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  • Author or Editor: N. Ahmed x
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Abstract  

The sorption of Fe(III) at low pH range from 1 to 4.5 on open cell polyether type HTTA-loaded polyurethane foam has been carried out using batch technique. The optimum shaking time for 2.5· 10–4M solution of Fe(III) was found to be 30 minutes. The concept of macropore and micropore nature of polyurethane foam sorbent offers unique advantages of adsorption. Freundlich and Langmuir adsorption isotherms are followed at low concentration range from 1·10–4 to 3·10–4M solution of Fe(III). The Freundlich constant (1/n=0.46±0.013 andK=9.16±1.39 mg·g–1) and Langmuir isotherm constants(M=21.78 mg·g–1 andb=88.41±9.731·g–1) were established. The sorption mean free energyE=12.22±0.09 kJ·mol–1 and loading capacityC m=145.21±6.1 mg·g–1 were evaluated using Dubinin-Radushkevich isotherm, which suggested that the adsorption mechanism was chemisorption.

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Abstract  

The batch kinetics of Fe(III) adsorption on HTTA-loaded polyurethane (PU) foam have been investigated. The rate of controlling the adsorption is found to be intraparticle diffusion. The reaction rate of adsorption and desorption was also evaluated and found to increase and decrease with temperature, respectively. This indicates an endothermic adsorption behavior of Fe(III) on HTTA loaded PU foam. The activation energy of adsorption (80±10 kJ·mol–1) and of desorption (–45±±2 kJ· mol–1) indicates the chemical adsorption rather than physical adsorption. The isosteric heat of adsorption ( H ads) was found to be –82.7±5.05 kJ·mol–1. This shows the formation of new chemical bonds among Fe(III)-HTTA-PU foam. The thermodynamic parameters of G, H and S, and equilibrium constantK c have been calculated. These functions further support that the process of adsorption of Fe(III) on HTTA-loaded PU foam is endothermic and chemisorption, stabilized through thermodynamic functions.

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Abstract  

Absorption bands in the range of 350–950 nm, induced in copper-containing lead borate glasses by -rays were identified and characterized. The effect of irradiation dose, copper oxide and lead oxide contents on the intensity and position of the induced absorption bands were also considered. Several induced absorption bands were observed. At least two bands in the ranges of 740–780 and 850–870 nm could be identified. They are suggested to be associated with induced Cu(2+) ions. The band in the 800–830 nm (1.6 eV) range is ascribed to the Pb(3+) ion, whereas others in the ranges of 600–630 and 650–730 nm are associated with the intrinsic defects formed in the base glass.

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Abstract  

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.

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Abstract  

Rice husk, an agricultural waste product, was studied as a potential decontaminant for chromium in the effluents of leather tanning industries. Physico-chemical parameters such as selection of appropriate electrolyte, shaking time, concentration of adsorbent and adsorbate were studied to optimize the best conditions in which this material can be utilized on commercial scale for the decontamination of effluents. The radiotracer technique was used to determine the distribution of chromium. In certain cases atomic absorption spectrophotometry was also employed. Maximum adsorption was observed at 0.01 mol·dm−3 acid solutions (HNO3, HCl, H2SO4 and HClO4) using 3.0 g of adsorbent for 2.73·10−3 mol·dm−3 chromium concentration in five minutes equilibration time. Studies show that the adsorption decreases with the increase in the concentrations of all the acids. The adsorption data follows the Freundlich isotherm over the range of 2.73·10−3 to 2.73·10−2 mol·dm−3 chromium concentration. The characteristic Freundlich constants, i.e., 1/n=0.86±0.06 andA=2.35±0.06 mmol·g−1 have been computed for the sorption system. Thermodynamic parameters, i.e., ΔG 0, ΔS 0 and ΔH 0 have also been calculated for the system. Application of the method to a test case of a medium size industry showed that 21 kg of rice husk was sufficient to maintain the NEQS limits of chromium for industrial effluents.

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Abstract  

The present investigation has been carried out to study the effect of -radiation on the absorption spectra of aerated solutions of alizarin complexone dye at different concentrations and pH values. The change in optical density for dosimeter concentrations ranging from 5·10–2 to 15·10–2 mM was observed to respond linearly to the increase of absorbed gamma dose. With the proper choice of concentration and pH value, the system is suitable for the accurate measurement of absorbed doses up to 5.3 kGy. This study includes also an investigation of the effect of environmental conditions on the stability of the dye solutions at different pH values during storage. Suggestions are made for possible low radiation dosimetry by means of spectrophotometric analysis of the absorption spectra.

