**3. Biosorption in multicomponent solutions**

Although most of industrial and household effluents and wastewater are composed by a cocktail of contaminants made of metal residues and organic compounds, few studies regarding the simultaneous removal of multicomponent solutions have been conducted and optimized, studies that would better simulate the behaviour of the pollutants present in real effluents. The effect that different types of contaminants (inorganic versus inorganic and inorganic versus organic) have on each other and the effect that different initial concentrations of metal exert on the bioremoval (biodegradation and biosorption among other biological processes) of the organic contaminant have also been poorly investigated. For these reasons, the authors opted to review the state of the art of biosorption from multicomponent solutions, from a laboratory scale to a pilot and/or industrial scale.

Costa and Tavares [3] studied the ability of two fungi and one bacteria (*Penicillium* sp., *Alternaria* sp. and *Streptococcus equisimilis*) to simultaneously treat tertiary solutions containing diethylketone, Cd(II) and Ni(II), and they determined the influence of the initial concentration of metal on (a) the microbial growth, (b) the biosorption capacity of these pollutants and (c) the biological activity after exposure. The results obtained regarding the tertiary solutions allowed to infer that *S. equisimilis* presented the best performance in terms of uptake, for all the conditions tested and that an increase in the initial concentration of metal promoted an increase in the uptake. For the same experimental conditions, the biosorption data obtained for the three microorganisms showed (i) a higher affinity of the biosorbents towards Ni(II) and (ii) a strong and detrimental effect of the metals either in the biosorption process or in the microbial growth. These results may be explained by the fact that not only Ni(II) can be used by the cells as a cofactor, competing actively and passively with Cd(III) but is also less toxic than Cd(II).

More complex systems were further evaluated [4] with a suspended bacterial culture of *Streptococcus equisimilis* with different initial concentrations of Ni(II) (5–450 mg/L) and Cd(II) (5–100 mg/L) in single-component solutions compared to vermiculite to decontaminate singlecomponent solutions composed either by diethylketone, Cd(II) or Ni(II) and binary-component solutions composed either by diethylketone and Cd(II) or diethylketone and Ni(II). A *S. equisimilis* biofilm supported on vermiculite to decontaminate binary solutions composed either by diethylketone and Cd(II) or diethylketone and Ni(II) was also evaluated. The principal aim of this research was the characterization of the interactions between the different concentrations of sorbates and the biosorbents used, when employed in single or binary solutions. For the first set of experiments (*S. equisimilis* and different concentrations of Ni(II) or Cd(II), it was observed that the uptake and percentage of influent Ni(II) sorbed depended on the initial concentration of the sorbate. No significant pH changes had occurred, and the uptake suffered a 30-fold increase with the increase of the initial concentration between 5 and 80 mg/L. Nevertheless, there were no significant changes (<10%) in terms of biosorption percentage for the same initial concentration. The biosorption of Cd(II) was also found to depend on the initial concentration, suffering fluctuations lower than 18%. In these assays, there was an increase in terms of pH (from 6.05 to 6.98). This increase resulted in an increase in the hydroxyl and other anionic functional groups, which made the bacterial surface more negative increasing the number of electrostatic interactions. For the second set of experiments, it was observed that the presence of Cd(II) decreases significantly the sorption percentage of diethylketone, but the presence of this organic compound increased Cd(II) sorption percentage. The presence of Ni(II) has a synergetic effect on diethylketone biosorption. For the third set of experiments, it was established that the presence of the biofilm is an advantage, obtaining promising results, specially taking into account not only the concentrations employed but also the toxicity of the metals. In these experiments, a common increase in terms of sorption efficiency was observed, and this may be explained by the functional groups present on the biofilm that can implement the substrate molecule adsorption and eventually promote the biodegradation of diethylketone and by the increase of the available sites for sorption.

the scale-up of sorption process field, from a laboratory scale to a pilot or industrial scale [21]. The team of the Centre of Biological Engineering from the University of Minho, Portugal, has also been contributing to the study and understanding of (i) the scale-up of biosorption processes from a laboratory scale to a pilot scale and (ii) the increase of solution complexity to be decontaminated, evolving from single-component solutions to multicomponent solutions, mixing organic and inorganic compounds [3, 4, 7, 9, 15, 24], the main subject of this chapter.

