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

Abstract This study evaluates the effectiveness of CO 2 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 CO 2 as the gas hydrate former at 274.15 K and 3.58 MPa. CO 2 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 Na 2 SO 4 and MgSO 4 (0.1 and 0.5 M). The results showed that CO 2 NBs significantly enhanced hydrate formation in both Na 2 SO 4 and MgSO 4 solutions, with CO 2 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 CO 2 NBs increased CO 2 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 CO 2 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 CO 2 NBs, respectively. This study represents the successful demonstration of the efficient application of the CO 2 NBs-boosted HBD method to treat high-salinity effluents and recover clean water for reuse. Graphical Abstract