Synthesis of Advanced Functional Nanomaterials for Sustainable Water Treatment Technologies

Tariqul Islam MD., University of Texas at El Paso

Abstract

Water is the most essential resource for the sustenance of life. Water is also necessary for agriculture, industry, household, and environmental conservation. However, due to large population growth and industrial expansion, access to clean water is becoming increasingly difficult around the world. Current water treatment technologies have not changed in over one hundred years and require a large infrastructure due to their low efficiencies and large-scale needs. In this context, the utilization of advanced functional nanomaterials and the adaptation of nanotechnology could potentially allow for miniaturizing water treatment and develop de-centralized solutions for rural areas. This dissertation presents the design, synthesis, characterization, and functional evaluation of functional nanomaterials such as noble metal nanoparticles, metal oxide nanoparticles, and polymeric nanoparticles for sustainable water treatment technologies. In Chapter 2, sodium squarate mediated novel method for the synthesis of gold nanoparticles (AuNPs) of about 22 nm in size is reported. The AuNPs were supported on cellulose fibers (CF) by mixing the AuNPs solution with the cellulose fibers. The AuNPs and its nanocomposites with CF exhibited excellent catalytic activity towards the reduction of 4-nitrophenol (4-NP) with sodium borohydride (NaBH4). The AuNPs were further utilized for the selective and naked-eye observable sensing of spectroscopically silent heavy metals viz. chromium (III) and lead (II) in water. Chapter 3 demonstrates the ability of sodium rhodizonate as a bifunctional reducing as well as a stabilizing agent for the synthesis of a series of noble metal nanoparticles viz. gold (Au), silver (Ag), platinum (Pt), and palladium (Pd). Transmission electron microscopy revealed that the Pt, Au, Ag, and Pd NPs had the average core diameter of about 2, 8, 26, and 39 nm, respectively. The ability of these nanoparticles towards the catalytic reduction of 4-NP with NaBH4 and the dual-catalytic oxidation of formic acid followed by the reduction of methyl orange (MO) was studied. Chapter 4 further studies the ability of sodium rhodizonate for the preparation of AuNPs of controlled size in water. At room temperature, the method can generate AuNPs with an average size of ~11 nm, whereas at 80 °C, it can generate AuNPs with an average size of ~7 nm. The rhodizonate-stabilized AuNPs were supported on CF and the CF-supported AuNPs were utilized for the catalytic reduction of 4-NP and organic dyes such as methyl orange (MO), methylene blue (MB) in water. The method was further extended to the synthesis of bimetallic (Au-Ag) nanoparticles and nanoporous gold nanoparticles. In Chapter 5, a facile method to prepare macroporous cellulose fibers supported PtNPs (PtNPs@KWP) is reported. The PtNPs@KWP exhibited excellent catalytic activity as well as cyclic stability towards the reduction of organic pollutant in the presence of hydrogen (H2) gas and FA. The FA and H2 gas were utilized as the clean and alternative reducing agents. The catalytic reduction of hexavalent chromium [Cr(VI)] to trivalent chromium [Cr(III)] was also studied using FA as the reducing agent. In chapter 6, a novel method for the synthesis of fullerene (C60) stabilized AuNPs is reported. The AuNPs were supported on titanium dioxide (TiO2) and the nanocomposites exhibited enhanced photocatalytic degradation of MO and catalytic reduction of 4-NP in water. Both the photocatalytic degradation of MO and the catalytic reduction of 4-NP were influenced by the size and the weight percent of the AuNPs loading. Furthermore, the photocatalytic generation of hydroxyl radical (•OH) was studied through the terephthalic acid photoluminescence tests. A novel and facile method for the synthesis of zinc oxide nanoparticles (nZnO) is demonstrated in Chapter 7. The transmission electron microscopy (TEM) images revealed the spherical shape of the nZnO with an average size of 35 nm. The band gap and the specific surface area of the nZnO were measured to be about 3.32 eV and 80.11 m2/g, respectively. The nZnO was utilized for the photocatalytic degradation of MO and MB in water under the ultraviolet (UV-B) light and sunlight irradiation. Almost a complete degradation of MO and MB was obtained within 30 min of UV-B light irradiation. Under the sunlight irradiation, more than 95 % of the MO solution undergone degradation within 30 min period of time. The photocatalytic generation of •OH was further studied by the terephthalic acid fluorescence tests. Sucrose mediated facile method for the preparation of high-surface-area Cobalt (Co), Nickel (Ni), and Copper (Cu) sponges is reported in Chapter 8. The Co, Ni, and Cu sponges were found to have highly porous morphology having specific surface areas of 17.39, 8.84 and 2.72 m²/g, respectively. The powder X-ray diffraction spectroscopy (XRPD) pattern demonstrated the crystalline metallic nature of the sponges and the thermogravimetric analysis (TGA) revealed the presence of a trace amount of carbon in the sponges. The catalytic activity of the metal sponges was studied by the reduction of organic pollutants viz. 4-NP, MO, and MB in water. It was found that the Cu sponge was much faster in the reduction of 4-NP, MO, and MB, which was followed by the Co and Ni sponges, respectively. Chapter 9 reports the preparation of a regenerable adsorbent viz. sulfonated resorcinol-formaldehyde (RF-SO3H) microspheres for the adsorptive removal of anionic and cationic organic pollutants from water. The equilibrium adsorption capacity was measured to be 710 mg/g and 511 mg/g for MO and MB, respectively. The adsorption of MO and MB from tap water matrix was also performed and shown to maintain similar adsorption capacity as in deionized water. In addition, a packed glass column was prepared to demonstrate the continuous adsorption of MO and MB under flow conditions. The findings of the above-mentioned works, especially the novel synthesis methods of the nanostructured materials, may promote further studies in the synthesis of a variety of metallic, mixed metallic nanoparticles, their oxides, and composites. Moreover, the nanomaterials, synthesized in this study, could potentially be useful in the area of electrocatalysis, energy storage, photothermal therapies, solar harvesting, photothermal distillations, drug deliveries, and so on.

Subject Area

Chemistry|Sustainability|Hydrologic sciences|Nanotechnology|Public health|Water Resources Management

Recommended Citation

Islam, Tariqul MD., "Synthesis of Advanced Functional Nanomaterials for Sustainable Water Treatment Technologies" (2019). ETD Collection for University of Texas, El Paso. AAI13884009.
https://digitalcommons.utep.edu/dissertations/AAI13884009

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