**Table 1.** The top 10 publications in the ISI Web of Science database (Web of Science Core Collection) for 'all years'

**Position Paper Times cited**

2 Biosorption of heavy metals *Biotechnology Progress* 11 (3): 235–250 1323

1402

1133

1002

903

832

759

757

749

1 Review of second-order models for adsorption systems *Journal of* 

3 A review of the biochemistry of heavy metal biosorption by brown

4 Application of biosorption for the removal of organic pollutants: A review *Process Biochemistry* 40 (3–4): 997–1026

5 Biosorbents for heavy metals removal and their future *Biotechnology* 

6 Application of chitosan, a natural aminopolysaccharide, for dye removal

7 Removal of Congo Red from water by adsorption onto activated carbon

8 Activated carbons and low cost adsorbents for remediation of tri- and

9 Adsorption of several metal ions onto a low-cost biosorbent: Kinetic and

from aqueous solutions by adsorption processes using batch studies: A review of recent literature *Progress in Polymer Science* 33 (4): 399–447

prepared from coir pith, an agricultural solid waste *Dyes and Pigments*

hexavalent chromium from water *Journal of Hazardous Materials* 137 (2):

equilibrium studies *Environmental Science & Technology* 36 (9): 2067–2073

10 Interactions of fungi with toxic metals *New Phytologist* 124 (1): 25–60 740

*Hazardous Materials* 136 (3): 681–689

algae *Water Research* 37 (18): 4311–4330

*Advances* 27 (2): 195–226

54 (1): 47–58

56 Biosorption

762–811

(1970–2016) with 'biosorption' in the topic.

Although most of industrial and household effluents and wastewater are composed by a cocktail of contaminants made of metal residues and organic compounds, few studies regarding the simultaneous removal of multicomponent solutions have been conducted and optimized, studies that would better simulate the behaviour of the pollutants present in real effluents. The effect that different types of contaminants (inorganic versus inorganic and inorganic versus organic) have on each other and the effect that different initial concentrations of metal exert on the bioremoval (biodegradation and biosorption among other biological processes)

**3. Biosorption in multicomponent solutions**

Attempting to mimetize the complexity of real effluents and wastewaters, biosorption experiments of multicomponent solutions (Al(III), Ni(II), Cd (II) and Mn(II)) by a *S. equisimilis* biofilm supported into vermiculite were performed first at a laboratory scale in batch system (4 g/L of diethylketone and 5–100 mg/L of each metal) and second at a pilot scale in open systems (7.5 g/L of diethylketone and 100 mg/L of each metal) [7]. Diethylketone was periodically added to the bioreactor and was used as the only carbon source. At laboratory scale, the authors observed that diethylketone and removal percentages higher than 95% were achieved in less than 4 hours for all the initial concentrations of metal tested and that the increase of the initial concentration of metals accelerates the complete bioremoval (by biodegradation and/or biosorption processes, for instance) of diethylketone. Regarding the results obtained for the four metals (5–80 mg/L), it is was found that they follow the sequence Al(III) > Cd(II) ≥ Ni(II) ≥ Mn(II), whereas for the experiment conducted with an initial concentration of 100 mg/L, the bioremoval efficiency followed a different sequence Al(III) > Ni(II) > Cd(II) > Mn(II). This difference may be explained by the increase in the initial concentration of metal, which will influence the ionic strength of the elements in solutions, and also by the fact that many divalent metal cations are structurally similar, allowing the substitution of essential metals, such as Ni(II) and Mn(II) for non-essential metals such as Cd(II). The uptake of all metals increased with the increase of the initial concentration of each metal.

of *Alternaria* sp. and *Penicillium* sp. when exposed to Ni(II) concentration ranging from 5 to 100 mg/L was enhanced [3], and when this metal was mixed with diethylketone, the entrapment metabolic pathway selected by those microorganisms was different, since no metabolite was formed during the experimental period, as opposite to what occurred when exposed only

Biosorption of Multicomponent Solutions: A State of the Art of the Understudy Case

http://dx.doi.org/10.5772/intechopen.72179

59

Although studies concerning the influence of metals on organic contaminant bioremoval are scarce, it has been demonstrated that those elements are able to inhibit organic contaminant

Cadmium, chromium (II), copper, mercury and zinc were found to inhibit the biodegradation of 2,4-DME in lake water samples inoculated with either a sediment or an aufwuch (floating algal mat) sample [26]. In the aufwuch samples, mercury revealed to be the most toxic metal, with a microbial inhibitory concentration (MIC) of 2 × 10−3 mg total mercury/L, whereas in the sediment samples, zinc was the most toxic metal with a MIC of 6 × 10−3 mg total zinc/L. Naphthalene (NAPH)-degrading *Burkholderia* sp. was used in a pure culture and reported a MIC of 1 mg solution-phase cadmium/ L [27]. Comparable values of MIC were reported for cadmium (0.629 mg total cadmium/L for aufwuch samples and 0.1 mg

