Method for removal of residual monomers from water-absorbing polymer particles

A process for removing residual monomers from water-absorbing polymer particles by thermally aftertreating the water-absorbing polymer particles in a mixer having rotating mixing tools, the water-absorbing polymer particles during the thermal aftertreatment having a temperature of at least 60° C. and a water content of at least 8% by weight, with addition of water or an aqueous solution before or during the thermal aftertreatment and/or of a steam-comprising gas stream during the thermal aftertreatment, wherein process comprises performing the thermal aftertreatment in the presence of at least one surfactant, the at least one surfactant having a polar group and a nonpolar group, the polar group and the nonpolar group of the surfactant not being joined via a carboxylic ester group, and the polar group having at least one hydroxyl group, a cationic group, or an anionic group and the nonpolar group having a C4- to C20-alkyl chain.