**4.1. Removal of organic pollutants**

Biosorption acquires meaning for the removal of hazardous substances. It can be used as an individual separation process or may be a part of others, biological processes. Aksu, in the review paper [39], deals with the application of biosorption to remove organic pollutants. Among the studied pollutants are pesticides, phenols that are toxic and persistent in the environment.

Various types of pesticides are used in agriculture. Some of them are persistent, have mutagenic and carcinogenic effects, and are generally toxic. Suitable sorbent for removing them appears to be activated carbon. Its disadvantage is the high price. Regeneration of granular activated carbon is also costly.

This has motivated researchers to explore the possibility of using alternative materials that originate in nature or are the waste of other processes, peat, soil, wood, eucalyptus bark, rice husk, chitin, fly ash, or surplus activated sludge. These are relatively inexpensive materials but are usually characterized by low adsorption power values. This disadvantage can be compensated by larger amounts of adsorbent [40, 41]. An alternative for the recovery and/or environmentally acceptable disposal of pollutants could be, passive adsorption of pollutants from aqueous solutions using a renewable non-living microbial mass. The specific surface properties of bacteria, fungi, yeasts, and algae allow the adsorption of various types of pollutants from solutions. More advantageous is the use of inactivated microorganisms. They are not dependent on creating conditions for maintaining metabolic function, including eliminating the effects of toxic substances. They can be stored for a longer period, easily regenerated and reused [39].

The biosorption mechanism on inertial biomass is influenced by the biomass itself, the properties of its surface characteristics, the physical and chemical properties of the adsorbed substances, their mutual affinities, and experimental conditions (pH, temperature, ionic strength, existence of competing organic substances or inorganic ligands in solution).

Conversely, due to the fact that hydrophobic organic pollutants show a high tendency to accumulate on microbial cells or sludge, living biomass can be used to remove very low concentrations of hazardous organic substances from wastewater [42, 43].

Most dyes are of synthetic origin. They are characterized by an aromatic structure, greater stability, and a worse biodegradability. They can affect the processes of photosynthesis in the aquatic environment to toxicise the aquatic ecosystem [44, 45]. Research results [44–46] show that there is a wide range of microorganisms, including bacteria, fungi, and algae, which are capable of biodegradation or bioaccumulation of azo dyestuffs in wastewater by anaerobic/ aerobic processes.

cells, the biosorption capacity varied within a wide range. Interestingly, however, it was found that the biosorption capacity of different biomass samples depended directly on the amount of total organic carbon released during the contact of biomass with the pollutant. However, this phenomenon is not elucidated, it can only be assumed that the biosorption capacity increases with the growing proportion of cells destroyed in the medium, which correlates with the total organic carbon content released into the medium. Cell fragments have a larger surface and thus a higher sorption capacity [38]. The authors further found that the biosorption capacity of active and deactivated (inactive/dead) biomass is almost the same for highly biodegradable pollutants.

Biosorption acquires meaning for the removal of hazardous substances. It can be used as an individual separation process or may be a part of others, biological processes. Aksu, in the review paper [39], deals with the application of biosorption to remove organic pollutants. Among the studied pollutants are pesticides, phenols that are toxic and persistent in the

Various types of pesticides are used in agriculture. Some of them are persistent, have mutagenic and carcinogenic effects, and are generally toxic. Suitable sorbent for removing them appears to be activated carbon. Its disadvantage is the high price. Regeneration of granular

This has motivated researchers to explore the possibility of using alternative materials that originate in nature or are the waste of other processes, peat, soil, wood, eucalyptus bark, rice husk, chitin, fly ash, or surplus activated sludge. These are relatively inexpensive materials but are usually characterized by low adsorption power values. This disadvantage can be compensated by larger amounts of adsorbent [40, 41]. An alternative for the recovery and/or environmentally acceptable disposal of pollutants could be, passive adsorption of pollutants from aqueous solutions using a renewable non-living microbial mass. The specific surface properties of bacteria, fungi, yeasts, and algae allow the adsorption of various types of pollutants from solutions. More advantageous is the use of inactivated microorganisms. They are not dependent on creating conditions for maintaining metabolic function, including eliminating the effects of toxic substances. They can be stored for a longer period, easily regenerated

The biosorption mechanism on inertial biomass is influenced by the biomass itself, the properties of its surface characteristics, the physical and chemical properties of the adsorbed substances, their mutual affinities, and experimental conditions (pH, temperature, ionic strength,

Conversely, due to the fact that hydrophobic organic pollutants show a high tendency to accumulate on microbial cells or sludge, living biomass can be used to remove very low con-

existence of competing organic substances or inorganic ligands in solution).

centrations of hazardous organic substances from wastewater [42, 43].

**4. Research and applications of biosorption**

**4.1. Removal of organic pollutants**

activated carbon is also costly.

environment.

