The authors thank FEDER and Spanish MINECO for financial support under projects MAT2013-40950-R, Consolider ORFEO. A.D. also thanks to Spanish Ministerio de Educación, Cultura y Deporte by their pre-doctoral FPU grant (AP2008-03942). The synchrotron measurement time was provided by ESRF (Grenoble, France) within the research project No. CH-3428. The authors thank staff members of BM25 (SpLine): Dr. Germán R. Castro, Dr. Iván Da Silva González and Dr. Pilar Ferrer Escorihuela for the technical support, guidance and useful suggestions on XANES data collection at the synchrotron facility.