Switchable biomaterials for wastewater treatment

Wang, Hongjie (2025) Switchable biomaterials for wastewater treatment. Masters thesis, Memorial University of Newfoundland.

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Abstract

The development of novel switchable biomaterials has gained significant attention due to their potential in wastewater treatment, offering sustainable and cost-effective solutions for contaminant removal. This thesis presents a comprehensive review of the diverse applications of switchable biomaterials, including chitosan, polylactic acid (PLA), cellulose, biochar, rubber, resin, and crude fibers. These materials exhibit stimulus-responsive functionalities that facilitate recyclability and pollutant recovery, making them promising candidates for environmental remediation. Despite substantial advancements, challenges such as stability, recyclability, and performance optimization remain. Future research should focus on improving these aspects while exploring novel hybrid materials to enhance their applicability in real-world scenarios. Based on the research gaps identified by the literature review, the thesis work further focuses on the development and optimization of a spiropyran-assisted cellulose aerogel (CNF-SP) aerogel with UV-induced switchable wettability, and the evaluation of its performance as an effective sorbent for oil spill cleanup. Beyond oil spill remediation, the switchable properties of the aerogel hold great potential for broader wastewater treatment applications, particularly in selectively adsorbing hydrophobic and hydrophilic contaminants. The aerogel initially exhibited strong hydrophobicity (124°) and showed UV-induced switchable wettability due to the photo-response structure of spiropyran. Upon UV irradiation, the hydrophobicity of the aerogel could be switched to hydrophilicity (31°), while visible light irradiation could restore its hydrophobicity. The three-dimensional (3D) porous structure of the CNF-SP aerogel combined with the hydrophobic properties of spiropyranol led to its great oil adsorption performance (27-30 g/g of oil adsorption ratio). To systematically optimize the material, the central composite design (CCD) was applied, as it allows for efficient exploration of the interaction effects among multiple factors. The raw materials, including carboxymethyl cellulose, carboxyethyl spiropyran, polyvinyl alcohol, and nano zinc oxide, were specifically chosen due to their roles in enhancing mechanical stability, responsiveness, and adsorption capacity. The optimized CNF-SP aerogel demonstrated a high oil sorption efficiency, particularly in acid and cold environments. Moreover, the switchable function indicated that the aerogel exhibited reusability and renewability, with the added benefit of UV-induced oil recovery. However, potential limitations, such as the scalability of the synthesis process and real-world deployment challenges, remain key concerns that require further investigation. Through the development of the CNF-SP aerogel, this thesis directly addresses challenges in oil spill remediation by offering a material capable of adapting to diverse environmental conditions while ensuring high oil adsorption efficiency and sustainability. The study underscores the transformative potential of switchable biomaterials in mitigating the environmental impact of water pollution, reaffirming their role as a critical advancement in the field of wastewater treatment.

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