In the copper mining industry, the impurity of the highest concentration is arsenic, with ore grades of up to 0.3% in mine minerals. During the copper production process via sulphide, arsenic is concentrated simultaneously with the copper closing the treatment cycle in copper smelting. Because of its toxic, mutagenic and carcinogenic characteristics, it should precipitate and be disposed of as a stable residue, in order to prevent it from infiltrating into the soil, and thus into the ground water. Ecometales has designed a process at industrial scale to stabilize arsenic from flue dust into the form of scorodite (FeAsO4∗2H2O), a highly stable compound. This process comprises the stages of primary leaching, oxidation and precipitation of arsenic in the form of scorodite. The present study aims at evaluating an optimization of the scorodite precipitation stage by using seeds in the primary precipitation stage. In this sense, laboratory tests were carried out simulating the industrial circuit. Parameters such as the precipitation kinetics and arsenic grade in the precipitated residue were verified. By using the seeds, a substantial improvement was obtained in: the precipitation kinetics (from 24 to 16 h) and in the arsenic grade in the obtained residue from 9 to 13%. The percentage of scorodite in the residue grew from 30 to 41%.