According to the current state of the art in reprocessing technology, the 129I contained in spent fuel elements can be completely transferred to the dissolver off-gas and efficiently adsorbed on AgNO3-impregnated silica (AC 6120). For future transmutation, the 129I should again be separated selectively and as completely as possible (>99%) from the AC 6120 adsorption matrix. Experimental studies show that a quantitative recovery of the iodine is possible by wet chemical and thermal processes. Extraction experiments using iodine-loaded AC 6120 with sodium sulfide solution provide recovery rates of 99 ± 1%. Reduction with hydrogen at 500°C, in which gaseous HI was liberated, provided recovery rates of >99%. After the separation of iodine, the reduced AC 6120 can be used again as an adsorbent for molecular iodine.