Nasir Khalid

POTENTIAL OF RICE HUSKS FOR ANTIMONY REMOVAL

The adsorption behavior of rice husks for antimony ions from aqueous solutions has been investigated as a function of appropriate electrolyte, equilibration time, hydrogen ions, amount of adsorbent, concentration of adsorbate, effect of diverse ions and temperature. The best conditions in which this material can be used as adsorbent have been explored. The radiotracer technique was employed to determine the distribution of antimony (122Sb) using a batch method. Maximum adsorption was observed at 0.01 mol L(-1) acid solutions (HNO3, HCl, H2SO4 and HClO4) using 1.0 g of adsorbent for 1.92 x 10(-5) mol L(-1) antimony concentration in 10 min equilibration time. Studies show that the adsorption decreases with the increase in the concentrations of all the acids. The adsorption data follow the Freundlich isotherm over the range of 1.92 x 10(-5) to 2.05 x 10(-4) mol L(-1) antimony concentration. The characteristic Freundlich constants i.e., 1/n = 0.82 +/- 0.05 and K = 4.61 +/- 0.07 m mol g(-1) have been computed for the sorption system. The uptake of antimony increases with the rise in temperature (299-323 K). Thermodynamic quantities i.e., deltaG0, deltaS0 and deltaH0 have also been calculated for the system. The sorption process was found to be endothermic.

REMOVAL OF MERCURY FROM AQUEOUS SOLUTIONS BY ADSORPTION TO RICE HUSKS

The adsorption of mercury ions from aqueous solutions on rice husk has been investigated as a function of appropriate electrolyte, contact time, concentrations of adsorbent and adsorbate, and temperature. The radiotracer technique was used to determine the distribution of mercury. Maximum adsorption was observed at 0.01 mol·dm−3 acid solutions (HNO3, HCl, H2SO4, and HClO4) using 1.0 g of adsorbent for 1.30 × 10−3 mol·dm−3 mercury concentration in 5 minutes of equilibration time. Studies show that the adsorption decreases with an increase in the concentrations of all the acids. The adsorption data follow the Freundlich isotherm over the range of 1.3 × 104 to 2.6 × 10−3 mol·dm−3 mercury concentration. The characteristic Freundlich constants, i.e., 1/n = 0.89 ± 0.05 andA = 208 ± 2.1 m·mol·g−1, have been computed for the sorption system. The uptake of mercury increases with a rise in temperature. Thermodynamic parameters, i.e., ΔG° ΔS° ΔH°, have also been calculated for the system. The sorption process was fo...

Removal of lead from aqueous solutions using rice husk

ABSTRACT Rice husk, an agricultural waste, was studied as a potential scavenger of lead from various aqueous solutions. Physicochemical parameters such as selection of appropriate electrolyte, shaking time, and the concentrations of adsorbent and adsor-bate were studied to optimize the conditions to be utilized on a commercial scale for the decontamination of effluents using a batch technique. Maximum adsorptionwas observed with 0.01 mol·dm−3 acid solutions (HNO3, HC1, H2SO4 and HC1O4) using 1000 mg of adsorbent for a 4.82 × 10−5 mol·dm−3 lead concentration in less than 10 minutes equilibration time. Studies show that the adsorption decreases with an increase in the concentrations of all the acids. The adsorption data follows the Freundlich isotherm over the 9.65 × 10−5to4.83 × 10−3 mol·dm−3 range of lead concentration. The characteristic Freundlich constants, i.e.,l/n = 0.93 ± 0.04 and A = 19.86 ± 0.82 m·mol·g−1, have been computed for the sorption system. Thermo- dynamic parameters, i.e.,ΔG°ΔSdeg;,and Δ...

Adsorption studies of lead on lateritic minerals from aqueous media

Minerals produced by lateritic weathering have been exploited to evaluate their potential for the decontamination of lead ions from aqueous solutions and for understanding decontamination mechanism in nature. Various physico-chemical parameters such as selection of appropriate electrolyte, equilibration time, amount of adsorbent, concentration of adsorbate, effect of diverse ions and temperature were studied in order to simulate the best conditions in which the particular material could be used as an adsorbent. Maximum adsorption was observed at 0.005 mol L− 1 acid solutions (HNO3, HCl, and HClO4) using 0.2 g of adsorbent for 4.82 × 10− 5 mol L− 1 lead concentration in five minutes equilibration time. Studies show that the adsorption of lead decreases with the increase in the concentrations of all the acids. The adsorption data follows the Freundlich isotherm over the range of 2.41 × 10− 6–9.65 × 10− 4 mol L− 1 lead concentration. The characteristic Freundlich constants, i.e., 1/n=0.42±0.02 and K=0.57±0.01 mmol g− 1 have been computed for the sorption system. The sorption mean free energy from the Dubinin–Radushkevich isotherm is 13.96 ± 0.74 kJ mol− 1 indicating an ion-exchange mechanism of chemisorption. The uptake of lead increases with the rise in temperature (278–323K). Thermodynamic quantities, i.e., ΔG, ΔS, and ΔH also have been calculated for the system. The sorption process was found to be endothermic.

Immobilization of arsenic on rice husk

The adsorption potential of rice husk was investigated for arsenic ions from aqueous solution as a function of the appropriate electrolyte, contact time, concentrations of the adsorbent and adsorbate, effect of diverse ions and temperature. A radiotracer technique has been used to determine the distribution of arsenic employing a batch method. Maximum adsorption was observed at 0.01 mol/l acid solution (HNO3, HCl, H2SO4 and HClO4) using 1.0 g of adsorbent for 5.97 × 10−3 mol/l arsenic concentration and an equilibration time of 5 min. Studies showed that adsorption decreased with an increase in the concentration of all the acids studied. The adsorption data conformed to the Freundlich isotherm over the concentration range from 8.69 × 10−5 to 1.73 × 10−3 mol/l arsenic. Characteristic Freundlich constants, i.e. 1/n = 0.83 ± 0.06 and K = 4.43 ± 0.16 mmol/g were computed for the sorption system. The uptake of arsenic increased with increasing temperature. Thermodynamic quantities, i.e. ΔG0. ΔS0 and ΔH0, were also calculated for the system. The sorption process was found to be endothermic.

