Acta Biotechnologica: Volume 7, Number 6 1987 [Reprint 2021 ed.] 9783112581704, 9783112581698

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Volume 7 • 1987 • Number 6

Journal of microbial, biochemical and bioanalogous technology

Akademie-Verlag Berlin ISSN 0138-4988 Acta Biotech noi., Berlin 7 (1987) 6, 4 8 5 - 572

Instructions to Authors

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Acta Blotectaiihiin Journal of microbial, biochemical and bioanalogous technology

Edited by the Institute of Biotechnology of the Academy of Sciences of the G JD.R., Leipzig and by the Kombinat of Chemical Plant Construction Leipzig—Grimma by M. Ringpfeil, Leipzig and G. Vetterlein, Leipzig

Editorial Board:

1987

A. A. Bajev, Moscow M. E. Beker, Riga H. W. Blanch, Berkeley S. Fukui, Kyoto H. G. Gyllenberg, Helsinki G. Hamer, Zurich J . Holló, Budapest M. V. Iwanow, Moscow P. Jones, El Paso F. Jung, Berlin H. W. D. Katinger, Vienna K. A. Kalunjanz, Moscow J . M. Lebeault, Compiégne

D. Meyer, Leipzig P. Moschinski, Lodz A. Moser, Graz M. D. Nicu, Bucharest Chr. Panajotov, Sofia L. D. Phai, Hanoi H. Sahm, Jülich W. Scheler, Berlin R. Schulze, Halle B. Sikyta, Prague G. K. Skrjabin, Moscow M. A. Urrutia, Habana

Number 6

Managing Editor:

L. Dimter, Leipzig

Volume 7

AKADE MI E - V E R L A G

B E R L I N

"Acta Biotechnologica" publishes original papers, short communications, reports and reviews from the whole field of biotechnology. The journal is to promote the establishment of biotechnology as a new and integrated scientific field. The field of biotechnology covers microbial technology, biochemical technology and the technology of synthesizing and applying bioanalogous reaction systems. The technological character of the journal is guaranteed by the fact that papers on microbiology, biochemistry, chemistry and physics must clearly have technological relevance.

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Acta Biotechnologica Herausgeber: Institut für Biotechnologie der AdW der DDR, Permoserstr. 15, DDR-7050 Leipzig, (Prof. Dr. sc. Manfred Ringpfeil) und VEB Chemieanlagenbaukombinat Leipzig—Grimma, Bahnhofstr. 3 - 5 , 7240-DDR Grimma, (Generaldirektor: Obering. G. Wohllebe). Verlag: Akademie-Verlag Berlin, Leipziger Straße 3 - 4 , PF 1233, DDR -1086 Berlin; Fernruf: 2 236201 und 223 6229; Telex-Nr.: 114420; Bank: Staatsbank der DDR, Berlin, Konto-Nr.: 6836-26-20712. Redaktion: Dr. Lothar Dimter (Chefredakteur), Käthe Geyler, Martina Bechstedt. Permoserstr. 15, DDR-7050 Leipzig; Tel.: 2392255. Veröffentlicht unter der Lizenznummer 1671 des Presseamtes beim Vorsitzenden des Ministerrates der Deutschen Demokratischen Republik. Gesamtherstellung: VEB Druckhaus „Maxim Gorki", DDR-7400 Altenburg. Erscheinungsweise: Die Zeitschrift „Acta Biotechnologica" erscheint jährlich in einem Band mit 6 Heften. Bezugspreis eines Bandes 180,— DM zuzüglich Versandspesen; Preis je Heft 30,— DM. Der gültige Jahresbezugspreis für die DDR ist der Postzeitungsliste zu entnehmen. Bestellnummer dieses Heftes: 1094/7/6. Urheberrecht: Alle Rechte vorbehalten, insbesondere der Übersetzung. Kein Teil dieser Zeitschrift darf in irgendeiner Form — durch Photokopie, Mikrofilm oder irgendein anderes Verfahren — ohne schriftliche Genehmigung des Verlages reproduziert werden. — All rights reserved (including those of translation into foreign languages). No part of this issue may be reproduced in any form, by photoprint, microfilm or any other means, without written permission from the publishers. © 1987 by Akademie-Verlag Berlin. Printed in the German Democratic Republic. AN (EDV) 18520 03000

Acta Biotechnol. 7 (1987) 6, 487—497

Microbial Recycling of Mineral Waste Products* BOSECKER, K .

