Al-substituted 11Å tobermorites were obtained from stoichiometrically adjusted mixtures of newsprint recycling waste, sodium silicate and calcium oxide via hydrothermal synthesis at 100°C. Hydrothermal processing in water yielded a highly crystalline 11Å tobermorite product with a Cs + cation exchange capacity of 85meq 100g −1 and selective Cs + distribution coefficient of ∼5500cm 3 g −1 . Conversely, a product of inferior crystallinity was obtained from hydrothermal synthesis in alkaline liquor whose Cs + ion exchange capacity and selective Cs + distribution coefficient were found to be 66.3meq100g −1 and ∼700cm 3 g −1 , respectively. Silicate chain configuration was found to have a modest impact on the number of cation exchange sites per unit cell, whereas the influence of structural defects on selectivity was more pronounced. The structures and ion exchange credentials of both 11Å tobermorite products corresponded well with those of their essentially phase-pure counterparts.