Solid state chlorination with NH4Cl as chlorinating agent represents a new way for rare earth recovery from end-of-life-magnets. Compared to hydrometallurgical recycling approaches this process provides a number of economic advantages. As a first step, solid state chlorination was adjusted with disused FeNdB magnets from a wind power plant. The SE yield of the chlorination step was optimized according to a 3(3)-Box-Behnken design with varying temperature, time, and NH4Cl/magnet ratio. Likewise, the process profits from leaching with a sodium acetate/acetic acid buffer following the chlorination step.