SYNTHESIS AND APPLICATION OF INORGANIC FUNCTIONAL ADSORBENTS AND POLYMER COMPOSITES FOR ANIONIC CONTAMINANT REMOVAL FROM WATER

Abstract

This thesis deals with the synthesis, characterization, and application of an inorganic functional materials as adsorbents for phosphorous, chromium, and fluorine removal from aqueous solutions. The inorganic functional materials presented in this study include iron oxide nanoparticle-chitosan composite, triamine-functionalized mesoporous silica-polymer composite, calcined Mg-Fe layered double hydroxide-PVDF/PVA composite, and quintinite. Iron oxide nanoparticle(ION)-chitosan composites were prepared using acidified chitosan, an environmentally friendly polymer, suspension to blend iron oxide nanoparticles by a cross-linking method. The removal of phosphate by ION-chitosan composites was verified by batch experiments, column experiments and pilot-scale adsorption tower experiment. The adsorption properties were analyzed and quantified using kinetic and equilibrium models and thermodynamic analysis. ION-chitosan composites successfully removed phosphate from aqueous solution and showed good reversibility, multicycle stability. It is a good candidate for environmentally friendly inorganic composites as adsorbents. The characterization of triamine-functionalized mesoporous silica-polymer composites for Cr(VI) removal was also studied. The mesoporous material with various amounts of functional group had high surface area. The kinetics of the functionalized mesoporous silica were found to be sufficiently fast and it was observed that maximum sorption capacity was 330.88 mg/g. The composites showed good performance of chromate removal from real industrial wastewater. The calcined Mg-Fe layered double hydroxide(LDH) was prepared through a co-precipitation and calcination at 300 oC. The calcined LDH could be used repeatedly for phosphate removal through desorption with 0.1 M NaOH solution. MgFe calcined LDH-PVDF/PVA composites also could be used for phosphate removal from aqueous solutions with regeneration and repeated use. The phosphate removal was relatively constant at an acidic and alkaline pHs. Quintinite was applied as adsorbents for removal of phosphate and fluoride. The maximum phosphate adsorption capacity was 4.77 mgP/g. The phosphate adsorption to quintinite was not varied at pH 3.0 – 7.1 (1.50 –1.55 mgP/g) but decreased considerably at a highly alkaline solution (0.70 mgP/g at pH 11.0). Experimental results showed that the maximum adsorption capacity of fluoride to quintinite was 7.71 mg/g. The adsorption of fluoride to quintinite was not changed at pH 5 – 9 but decreased considerably at the highly acidic (pH < 3) and alkaline (pH > 11) solution conditions. Therefore, this study elucidated that the inorganic functional materials removed phosphorous, chromium, and fluorine from aqueous solutions, effectively. These results also demonstrate that the functional polymer composites developed in this study can be applied to water treatment system.