Green chemistry-based electrospinning of functional membranes for pollutant mitigation in gas and aqueous phase

Due to the ease of making polymeric nanofibers, electrospinning can improve polymer membrane surface area and functioning. Due to their high specific surface area, electrospun membranes have been widely used in research for pollution remediation and other applications. Engineering electrospun membranes for air and water pollutant treatment is the impetus behind this effort. The first chapter introduces the thesis's problem statements and briefly describes the following work's methods and procedures. The second chapter examined how process factors affect electrospun fiber porosity. Binary and ternary solvent systems have been used to prepare cellulose acetate polymer electrospinning solutions to increase nanofibrous membrane surface area. The solvent selection considered solubility characteristics and vapor pressure, and electrospinning was done under varied humidity settings. The acquired morphologies were attributed to a putative phase separation mechanism. The paper provides a simple formula for making porous cellulose acetate membranes by carefully examining process factors. Environmental elements of the process were also considered, using balanced systems of benign/green solvents and biocompatible polymer. Photoactive membranes made by electrohydrodynamics techniques are used to remove volatile organic compounds from indoor air in the next chapter. Mechanosynthesis, a green procedure for photocatalyst TiO2 nanoparticle crystallographic changes, introduced orthorhombic polymorphs (TiO2-II). The polymorph evolves under high pressure and temperature, which ball milling provides. Comparing photodegradation of methanol over electrosprayed demonstrated that the treated catalyst performed better at different doses. Apart from enhanced porosity, the TiO2-II phase, which is responsive to visual irradiation, is responsible for better reaction kinetics than the pristine catalyst. Chapter 4 expands indoor air pollution treatment to include particulate matter and microorganisms in the confined environment. Electrospinning membranes made of PVDF and plant-derived polymers have been tested for pollutant removal. Electrospun membranes have been used to make triboelectric nanogenerators. The membrane materials were chosen based on the triboelectric series to incorporate interfacial electrification during flow-induced aeolian vibrations. The membrane pair, deployed parallelly for air-filtration investigations, removed a wide range of PM sizes better than separate membrane systems. Pressure drop studies before filtration operations showed good results for the membranes. Tannic acid, a biopolymer having antibacterial characteristics, is part of the plant-based polymer blend for air-borne microbe treatment. Advanced oxidation techniques are used to treat potable water containing per-fluoroalkyl compounds in chapter 5. Electrospinning and thermal imidization of polyamic acid (PAA) solution produced polyimide (PI) membranes for this purpose. The PAA solution and a polyvinylpyrrolidone (PVP) solution with the catalytic precursor were parallelly electrospun to insert TiO2 photocatalyst into the PI membranes. The PAA/PVP-TiO2 membrane is transformed to PI/TiO2, employing nanorod catalysts. PFOA treatment was tested with photoactive PI/TiO2 membranes in the presence and absence of UV irradiation. The pollutant, precursors for oxidative species such sulfate and hydroxyl radicals, and Fe(II) have been recirculated across a reactor using PI/TiO2 membranes for time-dependent abatement investigations. PFOA mineralization, peculiar to membrane-based systems, has shown promise. The results show that sulfate-mediated oxidation dominates without a UV source, but photocatalytic removal increases with UV light.