Multilayered Polyelectrolyte-coated Silica for the Removal of Toxic Metal Ions and Organic Contaminants: A Novel Protocol
Shaikh Asrof Ali, زكريا عبدالكريم جاميو
كلية العلوم-جامعة الملك فهد للبترول والمعادن · السعودية
A number of pH-triggerable ionic polymers with different type of charges and their densities on the polymer backbone have been prepared through Butler’s cyclopolymerization process using N,N-diallylaspartic and N,N-diallylglutamic acid hydrochloride salt monomers. SO2 spacer was introduced in similar polymerization protocol to obtain their respective copolymers. These cationic, anionic, and zwitterionic polymers having reactive groups on the pendants have been utilized to explore the complexation behavior between the synthesized polycation and polyanion. The basicity constants, viscosity and solubility behaviors of the polymers were determined. Anti-scaling behavior of some of the polymers were evaluated by studying their inhibition effects on the precipitation of CaSO4 from its supersaturated solution. These pH-triggerable homo- and co-polymers have demonstrated to be effective anti-scaling agents reaching up to 100% for the duration of the study. Furthermore, the aqueous two-phase systems (ATPSs) of the pH-triggerable polymers and polyoxyethylene have been studied. The transformation of these water-soluble polymers to insoluble forms within a workable pH window makes them a special kind of recyclable ATPSs for advanced application in the separation of protein and other biomolecules.Novel resins of these polymers were equally obtained by Butler’s cyclopolymerization of the respective monomers with the aid of cross-linker 1,1,4,4-tetraallylpiperazinium dichloride and with or without sulfur dioxide. The resins were found to be effective generally in the removal of toxic metal pollutants with Pb(II) and Co(II) as specific examples.Finally, these novel cationic, anionic, and zwitterionic polymers having reactive groups on the pendants have been utilized for the formation of multilayer coating on silica adsorbents by layer-by-layer (LBL) assembly. The efficiency and binding capacity of the polyelectrolyte complexes have been examined. The mechanically and thermally stable coated multilayered polyelectrolyte complex having relatively large surface areas have been used for the effective removal of toxic cadmium metal ions from aqueous solutions. In addition, some of the ionic polymers were also hydrophobically modified before LBL assembly. This has imparted the new material with the ability to attract and remove organic contaminants (methylene blue and eriochrome black T) from model and industrial wastewaters. Overall, the solid adsorbents coated with the synthesized ionic polymers containing interesting blends of carboxylate as well as trivalent nitrogens have imparted excellent complexation properties in water treatment processes.