Abstract: The entanglement in the scattering processes by the spin-fixed impurity and the Kondo impurity is investigated, respectively. The spin-fixed impurity is employed as a filter to concentrate entanglement. One Kondo impurity can create entanglement between two noninteracting particles and one scattered particle can do so between two noninteracting Kondo impurities.

Key words: entanglement, scattering, free electron, Kondo impurity