Federal Institute for Geosciences and Natural Resources 3000 Hannover 51, Stilleweg 2, F.R.G.

Summary The applicability of biotechnological methods to metal recovery from non-sulfide industrial waste products (slag, galvanic sludge, filter-press residue, filter dust, and fly ash) was investigated. From some products, copper, chromium, zinc or vanadium were completely extracted by sulfuric acid produced by Thiobacillus thiooxidans. The efficiency of bacterial metal solubilization varied depending on the type of waste material and on the pulp density. Stepwise increase of pulp density promoted bacterial growth and activity, resulting in metal concentrations of 6.6 g Cu/1, 6.3 g V/l, 24.4 g Zn/1 or 21 g Cr/1 in the leaching medium. In some eases bacterial leaching was as effective as chemical leaching with sulfuric acid. The efficiency of both processes is considered. In principal, bacterial metal recovery from industrial waste products seems to be feasible and may contribute to an increase in future supplies of raw materials, as well as to detoxification of industrial waste products resulting in reduced environmental pollution problems.

Introduction Enormous quantities of industrial waste are accumulating in many countries and need spécial treatment. Waste products from the mining and metal-refining industries, sewage sludge and residues from power stations and waste incineration plants often contain substantial amounts of heavy metals, which in case* of inadequate disposal may be mobilized and may cause hazardous environmental problems if they reach the soil or groundwater. Meanwhile, special waste disposal sites exist and special waste treatment plants have been established in several countries. Very often waste disposal is subject to strong governmental restrictions. Therefore the cost of waste removal continuously increases, and environmental protection restrictions may create economic problems. Industrial waste products which contain high concentrations of valuable metals (copper, zinc, lead, chromium or vanadium) may be regarded as metal resources, the extraction of which should be considered. Biotechnological leaching processes are being successfully applied to extract metals from various ores and ore concentrates [1—6]. Briefly, bioleaching is based on the bacterial oxidation of metal sulfides, in the course of which soluble metal sulfates and sul* Revised manuscript of a paper presented at the Leipzig Symposium on Biotechnology 1986"Biotechnology of Recycling" 1*

Acta Biotechnol. 7 (1987) 6

488

furie acid are produced. In the case of industrial waste products such as filter dust, slag or jarosite-type leach residues, which mainly contain non-sulfide metal compounds, only limited information is available concerning the microbial leaching of these residues. As shown by Ebner [7, 8] and S c h à f e r [9] copper and zinc are dissolved from oxide waste products by indirect bioleaching processes achieved by bacterial acid production. In view of these results and the growing problems in waste disposal, the feasibility of microbial metal recovery of various other industrial waste products such as galvanic sludge, filter-press residues, filter dust, fly ash, and slag was investigated. The general principles and results will be outlined and the effectiveness and efficiency of the leaching processes will be considered. Materials and Methods Substrates All waste materials except fly ash were obtained from special waste disposal sites in the Federal Republic of Germany. Samples of fly ash were supplied by various waste incineration plants. The main metal concentrations and pH values of the solid waste samples are listed in Table 1. The particle size of all samples was less than 0.200 mm. Therefore all leaching experiments were carried out in agitated flasks or in a stirred tank reactor. Tab. 1. Metal contents [ % ] and pH-values of industrial waste products Waste product

Cu

Soda slag Galvanic sludge 374 398

0.02

0.73

1.06

2.57 0.03

20.2 0.08

Filter-press residue 369 394 394 A 396 396 A

13.81 11.73 0.03 0.03 0.01

Filter dust F l y ash 418 419

Cr

Zn

Ni

Fe203

Pb

V

TiO a

pH

0.01

3.65

8.1

n.d.

0.08

10.5

0.22 5.77

0.64 0.03

2.65 29.89

0.07 0.04

n.d. n.d.

n.d. 0.23

6.7 5.9

5.14 11.28 18.67 2.23 1.60

1.78 5.78 0.01 0.03 0.01

0.17 0.00 0.06 0.01 0.07

6.09 0.46 0.60 41.31 39.87

0.11 0.08 n.d. 0.01 0.01

n.d. n.d. 5.04 1.18 1.03

0.05 0.03 0.07 5.99 8.23

8.1 7.3 6.7 8.0 7.3

0.18

0.15

7.70

0.02

48.18

1.36

n.d.

n.d.

