Within the Moroccan natural resources valorisation scheme, new adsorbents have been prepared from oil shale by chemical and physical activation processes. The activation process the authors have developed in this study give effective adsorbent materials. In view of the physico-chemical properties of these materials and application to the treatment of water loaded with a metal (Cr6+ ion) or organic (methylene blue (MB)) pollutant, it is concluded that the chemical activation process of oil shale at low temperature (250 degrees C) affords the best material. The materials yield is good in comparison with the physical activation at the same temperature and the process is energy saving differently from that at 450 degrees C. Moreover, the chemical activation of oil shale with phosphoric acid at 250 degrees C produces a material with a good yield (about 70%), a high specific surface area (approximately 600 m(2)/g) and a highly porous structure, which gives it a high retention of methylene blue and the Cr6+ ion.