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Title of Thesis

Mardan Ali
Institute/University/Department Details
Faculty of Engineering and Technology/ University of the Punjab Lahore
Engineering and Technology
Number of Pages
Keywords (Extracted from title, table of contents and abstract of thesis)
monodisperse resins, ion exchangers, silica beads, silica, sol-gel processe, jet break-up

Abstract of Part-I : Uniform sized spherical silica beads were prepared by sol-gel process type-v using different vibration single-fluid nozzles with the experimental set-up shown in fig. 3.3 This experimental set-up has a facility which allows to judge the quality of sol drops being produced. The gelling medium for the sol drops was paraffin oil containing non-ionic surfactant, span 80. The phenomenon of production of monodisperse drops of water was studied with single needle nozzle of 195 µm diameter at 22.5 oC and spinnerets (50 and 100 holes) of 80 µm diameter at 25 oC.

The effect of temperature on the gelling time of sols with different pH was studied at O,21 and 80 oC.From the gelling time studies, practical sols (having long gelling time at 0oC and short gelling time at 80 oC) were identified.

Silica batches were prepared with single needle nozzle, three needle nozzle and 100 hole spinneret of 80 µm hole diameter. Monodisperse silica beads were prepared with single needle nozzle, but the production rate was low and bead size was large. Silica beads with the increased production rate (three fold) were prepared with three needle nozzle with 84% w yield of uniform sized beads, High production rate of silica beads (6x105 drops per second and even higher is possible with better vibrator) was obtained by using the 100 hole spinneret.

The textural properties of different silica batches were measured by mercury porosimetery. The contact angle was found to be 139.3o. The air drying of hydrogels gives xerogels with the textural properties in the range, pore volume, Vp=0.49x10-3-0.97x10-3m3/kg; surface area, Aw = 329x 103 €“ 456x103 m2/kg; and pore diameter, Dp = 6.6- 8.5nm. However, the removal of water from the hydrogel under vacuum azeotropic distillation produces a xerogel with no agglomeration having Vp = 1.67 x 10-3 m3/kg, Aw = 547 x 103 m2/kg, and Dp = 12.26nm. Textural properties of various silica batshes were modified by the hydrothermal treatment in hydrogel and xerogel states. The correlation of hydrothermal treatment time with the textural properties was established for a set of temperatures. We have also described an apparatus for measuring crushing load of a single bead. The effect of Vp, Dp and Db (bead diameter) on the average crushing load of a single silica bead, L, was established.

Various poly (Sty/Dvb). Silica composites of either x =5 and Fs = 0 or x =20 and Fs =0.50 were prepared from silica lots, B-34/5 and B-35/3 with different specific coating , Cwpo. It was generally observed lthat the specific coating of polymer on the silica, Cwpo, is less than the specific monomer loading , Cwmo, in the polymerization reactor.

An inhomogeneous coating of polymer was observed in the composite prepared from narrow pore silica base (B-34/5). For these composites, Aw and Vp decreased while Dp remained constant as Cwpo increased. A uniform film type coating of the polymer is observed in the composites prepared from relatively wide pore silica base (B-35/3).In this type of coating, Vp, Aw and Dp decrease as Cwpo increases. The thickness of the polymer film coating of pores of silica beads was also calculated for a set of Cwpo values. The effect of pore forming solvents for the creation of pores inside the coated material is observed in very wide pore silica base (B-33/2) where Vp and Dp decreased but Aw increased by a factor of about 2. During the hydration of the sulphonated composite beads, breakage due to osmotic shock, was observed in the composite beads prepared from small pore silica base (B-34/5) and in the large beads with higher specific coating, The wet capacity was found to be 0.5x103eq/m3. The capacity of the sulphonated composites is lower than the organic ion exchanger of the same crosslinkage.

Self-diffusion coefficients of H+ and Na+ ions are calculated using Nernst-Plank from the experimental uptake curves. The composites mentioned in the thesis have better ion exchange kinetics and dimensional stability as compared to Dowex 50-X8. Therefore, the prepared composites are useful for the fine separations.

