Open AccessBioleaching of Heavy Metal Polluted Sediment: Influence of Sediment Properties (Part 2)
Author(s) -
Löser C.,
Zehnsdorf A.,
Hoffmann P.,
Seidel H.
Publication year - 2006
Publication title -
engineering in life sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.547
H-Index - 57
eISSN - 1618-2863
pISSN - 1618-0240
DOI - 10.1002/elsc.200520142
Subject(s) - bioleaching , sediment , leaching (pedology) , environmental chemistry , carbonate , environmental remediation , chemistry , geology , environmental science , contamination , soil science , soil water , ecology , organic chemistry , copper , biology , paleontology
A remediation process for heavy metal polluted sediment has previously been developed, in which the heavy metals are removed from the sediment by solid‐bed bioleaching using sulfuric acid as a leaching agent arising from added elemental sulfur ( S 0 ). This process has been engineered with Weiße Elster River sediment (dredged near Leipzig, Germany), as an example. Here, six heavy metal polluted sediments originating from various bodies of water in Germany were subjected to bioleaching to evaluate the applicability of the developed process on sediment of different nature: each sediment was mixed with 2 % S 0 , suspended in water and then leached under identical conditions. The buffer characteristics of each sediment were mainly governed by its carbonate and Ca content, i.e., by its geological background, the redox potential and oxidation state depended on its pre‐treatment (e.g., on land disposal), while the pH value was influenced by both. The added S 0 was quickly oxidized by the indigenous microbes even in slightly alkaline sediment. The microbially generated H 2 SO 4 accumulated in the aqueous phase and was in part precipitated as gypsum. Significant acidification and heavy metal solubilization only occurred with sediment poor in buffer substances. With the exception of one sediment, the behavior in bioleaching correlated well with the behavior in titration with H 2 SO 4 . Since the content in carbonate seemed to be the most important factor deciding on the leachability of a sediment, oxic Weiße Elster River sediment was mixed with 2 % S 0 and 0 to 100 g/kg of ground limestone to simulate various buffer capacities, suspended in water and then leached. The lime did not inhibit microbial S 0 oxidation but generated a delay in acidification due to neutralization of formed H 2 SO 4 , where the pH only started to decrease when the lime was completely consumed. The more lime the sediment contained, the longer this lag period lasted, and the higher the pH and the lower the fraction of the solubilized heavy metals finally was. Since Cu requires stronger acidic conditions for its solubilization, it responded more sensitively to lime addition than Zn, Ni, and Cd. Heavy metal polluted sediment containing large amounts of carbonate may, in principle, also be remediated by bioleaching, but metal solubilization requires excessive amounts of the leaching agent and is thus uneconomical.