Mohamed B. Saleh

Corrosion Inhibition of Mild Steel in Acidic Medium using 2-amino Thiophenoland 2-Cyanomethyl Benzothiazole

The corrosion inhibition characteristics of 2-amino thiophenol (ATP) and 2-cyanomethyl benzothiazole (CNMBT) on two types of steel in 1m HCl medium were investigated at different temperatures (25, 30, 35, 40 and 50°C). The pitting corrosion behaviour for the same system was studied using a potentiodynamic technique. The pitting corrosion resistance of steel samples increased with increase in concentration of the ATP and CNMBT. Some samples were examined by scanning electron microscopy. The effects of the inhibitors on the general corrosion of the two samples were investigated by using gravimetric and galvanostatic polarization techniques. The inhibition efficiencies increased with increase their concentration but decreased with increase in temperature. Free energies of activation, enthalpies and entropies for the inhibition processes were determined from rate constant data measured and different temperatures at different concentrations of ATP and CNMBT. Results were compared with fits obtained from the application of the Langmuir isotherm. Results were correlated to the chemical structure of the inhibitors. The inhibition efficiency of CNMBT is higher than that of ATP.

Novel mercury (II) ion-selective polymeric membrane sensor based on ethyl-2-benzoyl-2-phenylcarbamoyl acetate.

Mercury (II) ion-selective PVC membrane sensor based on ethyl-2-benzoyl-2-phenylcarbamoyl acetate (EBPCA) as a novel nitrogen containing sensing material is successfully developed. The sensor exhibits good linear response of 30 mV per decade within the concentration range 10(-6)-10(-3) mol l(-1) Hg(II). The sensor shows good selectivity for mercury (II) ion in comparison with alkali, alkaline earth, transition and heavy metal ions. The EBPCA-based sensor is suitable for use with aqueous solutions of pH 2.0-4.5 and exhibits minimal interference by Ag(I) and Fe(III), which are known to interfere with other previously suggested sensors. The nature and composition of the sensing material and its mercury complex are examined using Fourier-transform infrared analysis, elemental analysis and X-ray fluorescence techniques. The proposed sensor is applied as a sensor for the determination of Hg(II) content in some amalgam alloys. The results show good correlation with data obtained by atomic absorption spectrometric method.

Inhibition of chloride localized corrosion of mild steel by PO43-, CrO42-, MoO42-, and NO2- anions

The effect of phosphate (PO43−), chromate (CrO42−), molybedate (MoO42−) and nitrite (NO2−) ions on the pitting corrosion of steel in 0.1 M NaCl solution has been studied using potentiodynamic polarization and SEM techniques. The addition of increasing concentrations of PO43−, CrO42−, MoO42− and NO2− anions causes a shift of the pitting potential (Epit) in the positive direction, indicating the inhibitive effect of the added anions on the pitting attack. The adsorption characteristics of these anions on the steel surface play a significant role in the inhibition processes. The PO43−anion has a strong inhibitive effect of chloride pitting corrosion. The effect of different inorganic anions on the pitting corrosion of steel samples I and II (with different composition) was also studied in 0.1 M NaCl solution.

Alumina modified by dimethyl sulfoxide as a new selective solid phase extractor for separation and preconcentration of inorganic mercury(II)

