Effect of natural sorbents on the stabilization of trace metals in bottom sediments

Bottom sediments were tested in order to determine the possibility of immobilization of heavy metals with the use of natural sorbents, chitosan and bentonite. The content of Cu, Zn, Cd and Pb was determined, and speciation analysis was performed using the sequential Tessier methodology. The use of sorbents clearly changes the speciation forms of all tested heavy metals by comparing the distribution of metals before and after the application of the sorbent for both chitosan and bentonite. The addition of natural sorbents affect the immobilization of metals deposited in bottom sediments of water reservoirs. However, the behavior of metals in the presence of sorbents results from their properties and the nature of the sorbent. The positive effect of sorbents on metal immobilization was not observed in every case. The addition of the tested sorbents in the case of cadmium caused an increase in the content of Cd in the mobile fractions, for Zn, Pb and Cu, stronger binding of metals was found in the stable fractions IV and V. Chitosan stabilized metals more strongly than bentonite, which moved Zn, Pb and Cu to the first mobile fraction.