VOLUME 25, NO3, SEPT 2003

Thermal Decomposition of Precursor and the Formation of Superconducting Phases in the Pb-Bi-Sr-Ca-Cu-O (Pb- BSCCO) System

Superconducting phases in the Pb-BSCCO system have been produced by ethylenediaminetetraacetic acid (EDTA)-gel processing using nitrate solutions. The decomposition of EDT A-gd precursor has been studied by thermo-analytical techniques in conjunction with X-ray dilTraction (XRD) method. The thermo-analytical data are discussed in relation to the sequence of phase formation necessary for the production of superconducting phases. The effect of Pb is shown to lower the temperature of formation of the Bi2Sr2Ca2Cu3o,. (2223) high Tc phase. The Bi2Sr2Ca,Cu20y (2212) low Tc phase was observed as a main product at 800°C along with the Bi2Sr2Cu2o,. (220 I) phase and Ca2PbO •. Sintering at higher temperature (845°C) led to the formation of the high Tc phase (2223). 11 is shown that liquid phase sintering of the samples assisted the fomlation of the 2223 phase. There is an optimum level of Pb addition above which the 2223 phase is not produced even when heated for up to 60 hours at 845°C.read more

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N ARSHAD ,M ARSHAD ,F R SALE ,A H QURESHI ,S K DURRANI ,S U REHMAN ,

Preparation and Characterization of Activated Carbon from Date Pits by Physical Activation in a Fluidized Bed Reactor

The preparation of activated carnon Irom date pits was experimentally investigated by physical activation with a mi)\1ure of superheated steam and air in a fluidized bed reactor. The effect of different process parameters like particle size of the precursor. temperature of carbonization, time of activation and operating pressure of the fluidizing medium on different physical, chemical and adsorptive characteristics ofthe resultant products were studied. It was thereafter established, that granular activated carbon in 25% yield, of moderate activity in liquid phase and lower Ball Pan Hardness No. (BPH No.), than the desired ASTM Standard was obtained from date pits in particle size of 1.00 - 2.00 mm. The other operational variables optimized through this study were operating pressure of 20 psi in 60 minutes of activation time.read more

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M TAHIR ,T H USMANI ,I SIDDIQUI ,F A PERVEEN ,

Temperature Effect on the Sorption of Alkaline Earth Metal Cations on SiO2 Surface

The sorption of Ca2+ and Mg2+ ions on the silica was studied as a function of concentration and temperature. The extent of sorption of the metal cations was found to increase with the increase in both the concentration and temperature of the system. It was found that the Ca2+ ion with ,ts smallest hydrated radii was able to reach the surface easily and was held more strongly as compared to Mg2+ ion. The sorption of metal cations was accompanied by the release of H' to the bulk phase. The sorption data fitted the linear form of the Langmuir equation. The positive values of M-I for the uptake of the metal ions on Si02 showed their sorption mechanism to be endothermic in nature. Both the positive !'is and negative ~G values conftrmed the spontaneous nature of the sorption process. read more

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B DILHARA ,N REHANA ,S MURTAZA ,A NAEEM ,S Mustafa ,

Supersorbent Gels for the Separation of Proteins from Dilute Aqueous Solution

We have successfully used size selective P(N-Isopropyl acryl amide-co-Acrylic acid) gels to concentrate dilute aqueous solutions of high molecular weight Bovine serum albumin, dextran and poly vinyl pyrrolidone. Concentration factor of 2.4 with 96% efficiency was obtained for dilute solutlun while for semi dilute solution it was 1.77 with 81 % efficiency. Desired pore size of the gel is obtained by changing the concentration of monomer or cross linker while changed LCST is possible by modifying copolymer composition / change in pH of the aqueous environment. The resultant inexpensive and feasible under mild conditions separation process is alternative to ultrafilteration.read more

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Z IQBAL ,B AHMAD ,S BASHIR ,M NISAR ,