8 Biosorption

and reused [39].

For the modeling and optimization of processes using sorption on the activated sludge, the necessary is knowledge about the sorption of organic matter to the sludge. Modin et al. [47] compares primary, anaerobic, and aerobically activated sludge as biosorbent materials. Biosorptive capacity values were determined, process kinetics was studied, and some characteristics of sorbed organic matter were studied. Biosorption of dissolved organic substances occurred almost immediately. This was followed by a slower process that corresponded to firstorder kinetics. Biosorption of undissolved particles also corresponded to first order kinetics. However, there was no immediate sorption, but the particles were released during mixing.

Biosorption is used for wastewater treatment since the beginning of the last century, when the activation process was discovered. Controlled withdrawal of excess sludge together with significant participation of biosorption a bioaccumulation processes enable intensification of organic pollutants, nitrogen, and phosphorus removal. Bioaccumulation is usually an active process that is part of the metabolism of microorganisms. Biosorption is a passive process of adsorbing pollutants on the surface of microorganism cell walls. This leads to a decrease in the concentration of these substances in the purified water. However, such contamination remains a part of the activated sludge and its re-release to the environment is dependent on further treatment with the excess sludge produced, especially if the biosorption of these substances is reversible.

An increasingly serious challenge is dangerous (organic) and so-called emerging pollutants, e.g. pesticides, estrogens, personal care products, or pharmaceuticals. These can be removed in the wastewater treatment plant by biotic and abiotic processes, or they can pass through the sewage treatment plant to the recipients without any significant change. In the context of minimizing the production of excess sludge, its disintegration prior to the process of biological stabilization and degradation of biosorbable pollutants on activated sludge, the combined processes of biosorption and chemical oxidation, e.g. using ozone.

The solubility of the pollutant is an important property affecting biosorption. The inverse relationship between water solubility and accumulation of organic molecules with biomass was found [9]. In general, the different types of biomass observed had a greater biosorption capacity for less soluble pollutants. Organic molecules accumulate better in microbial biomass, the higher the biomass-water distribution coefficient (octanol-water model system), but as already mentioned above, there is no direct correlation between biosorbent capacity and lipid content in biomass.

If the contaminant dissociates in the aqueous phase (on a weak acid or a weak base), sorption of the dissociated and non-dissociated forms can take place with different sorption coefficient values for both forms [15]. The effect of the initial concentration of the pollutant on the rate of biosorption was monitored. After 10-fold increase in the initial concentration of the pollutants studied (lindane pesticides and diazinone), the rates of biosorption of these substances on activated sludge were higher for higher concentrations of pollutants.

Mustapha and Halimoon [19] examined the microorganisms and mechanisms of heavy metal

Introductory Chapter: Biosorption

11

http://dx.doi.org/10.5772/intechopen.78961

Bacterial biosorption is mainly used to remove pollutants from wastewater contaminated by pollutants that are no1t biodegradable, such as metal ions and dyes [19]. Rats are efficient and inexpensive biosorbents, because the requirement for algal nutrition is low. Based on a statistical analysis of algae potential in biosorption, algae were reported to absorb about 15.3–84.6%, which is higher than other microbial biosorbents. All types of brown algae were known to have a high absorption capacity. The metal ion biosorption occurs on the cell surface using the ion exchange method. Brown marine algae have the ability to absorb metals through chemical moieties on their surface such as carboxyl, sulfone, amino, as well as sulfhydryl [19].

The use of fungi as a biological sorbent has been shown to be an effective material, and is also one of the cost-effective and environmentally friendly methods that serve as an alternative to the chemically bonded processing process. The ability of many types of fungi to produce extracellular enzymes to assimilate complex carbohydrates for previous hydrolysis causes the degradation of various degrees of pollutants. Compared to yeast, fibrous fungi are less sensitive to nutrient sweeps, aeration, pH, temperature, and have a lower content of nuclei in

Microbial biomass is one of the cheap and effective biosorbents for removing heavy metals from solutions. The biosorption process has many attractive properties including the removal of metal ions in a relatively wide range of pH and temperature. Many researchers have studied the biosorbent performance of various microbial biosorbents that provide good arguments for introducing biosorption technologies for removing heavy metals from solutions, as well as

The large occurrence and presence of micropollutants (MPs) in the aquatic environment is one of the major challenges worldwide. For example, in 2012, some 143,000 compounds were registered on the European market, many of which at some point in their life cycle would end up in the aquatic environment. Most of them are not removed or transformed into conventional wastewater treatment plants (WWTPs), they can persist in the aquatic environment or create new chemicals by reaction with humic substances and sunlight, and they can be

Although present in almost undetectable (ppb; part per bilion) concentrations, their presence in the aquatic environment is associated with various deleterious effects in organisms such as

There is no legal regulation for removing MPs in WWTPs. However, there are some (EU) regulations that set limit values for certain substances that have specific MP properties, pesti-

MP can be divided into several categories such as pharmaceuticals personal care products (PPCP), household chemicals and industrial chemicals. A comprehensive list of 242 chemicals

understanding the mechanism responsible for biosorption [19].

biosorption in the environment.

biomass [50, 51].

