During a campaign of sediment sampling at a Sardinia South-Western lagoon, communicating with the sea, some sediment samples have been collected and tested in order to find the presence of heavy elements pollution, through some grain-size and chemistries analysis. A considerable concentration of those elements, over the limits previewed by the Italian law, was found particularly in the fine fractions. The contamination of those sediments by heavy metals depends on numerous factors, like the presence of old mines and industrial waste collection basins. The possibility of reducing the presence of the polluting elements through a cyclone process has been studied on the sediment samples collected. Therefore, on every sample collected and on a reconstituted representative sample a cyclone process has been set up. With a cut-size d50 about 30 µm it’s possible to get an overflow and an underflow. The overflow has been constituted by a pre-concentration of heavy elements that will be eliminated subsequently by a suitable hydrometallurgical process. The underflow has shown a pollution grade under the law limits.