Heavy Metal Biosorption

Fungi and yeasts (Puranik et al. 1995; Sag and Kutsal 1996; Volesky and May-Phillips 1995; Zhao and Duncan 1998) have in the past received the most attention in connection with metal biosorption systems, particularly because plentiful amounts of fungal biomass are generated as by-products of several types of industrial alcohol and antibiotic fermentations (Omar et al. 1996; Sag et al. 2000; Volesky and Holan 1995). One such system consisting of Aspergillus niger waste from citric acid production was shown to remove zinc (as dust), magnetite, and metal sulfides from wastewater (Singleton et al. 1990; Wainwright et al. 1990). This process was shown to be independent of metabolism but was favored by cell growth, with the particles eventually becoming entrapped within the matrix of the fungal hyphae. Al-Asheh and Duvnjak (1992) demonstrated that living mycelia of Aspergillus carbonarius were able to adsorb copper and chromium and noted that an increase in uptake correlated with an increase in pH. Sag et al. (1999) recently reported the simultaneous adsorption of chromate and divalent copper ions by living R. arrhizus in packed columns operated in continuous mode. Other fungal adsorbents were successfully demonstrated by Suhasini et al. (1999) to remove nickel ion from aqueous solutions, achieving uptake capacities of 214 mg Ni2+/g dry wt fungus.

Yeast similarly have proven to be effective research models for metal sorption studies. The abundant brewery and bakery yeast Saccharomyces cerevisiae has been the object of numerous biosorption studies. Wilhelmi and Duncan (1995) showed that immobilized cells of this yeast had the capability to adsorb Cu, Co, Cd, Ni, Zn, and Cr with an uptake averaging around 40 mmol/g in continuous flow packed bed columns through 8 repeated adsorption-desorption cycles. Optimum chromate removal from electroplating effluents has been recently demonstrated in fixed-bed columns at pH 2.5 using formaldehyde cross-linked S. cerevisiae (Zhao and Duncan 1998). Lead was found to adsorb at pH 5.5, to a nonliving cell mass of Saccharomyces uvarum, up to a maximum of 48.9 mg Pb/g dry wt biotrap. Given that carboxyl and amine groups served as the ligand to which the metal bound, it was assumed that chitin was the most likely provider of these groups (Ashkenazy et al. 1997).

Several authors now propose that biosorption processes utilizing whole cell biomass can realistically be considered as replacement technologies for existing metal-removal processes, or even as an effective polishing unit in place of existing treatment (Kapoor and Viraraghavan 1995; Volesky and Holan 1995). One recent promising report noted that dried powdered mycelium of Fusarium flocciferum can take up 19.2 mg Cd and 5.2 mg Ni, and between 4 and 6 for Cu, for each 100 mg of fungus (Delgado et al. 1998). Rather severe treatment regimens also may produce a biomass more capable of metal ion uptake. For example Brady et al. (1994) showed that hot alkali treatment of yeast biomass increased accumulation of divalent cation adsorption but limited success in removing chromate was reported. Formaldehyde treatment also was found to render baker's yeast more efficient in binding Cr(VI) (Zhao and Duncan 1998) but only a disappointing 6.3 mg Cr/g treated biomass was achieved. However Kapoor et al. (1999) recently reported that A. niger biomass was more effective than biomass treated by boiling in 0.1 N NaOH for the removal of Ni by biosorption. A number of questions regarding the behavior of dead vs. living biomass in the biosorption process was recently examined by Yetis et al. (2000) in a study of Pb(II) uptake by dead, resting and living Phanerochaete chrysosporium mycelia. Table 3 provides a comprehensive listing of a wide variety of biotraps (including some of bacterial origin as a comparison) capable of specifically sorbing copper from aqueous solutions.

Table 3 Copper biosorption by various types of microbial biomass

Experimental operating conditions Organism Biosorption -

Biomass type Biomass class Capacitya (mg Cu/g) pH T (°C) Cb (mg/l) Bio -mass (g/l) Reference

Z. ramigera

Bacterium

270

5.5

0-500(e)

0.83

Norberg (1984)

B. subtilis

Bacterium

152

Brierley and Brierley (1993)

Arthrobacter sp.

