Abstract
Heavy metals are used in many industrial processes and their cations are either valuable or environmentally harmful to discharge in wastewater. Thus, it is necessary to separate heavy metals in wastewater treatment. Amongst several technical methods of separation, use of permeable membranes is an important one. For separation processes, membranes can be selective towards a target heavy metal cation either against mono-valent common cations or against other similar heavy metal cations.
Synthesis of selective permeable membranes for separation purposes is an area of continuous research to meet specific needs in different applications. One of the common applications of selective separation by a permeable membrane is cation/anion separation processes using cation exchange and anion exchange membranes. Another application of selective permeable membranes is the separation of mono-valent cations from other higher valence cations.
Some researchers have focused on specific selective separation of heavy metal cation from other heavy metal cations having the same valent charge. Some use chelating particulates dispersed in a neutral polymeric membrane matrix and others applied a thin chelating film on the surface of a commercial cation exchange membrane.
In this work, the synthesis of novel permeable selective membranes and their use for selective separation between two di-valent heavy metal cations is presented. Three different sets of membranes were prepared in non-imprinted and imprinted forms. The ion imprinted membranes form is prepared by pre-reacting the target metal ion with the selective chelating monomer before applying in situ polymerization step, and in the non-imprinted membranes form this step is not considered. Their morphological and chemical structures were determined and their separation performances were investigated using a diffusion dialysis technique.
The first membrane (non-imprinted polyvinylidene fluoride-divinylbenzyl-triethylenetetramine (PVDF/diVB-TETA) and Cu-imprinted PVDF/diVB-TETA-Cu forms) was prepared by in situ polymerization of the chelating monomer divinylbenzyl-triethylenetetramine diVB-TETA (or diVB-TETA-Cu) within a PVDF substrate, using a divinylbenzene cross-linker. Fourier transform infrared FT-IR spectroscopy showed the successful in situ polymerization of the chelating monomer within the PVDF texture. The permeation study showed that the ion-imprinted membrane has a Cu2+ selectivity factor of 3.78, while the non-imprinted membrane has a Cu2+ selectivity factor of 1.65. In addition the Cu2+ permeation flux in the imprinted membrane is 3.9 time that in the non-imprinted membrane
For the second membrane, the synthesis is similar to the first membrane for both non-imprinted and imprinted forms (polyvinylidene fluoride-divinylbenzyl-triethylenetetramine-N,N'-methylenebis(acrylamide) (PVDF/diVB-TETA-N) and PVDF/diVB-TETA-N-Cu respectively), except that the used cross-linker was N,N'-methylenebis(acrylamide). In addition, sodium 4-vinylbenzyl sulfonate was added in selected percentages, (5-15% mol), to enhance the permeation flux. FT-IR spectroscopy analysis of the prepared membranes confirmed the chemical structure of diVB-TETA-N and sulfonate group into PVDF. Permeation and selective separation studies for the prepared membranes showed that the ion-imprinted membrane has a higher selectivity for copper permeation over the non-imprinted membrane. However imprinted membrane showed a lower flux for the permeated cations than that of the non-imprinted membranes The addition of the sulfonate groups to the prepared membranes enhanced the flux of the permeated cations, but the copper selective permeation decreased for both types (non-imprinted and ion-imprinted). Moreover, the ion-imprinted membrane PVDF/diVB-TETA-N-Cu showed a lower flux for the permeated cations than that of the non-imprinted membranes PVDF/diVB-TETA-N. Selective separation factors decreased to unity when the content of the sulfonate groups increased to 15% mol. Ion imprinted membrane prepared with 10% of sulfonate group showed optimum copper selectivity factor (α = 30304) and permeation flux for copper (0.4949 μmol cm‒2 h‒1)
The third membrane (non-imprinted Selemion TM cation exchange membrane-divinylbenzyl-triethylenetetramine (CMV-S/diVB-TETA) and ion-imprinted CMV-S/diVb-TETA-Cu forms) was prepared by in situ polymerization of the chelating monomer, diVB-TETA (or diVB-TETA-Cu), on the surface of the commercial cation exchange membrane, Selemion, using divinylbenzene as cross-linker. FT-IR spectroscopy confirmed the chemical structure of the chelating polymer on the CMV-S membrane surface. Permeation study showed that ion-imprinted CMV-S/diVB-TETA-Cu membrane reached high separation factor (α = 17), yet the flux is low (0.0391 μmol cm‒2 h‒1). Non-imprinted CMV-S/diVB-TETA membrane of thickness (0.115±0.005 mm) using cross-linker (10% DVB) showed reasonable copper selectivity factor (α = 2.723) and permeation flux (0.433 μmol cm‒2 h‒1) / Thesis / Doctor of Philosophy (PhD)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/18115 |
| Date | 11 1900 |
| Creators | Mohamed, Mohamed M. K. |
| Contributors | Dickson, Sarah, Kim, Younggy, Civil Engineering |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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