12.0

0.06 0.06

0.05 0.02

1.24 0.59

0.02 0.01

2.34 5.82

0.29 0.07

0.00 0.00

0.82 1.53

10.5 9.3

n.d. = not determined

Bacteria The strain used for the leaching experiments was specially selected from a variety of strains of T. thiooxidans maintained in our culture collection and is characterized by fast acid production and high tolerance of heavy metals. The latter characteristic is very important to bioleaching because high metal concentrations normally accumulate in the leaching medium. The strain we

BOSBCKEB, K., Recycling of Waste Products

489

chose is capable of growing at 1000 ppm Cu, 10000 ppm Cr and 50000 ppm Ni without any adaption. Very often strains may be adapted to still higher concentrations by the stepwise increase of metal concentration or pulp density [4, 10]. The bacteria were grown on a rotary shaker at 30 °C in an inorganic culture medium with elemental sulfur as the energy source [11].

Leaching Methods Initially, the bacterial leaching tests were run in 500 ml ERLENMEYER flasks which contained 100 ml of logarithmic phase cultures qf T. thiooxidans. In later experiments, the leaching process was run in a stirred tank reactor (Biostat S, BRAUN Melsungen). When the pH reached a value of about 1.5, various amounts of waste material were added to the cell suspension. The flasks were incubated at 30 °C on a rotary shaker, whereas the tank reactor was aerated with compressed air and COa. Periodically, samples were taken from the leach suspension to determine the pH, metal concentration and bacterial activity. As well as bacterial leaching chemical leaching was conducted at 30 °C and was tested in ERLENMEYER flasks containing 100 ml distilled water and 10 g of waste material. The flasks were incubated on a rotary shaker and sulfuric acid was carefully added until the p H in the leach suspension was adjusted to 2.0. Subsequently t h e metal concentrations in the leach suspension were determined.

Analysis Metal contents in the solid waste material were analyzed by X-ray fluorescence analysis. Soluble concentrations of copper, zinc, chromium and vanadium were determined by atomic absorption spectroscopy, titanium was determined colorimetrically.

Results and Discussion Metal Recovery by Chemical Acid Leaching In keeping with the physiological requirements of the leaching organisms, in general bacterial leaching is carried out in an acid environment of pH 2.0 to 2.5 [4]. Often, depending on the chemical and mineralogical characteristics of the individual leach material, sulfuric acid has to be added to the leach suspension in order to maintain suitable conditions for the growth of the bacteria. Addition of acid will cause easily soluble metal compounds to be dissolved and this will interfere with the bacterial leaching process, and affect the results. For this reason, to determine the true bacterial leaching efficiency, it is necessary to run chemical leaching tests under comparable pH conditions but in the absence of bacteria. The chemical shake flask experiments showed that all industrial waste products tested in this study were amenable to acid leaching. The results are given in Table 2. It was found that partly copper, chromium, zinc and vanadium were completely extracted by acid solutions of pH 2. According to the pH of the solid waste material different amounts of sulfuric acid and various periods of time were used for pH-adjustment. Metal Recovery by Bacterial Leaching General Aspects The results of chemical leaching experiments infer that bacterial leaching of industrial waste products is feasible as long as the leaching organism produces considerable arAounts of acid. For the leaching of sulfide minerals, Thiobacillus ferrooxidans is the

490

Acta Biotechnol. 7 (1987) 6

Tab. 2. Chemical leaching of valuable metals from industrial waste products during pH-adjustment Final pH: 2.0, Pulp density: 10 g/100 ml Waste product

Time [d]

H2S04 consumption [g/kg Waste]

Metal in solution [mg/I]

Metal extraction [%]

H 2 SO 4 consumption [kg/kg Metal]

Zn:

778

Zn: 78

131.7

Soda slag Galvanic sludge 374

14

1025

61

619

Cu: 1825 Cr: 20700 Zn: 225

Cu: 71 Cr: 100 Zn: 100

33.9 3.0 275.1

Filter-press residues 369

10

816

Cu: 12600 Cr: 3500

Cu: 91 Cr: 69

6.5 23.3

394

13

606

Cu: 9160 Cr: 10500 Zn: 5780

Cu: 78 Cr: 93 Zn: 100

6.6 5.8 10.8

394 A

44

466

Cr: 19420 V: 5045

Cr: 100 V: 100

2.4 9.2

Filter dust

9

744

Zn: 4305

Zn: 56

17.3

14

526

Cu: Zn:

