In this work, sorption of chromium on granular ferric hydroxide (GFH) has been investigated using batch and column techniques. The adsorption behavior of Cr on GFH, depending on pH, contact lime and sorbent amount were studied. The equilibrium adsorption capacity of GFH for Cr was measured and cxtrapo latcd using Freundlich isotherms. Metal ions bounded lo the GFH could be recovered by alkaline solution, and the GFH can be recycled. The sorption capacity of GFH was 25.0 mg/g. The ion exchange of chromium on GFH follows pseudo-first-order kinetics. The intraparticlc diffusion of chromium on GFH presents the limiting rate. The results indicated practical value of this method for industry and also provide strong evidence to support the proposed thesis about the adsorption mechanism.

An increasing number of municipal sewage treatment plants in Poland, desirable from an environmental perspective, raises the problem of managing the growing volume of sewage sludge. The thermal treatment of municipal sewage sludge (TTMSS) method, by greatly reducing the waste volume, increases the heavy metal concentration in fly ash (primary, end product of the treatment process), which may constitute a risk factor when attempting to utilize them economically. The research paper concentrates on determining the TTMSS fly ash heavy metal leaching level. For this purpose, ash samples were subjected to leaching with the batch and percolation tests, and the heavy metal content in eluates was determined by the FAAS method. The obtained results served as a base to determine the level of heavy metal immobilization in the ash, the element release mechanism (percolation test), and the impact of the L/S (liquid to solid) ratio and pH on the heavy metal leaching intensity (percolation test). The conducted research indicated high immobilization of heavy metals in TTMSS fly ash, regardless of the applied study method, which corresponds to the results of other researchers. Lead was the most intensively eluted metal.