Bacterium

148

3.5-6

30

180 (e)

0.4

Veglio et al. (1996)

P. notatum

Fungus

80

Siegel et al. (1980)

C. tropicalis

Yeast

80

Mattuschka and Straube (1993)

Activated sludge bacteria

Bacteria

50

5

25

15-200 (e)

0.5

Aksu et al. (1992)

C. vulgaris

Alga

42.9

4

25

10-260 (i)

Aksu et al. (1992)

B. licheniformis (CWP)

Bacterium

32

Beveridge (1986)

Z. ramigera

Bacterium

29

4

25

12-125 (i)

Aksu et al. (1992)

P. syringae

Bacterium

25.4

22

0-13 (i)

0.28

Cabral (1992)

C. resinae (MP)

Fungus

25.4

5.5

25

1-320 (i)

1

Gadd and deRome (1988)

G. lucidum

Fungus

24

5

5-50 (e)

Venkobachar (1990)

P. chrysosporium

Fungus

20.2

6

5-500(i)

dvan Say (2001)

R. arrhizus

Fungus

19

5.5

25

1.05

deRome and Gadd (1987)

C. resinae

Fungus

18

Gadd et al. (1998)

S. cerevisiae

Yeast

17

4-5

25

190 (e)

1

Volesky and May-Phillips (1995)

R. arrhizus

Fungus

16

Tobin et al. (1984)

R. arrhizus

Fungus

16

Tobin et al. (1984)

C. resinae

Fungus

16

5.5

25

1-320 (i)

1

Gadd and deRome (1988)

A. oryzae

Fungus

13.6

Huang et al. (1990)

P. guilliermondii

Yeast

11

Mattuschka and Straube (1993)

S. cerevisiae

Yeast

10

Mattuschka et al. (1993)

S. obliquus

Alga

10

Mattuschka et al. (1993)

R. arrhizus

Fungus

9.5

5.5

25

0.6-25 (i)

Gadd et al. (1998)

P. chrysogenum

Fungus

9

Niu et al. (1993)

S. noursei

Bacterium

9

5.5

30

06-65 (i)

3.5

Mattuschka and Straube (1993)

A. pullulans (MP)

Fungus

9

5.5

25

1-320 (i)

1

Gadd and deRome (1988)

A. niger

Fungus

7.22

Rao et al. (1993)

S. cerevisiae

Yeast

6.3

Brady and Duncan (1993)

A. pullulans

Fungus

6

5.5

25

1-320 (i)

1

Gadd and deRome (1988)

S. noursei

Bacterium

5

Mattuschka and Straube (1993)

Bacillus sp.

Bacterium

5

Cotoras et al. (1993)

A. niger

Fungus

4

5

5-100 (e)

Venkobachar (1990)

P. spinulosum

Fungus

3.6

Townsley and Ross (1985)

P. digitatum

Fungus

3

5.5

25

10-50 (e)

6.5

Galun et al. (1987)

A. niger

Fungus

1.7

Townsley et al. (1986)

T. viride

Fungus

1.2

S. cerevisiae

Yeast

0.8

4

25

3.2 (i)

2

Huang et al. (1990)

S. cerevisiae

Yeast

0.4

4

25

3.2 (i)

2

Huang et al. (1990)

P. spinulosum

Fungus

0.4-2

Townsley et al. (1986)

Table 3 is a compilation of data reported in previous reviews (Kapoor and Viraraghavan 1995; Veglio and Beolchini 1997; Volesky and Holan 1995). Areas in the table which are not filled imply that such data were not available to and/or not reviewed by the authors. References to the primary literature are given in the right-most column. CWP = cell wall preparation; MP = melanin preparation.

a Metal uptake as reported is not necessarily at maximum. b (i) = initial concentration; (e) = equilibrium concentration.

Table 3 is a compilation of data reported in previous reviews (Kapoor and Viraraghavan 1995; Veglio and Beolchini 1997; Volesky and Holan 1995). Areas in the table which are not filled imply that such data were not available to and/or not reviewed by the authors. References to the primary literature are given in the right-most column. CWP = cell wall preparation; MP = melanin preparation.

a Metal uptake as reported is not necessarily at maximum. b (i) = initial concentration; (e) = equilibrium concentration.

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