Mohamed M. Hassanien

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.

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 1x10(-3)-4x10(-6) M thallium (III) at 25 degrees 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 2x10(-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 mug 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 mug 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.

Synthesis and structural investigation of mono- and polynuclear copper complexes of 4-ethyl-1-(pyridin-2-yl) thiosemicarbazide

The reaction between 2-hydrazinopyridine and ethylisothiocyanate produced 4-ethyl-1-(pyridin-2-yl) thiosemicarbazide (HEPTS). Its reaction with copper fluoride, chloride, bromide, acetate, nitrate, perchlorate, sulfate, carbonate, hydroxide and copper metal produced 15 Cu(II) complexes. The copper metal is easily oxidized in aqueous-ethanol solution of HEPTS giving [Cu2(EPTS)(H2O)3(OH)3]EtOH. Different complexes for the same anion were synthesized by controlling the heating time. Characterization by elemental, thermal, magnetic and spectral (electronic, IR, mass and ESR) studies showed the formation of mono-, di-, tri- and tetra nuclear complexes. The room temperature solid state ESR spectra of the complexes show an axial spectrum with dx2-y2 ground state, suggesting distorted tetragonal geometry around Cu(II) center. The kinetic and thermodynamic parameters for the different decomposition steps in the complexes were calculated. HEPTS and its Cu(II) complexes showed high activity against gram negative bacteria; [Cu3(EPTS)2(EtOH)2Br4] has more activity.

Study of organically-modified montmorillonite clay for the removal of copper(II)

2-Oxyhydrazino-N-(2-methylen-yl-hydroxyphenyl)pyridinium (OMHP) ion was immobilized onto Na-montmorillonite clay (MMT). The modified clay (OMHP-MMT) was used for the removal of Cu(II). Experiments were carried out as a function of solution pH, stirring time, effect of some common ions and eluent type, concentration and volume. MMT, OMHP-MMT, and OMHP-MMT-loaded Cu(II) were characterized by X-ray diffractometry, electronic and infrared spectra, and elemental and thermogravimetric analyses. OMHP is suggested to be intercalated into MMT parallel to the aluminosilicate layers, with a capacity of 56.4 mEq/100g. OMHP-MMT shows good stability in 0.1-1 mol L(-1) hydrochloric or nitric acids, ammonia hydroxide, concentrated Na(+), K(+), NH(4)(+), Cl(-) or SO(4)(2-). It shows good removal efficiency and selectivity towards Cu(II) at pH 3.0-8.0 and stirring time 10 min with an removal capacity of 119 mEq/100g. Most common ions do not interfere with the removal process except Fe(3+). Extracted Cu(II) could be quantitatively recovered by 10 mL 1% thiourea in 0.1 mol L(-1) HCl with 100-fold preconcentration factor. OMHP-MMT was successfully applied to recover Cu(II) from different samples.

A cloud point extraction procedure for gallium, indium and thallium determination in liquid crystal display and sediment samples

A simple, sensitive and rapid cloud point extraction (CPE) methodology has been developed for the selective separation and preconcentration of gallium, indium and thallium, after complexation with gallic acid in the presence of Triton X-114 as a non-ionic surfactant. The quantitative extraction of gallium, indium and thallium was performed at pH 2.5, with 0.04 mmol L−1 gallic acid, and 0.05% (w/v) Triton X-114 at 40 °C. The dilution of the surfactant-rich phase with acidified methanol was performed after phase separation, and the metal ions were determined using flame atomic absorption spectrometry. Under the optimized experimental conditions, the calibration curve is linear over the concentration range of 6–150 ng mL−1 for gallium, 2–150 ng mL−1 for indium, and 2–100 ng mL−1 for thallium. The limits of detection, based on three times the standard deviation of a blank signal by seven replicate measurements were 3.50, 1.25 and 0.92 ng mL−1. The relative standard deviations of this method were 1.55, 1.40 and 1.82% for gallium, indium and thallium, respectively (C = 50 ng mL−1, n = 7). The results showed that the developed method was not susceptible to interference effects, providing good recoveries. The developed method was successfully applied to gallium, indium and thallium determination in sediments and mobile phone liquid crystal display samples with satisfactory results.