Abstract of part-II . A chomatograph with on-line gamma-detector compatible with corrosive eluants is described. The interplay among chromatographic resolution, speed of analysis, and precision of a radio-activity detector is reviewed Monodisperse polymer beads of different textural properties were sulphonated and their cation exchange capacities were measured with isotopic ion exchange methods. Different monodisperse cation exchangers were characterized by elution chromatography of Eu3+, Lu3+and Yb3+with α-hydroxy isobutyric acid, α-HIBA.Elution of Eu3+with α-HIBA, from 9.8µm, highly (> 40%) crosslinked macroreticular resins (XP-11, XP-3016) at 20 oC gives tailed elution peaks. The elution volume of the peaks decreases and column efficiency increases when the flow rate of the mobile phase increases. The elution of Eu3+at 60 oC from XP-11 and XP-3016 resins improves the column efficiency.

In elution chromatography of Eu3+ and Lu3+ with α-HIBA, the height equivalent to a theoretical plate, H, for Eu3+ is larger as compared to Lu3+ . An increased tailing and larger value of H were observed for elution of Lu3+ with α-HIBA as compared to Lu-isotopic exchange for XP-3016 resin. This due to the slow release of the LnL-4 complex ions from the microporous gel-phase. On the other hand, a monodisperse 10 µm, 5% crosslinked cation-exchanger (XP-7) has high column efficiency and a 3 x 10-2 m column separated the Yb-Lu pair, but it is unsuitable in an HPLC system where the ionic strength of mobile phase changes.

Improved column efficiencies and decreased tailing of Eu3+ and Lu3+ elution peaks with α-HIBA were shown by partially sulphonated monodisperse 5 and 10 µm, highly (>40%) crosslinked porous beads.Blocking of micropores of such highly crosslinked porous gels with n-dodecane before sulphonation further reduces the extent of sulphonation and improves column efficiency. Simultaneous choice of a smaller particle size and partial sulphonation improves the column performance.

Download Full Thesis
3024.69 KB
S. No. Chapter Title of the Chapters Page Size (KB)
1 0 Contents
265.78 KB
2 1 Review Of Processes For Preparing Spherical Silica Beads 4
91.31 KB
  1.1 Sol-Gel Processes 4
  1.2 Sol-Gel Processes For Preparing Spherical Silica Beads 5
  1.3 Screening Of Sol-Gel Processes For Preparation Of Spherical Silica Beads 11
3 2 Review Of Dispersers, Theory Of Jet Break-Up And Gelling Medium And Surfactant And Methods For Texture Modification Of Silica Gel 12
113.11 KB
  2.1 Disperser For Sol 12
  2.2 Theory Of Liquid Jet Break-Up 13
  2.3 Gelling Media For Sol-Gel Processes 20
  2.4 Selection Of Surfactant To Avoid Coalescence Of Sol Drops 22
  2.5 Methods For Modification Of Texture Of Silica Gel 24
4 3 Experimental 28
330.66 KB
  3.1 Chemicals And Equipment 28
  3.2 Production Of Uniform Sized Drops Of Water With Single Needle And With Spinnerets 30
  3.3 Preparation And Characterization Of Sodium Silicate Solutions 32
  3.4 Measurement Of Density And Viscosity 35
  3.5 Experimental Work On Production Of Silica Beads By Process Type-V 36
  3.6 Characterization Of Silica Gel 47
  3.7 Preparation Of Composite Cation Exchangers 53
  3.8 Ion Exchange Rate Studies 58
5 4 Results And Discussion 60
875.53 KB
  4.1 Uniform Sized Drops Of Water Produced With Single Needle Nozzle And With Spinnerets 60
  4.2 Silica Beads Produced By Process Type-V 69
  4.3 Composite Preparations 118
  4.4 Ion Exchange Rates Of Composite Cation Exchangers 134
  4.5 Summary Of Part-I And Further Work Suggested 141
6 5 Characterization And Modification Of Monodisperse Resins 149
1298.28 KB
  5.1 Review Of Some Considerations In Radio-Hplc 149
  5.2 Experimental 150
  5.3 Results And Discussion 159
  5.4 Summary Of Part-II 183
  5.5 Appendixes 185