Suhail Ahmed

Levels and sources of heavy metals in house dust

The concentration and the sources of heavy metals (Pb, Cd, Zn and Cu) in house dust samples of nine selected houses of Jalil Town, Gujranwala, Pakistan are determined and a comparison with the concentration of these metals in respective street dust samples is given. Sources, exterior as well as interior are identified. The extent of contribution of lead in house dust from exterior sources and interior sources is calculated by determining the isotopic ratios in house dust, street dust and paint used in the houses. It is noticed in the case of well ventilated houses, that most of the heavy metal contribution is from the exterior sources. However, in less ventilated houses, contribution from the interior sources is also significant.

DETERMINATION OF TRACE IMPURITIES IN NICKEL-BASED ALLOY USING NEUTRON ACTIVATION ANALYSIS

A radiochemical neutron activation analysis procedure has been applied to investigate 40 major, minor, and trace impurities in nickel-based alloy. The extensive use of these alloys in the electronic industry, telecommunications, manufacturing of aircraft engine turbine blades and chemical equipments desires for their precise characterization. The concentration of nickel in the nickel-based alloy was found to be 56.8%, whereas Fe, Cr, Ca, Mg, Ce, Mn, Na and V were the major components of the alloy, which constituted to more than 26%. The rest of the elements was present in minor or trace levels. Most of the rare earth elements except Ce were also present in trace amounts. Neutron activation analysis technique was preferably used because of its good sensitivity and multielement determination capabilities for the characterization of high purity materials. The comparison of RNAA and INAA indicated improvement in the detection limits utilizing radiochemical separation procedures developed in the present work.

Extraction of mercury(II) from aqueous thiocyanate solutions with 5-(4-pyridyl)nonane in benzene, and its subsequent atomic-absorption spectrometric determination

Tracer ( approximately 10(-8)M) mercury(II) can be quantitatively extracted with 5-(4-pyridyl)nonane in benzene from aqueous thiocyanate solutions that are up to 6M in HCl, 1M in H(2)SO(4) or 0.25M in HNO(3), in a single extraction. Optimal conditions for the extraction are given, based on a critical study of the relevant factors such as the effects of the acids, thiocyanate, salting-out and complexing agents and the reagent concentration. The mechanism underlying these extractions is discussed on the basis of the results obtained from partition and slope-analysis data. The extraction of the metal as Hg(PyN)(2)(SCN)(2) is indicated. The extracted mercury can be stripped from the non-aqueous layer with various aqueous solutions, including nitric acid (2M), sodium citrate ( 1M) and sodium thiosulphate (0.1 M). Common salts do not depress the extraction. Distribution coefficients and separation factors of several elements relative to mercury(II) are reported for media that contain the optimal concentrations of the mineral acids and are in 0.2M in potassium thiocyanate. The data have been applied for the determination of mercury in soil and water samples by atomic-absorption spectrometry.

Extraction of iron(III) with diphenyl-2-pyridylmethane dissolved in benzene from aqueous chloride solutions

The mechanism of extraction has been investigated by partition, slope analysis and loading-ratio data. The results obtained give a picture of the mechanism of extraction of FeCl4− ions in relation to the hydration and solvation of the compound extracted. The possible formula of the extracted species is (DPPM)3H3O+(H2O)n−FeCl4−. In dilute aqueous hydrochloric acid systems the influence of the concentration of a number of salts with cations of different electrical potentials (Ze/r), on iron(III) extraction, has been studied. Splitting of the organic phases occurs at high acid and/or high salt concentrations. The phenomenon is explained on the basis of the variability of the hydration number. Investigations have been made to understand the parameters controlling the extraction of the metal and its is shown that the extraction offers a simple, fast and selective separation method of iron from solutions.

Radiochemical neutron activation analysis of trace impurities in high purity aluminum

Rapid radiochemical neutron activation analysis (RNAA) procedures were developed and employed for the determination of 32 trace impurities in high purity aluminum thin foils. Anion exchange column chromatography was developed for the sequential group chemical separation of various elements which helped in reducing the spectral interferences and improving the sensitivity of the method. The procedure is simple and requires a very short time to separate the elements in three groups for radiometric assay. To determine very low contents of uranium and thorium,239Np and233Pa as activation products were separated using anion exchange and coprecipitation methods. The impurity contents were found to be low, therefore, their adverse effects on microelectronic devices would be negligible. Our data could partially be compared with the data reported in literature.

