Inhibition of typical phenolic compounds entering into condensed freshwater by surfactants during solar-driven seawater distillation

Abstract

Recently, solar-driven seawater desalination based on air-water interfacial heating has triggered significant research interest due to its high water evaporation rate, high photothermal conversion efficiency, low energy consumption, simple operation and low cost. However, as the air-water interface temperature reaches as high as 40–70 °C, volatile organic compounds (VOCs) will volatilize into the condensed desalinated water and results in the polluted freshwater. In this work, anionic, cationic, and nonionic surfactants were applied for the first time to inhibit the phenolic compounds such as phenol, p-methylphenol and p-chlorophenol entering into the condensed freshwater. Results showed that the concentration of phenol could be reduced by the addition of cetyl trimethyl ammonium bromide (CTAB). The phenol's distillation concentration ratio (RD) reduced from 76% to 35% due to the electrostatic interaction and the micellar encapsulation between the CTAB and phenol. Moreover, parameters including CTAB dose, initial phenol concentration, solar intensity, pH, and salinity that affecting the RD were also investigated. Finally, a real seawater solar-driven distillation experiment also revealed that the water quality of freshwater was improved by the addition of CTAB. This work revealed that the surfactants such as CTAB can be potentially used to inhibit VOCs entering into the condensed freshwater during solar-driven seawater distillation.