UCLA

In this thesis, the evolution of Reverse Osmosis (RO) technology toward ultra-high-pressure operations (UHPRO) is meticulously chronicled with the aim of achieving sustainable Minimum Liquid Discharge (MLD) and Zero Liquid Discharge (ZLD) processes. The investigative journey traverses from the diagnosis of existing limitations in UHPRO systems to the unveiling of novel Thin Film Crosslinked Composite (TFX) membranes, distinguished by their in-situ crosslinking approach.Chapter 2 initiates the discourse by pinpointing the key challenges afflicting current UHPRO applications, primarily membrane compaction and the associated permeance decline under extreme pressures. Chapter 3 expands upon this foundation, utilizing full-scale models to assess the feasibility and operational intricacies of UHPRO systems. Delving deeper, Chapter 4 exposes the profound impact of membrane compaction through controlled experiments and Nanoscale Molecular Dynamics (NEMD) simulations, establishing it as a principal obstacle to UHPRO's success. Chapter 5 supports this revelation by empirically affirming the hypothesis that thermoset membranes, due to their intrinsic robustness, significantly outperform their thermoplastic counterparts. The culmination of these insights is found in Chapter 6, which rigorously scrutinizes the optimization of the crosslinking process. Here, the superiority of in-situ crosslinked TFX membranes is highlighted, characterized by enhanced mechanical strength, thermal resistance, and thinner profiles which promise higher packing densities in spiral-wound modules. In synthesis, the thesis articulates the promise of in-situ TFX membranes in transcending the limitations of traditional RO systems. With their proven resilience against compaction, high salt rejection capabilities, and thermal robustness, these membranes stand at the forefront of UHPRO technology, marking a significant leap towards cost-effective and energy-efficient M/ZLD solutions. In summary, this thesis lays the groundwork for the next era of RO technology, advocating for the adoption of in-situ TFX membranes in high-salinity water treatment applications. Their deployment is projected to not only elevate the sustainability of desalination practices but also to reduce the environmental burden of water purification processes.