Liquid — Liquid extraction of silver(I) by diphenyl-2-pyridylmethane in benzene from aqueous mineral acid — Thiocyanate solutions

Liquid — liquid extraction of Ag(I) by diphenyl-2-pyridylmethane (DPPM) in benzene from aqueous nitric and sulfuric acid solutions containing thiocyanate ions has been studied at ambient temperature (24±2 °C). The metal is extracted quantitatively from 0.01M HNO3+0.02M KSCN; or 0.25M H2SO4+0.02M KSCN by 0.1M DPPM (optimum extraction conditions). Slope analysis indicates that two types of ion-pair complexes i.e. [(DPPMH)+·Ag(SCN)2−] and [(DPPMH)2+·Ag(SCN)32−] are involved in the extraction process. Separation factors determined at optimum conditions reveal the separation of Ag(I) from Cs(I), Br(I), Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Fe(III), Au(III) (from HNO3 solution only), Cr(III), Hf(IV), Ta(V), Sn(IV) and Cr(VI). With the exception of thiosulfate, other complexing anions like ascorbate, acetate, citrate, oxalate do not hinder the extraction of Ag(I) under optimum conditions.

Extraction of arsenic(III) from chloride-iodide solutions by diphenyl(2-pyridyl)methane and benzene

The variation of the partition coefficient of arsenic(III) between chloride-iodide solutions and diphenyl(2-pyridyl)methane in benzene has been studied. The effect of the concentration of hydrochloric acid and iodide in the aqueous phase has been assessed. The partition coefficients are maximal for concentrated acid solutions which are 0.02-0.1 M in potassium iodide. Slope-analysis studies were used to elucidate the composition of the extracted species. Polymerization of the solvent species tends to decrease the distribution coefficients of arsenic with increasing concentration of diphenyl(2-pyridyl)methane, especially with trace concentrations of the element. Arsenic can be selectively separated from copper, cobalt, nickel, iron, chromium and antimony, which are usually associated with it in various ores.

EXTRACTION-SEPARATION OF MERCURY WITH 1-NEPHTHYLTHIOCARBAMIDE

The extraction of mercury(II) has been studied from mineral acid solution using 1-nephthylthiocarbamide (ANTU) in chloroform-acetone mixture (9:1). The variables such as the concentration of acid and extractant have been optimized. The extractability of some other elements at the optimum conditions for mercury is also studied in order to establish the separation procedure. The probable composition of the extracted species has been deduced from log data. Effect of a number of foreign metal ions and anions has also been studied.

Selective extraction of Hg(II) from aqueous mineral acid solution containing iodide ions using 2-benzylpyridine in benzene

A method for the selective extraction of mercury has been developed. The extraction of Hg(II) by 2-benzylpyridine (BPy) in benzene from dilute mineral acid solution containing iodide ions has been investigated, and variables such as concentration of acids, iodide and the extractant have been optimized. The optimum conditions for the extraction of Hg(II) by 0.1M BPy/benzene are: 0.01M (HCl, HNO3, H2SO4)+0.01M KI. The distribution coefficients and separation factors of 19 elements relative to Hg(II), have been reported. Effect of anions such as ascorbate, acetate, citrate, oxalate and thiosulfate has also been studied. The method developed could find useful applications in selective extraction of small amounts of mercury from environmental samples.

Solvent extraction of trivalent lanthanide Pr(III), Ho(III) and Er(III) with N-benzoyl-N-phenylhydroxylamine

Extraction of Pr(III), Ho(III) and Er(III) has been studied in the pH range of 1–10 with N-benzoyl-N-phenylhydroxylamine (BPHA) in benzene. The separation was found to be quantitative in borate media from pH 7 to 10, at an ionic strength of 0.1M (H+, BO33−). The stoichiometric composition of the complexes under the optimal conditions of shaking time, pH and reagent concentration was formulated using slope analysis and found to be M(BPHA)3, where M=Pr(III), Ho(III) and Er(III). The effect of various masking agents shows that citrate, ascorbate, EDTA, oxalate, fluoride and phosphate form stable complexes with these rare earths as compared to BPHA. The decontamination factors for different cations with respect to these rare earths under the optimum conditions have been evaluated.