The sorptive potential of sunflower stem (180-300 μm) for Cr(III) ions has been investigated in detail. The maximum sorption (≥85%) of Cr(III) ions (70.2 μM) has been accomplished using 30 mg of high density sunflower stem in 10 min from 0.001 M nitric and 0.0001 M hydrochloric acid solutions. The accumulation of Cr(III) ions on the sorbent follows Dubinin-Radushkevich (D-R), Freundlich and Langmuir isotherms. The isotherm yields D-R saturation capacity Xm = 1.60 ± 0.23 mmol g−1, β = −0.00654 ± 0.00017 kJ2 mol−2, mean free energy E = 8.74 ± 0.12 kJ mol−1, Freundlich sorption capacity KF = 0.24 ± 0.11 mol g−1, 1/n = 0.90 ± 0.04 and of Langmuir constant KL = 6800 ± 600 dm3 mol−1 and Cm = 120 ± 18 μmol g−1. The variation of sorption with temperature (283-323 K) gives ΔH = −23.3 ± 0.8 kJ mol−1, ΔS = −64.0 ± 2.7 J mol−1 K−1 and ΔG298k = −4.04 ± 0.09 kJ mol−1. The negative enthalpy and free energy envisage exothermic and spontaneous nature of sorption, respectively. Bisulphate, Fe(III), molybdate, citrate, Fe(II), Y(III) suppress the sorption significantly. The selectivity studies indicate that Cr(III), Eu(III) and Tb(III) ions can be separated from Tc(VII) and I(I). Sunflower stem can be used for the preconcentration and removal of Cr(III) ions from aqueous medium. This cheaper and novel sorbent has potential applications in analytical and environmental chemistry, in water decontamination, industrial waste treatment and in pollution abatement. A possible mechanism of biosorption of Cr(III) ions onto the sunflower stem has been proposed. 相似文献
Two novel chromogenic cone calix[4]dibenzothiacrown ethers 3 and 4 in which nitrophenylazo groups attached at the phenyl ring of dibenzothiacrown unit were described. The extraction properties
of 3 and 4 toward different transition metal ions have been studied using conductometric technique and found to exhibit Cu2+ and Hg2+ selectivity with very high stability constants range from log Kassoc = 5.19 to log Kassoc = 8.72. 相似文献
Phytochemical investigation of Symplocos racemosa resulted in the isolation of two new glycosides, symploracemoside ( 1 ) and symplomoside ( 2 ), which are structurally related to the reported benzoylsalireposide ( 3 ) and salireposide ( 4 ). The structure elucidation of the isolated compounds was based primarily on 1D‐ and 2D‐NMR analysis, including COSY, NOESY, HMQC, and HMBC correlations. These glycosides showed inhibitory activity against snake‐venom phosphodiesterase I. 相似文献
Two new oleanane triterpenes; 2alpha,3alpha,24-trihydroxyolean-12-ene-28,30-dioic acid ([structure: see text]) and 2alpha,3alpha,24,28-tetrahydroxyolean-12-ene ([structure: see text]) have been isolated from the roots of Atropa acuminata. Anti-oxidant p-hydroxyphenethyl trans-ferulate ([structure: see text]), beta-sitosterol-3-O-beta-D-glucopyranoside ([structure: see text]) and oleanolic acid ([structure: see text]) have also been reported for the first time from this species. The structures were determined by spectroscopic studies including 2D-NMR. 相似文献
A new phase of ‘organic-inorganic’ composite system, polypyrrole polyantimonic acid, prepared by mixing the inorganic precipitate of hydrated antimony oxide with organic conducting polymer i.e., polypyrrole, providing a novel granular form hybrid cation-exchanger suitable for column operation with better chemical and thermal stability, good ion-exchange capacity, reproducibility and selectivity for heavy metals. The physicochemical properties of this material were studied using elemental analyses, AAS, SEM, XRD, FTIR and simultaneous TGA-DTA studies. Ion-exchange capacity, pH-titrations, elution and distribution behavior were also carried out to characterize the material. Distribution studies revealed the cation-exchange material to be highly selective for Hg(II) and its selectivity was performed by achieving some important binary separations like Hg2+-Zn2+, Hg2+-Ni2+, Hg2+-Cu2+, Hg2+-Fe3+, Hg2+-Cd2+, Hg2+-Mg2+ etc. on its column. Using this electroactive composite material, a new heterogeneous precipitate based selective ion-sensitive membrane electrode was fabricated for the determination of Hg(II) ions in solutions. The membrane electrode is mechanically stable, with a quick response time, and can be operated within a wide pH range. The selectivity coefficients for different cations determined by mixed solution method were found to be less than unity The electrode was also found to be satisfactory in electrometric titrations. 相似文献