Dimethyl sulfoxide (DMSO) was simply immobilized to neutral alumina via quite strong hydrogen bonding between sulfoxide oxygen and surface alumina hydroxo groups. The produced alumina-modified dimethyl sulfoxide (AMDMSO) solid phase (SP)-extractor experienced high thermal and medium stability. Moreover, the small and compact size of DMSO moiety permit high surface coverage evaluated to be 2.1+/-0.1 mmol g(-1) of alumina. Hg(II) uptake was 1.90 mmol g(-1)(distribution coefficient log K(d)=5.658) at pH 1.0 or 2.0, 1.68 mmol g(-1) (log K(d)=4.067) at pH 3.0 or 4.0 while the metal ions Ca(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Pb(II) showed low values 0.513-0.118 mmol g(-1) (log K(d)<3.0) in the pH range 4.0-7.0. A mechanism was suggested to explain the unique uptake of Hg(II) ions by binding as neutral and chloroanionic species predominate at pH values< or =3.0 of a medium rich in chloride ions. A direct and fast batch separation mode was achieved successfully to retain selectively Hg(II) in presence of other eight coexisting metal ions. Thus, Hg(II) was completely retained; Ca(II), Co(II), Ni(II) and Cd(II) were not retained, while Pb(II), Cu(II), Zn(II) and Fe(III) exhibited very low percentage retention evaluated to be 0.42, 0.49, 1.4 and 5.43%, respectively. The utility of the new modified alumina sorbent for concentrating of ultratrace amounts of Hg(II) was performed by percolating 2l of doubly distilled water, drinking tap water, and Nile river water spiked with 10 ng/l over 100mg of the sorbent packed in a minicolumn used as a thin layer enrichment bed prior to the determination by CV-AAS. The high recovery values obtained (98.5+/-0.5, 98.5+/-0.5 and 103.0+/-1.0) based on excellent enrichment factor 1000, along with a good precision (R.S.D.% 0.51-0.97%, N=3) demonstrate the accuracy and validity of the new modified alumina sorbent for preconcentrating ultratrace amounts of Hg(II) with no matrix interference.

On the pitting corrosion of tin by sulphate anion

Abstract The corrosion behaviour of tin in Na 2 SO 4 solutions at concentrations of 0.1–1.0 M and in the pH range 3–11 was investigated by using potentiodynamic and cyclic voltammetry techniques. The voltammograms involve two anodic peaks prior to the initiation of pitting corrosion. The first peak corresponds to the formation of Sn(OH) 2 and/or SnO. The second peak correlates to the formation of Sn(OH) 4 and/or SnO 2 . The pitting initiation can be explained through the adsorption competition between sulphate anions and the passivating species on the passivated electrode surface. The critical pitting potential depends on the sulphate concentration, pH and scan rate. Three cathodic peaks are observed on the negative-going scan, corresponding to the reduction of the dissolved pitting corrosion products, SnO 2 and SnO respectively. Successive cycling has no significant influence on the pitting potential, but leads to a progressive decrease in the heights of the anodic peaks as a result of incomplete reduction during the cathodic sweeping.

Novel Sm(III) ion-Selective polymeric membrane sensor based on spiro[oxirane-pyrazolidinedione] derivative ionophore

Abstract A poly vinyl chloride (PVC) membrane sensor for Sm(III) ions based on [1‐phenyl‐3′(2‐nitrophenyl) spiro[Oxirane‐2.4‐Pyrazoline]‐3,5‐dione] (PNSOP) as a membrane carrier was developed. This sensor exhibits a rapid and good Nernstian response towards Sm(III) ions in the range of 10−1 to 10−6 mol l−1 with a slope of 19.3±0.2 mV per decade and a detection limit of 6.1×10−7 mol l−1. The sensor response and selectivity remained almost unchanged for at least 4 months. It has a fast response time about of 5 s. The sensor can be used in a pH range from 4.0 to 8.2 and demonstrates good discriminating power over a wide variety of other metal ions. The formation constant of ionophore complex with Sm(III) was calculated by using the segmented sandwich membrane method. The nature of the PNSOP ionophore and its Sm(III) complex is examined using Fourier‐transform infrared analysis and elemental analysis technique. The proposed sensor was successfully applied as an indicator electrode in potentiometric titration of oxalate and carbonate ions and determination of acetylsalicylate and carbonate ions in some drugs.

A Novel Hg(II) PVC Membrane Sensor Based on Simple Ionophore Ethylenediamine Bis‐Thiophenecarboxaldehyde