Cu: 100 Zn: 78

848.4 54.6

Fly ash 418

62 963

most effective organism. In addition to dissolving metals this bioleaching process generates sulfuric acid according to the overall reaction: 4 FeS 2 + 15 0 2 + 2 H 2 0

T'lerrooxidms

> 2 Fe 2 (S0 4 ) 3 + 2 H 2 S 0 4

Another biochemical process in bioleaching which produces acid more effectively than pyrite oxidation is bacterial oxidation of sulfur, which is described by the following equation: 2S + 302 + 2H20

2H2S04

T. thiooxidans oxidizes elemental sulfur more efficiently and more rapidly than T. ferrooxidans. Under conditions where elemental sulfur is the only energy source T. thiooxidans definitely predominates and within a very short time the sulfur is oxidized to sulfuric acid lowering the pH to about 0.5 when STARKEY'S sulfur medium [11] is used. Therefore, bioleaching could be used for recovering valuable metals from non sulfide industrial waste products, if a sulfuric acid producing substrate is added. A feasible process would be dissolution by sulfuric acid production via T. thiooxidans. In contrast to the direct leaching of sulfide minerals this process will be called an indirect one in which the leaching agent (H 2 S0 4 ) is produced by bacterial sulfur oxidation. Bacterial Metal Recovery at Constant Pulp Density In case of shake flask or tank leaching methods, the efficiency of bacterial leaching depends, among other factors, on the pulp density. A rise in pulp density involves an increase in the total particle surface area, which will accelerate the leaching process;

BOSECKEK, K . ,

Recycling of Waste Products

491

on the other hand,, higher pulp densities will increase the amount of soluble and dissolved compounds in the leach suspension, whereby bacterial activity may be inhibited. Initially, the effect of pulp density on the bacterial acid production and on the metal extraction was investigated. Table 3 presents data for the leaching of several industrial waste products at" constant pulp density. From these results it was inferred that industrial waste products contain high enough concentrations of certain components to inhibit bacterial activity. Filter-press residue 369 seemed to be very toxic because even at a very low pulp density (1 g/100 ml) no bacterial growth occurred. Adaptation to the specific substrate may be brought about by serial subculturing at low concentrations of industrial waste products [12]. Tab. 3 . Leaching of industrial waste products in cultures of T. thiooxidans with 1% S°) at constant pulp density Waste product

Pulp density [g/100 ml]

Time [d]

pH Initial

Final

Metal

Extraction [%]

Galvanic sludge 398

5

43

2.2,

1.1

Zn

95

Filter-press residue 369 396

1 1

14 49

1.9 1.3

3.9 0.2

396

3

49

1.3

0.2

396

6

22

1.3

2.7

396 A

1

29

2.4

0.6

396 A

5

23

2.4

0.9

396 A

10

15

2.4

5.1

Cu Cr V Cr y Cr V Cr V Cr V Cr V

13 43 100 39 97 5 27 85 100 47 100 0.2 5

1

14

2.4

1.2

Zn

14

Filter dust

(STAKKEY

Medium

Bacterial growth

+ —

+ + —

+ + —

+•

Bacterial Metal Recovery at Gradually Increasing Pulp Density Microorganisms can also very often be adapted to higher concentrations of toxic compounds by increasing the substrate concentration stepwise. The effect of gradually increasing the pulp density is shown in Fig. 1, which demonstrates bacterial leaching of copper from filter-press residue 369. As already shown in Table 3, at a pulp density of 1 g/100 ml, no bacterial growth was observed after 14 days of incubation; within this period, due to the initial pH of 1.9, 13% copper was extracted. Starting at a pulp density of 0.5 g/100 ml a slight rise in pH was observed during the first day; this was followed by a fall in pH on the second day. On the third day the concentration of waste material was increased to 1 g/100 ml. Thereafter, fresh waste material was added whenever bacterial acid production resulted in a pH of about 1.5. In the beginning of the leaching experiments, the pulp density was normally raised in steps of 0.5 g/100 ml; later on, higher amounts of waste material were added without inhibition of bacterial growth. In this way, a pulp density of 5 g/100 ml was achieved after 30 days and 98% of the copper was dissolved. In addition to copper, 84% chromium and 98% zinc were recovered from filter-press residue 369.