Solvent Dependent l3C NMR Chemical Shifts in 6-Methylquinoline and 8-Methylquinoline

Solvent effect on 13C chemical shifts of 6-methylquinoline and 8-Methylquinoline has been studied in eight different solvents. 13C chemical shifts of these compounds have been measured in 30% (v/v) solution using DMSO-~ as an internal locking agent and Hexamethyldisiloxane (HMDSO) as an external reference. Carbon tetrachloride (CCL,) has been taken as a reference compound for comparison of these shifts because this is non polar. The purpose of the present study is to see the solvent effects of various solvents in the light of Buckingham, Schaefer and Schneider (BSS) theory. Present study has shown that polar solvents like chloroform, dimethylsulphoxide, acetone, methanol and ethanol, show positive deviation from CCL" while benzene show negative deviation. More negative shifts behavior at C8, C9 and CIO carbon atoms in these compounds is due to neighboring nitrogen atom whose lone pair of electron causes this change. C2 carbon atom shifts are also affected by nitrogen atom. Benzene shows negative shifts and entirely different behavior because of 1t-bonding and ring current phenomenon. Cyclohexane is a non-polar compound and it shows negative behaviour, because it has low dielectric constant compared to carbon tetrachloride.The present study on solvent dependent I3C chemical shifts has been done at a frequency of 22.50 MHz using JEOL FX-90Q IT NMR.read more

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M H PHULPOTO ,A R SOLANGI ,A W K KHANZADA ,S A PATHAN ,

Comparison of Sample Preparation Methods for the Determination of Essential and Toxic Elements in Important Indigenous Medicinal Plant Aloe barbadensis

The role of elements particularly trace elements in health and disease is well established. In this paper the authors investigate the presence of various elements in very impor1ant herb Aloe barbadensis (Aloe vera), it is commonly used in different ailments especially of elementary tract and skin problems. Four acid digestion methods for the determination of total elements in Aloe barbadensis were made. The samples of the plant were collected from surrounding of Hyderabad city, Sindh University, Jamshoro and vouchers specimens were prepared following the standard herbarium techniques. In total fifteen essential, trace and toxic elements such as Zo, Cr, K, Mg, Ca, Na, Cu, Fe, Pb, AI, Ba, Mil, Co, Ni, and Cd were determined in the plant, and in its decoction, using Atomic absorption spectrophotometer Hitachi Model 180-50. The procedure found to be more efficient than other methods of decomposes the biological material in nitric acid and 30% hydrogen peroxide. The validation of the methods was checked with the NBS-I570 (Spanish) as standard reference material. The yielded element values were in close agreement with certified values. The percentage recovery of different elements was found to be better i.e. (98-99%) as compared to other method of digestion. It was noted that level of essential elements was high as compared to the level of toxic elements read more

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Q SHAIKH ,T G KAZI ,M A JAKHRANI ,S R SAHITO ,M A MEMON ,G Q SHAR ,G H KAZI ,

Total Phenols as Pollution Indicator of Sewage and Sewage Contaminated Canal

Total phenol concentration was examined in Hyderabad city sewage, before and after addition of sewage to Fuleli canal and river Indus-Total phenol was observed within the ranges 0.23-2.5 mg/L in sewage, below detection limits to 0.95 mg/L at Fuleli canal and below detection limit to 0.08mgfL at river Indus at Kotri barrage. The variation of phenol contents with water discharge and seasons at river Indus and Fuleli canal were also investigated and inverse relation of concentration of phenol with water discharge was observed. The concentration of phenols in sewage and Fuleli canal exceeded the permissible limits for sewage and surface water respectively-read more

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I A ANSARI ,V K DEWANI ,M Y KHUHAWAR ,

Improved Extraction Method for the Determination of Fe, Cu, Zn, and Ni in Fat Samples Using Atomic Absorption Spectrophotometer