Not all studies were focused on the effect of single metals on bioremoval of a single, pure organic pollutant. Benka-Coker and Ekundayo [28] investigated the impact of copper, manganese, lead and zinc on crude oil biodegradation by *Pseudomonas* sp. and *Micrococcus* sp. These authors inferred that the crude oil was mostly reduced by zinc and slightly by manganese. Interestingly, combinations of these metals presented a lesser toxic profile than some single metals. For instance, toxicity of 0.5 mg total zinc/L was mitigated by the addition of 0.5 mg total copper, lead

It is acknowledged that the bioremoval of an organic pollutant decreases as the concentration of bioavailable metal increases in co-contaminated systems (**Figure 3**). However, this pattern is not always observed. Two other additional patterns describing the effect of metals on the

Low metal concentration enhances bioremoval of organic pollutant; high metal concentrations inhibit it—additional pattern 1: diverse studies showed a pattern of metal toxicity in which low metal concentrations enhance bioremoval activity, till the maximum level of stimulation is reached. After this point, an increase in metal concentration will lead to an increase in metal toxicity (**Figure 3**, Line 2). Sustaining this pattern is the result obtained by Capone et al. [29]

Bioremoval inhibition of organic pollutants is due to low metal concentration; lower bioremoval inhibition of organic pollutants is due to high metal concentration—additional pattern 2: several studies suggested that low concentrations of metal strongly inhibit bioremoval activity, until a maximum of inhibition is achieved (**Figure 3**, Line 3). After this point, an

**3.2. Correlation between metal concentration and bioremoval inhibition**

showing that methanogenesis was enhanced by the addition of some metals.

bioremoval, under both aerobic and anaerobic conditions.

total cadmium/L for sediment samples) [26].

bioremoval of organic pollutants have been shown.

to diethylketone.

and manganese/L.

At a pilot scale, it was observed that the biosorption percentage of all the sorbates (organic and inorganic) tended to increase through time and followed the sequence diethylketone > Al(III) > Cd(II) ≈ Ni(II) ≥ Mn(II), and this is explained by the bioavailability and structural similarity between Ni(II) and Cd(II) that promote the uptake of Cd(II) by the cell enzymes instead of Ni(II) and by the combination of the reduced size of the ionic radius of Mn(II) associated with its reduced electronegativity and the small porosity of the support. The complete bioremoval of diethylketone and its metabolites was achieved, even after the addition of diethylketone to the bioreactor and the sorption percentage of each metal increased through time.

The effect of different initial concentrations of Cd(II), Cu(II), Zn(II), Pb(II) and As(II) (10 mg/L or 100 mg/L) on the bioremoval of fluorene (10 mg/L) by *Sphingobacterium* sp. KM-02 was also assessed [25]. The presence of those metals at 10 mg/L decreased fluorine bioremoval, and the microbial growth and the inhibition effect followed the trend Cd(II) ≈ Cu(II) > Zn(II) > Pb (II) > As(II). Cd(II) and Cu(II) strongly inhibited fluorene bioremoval and microbial growth, whereas Zn(II) and Pb(II) exert a modest inhibitory effect. As(II), on the other hand, has no negative effect on microbial growth and fluorene bioremoval.

#### **3.1. Correlation between metal concentration and microbiological processes**

Metals including cadmium, chromium (III and VI), copper, lead, mercury, nickel and zinc are reported to inhibit microbiological processes such as acidogenesis, methanogenesis, nitrogen transformation, biomass production and enzymatic activity [22]. *S. equisimilis* exposure (in the form of biofilm supported into vermiculite or in suspension) to solutions containing either Cd(II) or Ni(II) (5–100 mg/L) led to microbial growth inhibition [3, 4]. Nevertheless, it is important to mention that the addition of metals may also have the opposite effect and enhance and/or stimulate microbiological processes. The growth of a suspend culture of *Alternaria* sp. and *Penicillium* sp. when exposed to Ni(II) concentration ranging from 5 to 100 mg/L was enhanced [3], and when this metal was mixed with diethylketone, the entrapment metabolic pathway selected by those microorganisms was different, since no metabolite was formed during the experimental period, as opposite to what occurred when exposed only to diethylketone.