492

Acta Biotechnol. 7 (1987) 6

Days

Fig. 1. Bacterial copper leaching and pH change at increasing pulp density of filterpress residue 369

Fig. 2. Bacterial vanadium leaching and pH change at increasing pulp density of filter-press residue 394 A

Apart from bacterial adaptation to higher concentrations of dissolved components, the appropriate dosage of fresh waste material adjusted the p H in the leaching suspension to a suitable growth range. Thus extreme p H values, which inhibit bacterial activity, were avoided. Leaching at increased pulp densities was conducted mainly in a tank reactor which was equipped with automatic p H recorder. Table 4 presents data on the Tracterial leaching of the industrial waste products with stepwise increase of pulp density. In another example, soda slag was added stepwise to the leaching medium, up to a final pulp density of 2 g/100 ml. In spite of physiologically suitable p H conditions and low

BOSECKER, K . , Recycling of Waste Products

493

metal concentrations in the leach suspension bacterial growth did not occur. Therefore the soda slag probably contained highly toxic compounds which have so far not been identified. Filter-press residue 394 and fly ash 418 also appeared to contain unknown toxic compounds because T. thiooxidans did not grow at final pulp densities of 2.5 and 3.5 g/100 ml respectively. Owing to the low pH conditions at the beginning of the experiment, copper, chromium and zinc were almost completely recovered. Comparison with other data in Table 4 shows that the concentration of copper, chromium and zinc in the culture medium was too low to inhibit bacterial activity. With other industrial waste products, pulp densities up to 40% were achieved without affecting bacterial growth. In general, even at high substrate concentrations, acid production by T. thiooxidans was strong enough for dissolution of copper, zinc, chromium, and vanadium. In some cases complete metal extraction was observed. Depending on the type of waste and on the pulp density in the various leaching experiments, up to 6.6 g of copper, 24.4 g of zinc, 21 g of chromium and 6.3 g of vanadium per liter were determined in the leach suspension. Graphic presentations of vanadium and chromium leaching, related pH changes and increase of pulp density are shown in Figs. 2 and 3.

3: Q.

0

10

20

30

40

Days

50

60

70

80

Fig. 3. Bacterial chromium leaching and pH change at increasing pulp density of filter-press residue 394 A

As reported by SULLIVAN et al. [ 1 3 ] chemical and biological leaching of vanadium from flexicoker coke was restricted to low pH conditions; even below pH 1, only 30% vanadium was extracted. In our investigations, vanadium and chromium were leached within a range of pH 1.2 to 1.5 and both metals were completely recovered from the filter press residue 394 A (Table 4). Bacterial leaching of residues 396 and 396 A, also conducted within a similar range of pH (1.3 to 1.5), was less effective with regard to extraction of chromium. As illustrated in Fig. 4, vanadium was totally extracted, whereas chromium extraction was no higher than about 50%. Leaching of titanium in an acid medium of pH 1.5 has been reported by authors from the U.S.S.R. [3]. According to our investigations, extraction of titanium was very poor, and only 1—5% of total titanium was released from filter-press residue 396 A. These data are in good agreement with the results of SULLIVAN et al. [13].

494

Acta Biotechnol. 7 (1987) 6

Tab. 4. Leaching of industrial waste products in cultures of T. thiooxidans (STARKEY medium with 1% 8°) at gradually increasing pulp density Waste product

Pulp density [g/100ml] Initial

Time [d]

Final

pH

Metal in solution

Metal extraction [°/o]

Initial

Final

[mg/1]

Soda slag

0.5

2

77

2.0

1.5

Zn:

Galvanic sludge 374

0.5

10

146

1.4

2.4

Cu: 1550 Cr: 12960 Zn: 120

Cu: 95 Cr: 100 Zn: 85

+

0.5

40

105

1.6

1.6

Cu: 33 Zn: 16930

Cu: 41 Zn: 100

+

Filter-press residue 0.5 369

5

33

1.9

1.0

Cu: 6600 Cr: 1920 Zn: 806

Cu: 98 Cr: 84 Zn: 98

+

2.5

28

1.3

1.9

Cu: Cr: Zn:

