Comparative evaluation of EDTA, pyridine and acetic acid for the assessment of available heavy metals from domestic and industrial sludges
Various sludge samples from different domestic and industrial wastewater treatment plants were analyzed by Flame Atomic Absorption Spectrometry (FAAS) to evaluate their total and available contents of heavy metals (Pb, Hg, Cd and Zn). The EDTA, pyridine and acetic acid single extraction techniques were applied to these samples with the objective of studying the leaching behavior of the metals in different sludges and also to predict their possible mobility when these wastes are disposed on the environment and landfills. In EDTA, higher extraction efficiency was observed for major part of the elements studied in the industrial sludges except for Hg and Cd, which were also considerably released from domestic sludges. Acetic acid and pyridine gave a better extraction efficiency for Zn in industrial sludge than EDTA. Moreover, the results of total digestions were compared, for total metal contents, with those obtained using pseudototal digestion procedure and a good correlation (r2 = 0.95) was found between the two methods of digestion.