Synthesis of Controlled‐Pore Silica Glass Functionalized with Quercetin and Its Application for the Separation and Preconcentration of Mn(II), Co(II), Ni(II), Cu(II), and Zn(II)

Abstract Quercetin was anchored to controlled‐pore silica glass (CPSG). The chemical bonding of quercetin based on CPSG (QCPSG) was characterized by elemental analysis, infrared reflectance analysis, ultraviolet spectroscopy, and solid state 13C‐nuclear magnetic resonance (NMR), in comparison with the monomer phase prepared from quercetin and aminopropyltrihydroxysilane. Controlled‐pore silica glass, used as support for quercetin or aminopropyl moiety, showed obvious stability against Si dissolution at pH 8 in comparison with silica gel. Also, the involvement of the amine group in the bonding to quercetin was observed to relieve its local basisity, enabling low capacity fading (10%) after 40 loading/elution cycles. The QCPSG also was used for the separation and preconcentration of Mn(II), Co(II), Ni(II), Cu(II), and Zn(II) prior to their determination by inductively coupled plasma‐mass spectrometry (ICP‐MS). The optimum pH range for the separation of these metal ions is 7.5–8.5 at 30 min stirring time, giving an efficiency of 98.1%, 94.4%, 95.9%, 90.7%, and 87.9%, respectively, in the presence of sodium acetate. The sorption capacity of QCPSG for these metal ions is in the range of 0.24–0.46 mmol g−1 indicating a 1:2 quercetin/metal chelation for all metal ions except for Mn(II), as a 1:1 ratio is suggested. The QCPSG was used for the separation and preconcentration of the investigated metal ions in some water samples, using ICP‐MS for determination (relative standard deviation, RSD 1.74–6.10%). The method also was applied for the determination of these metal ions in granite ores and certified samples, and the results are in good agreement with the reported values, which indicates that the method is accurate.

Immobilization of methylene blue onto bentonite and its application in the extraction of mercury (II)

Methylene blue was immobilized onto bentonite (BNT). The modified clay (MB-BNT) was used to extract Hg(2+) at pH 6.0 yielding Hg-MB-BNT. BNT, MB-BNT and Hg-MB-BNT were characterized by X-ray diffractometry, infrared spectra, and elemental and thermogravimetric analyses. MB is suggested to be intercalated into the major phase of BNT; montmorillonite mineral (MMT), lying parallel to the aluminosilicate layers, with a capacity of 36 mequiv./100g. MB-BNT shows good stability in 0.1-1M hydrochloric or nitric acids, ammonium hydroxide, and concentrated Na(+), K(+) or NH(4)(+) chlorides or iodides. It shows good selectivity towards Hg(2+) with an extraction capacity of 37 mequiv./100g in the presence of I(-) giving rise to a ratio of MB/Hg(2+)/I(-) 1:1:3 in the clay phase. Extracted Hg(2+) could be quantitatively recovered by ammonia buffer at pH 8.5. MB-BNT was successfully applied to recover Hg(2+) from spiked natural water and cinnabar mineral samples using the optimum conditions; pH 6.0, time of stirring 10 min and 10 mL of 0.05 M NH(4)Cl/NH(4)OH at pH 8.5 as eluent.

Cloud point extraction of some precious metals using Triton X-114 and a thioamide derivative with a salting-out effect

Abstract A cloud point extraction procedure is proposed for preconcentration of trace amounts of palladium (II), silver (I) and gold (III) in aqueous medium. The metal ions in the initial aqueous solution were extracted using the non-ionic surfactant, Triton X-114 after complex formation with 4-(p-chlorophenyl)-1-(pyridin-2-yl)thiosemicarbazide at pH 6.0 in the presence of 0.3 mol L−1 sodium sulfate as a salting-out agent at 25 °C. Dilution of the surfactant-rich phase with acidified methanol was performed after phase separation, and the metal ions were determined by electrothermal atomic absorption spectrometry. The main factors affecting extraction procedure, such as pH, concentration of the ligand, and amount of Triton X-114 were studied in detail. Under the optimum experimental conditions, the calibration graphs were linear upto 125, 50 and 100 μg L−1 and the enrichment factors were 52, 46 and 56 for palladium, silver and gold, respectively. The limits of detection, based on three times of standard deviation of blank signal by 10 replicate measurements divided by the slope of calibration curves were 0.12, 0.08 and 0.30 μg L−1 for palladium, silver and gold, respectively. The accuracy of the results was verified by analyzing spiked water samples. The proposed method has been applied for the determination of the metal ions in soil and rock samples with satisfactory results.