2130 1830 1255

Cu: 94 Cr,: 96 Zn: 100

398

102

Zn:

Bacterial growth

87

394

0.5

394 A

0.5

11

84

1.2

1.5

Cr: 21000 V: 6300

Cr: 96 V: 100

396

0.5

30.5

80

1.4

1.5

396 A

0.5

18

79

1.3

1.6

Cr: V: Cr: V: Ti:

900 1560 980 1690 473

Cr: V: Cr: V: Ti:

Filter dust

1.0

5

16

1.5

1.2

Cu: Cr: Zn:

37 23 3000

Fly ash 418 419

0.5 0.5

3.5 16

49 102

1.3 1.2

1.5 0.8

Zn: Zn:

260 347

—

—

+•

20 63

+

32 85 5

+

Cu: 37 Cr: 28 Zn: 71

+

Zn: Zn:

90 66

—

+

Because of the enormous diversity of industrial waste products, even if derived from the same or at least from similar processes, the differences in leaching behaviour are difficult to explain and the leachability of industrial waste products is difficult to predict. For this purpose a comprehensive chemical and mineralogical analysis is required. Furthermore, chemical interactions influencing the rate and extent of metal extraction have to be considered in chemical as well as in bacterial leaching processes. Efficiency of Chemical and Bacterial Metal Recovery Microbial leaching tests on various non-sulfide industrial waste products have shown that valuable metals such as copper, chromium, zinc, and vanadium in some cases are completely extracted by sulfuric acid production with Thiobtteillus thiooxidans. The efficiency of bacterial metal recovery depends mainly on the type of waste material, i.e. on the chemical and mineralogical composition of the waste product, and on the ability of the bacteria to tolerate or to become adapted to a high pulp density of a particular

BOSECKER, K . ,

495

Recycling of Waste Products

V

Days

Fig. 4. Extraction of chromium and vanadium from filter-press residue 396 A by bacterial leaching at a pulp density of 5 g/100 ml

waste product. Bioleaching of soda slag, for example, failed because this material seems to be highly toxic and adaptation did not occur, whereas bacterial metal extraction from galvanic sludge and from filter-press residues turned out to be promising. Besides bacterial leaching, all waste samples were subjected to sterile chemical leaching with sulfuric acid. The results of chemical leaching correspond to those of the bacterial leaching tests and about the same yields of metal extraction were achieved (Table 5). At present there is no real basis upon which to determine whether the chemical or thebiological process is more effective or more economic. Primarily the leachability of about 40 industrial waste products has been investigated, but none of the individual leaching processes has as yet been optimized. In a very rough cost calculation, bacterial acid production seems to be cheaper than direct use of sulfuric acid. If we take into account only the cost of chemicals, the substrate for bacterial acid production costs 1.00DM/kg Tab. 5. Chemical and bacterial leaching of valuable metals from industrial waste products Waste product

Chemical leaching

Bacterial leaching

Pulp density

Final H 2 S0 4 pH consumption [g/100 ml] [g/kg waste]

Metal extraction [%]

Galvanic sludge 374

10

2.0

619

Cu: 71 Cr: 100 Zn: 100

398

5

2.0

239

Zn: 100

Filter-press residue 369 10

2.0

816

Cu: 91 Cr: 69

I?ulp density

Final Metal pH extraction [g/100 ml] [%]

Metal in solution

10

2.4

Cu: 95 Cr: 100 Zn: 85

Cu: 2400 Cr: 20600 Zn: 186

40

1.6

Zn: 100

Zn: 24400

1.0

Cu: 98 Cr: 84 Zn: 98

Cu: Cr: Zn:

[mg/1]*

6600 1920 806

394 A

10

2.0

466

Cr: 100 V: 100

11

1.6

Cr: 96 V: 100

Cr: 21000 V: 6300

396

30

1.0

444

Cr: Y:

30

1.5

Cr: V:

Cr: V:

