| Popis: |
Alkaline solid residue is a by-product of the extraction of zinc and lead from electric arc furnace dust (EAFD) as part of pre-treatment method of EAFD prior to its permanent disposal. After extraction of zinc and lead from EAFD in strong alkaline solution and elevated temperature and solid/liquid separation the remaining solid residue has high potential for neutralization/purification of various acetous industrial fluids. Among them are electroplating wastewaters characterized with low pH value and high concentrations of heavy metals. Removal efficiency at optimum purification conditions (pH 8 and mixing time ; 20 minutes) for the elements Pb, Cr (VI), Cr (III), Fe, Ni, Cu and Zn were 94.92%, 97.58%, 99.59%, 99.48%, 97.25% and 99.97% respectively. Concentrations of all the elements in the purified water were significantly lower compared to upper permissible limit for the wastewaters suitable for discharge into the environment. According to sequential extraction analyses and preliminary leaching tests it seems that chemisorption was the predominant mechanism in heavy metal removal. Due to low concentrations of heavy metals in the leachates this waste material could be safely deposited at non-hazardous waste repositories after volume reduction. Non-toxicity of this material should be confirmed with appropriate toxicological tests. |
