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Title of Thesis

Institute/University/Department Details
Department of Chemistry/ Quaid-i-Azam University, Islamabad
Number of Pages
Keywords (Extracted from title, table of contents and abstract of thesis)
toxic metal ions, radiotracer technique, sunflower stem, sorption, chromium, mercury, agricultural waste, cadmium, sorption mechanism, sorbate

The sorptive potential of sunflower stem, a cheap agricultural waste abundantly available, has been exploited for Cr(III), Cd(II), Sb(III) and Hg(II) ions. The sorption of each toxic metal onto sunflower stem is optimized with respect to the nature of electrolytes (buffers of pH 1-10, acids and deionized water), amount of sorbent and sorbate, equilibration time between the two phases at fixed temperature. The sorption of metal ions onto the sorbent surface is monitored using radiotracer and batch technique as a function of a parameter keeping the rest constant in order to accumulate maximum amount of sorbate onto sunflower stem.

The sorption data of Cr(III), Cd(II), Sb(III) and Hg (II) ions have been subjected to Langmuir, Freundlich and Dubinin-Redushkevich (D-R) isotherms. The sorption of each metal ion has followed all three models. The sorption capacity, intensity and energy of each sorbate have been estimated using regression analysis. The values of correlation coefficient γ of such analyses are close to unity. The sorption mean free energy evaluated from D-R isotherm ranges between 8.66-10.33 kJ mol-1. The kinetic data have been applied to Lagergren, Reichenberg and Morris Weber equations. The linear follow up of the sorption of Cr(III), Sb(III) and Hg (II) to Lagergren equation indicates first order sorption whereas the Reichenberg equation reflects the effectiveness of the diffusion of trace metal ions within sorbent particles. The linear follow up of kinetic data of the sorption of Cr(III) ions to the Morris-Weber equation indicates the partial intraparticle diffusion of Cr(III) ions.

The variation of sorption as a function of temperature was carried out for all four sorbates. The thermodynamic coefficients ”H, ”S and ”G have been evaluated using regression analysis. The negative values of ”G for all metal ions studied indicate spontaneous nature and feasibility of the sorption. The negative values of ”H for Cr(III) and Hg (II) ions show exothermic, while the positive values of ”H of Cd(II) and Sb(III) ions represent the endothermic nature of the sorption respectively.

The influence of common anions, cations and complexing agents on the sorption of sorbates has also been investigated. Bisulphate, Fe(III), molybdate, citrate, Fe(II) and Y(III) ions suppress the sorption of Cr(III) ions significantly. Fe(III). EDTA, Pb(II) and thiosulphate ions reduce the sorption of Cd(II) ions drastically, whereas, tartrate , dichromate, Ca(II) and Sn(II) impede sorption of Cd (II) ions. The sorption of Hg (II) ions is enhanced in the presence of ascorbate, Sr(II) and Y(III), whereas it is suppressed in the presence of disuphite, iodide, Cd(II), bisuphite and thiocyanate. Bismuthate, Sn(lI) and Fe (III) increase the sorption of Sb(III) ions whereas molybdate, chromate, iodate, sulphate, fluoride and thiocyanate reduce the same.

The sorption of other elements from different groups of periodic table and oxidation states have been investigated under optimised conditions selected for each sorbate. This selectivity study indicates that Cr(III), Eu(III) and Tb(III) can be separated from I(I) and Tc(VII); Hg (II) and Tc(VII) ions from I(I) and Cs(I); Cd(II) and Eu(IIIl) ions from Cs (I) and Sb(III), Eu(III) and Sc(III) can be separated from Se(IV), Cs(I) and As(III) using sunflower stem column.