* calculated with regard to dilution

19 65

20 63

1360 2280

496

Acta Biotechnol. 7 (1987) 6

waste. Referring to Table 2, chemical leaching of galvanic sludge 374 needed 620 g H 2 S0 4 /kg waste at a cost of 2.50 DM and for the chemical leaching of the filter-press residue 369 as much as 3.30 DM/kg waste is required for an adequate supply of sulfuric acid. In any case, bacterial leaching with T. thiooxidans would be advantageous if transportation costs for the acid used in chemical leaching are high and if there is sufficient sulfur on-site for bacterial acid production. On the other hand, the amount of metal recovery apparently depends on pH. During bacterial leaching the pH only gradually decreases as the bacteria become established and overcome the inhibiting action of the waste product. During this process, certain metals are dissolved selectively and successively according to their solubility as shown in Figure 4 and they can be recovered selectively from the leach suspension. In addition, biological redox reactions may dissolve metal compounds which are not dissolved under normal acid conditions. So far, metal recovery from final industrial waste products has been considered. In some cases, it might be better to consider the leachability not of the final product but of intermediate products, e.g. flotation residues from zinc production, which are utilized for sulfuric acid production. In this case, the final waste product, although it contains about 40—50% iron, cannot be used for steel production or as an additive in building materials because of residual amounts of zinc and thallium; consequently, about 500000 t/year have to be disposed of at a considerable cost. Chemical and bacterial leaching of the final oxide waste product has been tried but was unsuccessful. However, bacterial leaching of the intermediate product, the flotation residue, might be feasible, since it consists predominantly of sulfides. The zinc and thallium could then be extracted before sulfuric acid production. After detoxification, the final waste product could be used for further applications without causing environmental problems. The preliminary leaching experiments which are being run with Thiobacillus ferrooxidans look promising. Future Aspects So far, only the autotrophic thiobacilli have been considered for metal recovery and detoxification of industrial waste products. Meanwhile new methods are being developed for the extraction of valuable metals from oxide and silicate minerals and ores using heterotrophic microorganisms. The efficiency of heterotrophic microorganisms (bacteria, fungi) depends on metabolic compounds which are released into the culture medium and which will dissolve metal compounds mainly by chelating or formation of organic salts. Bioleaching with heterotrophic organisms has been described especially for the extraction of aluminium, nickel and titanium [15 — 17]. Therefore it would be worthwhile investigating the possibility of using heterotrophic leaching methods for the recovery of valuable metals from industrial waste products, primarily with respect to the recycling of aluminium and titanium from aluminium processing residues such as red mud and from cinders and. ashes from power stations. Conclusion In principal, microbial metal recovery from industrial waste products is feasible. Bioleaching of valuable metals from industrial waste products would not only contribute to an increase in the supply of raw materials in the future but would also be useful for detoxification of industrial waste products, thus overcoming some of our environmental pollution problems. Received December 5, 1986

BOSECKER, K . ,

Recycling of Waste Products

497

References W.: Conference Bacterial Leaching 1 9 7 7 . Weinheim: Verlag Chemie, 1 9 7 7 . L. E . , T O R M A , A. E . , B R I E R L E Y , J . A. : Metallurgical Applications of Bacterial Leaching and Related Microbiological Phenomena. New York: Academic Press, 1978. [ 3 ] K A R A V A I K O , G . I . , KTTZNETSOV, S. I . , G O L O N I Z I K , A . I . : The Bacterial Leaching of Metals from Ores. Stonehouse: Technicopy Ltd., 1977. [4] T O R M A , A. E., B O S E C K E R , K. — In: Progress in Industrial Microbiology. Ed.: B U L I I , M. J . Amsterdam: Elsevier Scientific Publishing Company, 1982. 77 — 118. [5] Rossi, G., T O R M A , A. E.: Recent Progress in Biohydrometallurgy. Iglesias, Italy: Associazione Mineraria Sarda, 1983. [ 6 ] B R I E R L E Y , C.: Sci. American 2 4 7 ( 1 9 8 2 ) , 4 4 . [ 7 ] E B N E R , H . G . — In: Conference Bacterial Leaching 1 9 7 7 . Ed.: S C H W A R T Z , W. Weinheim: Verlag Chemie, 1 9 7 7 . 2 1 7 - 2 2 2 . [8] E B N E R , H. G . — In: Metallurgical Applications of Bacterial Leaching and Related Microbiological Phenomena. Eds. : M U R R , L. E., T O R M A , A. E., B R I E R L E Y , J . A. New York : Academic Press, 1978. 195-206. [ 9 ] S C H Ä F E R , W . — In: Recent Progress in Biohydrometallurgy. Eds.: Rossi, G . , T O R M A , A . E . Iglesias, Italy: Associazioni Mineraria Sarda, 1983. 427—440. [ 1 0 ] D U N C A N , D . W . , W A L D E N , C: C., T R U S S E L L , P . C., L O W E , A. E.: Trans. Soc. Min. Eng. AIME [ 1 ] SCHWARTZ, [2] MURR,

2 3 8 (1967), 122.

