Method for reclaiming anionic surface-active agent in waste water

The invention relates to a method for recovering negative ion surface active agent in waste water, which comprises the following steps of: (1) dissolving a calcium chloride in water to prepare a calcium chloride solution; (2) mixing the calcium chloride solution with waste water or foam liquid containing negative ion surface active agent fully to generate solid precipitate after reaction; (3) solid-liquid separation; and (4) drying the solid precipitate. In order to improve the recovery efficiency, the calcium chloride solution is a saturation calcium chloride solution; the concentration of negative ion surface active agent in the waste water or foam liquid is larger than 500mg/L; and the negative ion surface active agent is a sodium dodecyl benzene sulfonate. The method reduces the treatment cost of waste water, saves energy and reduces drainage for enterprises in a real sense, and has a profound influence on the industrial application of recovering the negative ion surface active agent in waste water. The m