Beyond Membranes and Thermal Processes: A Unified Solar-Optimized Aggregation-Driven Framework for Low-Energy Seawater Desalination

Freshwater scarcity is an escalating global constraint, with over 2 billion people currently exposed to water stress, driving urgent demand for desalination technologies that are both energy-efficient and scalable. Conventional desalination methods, including reverse osmosis (RO) and thermal distillation, are fundamentally constrained by thermodynamic and operational limitations, requiring energy inputs on the order of ~3–6 kWh·m⁻³ for RO and significantly higher for thermal processes, while also suffering from membrane fouling, scaling, and brine management challenges.

This study introduces a fundamentally distinct, system-integrated desalination paradigm that combines aggregation-mediated ionic restructuring with multiplicative solar energy loss-regulation, thereby simultaneously addressing the dual bottlenecks of energy efficiency and separation mechanism. Unlike conventional approaches that rely on overcoming osmotic pressure or inducing phase change, the proposed method operates by driving dissolved ions into metastable aggregated states via low-voltage electrochemical forcing (0–6 V) and material-assisted interactions. These aggregates exhibit increased effective density and reduced mobility, enabling gravity-driven sedimentation and the formation of a stratified fluid system with an ion-enriched lower phase and a reduced-salinity upper phase.

A unified multi-physics framework is developed, coupling ion aggregation kinetics ka, dissociation dynamics (kd), and sedimentation transport (vs) with a system-level solar energy survival factor (Ψ), defined as a multiplicative function of real-world loss mechanisms. The model demonstrates that desalination performance is maximized under the regime ka≫kd and Pe≫1, ensuring aggregation-dominated transport and suppression of diffusive remixing. In parallel, solar energy delivery is enhanced through coordinated loss suppression, increasing the effective energy utilization factor from Ψ≈0.25–0.35 in degraded systems to Ψ≈0.70–0.80, corresponding to a 2.5–3× increase in usable electrical output under identical irradiance conditions.

Model-guided experimental validation (2 L batch reactor, 35 g·L⁻¹ seawater equivalent, 4–6 V, 60–90 min) demonstrates consistent salinity reduction of ~12–18% in the upper layer (to ~28–30 g·L⁻¹), accompanied by lower-phase enrichment up to ~41–42 g·L⁻¹, yielding separation indices exceeding 0.30. The specific energy consumption is estimated in the range of ~0.4–2.0 kWh·m⁻³, which is comparable to or lower than conventional RO pre-treatment processes, while eliminating the need for high-pressure systems or semi-permeable membranes.

Importantly, the proposed framework remains fully consistent with thermodynamic constraints, as it does not remove ionic mass from the system but redistributes it spatially through externally applied work. The integration of structure-driven desalination with energy loss-regulated solar input establishes a new class of hybrid water treatment systems characterized by low energy intensity, reduced fouling susceptibility, and modular scalability.

This work provides a theoretically grounded and experimentally supported foundation for next-generation desalination technologies, with potential applications in decentralized water systems, hybrid RO pre-treatment, and renewable-powered water infrastructure in resource-constrained environments.

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