The equilibrium adsorption of tungstophosphoric, molybdophosphoric, tungstosilicic or molybdosilicic heteropolyacids on activated zirconia, silica, titania, alumina and/or carbon from solutions was studied at 20ºC. It was found that the adsorption characteristics depended on the heteropolyacid and the support. The equilibrium adsorption isotherms fitted the classical Langmuir model for tungstophosphoric acid on zirconia and alumina, for molybdophosphoric acid on alumina and for all the studied heteropolyacids on carbon. The equilibrium adsorption constant and the number of adsorption sites were estimated. The greatest solute-support interaction was displayed by tungstophosphoric acid on alumina and carbon, in accordance with its highest acidity. The main species in the solutions was the undegraded anion of the corresponding acid, characterized by UV-visible and nuclear magnetic resonance spectroscopies. The dried solids presented a high dispersion of the adsorbed species and/or amorphous heteropolyacid by X-ray diffraction. In addition, the [P(Si)W(Mo)₁₂O₄₀]^3- anion was the main species in solid samples of the heteropolyacids adsorbed on ZrO₂, SiO₂, TiO₂ and C, as shown by ³¹P MAS nuclear magnetic resonance, diffuse reflectance and Fourier transformer infrared spectroscopies. This species kept stable during thermal treatment up to 250-365ºC, depending on the system. For tungstophosphoric acid adsorbed on Al₂O₃, the present species were the [P₂W₂₁O₇₁]^6- and [P₂W₁₈O₆₂]^6- anions.