Sustainable Water Recovery from a Hydrometallurgical Effluent Using Gas Hydrate-Based Desalination in the Presence of CO₂ Nanobubbles

Hydrometallurgical processes generate large volumes of aqueous effluents, which are being treated and disposed in tailings ponds. Effluent desalination, i.e., clean water recovery for reuse in process circuits, is key to attain a zero liquid discharge future in the industry. In this study, we report on the use of hydrate-based desalination (HBD) to treat a synthesized effluent from the zinc industry. HBD is an innovative, energy-efficient, and sustainable desalination technology, capable to treat hydrometallurgical effluents to recover water in the form of gas hydrates by consuming CO₂. Water recovery and total dissolved solids (TDS) removal efficiency of 42 ± 2% and 60 ± 4% were achieved in a three-stage HBD process. Further, CO₂ nanobubbles (NBs) were tested as a sustainable kinetic promoter of the process. The desalination outcomes verified that CO₂ NBs played a crucial role in enhancing the kinetics of the process. Specifically, the presence of CO₂ NBs resulted in a notable increase in water recovery, which reached 60 ± 2%, accompanied by a TDS removal efficiency of 53 ± 1% in a three-stage HBD process.