Elimination of heavy metals from microbial cultures by chemical and biological leaching under decreased values of pH

• Published in: Journal of hazardous materials 1994, Vol.37 (1), p.49-67
• Main Authors: Kaštanek, František, Bizek, Vladimir, Matějka, Miroslav
• Format: Article
• Language: English
• Subjects: Applied sciences; Biological and medical sciences; Biotechnology; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; Other wastes and particular components of wastes; Pollution; Wastes
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/0304-3894(94)85033-X

The article compares experimental results of the effectiveness of the extraction of heavy metals contained in mixed microbial cultures forming activated sediments from communal sewage disposal plants. The methods used were elimination of the metals from the sediments based on their extraction with strong inorganic acids under pH 1, extraction with the aid of acid ion exchangers and simultaneous oxidation of the sludge with chlorine and ozone in the pH area 2.7 - pH 3 and a method of biological leaching through the effect of the micro-organism Thiobacil lus ferrooxidans under pH 2. Relatively the most effective method appears to be extraction with acids under pH l when, with the exception of copper and lead, the other metals are extracted with great efficiency. Chrome is also well extracted with these low pH, in contrast, for instance, with the ion exchanger method. But this second case is good for the extraction of copper. Ni and Cd are well extracted by both methods. Biological leaching is shown to be the most suitable for the extraction of zinc, but it can also be used as an auxiliary method for disrupting the strong bonds even of sulphides of other heavy metals with their receptors on the surface of cell membranes. It seems from our results that the majority of metals are mainly bound just on the surface of the cells, with the exception of copper, which evidently penetrates into the volume of the cells, from which it can be partially washed out only after disrupting the cell walls through the effect of strong oxidative agents. It is stated, on the basis of evaluation of the experiments that successive application of all three methods could be practically utilizable as an effective way of extracting heavy metals from sludge from sewage treatment plants.