Attempting to mimetize the complexity of real effluents and wastewaters, biosorption experiments of multicomponent solutions (Al(III), Ni(II), Cd (II) and Mn(II)) by a *S. equisimilis* biofilm supported into vermiculite were performed first at a laboratory scale in batch system (4 g/L of diethylketone and 5–100 mg/L of each metal) and second at a pilot scale in open systems (7.5 g/L of diethylketone and 100 mg/L of each metal) [7]. Diethylketone was periodically added to the bioreactor and was used as the only carbon source. At laboratory scale, the authors observed that diethylketone and removal percentages higher than 95% were achieved in less than 4 hours for all the initial concentrations of metal tested and that the increase of the initial concentration of metals accelerates the complete bioremoval (by biodegradation and/or biosorption processes, for instance) of diethylketone. Regarding the results obtained for the four metals (5–80 mg/L), it is was found that they follow the sequence Al(III) > Cd(II) ≥ Ni(II) ≥ Mn(II), whereas for the experiment conducted with an initial concentration of 100 mg/L, the bioremoval efficiency followed a different sequence Al(III) > Ni(II) > Cd(II) > Mn(II). This difference may be explained by the increase in the initial concentration of metal, which will influence the ionic strength of the elements in solutions, and also by the fact that many divalent metal cations are structurally similar, allowing the substitution of essential metals, such as Ni(II) and Mn(II) for non-essential metals such as Cd(II). The uptake of all metals increased with the increase of the initial concen-

At a pilot scale, it was observed that the biosorption percentage of all the sorbates (organic and inorganic) tended to increase through time and followed the sequence diethylketone > Al(III) > Cd(II) ≈ Ni(II) ≥ Mn(II), and this is explained by the bioavailability and structural similarity between Ni(II) and Cd(II) that promote the uptake of Cd(II) by the cell enzymes instead of Ni(II) and by the combination of the reduced size of the ionic radius of Mn(II) associated with its reduced electronegativity and the small porosity of the support. The complete bioremoval of diethylketone and its metabolites was achieved, even after the addition of diethylketone to

The effect of different initial concentrations of Cd(II), Cu(II), Zn(II), Pb(II) and As(II) (10 mg/L or 100 mg/L) on the bioremoval of fluorene (10 mg/L) by *Sphingobacterium* sp. KM-02 was also assessed [25]. The presence of those metals at 10 mg/L decreased fluorine bioremoval, and the microbial growth and the inhibition effect followed the trend Cd(II) ≈ Cu(II) > Zn(II) > Pb (II) > As(II). Cd(II) and Cu(II) strongly inhibited fluorene bioremoval and microbial growth, whereas Zn(II) and Pb(II) exert a modest inhibitory effect. As(II), on the other hand, has no

Metals including cadmium, chromium (III and VI), copper, lead, mercury, nickel and zinc are reported to inhibit microbiological processes such as acidogenesis, methanogenesis, nitrogen transformation, biomass production and enzymatic activity [22]. *S. equisimilis* exposure (in the form of biofilm supported into vermiculite or in suspension) to solutions containing either Cd(II) or Ni(II) (5–100 mg/L) led to microbial growth inhibition [3, 4]. Nevertheless, it is important to mention that the addition of metals may also have the opposite effect and enhance and/or stimulate microbiological processes. The growth of a suspend culture

the bioreactor and the sorption percentage of each metal increased through time.

**3.1. Correlation between metal concentration and microbiological processes**

negative effect on microbial growth and fluorene bioremoval.

tration of each metal.

58 Biosorption

Although studies concerning the influence of metals on organic contaminant bioremoval are scarce, it has been demonstrated that those elements are able to inhibit organic contaminant bioremoval, under both aerobic and anaerobic conditions.

Cadmium, chromium (II), copper, mercury and zinc were found to inhibit the biodegradation of 2,4-DME in lake water samples inoculated with either a sediment or an aufwuch (floating algal mat) sample [26]. In the aufwuch samples, mercury revealed to be the most toxic metal, with a microbial inhibitory concentration (MIC) of 2 × 10−3 mg total mercury/L, whereas in the sediment samples, zinc was the most toxic metal with a MIC of 6 × 10−3 mg total zinc/L. Naphthalene (NAPH)-degrading *Burkholderia* sp. was used in a pure culture and reported a MIC of 1 mg solution-phase cadmium/ L [27]. Comparable values of MIC were reported for cadmium (0.629 mg total cadmium/L for aufwuch samples and 0.1 mg total cadmium/L for sediment samples) [26].

Not all studies were focused on the effect of single metals on bioremoval of a single, pure organic pollutant. Benka-Coker and Ekundayo [28] investigated the impact of copper, manganese, lead and zinc on crude oil biodegradation by *Pseudomonas* sp. and *Micrococcus* sp. These authors inferred that the crude oil was mostly reduced by zinc and slightly by manganese. Interestingly, combinations of these metals presented a lesser toxic profile than some single metals. For instance, toxicity of 0.5 mg total zinc/L was mitigated by the addition of 0.5 mg total copper, lead and manganese/L.