The present work dealt with a rapid, u1trasonically assisted acid extractive method applicable for the determination of iron, copper, nickel and zinc in margarine and shortening samples using the atomic absorption spectrophotometer as analytical tool. The percent recovery ofeu, Fe, Ni and Zn was found to be 96.45-97.08, 96.5-97.85, 95.8-97.5 and 96.0­97.8 % as compared with the conventional extraction method of 80.52, 81.94, 84.09 and 85.68% respectively, in the margarine and shortening samples which were fortified with 0.0, 0.125,0.25,0.5,1.0 and 2.0 ~gm of each metal ion using the standard addition method. The use of ultrasonic intensification in the present method reduced the conventional acid extraction time from 180 to 10 minutes only, with detection limit achieved down to nanomole level.Most of the investigated samples of different brands were found contaminated with notable amount of iron and nickel ranged 0.52 to 2.38 Ilg /g and 0.0.41 to 3.40 ~g respectively. The magnitude of occurrence for copper and zinc was low within the range of 0.03 - 0.08 ~ /g. Results of the proposed method were also found in complete agreement to those of wet digestion method and showed very good statistical correlation with coefficient of variation below 2.2 %.read more

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S R SAHITO ,R SULTANA ,F ANWAR ,M A JAKHARANI ,T G KAZI ,

Levels of Trace and Toxic Elements in Pakistani Varieties of Maize (Zea mays L.)

In the present investigation the level of trace and toxic elements were determined in six different varieties of maize by flame atomic absorption spectrophotometric technique. Maize varieties contained higher concentration (in mWkg) of AI, Sa, Cd, Co, Cr, Ni and Pb (28.42 ± 2.46,4.70 ± 0.43,0.81 ± 0.06, 0.S6 ± 0.04,0.49 ± O.OS, 0.74 ± 0.11 and 1.66 ± 0.10) were estimated in M2, MS, MI, M4, M6, M2 and M4 varieties respectively. The results obtained &om the collected and certified samples were compared by conducting the t-test at 9S% confidence limit The concentration of trace and toxic elements in all maize varieties collected and certified samples is below the values recommended by WHO and hence is .cheepedread more

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G Q SHAR ,S R SAHITO ,A N MEMON ,T G KAZI ,

Characterization of Effluents from Marble Industries Located in the Industrial Estates of NWFP (Pakistan)

Effluent samples were collected from some of the marble industries located in the Industrial Estates of NWFP and were chemically evaluated for the panmeters like TSS, TDS, BOD, COD, and metl.lslike Cr+', Fe+2, Zn+2, Pb+2, eu+2 and Ni'2, These values were compared with the National Environment Quality Standards, (NEQS) and it wu found that most of the values are higher then the standard limit ofNEQS.The TSS values are in the range of 1915 to 2915 mwL for the samples collected from Industrial Estate Hayatabad. Its values ranges from 985·2219 mWL for Industrial Estate Hattar and from 675·2212 mwL for Industrial Estate Oadoon 525·1612 mWL (or G.T.Road and 824­4010 mWL for scattered Industries. Similarly the TDS vallies ranges from 2617·2840 mWL for Industrial Estate Hayatabad, 2328·3955 mWL for Industrial Estate Hattar, 2140·3688 mWL for I.E. Oadoon, 1523·3880 mwL for G. T. Road and 1617·2280 niWL for scattered Industries. The COD values ranges from 50·75 mWL for Industrial Estate Hayatsbad, 96·160 mwL for Industrial Estate Hattar, 110-240 mWL for Industrial Estate Oadoon, 82·210 mwL for G.T:Road and 96·128 mWL for scattered Industries. The BOD values in almost all the samples of the Industrial Estates were found to be within the permissible limits of 43·59 mWL Trace toxic metl.ls were also found to be within the permissible range. however in some samples they exceed the NEQS read more

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M KHAN ,IMAD ULLAH ,A R KHAN ,U KALSOOM ,F KHAN ,