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Summary

Bis(salicylaldehyde) orthophenylenediamine (BSOPD) is reported here as a complexing reagent for simultaneous determination of six metal ions, gold, chromium, iron(II)/(III), uranyl, and nickel, by capillary zone electrophoresis. The pre-derivatized complexes were injected onto 50 cm bare silica capillary (i.d. 75 µm) with background electrolyte 50 mM citrate:oxalate buffer in 1:1 at pH 4. All metal ions were separated within 15 min including coexisted ions at applied voltage of −15 kV at detection wavelength of 250 nm. Under the abovementioned conditions, limits of quantification and detection were found to be 0.5, 1.0, 1.0, 10.0, 1.0, and 10.0 µg mL−1; and 0.16, 0.33, 0.33, 3.33, 0.33, and 3.33 µg mL−1 for Au(III), Cr(VI), Fe(III), Fe(II), UO2(II), and Ni(II), respectively. Linear calibration graphs were obtained in the ranges of 0.5–100, 1–200, 10–100, 1–100, 1–100, and 10–200 µg mL−1 with the correlation coefficient values 0.9964, 0.9948, 0.9900, 0.9999, 0.9992, and 0.9918 for Au(III); and Cr(VI), Fe(III), Fe(II), UO2(II), and Ni(II), respectively. Applicability of the method has been evaluated by determining gold from wastewater samples of goldsmith factories and uranyl from ore samples. The developed method was also used for the determination of chromium in selected environmental waters (drinking and polluted). The data obtained with developed method were compared with those obtained from atomic absorption spectroscopy, and the results of the analysis were found to be in good agreement.

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Abstract  

A simple and rapid, laser fluorimetric method for the determination of uranium concentration in raffinate stream of Purex process during reprocessing of spent nuclear fuel has been developed. It works on the principle of detection of fluorescence of uranyl complex formed by using fluorescence enhancing reagent like sodium pyrophosphate. The uranium concentration was determined in the range of 0–40 ppb and detection limit of 0.2 ppb. The optimum time discrimination is obtained when the uranyl ion is complexed with sodium pyrophosphate. Need of preconcentration step or separation of uranium from interfering elements is not an essential step.

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Abstract  

A spectrophotometric method is developed for the determination of dissolved tri-n butyl phosphate (TBP) in aqueous streams of Purex process used in nuclear fuel reprocessing. The method is based on the formation of phosphomolybdate with added ammonium molybdate followed by reduction with hydrazine sulphate in acid medium. Orthophosphate and molybdate ions combine in acidic solution to give molybdophosphoric (phosphomolybdic) acid, which upon selective reduction (with hydrazinium sulphate) produces a blue colour, due to molybdenum blue. The intensity of blue colour is proportional to the amount of phosphate. If the acidity at the time of reduction is 0.5 M in sulphuric acid and hydrazinium sulphate is the reductant, the resulting blue complex exhibits maximum absorption at 810–840 nm. The system obeys Lambert–Beer’s law at 830 nm in the concentration range of 0.1–1.0 μg/ml of phosphate. Molar Absorptivity was determined to be 3.1 × 10L mol−1 cm−1 at 830 nm. The results obtained are reproducible with standard deviation of 1 % and relative error less than 2 % and are in good agreement with those obtained by ion chromatographic technique.

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Bacillus thuringiensis (B.t) is well known for its biocontrol potential against a variety of insects. Nematicidal potential of ten B.t isolates was tested against root-knot nematodes (Meloidogyne javanica (Treub) Chitwood) in vitro, under greenhouse as well as in field conditions. Eggs and second stage juveniles (J2) were exposed to 5 and 25% concentrations of bacterial cell-free aqueous extracts up to 96 h. B.t isolates showed lesser degrees of nematicidal activity at 5% concentration. However, some B.t isolates (B.t-14, B.t-16 and B.t-64) greatly reduced egg hatching and increased J2. All B.t isolates revealed suppressed egg hatching and increased mortality of J2 at 25% concentration. Soil applications with most of the B.t isolates under greenhouse and field conditions significantly improved height and fresh weights of root-knot nematode parasitized okra (Abelmoschus esculentus (L.) Moench). Some isolates, including B.t-64 reduced the number of galls and egg masses. B.t-64 reduced gall formation up to 70% under greenhouse conditions. However, 29% of decrease was observed in field conditions. Similarly, B.t-64 treated plants showed a 56% decreased in eggs/egg mass in a field experiment. Population of root-knot nematodes in the rhizosphere was decreased up to 61% in the field experiment as compared to control.

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