As it is well-known, one of the uses of TiO₂ is for water treatment because it has great photocatalytic efficiency under UV-Vis light. However, TiO₂ presents large bandgaps in all its polymorphs and therefore has little photoactivity under solar radiation. One of the strategies for reducing its band gap is doping TiO₂ with trivalent rare earths (RE³⁺) cations. These cations are also good adsorbents of many organic pollutants. For these reasons, in this work, undoped and Nd-doped mesoporous self-supported TiO₂ membranes (Nd = 0.5, 1, 2, 3, 5, and 10 mol%) were studied. They were obtained by controlled gelling of sols and after by controlled drying of the resulting hydrogels. The sols were prepared by a “green sol-gel route” in aqueous media. The resulting membranes were characterized by nitrogen adsorption-desorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy-energy dispersive x-ray (FEG-SEM-EDX), high resolution electron microscopy (HREM) coupled with selected area electron diffractometry (SAED), and diffuse reflectance (DR) UV-vis spectroscopy. Finally, they were evaluated as adsorbents and photocatalysts of an ionic dye (crystal violet, CV) for remediation. Nd doping influences both the textural properties of the membranes and their phase composition. In addition, the DR measurements show that Nd doping shifts the optical absorption edge from UV to visible. XPS measurements allow us to determine the quantitative composition of membrane surfaces, focusing especially on the different types of oxygen present as oxides and hydroxides. The proportion of these species also depend on Nd content. As it is expected, all materials are active from the photochemical point of view.  Furthermore, the thermodynamic studies show that 0.5 mol% Nd is in the smaller range of Gibbs energy values indicating that the adsorption process is more probable and therefore more efficient in discoloration. The photocatalytic measurements agree well with our thermodynamic calculations. According to all the parameters studied it seems that the highest efficiency of the photocatalytic process was achieved due to an optimal combination of a narrow band gap, a high surface area, adequate phase and chemical compositions, a low Gibbs energy value, and an improved electron-hole separation. The membrane with 0.5 mol% Nd presents the best combination of all these variables being then the best adsorbent and photocatalytic material.