BACKGROUND: The defluorination of fluoride contaminated groundwater by emulsion liquid membrane using primary amine LK-N21 as fluoride carrier and Span 80 as surfactant has been investigated. RESULTS: The purification process comprised preparation of W/O emulsion, extraction and demulsification operations. The transport mechanism of fluoride by emulsion liquid membrane using primary amine LK-N21 as fluoride carrier was determined. The extraction conditions, i.e. surfactant and carrier concentration, type and concentration of precipitant, emulsification time and speed, volume ratio of internal phase to organic membrane phase, external phase pH and volume ratio of external phase to W/O emulsion for purification of the fluoride contaminated groundwater were studied. CONCLUSIONS: The treated natural groundwater samples finally were found to have been treated with high extraction efficiency, thus meeting the limiting values of the quality standard of class II for groundwater in China. Equilibrium extraction correlation was found to represent well the fluorine equilibrium relation in the emulsion membrane extraction system from the experimental data. Optimization of the purification conditions and system enabled realization of the practical defluorination needs for fluoride contaminated groundwater. (C) 2016 Society of Chemical Industry