Trace metal ions in highly saline samples such as urine were determined with capillary electrophoresis (CE) without desalting or off-line preconcentration. By mixing with a dye, 4-(2-pyridylazo) resorcinol (PAR), the metal ions were converted into anionic complexes having strong absorbance near 500 nm. A large volume of the metal-PAR complex sample solution injected into a coated capillary was stacked isotachophoretically and separated under a reverse potential. The salt anion (chloride) and PAR in the sample matrix acted as the leading and terminating electrolytes, respectively. In a sample containing a 250 mM NaCl matrix, more than 400-fold enhancement in the absorbance detector response was realized compared to the normal CE injection mode. Combination of the dye complexation and isotachophoretic stacking provided excellent detection limits (S/N = 3) for three trace metal ions in the low ppb range (Fe(2+), 0.7 ppb, Ni(2+), 0.4 ppb; Zn(2+), 1.2 ppb) with absorbance detection. The migration time reproducibility was excellent (relative standard deviations: standard samples < 1%, urine samples approximately 1%). The proposed method is convenient and fast, and the sample analysis can be completed within 20 min. 相似文献
In this study, the Co-based catalyst was prepared by cobalt immobilization on the surface of functionalized silica-coated magnetic NPs (Fe3O4@SiO2-CT-Co) as a magnetically core–shell nanocatalyst and characterized by FT-IR, TGA, XRD, VSM, SEM, TEM, EDX, EDX mapping, and ICP techniques and appraised in the Suzuki–Miyaura cross-coupling reaction under mild reaction conditions. The results displayed the superparamagnetic behavior of the Fe3O4 NPs core encapsulated by SiO2 shell, and the size of the particles was estimated about 30 nm. Compared with the previously reported catalysts, the engineered Fe3O4@SiO2-CT-Co catalyst provided perfect catalytic performance for the Suzuki–Miyaura cross-coupling reaction in water as a green solvent and it was much cheaper in the comparison with the traditional Pd-based catalysts. Importantly, the durability of magnetic nanocatalyst was studied and observed that it is stable under the reaction conditions and could be easily reused for at least six successive cycles without any significant decrease in its catalytic activity.
Let R be a commutative integral domain. An element x of R is calledrigid if for all r,s dividing x; r divides s or s divides r. In our terminology, R issemirigid if each non zero non unit of R is a finite product of rigid elements. We show that semirigid GCD domains have a type of unique factorization, and are a known generalization of Krull domains. 相似文献
The central idea of this paper is to construct a new mechanism for the solution of Abel’s type singular integral equations that is to say the two-step Laplace decomposition algorithm. The two-step Laplace decomposition algorithm (TSLDA) is an innovative adjustment in the Laplace decomposition algorithm (LDA) and makes the calculation much simpler. In this piece of writing, we merge the Laplace transform and decomposition method and present a novel move toward solving Abel’s singular integral equations. 相似文献
Journal of Radioanalytical and Nuclear Chemistry - We measured excitation functions for the production of the 108m,108g,109g,110m,110g,111gIn, the 109g,111mCd, and the 105g,106m,110m,111gAg in... 相似文献