The role of adsorption in microalgae biological desalination: Salt removal from brackish water using Scenedesmus obliquus

In this study, the effects of different operating conditions on the salt removal from brackish water by dry and fresh Scenedesmus obliquus (S. obliquus) were investigated to explore the mechanisms of algae biological desalination process. It was identified that, within only 30 min contact time, the salt removal increased with the increasing salinity, which was probably due to the higher NaCl concentration gradient from the bulk solution to the algae surface. Compared to other study with a longer algae cultivation period (16 days), this study demonstrated that both adsorption and absorption contributed to the NaCl removal, but adsorption played a more significant role (two thirds of the NaCl removal). The full adsorption can be reached within a relatively short period (1–30 min), and the salts removed by absorption is negligible when the contact time was short. The Langmuir isotherm adsorption model can accurately predict the NaCl adsorption, which indicated the formation of a single molecular layer on the algae surface. The FT-IR analysis further demonstrated different functional groups on the cell wall of S. obliquus can effectively combine the Na+ and Cl−. Overall, the fresh algae showed much faster adsorption kinetics. The results of this study showed promise for the search of alternative desalination technology with an environmentally friendly algae-based biological system.

Jaar van publicatie:2020