Marjatta Louhi-Kultanen and Hasan Mehdi, Lappeenranta University of Technology, Finland, have frozen unsaturated Na2SO4 solutions to develop an energy-efficient wastewater purification method. The idea is to freeze wastewater from mines in special outdoor pools. The wastewater is purified through the formation of a cleaner layer of ice which can be removed by breaking the ice, leaving more concentrated wastewater in the pool. In a second pool the treated wastewater would then be recycled or undergo further treatment using separation techniques such as membrane filtration. Energy would only be needed for breaking the ice and transporting it from the pool.
The researchers have developed a model to estimate the thickness of the ice layer formed from solutions at different freezing conditions. For this they determined the influence of parameters such as the solution concentration, temperature, and the freezing rate on the efficiency of the purification process.
Application of this technology is seen by the researchers in the mineral extraction industry particularly in the Arctic region which produces large amounts of wastewater.
- Ice growth kinetics modeling of air-cooled layer crystallization from sodium sulfate solutions,
Hasan Mehdi, Louhi-Kultanen Marjatta,
Chem. Eng. Sci. 2015; in press.
