorption was completed within 10?min. The experimental data were well fitted with Langmuir isotherm model and pseudo-second order kinetic model. According to this kinetic model, the sorption capacity and the rate constant were 0.455?mmol UO₂ ²⁺/g dry biomass and 1.89?g?mmol^?1?min^?1, respectively. The Langmuir isotherm indicated high affinity and capacity of the adsorbent for uranyl biosorption with the maximum loading of 0.477?mmol UO₂ ²⁺/g dry weight.