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THE STUDY OF HEAVY METAL IONS (NI++, CU++, ZN++, CD++ & PB++) ABSORPTION ON ACTIVATED CHARCOAL WITH SPECIAL REFERENCES TO ENVIRONMENTAL POLLUTION

Khattak, Manzoor Iqbal (1995) THE STUDY OF HEAVY METAL IONS (NI++, CU++, ZN++, CD++ & PB++) ABSORPTION ON ACTIVATED CHARCOAL WITH SPECIAL REFERENCES TO ENVIRONMENTAL POLLUTION. PhD thesis, University of Karachi, Karachi.

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Abstract

The work presented in this thesis has been divided into three sections. The first section deals with the characterization of activated charcoal. This includes instrumental method for the determination of moisture content, carbon content, metals impurities densities measurement, surface area, pore volume, porosity and average particle diameter of the activated charcoal in the solid state. The solid was further put to X-rays diffraction test in order to determine its amorphous or crystalline nature. The filtrate of doubly distilled water after having been shaken with the activated charcoal is amorphous and acidic in nature and contains phosphate, nitrate and sulphate ions. The carbon content was found to be about 70% and the metals impurities determined are nickel, copper, cobalt, iron magnesium and aluminum. The thermo gravimetric study of activated charcoal showed that the weight loss occurs in two distinct regions: one endothermic (dehydration) and the other exothermic (combustion). The moisture contents were found to 11%. The densities of activated charcoal varied in the sequence true density > tap density > bulk (loose) density. The pore size distribution curve and D-R analysis of nitrogen adsorption isotherm indicates the microporous nature of the activated charcoal with surface area values 10000m2/g, porosity 75.74% and pre volume 1.43cm3/g The second section deals the adsorption of heavy metal ions on activated charcoal from aqueous solutions. The adsorption experiments were carried out by method of simple titration with EDTA. The percentage adsorption and distribution coefficients KD were determined for each metal ions (Ni++, Cu++, Zn++, Cd++ & pb++) as function of all pertinent variables like shaking time, pH, amount of adsorbent, adsorbate, concentration and temperature From kinetic study, it was observed that adsorption equilibrium for all metals were nearly equal and followed 1st order rate law upto about twenty minutes. The pH effect on the adsorption of the above mentioned metal ions on activated charcoal showed that maximum adsorption in order of pb++>Cu++.Ca++>Zn++.Ni++ was observed at pH values of 10,10,10,5 & 10 respectively The data of heavy metal ions’ adsorption on activated charcoal was fitted to Freundlich, Langmuir and Dubinin-Rudushkevich equations but only followed by Freundlich equation. The temperature effect on adsorption of Ni++, Cu++, Zn++, Cd++ & Pb++ showed that the KD values increase with the rise in temperature. The thermodynamic parameters such as enthalpy change (ΔH°), entropy change (ΔS°) and free energy change (ΔG°) were calculated and interpreted The third section deals adsorption of heavy metals with special references to environmental pollution, generally metallic air pollution and particularly, purification of industrial waste waters in light of heavy metal ions (Ni++, Cu++, Zn++, & Pb++) using activated charcoal as an adsorbent by the process of glass column through technique of atomic absorption spectrophotometer (Pakistan-Elmer Model 2380) for determination of initial and final concentrations of the metals required. The percentage adsorption for each metal was determined at ambient temperature and with agitation at 500 min-1 for 2 h. the feasibility of using activated charcoal Desorption tests were carried out by (NH4)2SO4, HNO3 & NH4H2PO4, of deactivated charcoal by adsorbing heavy metals at the said temperature, it has been observed that activated charcoal is a good material which can adsorb heavy metals at lower concentration and most of heavy metals adsorbed on activated charcoal can be desorbed with NH4+ in the form of (NH4)2SO4 & NH4H2PO4 along with HNO3 solutions (cations & anions effects). Therefore, this cheaper material (deactivated charcoal) with desorption by (NH4)2SO4 may be used as an ion-exchange medium for the treatment of industrial waste waters contining heavy metal ions

Item Type:Thesis (PhD)
Uncontrolled Keywords:heavy metal, ni++, cu++, zn++, cd++ & pb++, activated charcoal, environmental pollution, moisture content, carbon content, metals impurities, densities measurement, surface area, pore volume, porosity, average particle diameter, adsorption, distribution coefficients, water pollution
Subjects:Physical Sciences (f) > Chemistry(f2)
ID Code:1394
Deposited By:Mr. Muhammad Asif
Deposited On:19 Feb 2007
Last Modified:04 Oct 2007 21:06

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