Chemisorption of Eu3+ and Tb3+ on SBA-15 functionalized with succinic groups has been studied by in situ steady-state fluorescence measurements. The enhancement of the emission sensitive bands indicates that both ions adsorb forming inner-sphere surface complexes. Adsorption is a fast process that attains equilibrium in about 5 min. The variation of the peaks maxima (I-592 and I-616, for europium, and I-490 and I-545, for terbium) with the total ion concentration is accounted for by the sum of the contributions due to the adsorbed and free ions. The former contribution is langmuirian. At pH 4.5, the respective adsorption constants are 5 x 10(5) and 3 x 10(5) M-1, and the maximum adsorption capacities are 5.10 x 10(-4) and 5.23 x 10(-4) mol g(--1). The mismatch between the latter values and the number of attached carboxylic groups is discussed. Comparison with other functionalized mesoporous silicas indicates that the anchored succinic groups are very efficient for removing lanthanide ions from aqueous solutions. (C) 2017 Elsevier Inc. All rights reserved.