In this study purification of montmorillonite was done using sodium hexametaphosphate as dispersing agent. The raw bentonite was supplied by Salafchegan mine. The XRD results showed that the main minerals in the bentonite was the montmorillonite, quartz, cristobalite, and calcite. The sedimentation process in assistance of centrifuge force was used for purification of montmorillonite and the XRD results showed that huge amount of impurities was removed from the montmorillonite. Results of this study could be used for preparation of nanoclay for variety of applications such as drug delivery. As the organo-modified nanoclay is used for improvement of phisico-mechanical properties clay-polymer nanocomposites there is a big effort in preparation of organo-modified nanoclay. However as the clay is usually supplied as raw materials from mines it is really important to purify it before preparation of organo-modified nanoclay. In this regards we have prepared pure montmorillonite using sodium hexametaphosphate as dispersant and the effect of using dispersant in the modification process with HDTMA was analyzed. The results indicated that when dispersant is used for preparation of pure montmorillonite the arrangement of organic materials in between montmorillonite layered could alter. This phenomenon is due to change in the surface charges of the montmorillonite when treated with dispersant. Results of this study could be used for improvement of characteristics of organo-modified nanoclay.