[11]

R. L.: J. Bacteriol. 10 (1925), 135. A. E . , G A B R A , G . G . : Ant. v. Leeuwenhoek 4 3 ( 1 9 7 7 ) , 1 . [ 1 3 ] S U L L I V A N , E. A., Z A J I C , J . E., J A C K , T . R . — In: Biogeochemistry of Ancient and Modern Environments. Eds.: T R U D I N G E R , P . A., W A L T E R , M. R . , R A L P H , B. J . Canberra: Australian Academy of Sciences, 1980. 557—562. [14] M C E L R O Y , R. 0., B R U Y N E S T E Y N , A. — In: Metallurgical Applications of Bacterial Leaching and Related Microbiological Phenomena. Eds.: M U R R , L. E., T O R M A , A. E., B R I E R L E Y , J . A. New York: Academic Press, 1978. 441—462. [ 1 5 ] H E N D E R S O N , M . E . K . , D U F F , R . B . : J . Soil Sci. 1 4 ( 1 9 6 3 ) , 2 3 6 . [16] M E H T A , A. P., T O R M A , A. E., M U R R , L. E.: Biotechnol. Bioeng. 2 1 (1979), 875. [17] K I E L , H . , S C H W A R T Z , W . : Z . Allgem. Mikrobiol. 2 0 (1980), 627. STARKEY,

[ 1 2 ] TORMA,

Acta Biotechnol. 7 (1987) 6, 498

Book Review K A T S F Y A H A Y A S H I , N A O T O SAKAMOTO

Dynamic Analysis of Enzyme Systems — An Introduction Tokyo: Japan Scientific Press; Berlin, Heidelberg, New York, Tokyo: Springer-Verlag, 1986. 370 pp., 318 fig., 68 tab., 98 DM

Contents: 1. Derivation of Rate Equations for Enzymatic Reactions. 2. Approximation Methods for Analysis of Rate Equations. 3. Numerical Methods for Solution of Rate Equations. 4. Analysis of Enzymatic Reactions in Closed Systems. 5. Microscopic Analysis of Enzyme Systems (The chapter deals mainly with the allosteric enzymes. Microscopic analysis refers to the procedure in which the rate equation is derived directly from the reaction mechanism). 6. Macroscopic Analysis of Enzyme Systems (The macroscopic analysis is performed for a cyclic enzyme system and leads to characterization of the system as a whole). 7. Analysis of Reaction-Diffusion Systems. 8. Determination of Reaction Scheme and Kinetic Parameters. 9. Related Topics in Dynamic Analysis. This book is concerned with a quantitative analysis of dynamic behaviour of enzymatic reaction systems by mathematical modeling and computer simulation. Quantitative analysis of the dynamics of biochemical reactions is directed to elucidation of the relationship between the structure and the function in biochemical systems on a molecular level and should be exemplary for the systems exploited in biochemical and biomedical engineering. The authors are successfully engaged in research seeking to clarify regulatory characteristics of enzymatic reactions in vivo and control mechanisms suitable for enzyme technology. The book concentrates in the field of research of the authors. Hence it is not representative for the state of art in the dynamic analysis of biochemical systems. This is indicated by the references or by the absence of topics as the control theory of metabolic systems. The models discussed in this volume are mainly expressed by nonlinear autonomous differential equations. Numerical methods for the solution of nonlinear equations are extensively discussed (standard methods of numerical mathematics as the GAtrss-procedure for the solution of linear algebraic equations, the RusrGE-KtrTTA-procedure for the integration of ordinary differential equations or optimization methods for evaluation of model-parameters are included), while the presentation of approximation methods commonly employed for treatment of nonlinear systems is rather short. The book gives a lot of interesting informations for the advanced reader. W . SCHELLENBERGEB

Acta Biotechnol. 7 (1987) 6, 4 9 9 - 5 0 5

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