The purpose of this study was to investigate the possibility of the utilization of leonardite as a low cost adsorbent.The study focuses on the "leonardite" low rank coal filter material from Mae Moh basin supplied to Mae Moh power plants. The samples were crushed, passed and sieved in the usual manner to recover the 60 mesh reaction for testing. The leonardite analyses (thermogravimetric (TGA) and proximate) are shown. The composition of the mineral matter of the leonardite was also determined. The research on carbon development is directed towards investigating the key parameters in the preparation of activated carbons from low-rank coals. Activated carbons were produced by a two-step process: oxidation of the Leonardite samples in air at 150-250°C for 2 hours, devolatilization of these oxidized in nitrogen.