Interfacial Evaporation Systems for Volumetric Reduction of Complex Particle-laden Suspensions

Wastewater generated from mining operations is stored in tailing ponds, which now occupy vast areas of land and have exceeded 1.18 trillion liters in volume, growing continuously annually, particularly in the Athabasca region of western Canada. Dewatering of tailings remains a significant challenge due to the cohesive nature of fine particles trapping water within its constitution. Existing dewatering methods employed, such as chemical flocculation, mechanical techniques (e.g., membrane filtration), freeze–thaw cycles, centrifugation, and tail-lift drying suffer from high energy requirements, elevated operational costs, and restricted throughput, particularly at elevated solid concentrations. Critically, most of these techniques struggle to achieve the target solid content of 75 wt%, which is considered essential for effective dewatering. Interfacial evaporation presents an optimal strategy for wastewater treatment, offering zero operational energy costs, minimal capital investment, and effective harnessing of renewable energy. While extensive research has focused on brine wastewaters, its application to particle-laden wastewater remains largely unexplored. This Ph.D. thesis focuses on exploration on the interfacial evaporation technology as a sustainable approach for the volumetric reduction of particle-laden wastewater. Firstly, solar-assisted interfacial evaporation systems are explored for particle-based suspensions, including industrial tailing wastewater. Convective flow is next introduced to develop a wind-assisted interfacial sailboat evaporator setup, with optimized dimensions and sailboat features. Furthermore, an optimized biomimetic root structure is designed especially for high solid concentration regime to enhance the evaporation performance and better utilize the inaccessible moisture within the suspension composition. These results are supported with an extensive analysis of the evaporation phenomena against particle-suspensions at the high solid concentration regime. Lastly, additional techniques are explored to further sustain efficient evaporation performance close to 80 wt% solid concentration, reducing variance in the spatial moisture distribution. This thesis will start with an Introduction, then a Literature review. The main findings are covered in Chapter 3 to 6. In Chapter 3, we introduce a novel root-based solar interfacial evaporation strategy aimed at accelerating slurry drying. By adjusting the total root surface area, the water conduction rate was optimized across different levels of solar radiation. The best-performing configuration achieved a high evaporation rate of 1.15 kg/(m²·h) under 1 sun, successfully drying the slurry to a solid concentration of 75 wt%. It further removed water until the solid content exceeded 90 wt% over a total duration of 40 hours. The drop-in evaporation rate at higher solid concentrations was linked to the breakdown of continuous capillary water bridges between particles. Large-scale outdoor trials using a 625 cm² setup maintained high evaporation rates like the smaller systems, confirming its scalability for large-volume wastewater treatment. In Chapter 4, we developed a sustainable, clean, and efficient wind-driven interfacial evaporation technology to accelerate the drying of particle-laden wastewater. A self-floating mini-boat setup achieved evaporation rates of 8 kg/(m²·h) at solid concentrations exceeding 75 wt%, performing 18 times faster than natural evaporation. Prior to reaching a critical solids threshold, the evaporation rate scaled with the wind Peclet number to the power of 0.5, driven by enhanced mass transfer at the sail interface. Trials with actual tailings wastewater demonstrated effective volumetric reduction, achieving over 80 wt% solids in the final dried product. In Chapter 5, we developed a bio-mimetic root structure that enables rapid water conduction from dense particle-water mixtures, paired with a porous sail surface optimized for wind-driven evaporation. This setup achieved an evaporation rate (ER) of 3.9 kg/(m²·h) for a 75 wt% slurry, representing a tenfold improvement over natural evaporation under mild wind conditions. The evaporator’s extended roots were also capable of drawing water from slurry layers located beneath a 75 cm thick supernatant water column. In large-scale outdoor trials with 20 L of real, concentrated industrial slurry, the system achieved significant volumetric reduction, reaching final solid concentrations above 75 wt%. In Chapter 6, we report a range of strategies to enhance evaporation in a sailboat-style interfacial evaporator designed for particle-laden wastewater. Through spatial replantation—relocating the evaporator to a different position within the slurry—we achieved an impressive evaporation rate (ER) of 4 kg/(m²·h) at approximately 80 wt% solids, representing a 25% increase compared to non-replanted samples. In addition, extended evaporation periods were sustained at high solid concentrations by applying hydrodynamic flushing to the evaporator roots, which effectively removed dense particulate deposits.

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