Abstract A mercury (II) ion‐selective polyvinyl chloride (PVC) membrane sensor based on ethylenediamine bisthiophenecarboxaldehyde (EDBT) as a novel nitrogen‐ and sulfur‐containing sensing material was successfully developed. The ionophore was produced through Schiffs base formation between ethylenediamine and 2‐thiophenecarboxaldehyde. These two reagents have the advantages of low cost and simple chemical compounds. Ortho‐nitro phenyl pentyl ether (o‐NPPE) as solvent and sodium tetraphenyl borate (NaTPB) as a lipophilic salt were chosen. The sensor exhibited a good linear response of 30.0±0.4 mV per decade within the concentration range of 10−7–10−2 and a detection limit of 7.0×10−8 mol L−1 Hg(II). The sensor showed good selectivity and fast response for the mercury (II) ion with respect to some alkali, alkaline earth, transition, and heavy metal ions. The EDBT–based sensor was suitable for aqueous solutions of pH range from 2.0 to 4.5. It can be used for about 3 months without any considerable divergence in potential. The formation constant of ionophore complex with Hg(II) ion was calculated by using the segmented sandwich membrane method. The structure of both the ionophore and its Hg(II) complex were examined using infrared spectra and elemental analysis. The proposed sensor was applied for the determination of Hg(II) content in some dental amulgum alloys and as an indicator electrode for potentiometric titration of Hg(II) ion with EDTA solution, as well as with I−, OH−, and IO3 − ions. In addition, the solubility products of the previous ions were determined by using this sensor.

Novel Zinc Ion-Selective Membrane Electrode Based on Sulipride Drug

Sulipride drug N-[(ethyl-1 pyrrolidinyl-2)methyl] methoxy-2 sulfamoyl-5 benzamide was used as a novel electroactive material for the preparation of PVC-based Zn2+-selective electrode. The PVC membrane electrode exhibited a working concentration range of 10−5–10−1 M, with a Nernstian slope of 29.3 mV per decade and a fast response time of 20 s. The valid pH range for the membrane electrode is 4.0–6.5. The electrode exhibits very good selectivity over alkali, alkaline earth and transition metal ions. The nature and composition of the electroactive material and its zinc complex are examined using infrared analysis, elemental analysis and X-ray diffraction techniques. The proposed electrode can be used to determine zinc(II) contents in some rock materials and was applied as indicator in the potentiometric titration of Zn2+ against EDTA for the determination of end point.

New cesium ion-selective electrodes based on anilino-(1,3 -dioxo-2-indanylidene) acetonitrile derivatives

Cesium ion-selective PVC membrane electrodes based on anilino-(1,3-dioxo-2-indanylidene) acetonitrile derivatives as a novel class of neutral ionophores were examined. The ionophores were p-methoxyanilino-(1,3-dioxo-2-indanylidene) acetonitrile, p-methylanilino-(1,3-dioxo-2-indanylidene) acetonitrile and p-N,N-dimethylanilino-(1,3-dioxo-2-indanylidene) acetonitrile. The anilino-(1,3-dioxo-2-indanylidene) acetonitrile proved to work well with cesium, the corresponding electrodes display a response to this ion. The most favourable ionophore was p-methoxyanilino-(1,3-dioxo-2-indanylidene) acetonitrile, especially when the secondary ion exchanger potassium tetrakis (4-chlorophenyl) borate was incorporated in 2-nitrophenyl octyl ether for ion-selective electrode membrane construction. The response function was linear within the concentration range 10(-1)-2.5x10(-5) mol l(-1) and the slope was 52 mV decade(-1). The detection limit remained at 6.3x10(-6) mol(-1). The selectivity and response time of the electrode was studied and it was found that the electrode exhibited good selectivity for cesium over alkali, alkaline earth and some transition metal ions. The electrode response was stable over a wide pH range. The lifetime of the electrode was about 1 month.

Iron(III) ionophores based on formylsalicylic acid derivatives as sensors for ion-selective electrodes

Novel iron(III)-selective PVC membrane electrodes based on formylsalicylic acid derivatives were studied. The electrode based on p-chloroaniline-3-formylsalicylic acid as a sensor, containing potassium tetrakis(4-chlorophenyl)borate as a lipophilic salt and o-nitrophenyl octyl ether as a plasticizer, gave the best performance. The electrode exhibits a good Nernstian response for 10−1–5.0 × 10−5 mol l−1 FeCl3 with a slope of 20 mV per decade. It shows a high selectivity for iron(III) in comparison with alkali, alkaline earth and heavy metal ions. The electrode response and selectivity remained almost unchanged for at least 1 month. The effects of plasticizers, membrane supports, lipophilic salts and pH on the potential response of the electrode were also studied. The electrode was successfully applied to the determination of iron(III) contents in some rocks.