The sorption potential of sunflower stem for the ions Cr(III), Cd(II), Sb(III) and Hg (II) have been evaluated and compared with other biosorbents in the relevant sections of result discussions. Its sorptive behaviour is better or comparable with other biosorbents. Based on the chemical composition of sunflower stem and functional groups present in the sorbent matrix, a possible mechanism of biosorption of ions of Cr(III), Cd(II), Sb(III) and Hg(II) ions onto the sunflower stem has been suggested. This cheaper and novel sorbent has potential applications in water decontamination, industrial water treatment and in pollution abatement, in analytical and environmental chemistry

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S. No. Chapter Title of the Chapters Page Size (KB)
1 0 Contents
139.64 KB
2 1 Introduction
394.07 KB
  1.1 Essential, non essential and toxic elements 1
  1.2 Occupational sources of toxic elements 2
  1.3 Dispersal of toxic elements in the environment and necessity of their decontamination 4
  1.4 Techniques for the removal of toxic metal ions from aqueous system 8
  1.5 Kinetics studies of sorption 31
  1.6 Thermodynamics parameters 34
  1.7 Surface energies 35
  1.8 Speciation 35
  1.9 Objectives of the present research project 36
3 2 Experimental 38
153.76 KB
  2.1 Reagents/Chemicals 38
  2.2 Buffers Solutions 38
  2.3 Sunflower stem 38
  2.4 Instruments/ Apparatus 43
  2.5 Radiotracer technique 43
  2.6 Sorption Procedure 45
  2.7 Data manipulation 47
  2.8 Quality control experimental 48
4 3 Sorption of Cr(III) onto sunflower stem from aqueous solution 49
270.94 KB
  3.1 Significance of chromium from biological standpoint 49
  3.2 Speciation of chromium ions in aqueous solutions 50
  3.3 Occupational exposure of chromium metal and its compounds 51
  3.4 Review of literature on the sorption ofCr(III) ions onto agriculture waste 51
  3.5 Optimization of sorption of Cr (III) ions onto sunflower stem under various conditions 52
  3.6 Sorption isotherms 56
  3.7 Kinetic studies 59
  3.8 Thermodynamic parameters 61
  3.9 Influence of diverse ions 63
  3.10 Selectivity of the sorbent 66
  3.11 Sorption mechanism 66
  3.12 Conclusions 69
5 4 Sorption of Hg (II) onto sunflower stem from aqueous solution 70
221.63 KB
  4.1 Impact of various forms of mercury on the environment 70
  4.2 Glimpses of earlier work on the sorption of Hg2+ ion onto the agricultural waste 71
  4.3 Optimization of sorption 71
  4.4 Kinetic studies 73
  4.5 Sorption isotherms 76
  4.6 Thermodynamics 79
  4.7 Influence of diverse ions 81
  4.8 Selectivity of the sorbent 81
  4.9 Sorption mechanism 85
  4.10 Conclusions 86
6 5 Sorption of Cd (II) onto sunflower stem from aqueous solution 87
207.18 KB
  5.1 Cadmium its biological significance, source and toxicity 87
  5.2 Review of literature on the sorption of Cr(III) ions onto agriculture waste 89
  5.3 Optimization of sorption 90
  5.4 Sorption Isotherms 93
  5.5 Thermodynamic parameters 97
  5.6 Effects of diverse ions 97
  5.7 The selectivity of the sorbent 101
  5.8 Sorption mechanism 101
  5.9 Conclusions 103
7 6 Sorption of Sb(III) onto sunflower stem from aqueous solution 104
171.36 KB
  6.1 Role of antimony on the environment 104
  6.2 Glimpses of earlier work for sorption of Sb(III) on cheaper material 105
  6.3 Optimization of sorption 105
  6.4 Sorption isotherms 110
  6.5 Thermodynamic parameters 112
  6.6 Interfering ions 112
  6.7 Selectivity of the sorbent 116
  6.8 Kineties 116
  6.9 Sorption mechanism 119
  6.10 Conclusions 120
8 7 Overall Conclusions 121
42.96 KB
  7.1 Publication based on this investigation
9 8 References 125
78.89 KB
  8.1 References 126