Kinetic Modeling and Assessment of a CO2 Nanobubble-Enhanced Hydrate-Based Sustainable Water Recovery from Industrial Effluents.

Abstract

This study evaluates the effectiveness of CO₂ nanobubble-enhanced hydrate-based desalination (HBD) to treat industrial effluents from the mining and metals industry. Testing was conducted in a high-pressure reactor apparatus that employed CO₂ as the gas hydrate former at 274.15 K and 3.58 MPa. CO₂ nanobubbles (NBs) were used to promote hydrate formation, aiming to streamline an HBD process without separation steps for the additives/chemicals used. Due to the limited studies on hydrate formation in sulfate-containing aqueous solutions, this research focused on the kinetics of hydrate formation in varying concentrations of Na₂SO₄ and MgSO₄ (0.1 and 0.5 M). The results showed that CO₂ NBs significantly enhanced hydrate formation in both Na₂SO₄ and MgSO₄ solutions, with CO₂ consumption increasing by up to approximately 51% and 35%, respectively. Additionally, a kinetics study on a real effluent from the mining and metals industry showed that the presence of CO₂ NBs increased CO₂ consumption by around 20% after 180 min. This research also evaluated water recovery and desalination efficiency in a 3-stage HBD process applied to the effluent, the concentration of which exceeded the operating range of reverse osmosis. The results indicated an improvement in water recovery from 25.13 ± 2.04% to 40.16 ± 1.43% with CO₂ NBs, underscoring their effectiveness in treating highly saline water. Moreover, desalination efficiencies of 49.54 ± 2.39% and 42.03 ± 3.43% were achieved without and with CO₂ NBs, respectively. This study represents the successful demonstration of the efficient application of the CO₂ NBs-boosted HBD method to treat high-salinity effluents and recover clean water for reuse.

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