**4.3. Removal of micropollutants**

bioactive and can bioaccumulate [52–56].

estrogenicity, mutagenicity, and genotoxicity [57].

cides, lindane, nonylphenol, and synthetic hormones [58] in water.

It can be assumed that in a system containing a mixture of several pollutants of a similar nature, the biosorption capacity of the individual components of the mixture will be affected by the concentration of the other substances in the mixture. A reduction in biosorbent capacity of tetrachloroethane on the *Rhizopus arrhizus* biomass has been shown to be up to 14% in the presence of the same concentration of trichloroethane [13]. Biosorption is usually an exothermic process, so biosorption capacity usually increases with decreasing temperature. However, the change in temperature does not significantly affect the rate of biosorption [8].

Simjonato et al. [9] studied the process of adsorption of blue remazol and black remazol five dyes with chitin and chitosan, which they performed in the column and an aqueous suspension. The results show that better results were obtained in the column with arthritis than in the chitin-packed column. Comparing the results measured in the column and suspension results in better suspension results. A very good description of Langmuir isothermal experimental values was obtained, with the difference between the measured and calculated adsorption capacity values being insignificant.

Biosorption of hazardous pollutants is a suitable technology for removing dyestuffs from municipal and industrial wastewater. Various low-cost biosorbents, such as, for example, biomass of algae, yeast, fungi, vegetable waste, fiber, fruit waste, chitosan, and agricultural waste were studied [48].

### **4.2. Removal of heavy metals**

Biosorption and bioaccumulation can also be applied to remedy environments contaminated with heavy metals as complementary methods to currently used physical and chemical methods. It was found that removal of heavy metals from the environment with biotechnological methods should consider a number of physicochemical factors such as temperature, pH, contact time of biomass, and a solution containing metals, concentration and age of biomass, and toxicity when living microorganisms are applied. Improving the efficiency of removal of metals can be performed through physical and chemical modifications and immobilization of biomass. The most frequently applied reactors include stirred tank reactors, fixed-bed, reactors and fluidized-bed reactors [49].

In the process of biosorption, ions of metals are adsorbed on the surface of a sorbent. Biosorption is a metabolically passive process that uses dead biomass. Biosorption is the first step of bioaccumulation [49].

Environmental pollution of heavy metals is one of the most serious environmental problems. Various biosorbents such as fungi, yeast, bacteria, and algae are used to remove them. These biomaterials are considered to be cost-effective for high-volume and low-heavy wastewater treatment (from 1 to 100 mgl−1). The promising biomaterials for heavy metal removal include *Saccharomyces cerevisiae* fungus. This fungus is commonly used in food and beverage production. Low-cost media is sufficient to cultivate it. It is a by-product/waste from the fermentation industry.

Mustapha and Halimoon [19] examined the microorganisms and mechanisms of heavy metal biosorption in the environment.

Bacterial biosorption is mainly used to remove pollutants from wastewater contaminated by pollutants that are no1t biodegradable, such as metal ions and dyes [19]. Rats are efficient and inexpensive biosorbents, because the requirement for algal nutrition is low. Based on a statistical analysis of algae potential in biosorption, algae were reported to absorb about 15.3–84.6%, which is higher than other microbial biosorbents. All types of brown algae were known to have a high absorption capacity. The metal ion biosorption occurs on the cell surface using the ion exchange method. Brown marine algae have the ability to absorb metals through chemical moieties on their surface such as carboxyl, sulfone, amino, as well as sulfhydryl [19].

The use of fungi as a biological sorbent has been shown to be an effective material, and is also one of the cost-effective and environmentally friendly methods that serve as an alternative to the chemically bonded processing process. The ability of many types of fungi to produce extracellular enzymes to assimilate complex carbohydrates for previous hydrolysis causes the degradation of various degrees of pollutants. Compared to yeast, fibrous fungi are less sensitive to nutrient sweeps, aeration, pH, temperature, and have a lower content of nuclei in biomass [50, 51].

Microbial biomass is one of the cheap and effective biosorbents for removing heavy metals from solutions. The biosorption process has many attractive properties including the removal of metal ions in a relatively wide range of pH and temperature. Many researchers have studied the biosorbent performance of various microbial biosorbents that provide good arguments for introducing biosorption technologies for removing heavy metals from solutions, as well as understanding the mechanism responsible for biosorption [19].
