Separation and preconcentration in a batch mode of Cd(II), Cr(III, VI), Cu(II), Mn(II, VII) and Pb(II) by solid-phase extraction by using of silica modified with N-propylsalicylaldimine

The complexes formed between IE11 and Cd(II), Cr(III), Cu(II), Mn(II) and Pb(II) were identified and confirmed by IR, UV and pH-metric titration. The uptake behavior of porous silica modified with N-propylsalicylaldimine (IE11) and these metal ions were studied. Log k(d) was found to be within the range 2.19-5.16 depending on pH and time of stirring. IE11 was used in the separation and preconcentration of Cd(II), Cr(III, VI), Cu(II), Mn(II, VII) and Pb(II) from some natural water samples. Data were compared with those obtained by the solvent extraction method APDC/MIBK. The proposed methodology allows to verify an improvement in the water quality of Nile River probably attributed to high to moderate floods in the last few years. The method was found to be accurate and not subject to random error, i.e. precise.     

Spin squeezing and quantum correlations

We discuss the notion of spin squeezing considering two mutually exclusive classes of spin-s states, namely, oriented and non-oriented states. Our analysis shows that the oriented states are not squeezed while non-oriented states exhibit squeezing. We also present a new scheme for construction of spin-s states using 2s spinors oriented along different axes. Taking the case of s=1, we show that the ‘non-oriented’ nature and hence squeezing arise from the intrinsic quantum correlations that exist among the spinors in the coupled state.     

Theory of sheath in a collisional multi-component plasma

The aim of this brief report is to study the behaviour of sheath structure in a multi-component plasma with dust-neutral collisions. The plasma consists of electrons, ions, micron size negatively charged dust particles and neutrals. The sheath-edge potential and sheath width are calculated for collisionally dominated sheath. Comparison of collisionless and collisionally dominated sheath are made.     

Analysis of a shielded TE011 mode composite dielectric resonator for stable frequency reference

Analysis of a TE₀₁₁ mode composite sapphire-rutile dielectric resonator has been carried out to study the temperature variation of resonance frequency, close to the Cs atomic clock hyperfine frequency of 9.192 GHz. The complementary behavior of dielectric permittivity with temperature of the composite has been exploited to obtain the desired turning point in the resonant frequency. The frequency of the composite structure is found to be independent of the shield diameter beyond four times the puck diameter.     

Stabilization of quercetin-functionalized silica gel against hydrolysis by blocking silanol groups with TiO<Subscript>2</Subscript> or ZrO<Subscript>2</Subscript> and its application for the removal of Hg(II)

Free silanol groups of silica-gel functionalized with quercetin (QSG) were blocked with TiO₂ or ZrO₂ to produce TiO₂-QSG and ZrO₂-QSG, respectively. The silica materials were characterized by infrared, Raman spectra, thermogravimetric, elemental analyses, magic angle spinning ¹³C-nuclear magnetic resonance, BET specific surface area measurements and inductively coupled plasma—optical emission spectrometry-monitored silica hydrolysis. Siloxane groups are reinforced in the blocked QSG samples without affecting the hydrophilic nature or the porosity of silica. Quercetin is unaffected by the titania layer in contrary to zirconia. Also, the stability of silica against hydrolysis in TiO₂-QSG and ZrO₂-QSG was remarkably improved in the range of pH 3.5–9.1, attributed to the interruption of the intramolecular interaction of silanol groups with the amino groups. The hydrolyzed silica of TiO₂-QSG and ZrO₂-QSG decreased to 46.6 and 18.5%, of that of QSG and to 7.6 and 3.1%, of that of 3-aminopropylsilica gel at pH 9.1, respectively. TiO₂-QSG was applied for the extraction of Hg(II) with separation efficiency of 99.0 ± 0.6% at pH 8.5. The capacity loss of TiO₂-QSG per recovery cycle of Hg(II) was lowered in comparison with the uncovered material. It was successfully applied for the recovery of Hg(II) from spiked water and referenced samples.     

Structure Investigation and Electrochemical Behavior of γ-MnO2 Synthesized from Three-Dimensional Framework and Layered Structures

MnO₂ was chemically prepared from birnessite (CMD_2D) and from spinel-like LiMn₂O₄ (CMD_3D) by acid leaching. X-ray diffractometry, FTIR spectrometry, chemical and thermal analyses were used to determine the structure and chemical disorder. On the basis of cation vacancy model, the structural water was found to be mainly due to Coleman protons in both samples. Both samples were found to be of very close structure belonging to γ-MnO₂ type I according to Chabre and Pannetier classification with de Wolff disorder (P_r) of 0.19 and 0.30 and microtwinning (Tw) of 9.9 and 17%, respectively. The activation energy of structural water release calculated from thermal analysis was apparently higher than that of other γ-MnO₂ types (150 and 156.6 kJ/mol, respectively).A high reduction capacity in aqueous and non-aqueous batteries was delivered for both samples except for the electro- chemical lithium insertion of CMD_2D, which was attributed to the different oxygen packing.     