Biological screening, DNA interaction studies, and catalytic activity of organotin(IV) 2-(4-ethylbenzylidene) butanoic acid derivatives: synthesis, spectroscopic characterization, and X-ray structure

A series of organotin(IV) carboxylates, [Me2SnL2] (1), [Bu2SnL2] (2), [Oct2SnL2] (3), [Me3SnL] (4), and [Ph3SnL] (5), where L = 2-(4-ethylbenzylidene) butanoic acid, have been synthesized and characterized by elemental analysis, FT-IR, and NMR (1H, 13C, and 119Sn). [Me3SnL] (4) was analyzed by single crystal X-ray analysis which showed polymeric structure with distorted trigonal bipyramidal geometry. The complexes were screened for biological activities including antibacterial, antifungal, and cytotoxic activities. UV–vis absorption studies of HL, 1 and 4 with SS-DNA revealed groove binding as well as intercalation, which may be due to the presence of planar phenyl groups that facilitate interaction with DNA. The determined intrinsic binding constants, 6.04 × 103 M−1 (HL), 9.6 × 103 M−1 (1), and 1.7 × 104 M−1 (4), showed that HL and 1 have less binding strength than 4. The catalytic activities of di- and tri-organotin(IV) complexes were assessed in transesterification of triglycerides (linseed oil) into fatty acid methyl esters (biodiesel). The tri-organotin(IV) complexes have better catalytic activity than their di-analogs. The synthesized compounds interact with SS-DNA via intercalative binding mode of interaction in which the compound insert itself into the base pair of DNA resulting in hypochromic and bathochromic shift.

Separation and Preconcentration of Lead and Cadmium with 4-(4-Chlorophenyl)-2-phenyl-5-thiazoleacetic Acid and Its Application in Soil and Seawater

Abstract A simple and rapid extraction method for lead and cadmium with a new reagent 4-(4-chlorophenyl)-2-phenyl-5-thiazoleacetic acid (HCPTA) in n-butyl acetate and their subsequent determination by flame atomic absorption spectrometry has been investigated. The quantitative extraction was observed at pH 8.4. The stoichiometric composition of the extracted species was formulated as M(CPTA)2, where M = Pb or Cd. The extraction constant (log K ex) of lead and cadmium were found to be −9.7 ± 0.11 and −10.44 ± 0.11, respectively. The effect of various anions and cations on the extraction of lead and cadmium has also been studied. The mutual separation of lead and cadmium has also been proposed. The developed procedure was applied to the determination of these metals in seawater, IAEA (SRM) of soil-7, and copepod-MA-A-1. Higher preconcentration factors can be achieved by using a higher aqueous-to-organic phase ratio.

Non-occupational lead exposure and hypertension in Pakistani adults

Hypertension is one of the most prevalent diseases in the developed and developing countries. Based on the long historical association and the provocative findings of blood pressure effects at low level of lead exposure a study was carried out to determine if an association existed between low blood lead concentration and hypertension. In this study the effects of low-level exposure to lead on blood pressure were examined among 244 adults using atomic absorption spectrometer. For quality assurance purpose certified reference materials i.e., Animal blood A-13, Bovine liver 1577 and cotton cellulose V-9 from IAEA (International Atomic Energy Agency) and NIST (National Institute of Standard Technology) were analyzed under identical experimental conditions. The mean age of hypertensive adults was 52 years (range 43∼66). The mean values of systolic and diastolic blood pressure were (209±11.7) (range 170∼250) and (117±2.9) (range 105}140) mmHg respectively. Blood lead concentration ranged from 78∼201 μg/L with a mean of 139 μg/L and 165∼497 μg/L with a mean of 255 μg/L in normal and hypertensive adults respectively. Increase in systolic blood pressure was significantly predictive with increase in blood lead levels. Body mass index (BMI) and lipid profile including total cholesterol, low density lipoprotein cholesterol, high density lipoprotein cholesterol and triglyceride correlated with blood pressure.

Assessment of air quality of two metropolitan cities in Pakistan: Elemental analysis using INAA and AAS

Summary For the assessment of air quality of two cities in Pakistan, Instrumental Neutron Activation Analysis (INAA) and Atomic Absorption Spectrometry (AAS) have been used. In all 26 elements were determined in suspended particulate matter (SPM) and soil samples. The SPM levels from different locations of Rawalpindi and Lahore indicate unhealthy to hazardous air quality much above the World Health Organization (WHO) guidelines. Metrological conditions and nature of soil that contains clay components mainly contribute to the inventory of the SPM elements of these cities. The calculated enrichment factors (EF) also indicate the dominance of the soil components. Contributions of inorganic elements due to heavy traffic with automotive exhaust and other commercial activities in this area have been identified. Areas of Qurtaba Chowk and Bank Square in Lahore in particular showed high EF for lead depicting burning of the automotive fuel and road dust. The accuracy and precision of the work has been maintained through the concurrent use of IAEA Reference Materials.

Determination of trace elements in integrated human diet for dietary assessment

Neutron activation analysis in combination with atomic absorption spectrometry was utilized for the determination of 21 elements in integrated diet samples of the inhabitants of the Rawalpindi/Isla...