Mixed micelle-mediated extraction of alizarin red S complexes of Zr(IV) and Hf(IV) ions prior to their determination by inductively coupled plasma-optical emission spectrometry

A modified cloud-point extraction method using a mixed surfactant has been developed for the preconcentration of Zr(IV) and Hf(IV) prior to their determination by inductively coupled plasma-optical emission spectrometry (ICP-OES). The method is based on the complexation of Zr(IV) or Hf(IV) with Alizarine Red S (ARS) at pH 2.5 in the presence of cationic surfactant cetyl trimethyl ammonium bromide (CTAB) and non-ionic surfactant Triton X-114. Phase separation was accomplished at room temperature in the presence of 0.1 mol L−1 sodium sulphate. The surfactant-rich phase containing Zr(IV) or Hf(IV) was separated then diluted with methanol/concentrated nitric acid mixed solvent (5 : 1) before its introduction into ICP-OES for the determination. The optimal extraction and reaction conditions were evaluated and optimized. Under the optimized conditions, the calibration graphs were linear in the range of 0.5–1000 and 0.5–850 ng mL−1 with detection limits of 0.18 and 0.25 ng mL−1 for Zr(IV) and Hf(IV), respectively. The RSD values for five replicates of Zr(IV) and Hf(IV) at 50 ng mL−1 concentrations were 2.1 and 2.3%, respectively, and the enrichment factors for 100 mL samples were obtained as 120 and 105 for Zr(IV) and Hf(IV), respectively. The accuracy of the results was verified by analyzing the spiked water from different sources and synthetic mixtures. The proposed method has been applied for the determination of Zr(IV) and Hf(IV) in some real samples such as clay, rocks and silver alloy samples with satisfactory results.

Synthesis, spectral, thermal and biological studies on N(-)(2,4-dinitro-phenyl)-2-mercaptoacetohydrazide and its metal complexes.

Complexes of VO(2+), Cr(3+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+) and Hg(2+) ions with N(-)(2,4-dinitrophenyl)-2-mercaptoacetohydrazide (H2L) have been prepared and characterized on the basis of elemental analysis, molar conductance, thermal (TGA, DTGA), spectral (IR, NMR, UV-Visible, MS) and magnetic measurements. The IR spectra show that H2L behaves in a mononegative and/or binegative bidentate manner. The sulfate bridged the two complex molecules in [Cu(HL)(H2O)2(½SO4)]⋅3H2O. The acetate functions as a monodentate in [Ni(HL)(OAc)(H2O)3] and [Cr(HL)(OAc)2(H2O)(EtOH)]. Different stereochemistries are proposed: octahedral for Cr(III), Ni(II), Hg(II) and [Cu(HL)(H2O)2(SO4)0.5]⋅3H2O, square-based pyramid for [VO(HL)2]⋅EtOH, square-planar for [Co(L)(EtOH)(H2O)]⋅H2O, [Cu(L)(H2O)2] and tetrahedral for [Zn(L)(EtOH)(H2O)], [Cd(L)(EtOH)(H2O)] and [Cu2(HL)(H2O)6]Cl3⋅H2O according to the data of electronic spectra and magnetic measurements. The TGA data support the formula and indicate the outer and inner solvents as well as the final residue. The thermodynamic parameters are calculated using the Coats-Redfern and Horowitz-Metzger methods. H2L and [Zn(L)(EtOH)(H2O)] showed the highest cytotoxic activity while H2L has a higher antioxidant activity than ascorbic acid. The ionization constant of the ligand and the stability constant of the Cu(II)H2L in absence and presence of hexamine buffer were calculated.