A novel tetrachlorothallate (III)-PVC membrane sensor for the potentiometric determination of thallium (III)

A novel tetrachlorothallate (III) (TCT)-selective membrane sensor consisting of tetrachlorothallate (III)-2,3,5-triphenyl-2-H-tetrazolium ion pair dispersed in a PVC matrix plasticized with dioctylphthalate is described. The electrode shows a stable, near-Nernstian response for 1×10⁻³-4×10⁻⁶ M thallium (III) at 25 °C with an anionic slope of 56.5±0.5 over the pH range 3-6. The lower detection limit and the response time are 2×10⁻⁶ M and 30-60 s, respectively. Selectivity coefficients for Tl(III) relative to a number of interfering substances were investigated. There is negligible interference from many cations and anions; however, iodide and bromide are significantly interfere. The determination of 0.5-200 μg ml⁻¹ of Tl(III) in aqueous solutions shows an average recovery of 99.0% and a mean relative standard deviation of 1.4% at 50.0 μg ml⁻¹. The direct determination of Tl(III) in spiked wastewater gave results that compare favorably with those obtained by the atomic absorption spectrometric method. The electrode was successfully applied for the determination of thallium in zinc concentrate. Also the tetrachlorothallate electrode has been utilized as an end point indicator electrode for the determination of thallium using potentiometric titration.     

Modification of aminopropyl silica gel with some chelating agents and their effect on its stability against hydrolysis

The stability of aminopropyl-silica gel (AP-SG) against hydrolysis was investigated after modification by 2,3-butanedione monoxime (BDMO), 8-hydroxyquinoline-2-carboxaldehyde (HQC) or isatin (Is) by Schiff’s base condensation reaction. The hybrid modified silica gel (HMSG) compounds; BDMO-SG, HQC-SG and Is-SG were characterized by IR, thermogravimetric and elemental analyses, magic angle spinning-¹³C-nuclear magnetic resonance, pH-metric titration and inductively coupled plasma–optical emission spectrometry-monitored silica hydrolysis. The stability of the HMSG’s was found to be dependant on the type of the functionalization group, which may protect the silica surface via; (1) the delocalization of the free lone pair of electrons on nitrogen of the propylamine group in the aromatic rings, which reduces local basicity experienced on the silica surface, (2) the hydrophobic nature of the organic substrates, which hinders the attack of hydroxide ions and water molecules, and (3) the bulky organic substrate, which hinders nucleophilic attack on silicon. HQC-SG is recommended as an optimal modification to meet the requirements of stability, capacity and separation efficiency of Hg(II) at pH 4.1.     

Synthesis and characterisation of morin-functionalised silica gel for the enrichment of some precious metal ions

Silica gel was firstly functionalised with aminopropyltrimethoxysilane obtaining the aminopropylsilica gel (APSG). The APSG was reacted subsequently with morin yielding morin-bonded silica gel (morin-APSG). The structure was investigated and confirmed by elemental and thermogravimetric analyses, IR and (13)C NMR spectral studies. Morin-APSG was found to be highly stable in common organic solvents, acidic medium (<2molL(-1) HCl, HNO(3)) or alkaline medium up to pH 8. The separation and preconcentration of Ag(I), Au(III), Pd(II), Pt(II) and Rh(III) from aqueous medium using morin-APSG was studied. The optimum pH values for the separation of Ag(I), Au(III), Pd(II), Pt(II) and Rh(III) on the sorbent are 5.7, 2.2, 3.7, 3.7 and 6.8, giving rise to separation efficiencies of 43.9, 85.9, 97.7, 60.9 and 91.0%, respectively, where the activity was found to be >90% in the presence of acetate ion. The ion sorption capacity of morin-APSG towards Cu(II) at pH 5.5 was found to be 0.249mmolg(-1) where the sorption capacities of Ag(I) and Pd(II) were 0.087 and 0.121mmolg(-1) and 0.222 and 0.241mmolg(-1) at pH 2.2 and 5.7, respectively. This indicates a 1:1 and 1:2 morin/metal ratios at pH 2.2 and 5.7, respectively. Complete elution of the sorbed metal ions was carried out using 10mL (0.5molL(-1) HCl+0.01molL(-1) thiourea) in case of Au(III), Pd(II), Pt(II) and Rh(III) and 10mL 0.5molL(-1) HNO(3) in case of Ag(I). Morin-APSG was successfully employed in the separation and preconcentration of the investigated precious metal ions from some spiking water samples yielding 100-folds concentration factor. The relative standard deviation (R.S.D.) and the T-test (|t|(1)) were calculated.     

Controlled-pore silica glass modified with N-propylsalicylaldimine for the separation and preconcentration of trace Al(III), Ag(I) and Hg(II) in water samples.

Controlled-pore silica glass modified with N-propylsalicylaldimine (SCPSG) has been investigated as a surface-active matrix for the separation of some metal ions. The porous silica glass base was confirmed to have better stability towards hydrolysis in aqueous solution buffered at pH=9 in comparison to silica gel, which showed twice the surface area of controlled-pore silica glass. The different analytical parameters affecting the batch mode separation and preconcentration of trace Al(II), Ag(I) and Hg(II) in environmental samples using SCPSG, prior to their determination using inductively coupled plasma mass spectrometry (ICP-MS), were studied. The optimum conditions are pH 9.0 +/- 0.1, time of stirring 30 min and the eluent concentration 0.5 mol dm(-3) HNO3. The ion-exchange capacity of SCPSG with respect to Al(III), Ag(I) and Hg(II) was 0.27, 0.18 and 0.23 mmol g(-1), respectively. The recovery values for the metal ions were 96.8 +/- 0.86, 98.1 +/- 0.60 and 96.2 +/- 1.06%, and the analytical detection limits were 26.1, 1.49 and 0.44 pg cm(-3), respectively, for a preconcentration factor of 100. The method has been applied to the determination of the investigated metal ions in natural water samples as well as certified and reported samples and the results were found to be accurate.