Search Results

You are looking at 1 - 10 of 10 items for

  • Author or Editor: N. A. A. Rahman x
  • All content x
Clear All Modify Search

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.

Restricted access

A preconditioned conjugate gradient (PCG)-based domain decomposition method was given in [11] and [12] for the solution of linear equations arising in the finite element method applied to the elliptic Neumann problem. The novelty of the proposed algorithm was that the recommended preconditioner was constructed by using symmetric-cyclic matrix. But we could give only the definitions of the entries of this cyclic matrix. Here we give a short description of this algorithm, the method of calculation of matrix entries and the results of calculation. The numerical experiments presented show, that this construction of precondition in the practice works well.

Restricted access

Summary  

A national intercomparison exercise was conducted to remove inconsistencies and improve analytical procedures in the measurement of hafnium and zirconium in zirconium ores. The ZH-A series of reference samples, prepared at the Pakistan Institute of Nuclear Science and Technology (PINSTECH), were used for this purpose. It was observed that measurement errors decreased with increasing Hf concentration (~298-17500 ppm) for most techniques, especially for AAS due to the sample preparation procedure required for this technique. Of all the tested techniques most reliable results were obtained with neutron activation analysis (NAA) for the measurement of Hf and Zr in such matrices.

Restricted access

Abstract  

Tuna fish flesh homogenate, IAEA-436, was received under the IAEA Analytical Quality Control Services (AQCS) intercomparison programme. Instrumental neutron activation analysis (INAA) was used to determine Al, As, Br, Ca, Ce, Cl, Co, Cr, Cs, Eu, Fe, Hg, K, Mg, Mn, Na, Rb, Se, Sb, Sm, and Zn in this proposed reference material (RM). IAEA-407 (Fish Homogenate) and NIST-SRM-1572 (Citrus Leaves) were used for quality assurance (QA) purposes. Due to the very low levels of most elements in IAEA-436, large discrepancies were observed between our results for IAEA-436 and data cited by the IAEA.

Restricted access

Abstract  

instrumental neutron activation analysis (INAA) has been employed to determine 19 essential and other trace elements of fourteen fruits harvested in Pakistan. Most of the fruits investigated contain substantial Ca, Cl, Fe, Mg, K and Na concentration levels. Fruits were found to be an adequate source of Co and Fe. Winter season provides a variety of fruits with highest adequacy for most of the essential elements while the fruits ingested in the summer season provide the minimum nutrient adequacy for these elements with the exception of Cl.

Restricted access

Stomatal conductance is an important heat avoidance mechanism and its association with higher yield and heat resistance has been established in Pima cotton. Experiments were carried out on upland cotton under heat-stressed and non-stressed greenhouse and field regimes, to understand the impact of heat-stressed and non-stressed environments on the genetic and combining ability variations for stomatal conductance. The experimental material comprised 8 upland cotton cultivars and their 15 F 1 cross combinations obtained in a line × tester mating arrangement. The results showed high genetic variability for stomatal conductance in a single environment, but low genetic variability across environments, due to the higher magnitude of the environmental interaction, especially that caused by temperature regimes. The interaction effect of temperature regimes also substantially modified general and specific combining ability variations for stomatal conductance. The relative contributions of general and specific combining abilities to total phenotypic variation for stomatal conductance also underwent a great change across field temperature regimes. The non-stressed regime favoured the expression of genes causing the additive type of genetic variability. The heat-stressed field regime, however, favoured the expression of both additive and non-additive types of genetic variation for stomatal conductance in upland cotton. Recurrent selection for the accumulation of favourable genes for general combining ability under non-stressed conditions was suggested for improving stomatal conductance in applied cotton breeding programmes.

Restricted access

Abstract  

Instrumental neutron activation analysis (INAA) and electro-thermal atomic absorption spectrometry (ETAAS) were employed to determine the toxic elements in fourteen fruits harvested in Pakistan. As, Br, Hg, Sb and Se were determined using INAA. Cadmium and Pb were determined using ETAAS. The intake levels of all toxic elements have been calculated. The data show that dates supply the maximum amount of most of the toxic elements. Peels of apple and pear have also been investigated and were found to contain higher concentration of toxic elements than their edible parts. The reliability of the techniques has been established by the use of standard reference materials. This study shows that all investigated fruits cultivated and consumed in Pakistan are safe for human consumption.

Restricted access

Eight descriptive sensory textural attributes of whole date fruit were evaluated by twenty trained panel members and correlated with sixteen physicochemical properties. All sensory parameters, except gumminess, significantly correlated (Ps<0.05) with pectin, crude fibre, and moisture content. In addition, sensory hardness, cohesiveness, elasticity, and resilience correlated significantly with length of whole fruit (P<0.05), sensory adhesiveness with glucose content (P<0.05), sensory chewiness with mass of whole fruit (P<0.05), and sensory gumminess with fructose, glucose, and total sugar content (P<0.10). Sweetness, however, correlated only with moisture content (P<0.05). CA and the biplot (i.e. including all products, their sensory texture and physicochemical attributes) generated through PCA recognized three groups of dates as hard-chewy, soft-(medium-chewy), and soft-(non-adhesive).

Restricted access

Summary  

The batch removal ofCs+, Sr2+, Ca2+and Mg2+ions from aqueous solutions using synthetic zeolite A was investigated. The influence of the initial ion concentration, pH and temperature was studied. The obtained isotherm data have been correlated with Langumir, Freundlich, and Dubinin-Radushkevich(D-R) isotherm models. The effect of the temperature on the equilibrium distribution values has been utilized to evaluate the standard thermodynamic parameters such as free energy (DG), enthalpy (DH) and entropy (DS). Based on the D-R isotherm expression, the maximum ion-exchange capacity and the mean free energy of each studied ion has been determined. The selectivity sequence, deduced from the equilibrium isotherm data is: Sr2+>Ca2+>Mg2+>Cs+>Na+.

Restricted access