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Bioremediation for Sustainable Environmental Cleanup

13.2.1 Biosorption

The capacity of biological materials to concentrate heavy metals from wastewater via metabolically

mediated or physico-chemical pathways is called biosorption (Fourest and Roux 1992). The

biological material can bind heavy metals from an aqueous solution. It has the characteristics of

some substances to concentrate and bind some ions from metal-containing water (Volesky 2007).

The best biosorbents that adsorb metals are bacteria, fungi, yeasts and algae. Biosorption is an

alternative rapid method for the removal of pollutants by using non-active and nonliving microbes.

The advantage of this process are as follows:

• No additional nutrient requirement

• biosorbent can be regenerated

• metal recovery

• low cost

• high efficiency



The process of biosorption is affected by various physico-chemical parameters such as

temperature, pH, metal ion’s initial concentration, biosorbent concentration and speed of mixing of

biosorbent and solution. The entire biomass of biosorbent can be treated physically and chemically

before use and can be made economical by recycling and reusing the biosorbent material after

removing the metals. Various bioreactors can be used in biosorption for the removal of metal ions

from large volumes of water or effluents (Kanamarlapudi et al. 2018). When the physico-chemical

interaction of metal ions occurs with cellular compounds heavy metals can be adsorbed.

13.2.2 Bioaccumulation

This is an active metabolic process that relies on the import-storage system. Using transporter

proteins, the system moves heavy metal ions through the lipid bilayer and into the cytoplasm or

intracellular regions. The heavy metals that these entities sequester might exist in particulate forms,

insoluble forms and their by-products. The metal ions are sequestered by metal-binding entities such

as proteins and peptide ligands. The process in which ions of metals accumulate in the living cell

is called bioaccumulation. It is a complex and irreversible process that depends on cell metabolism

and is mainly done by microorganism biomass cultivation. The metabolic process starts in the

organism that activates the intracellular transport system (Srichandan et al. 2014, Gu et al. 2018).

A few examples include; the yeast Pichia stipites can bio-accumulate Cr³⁺ and Cu²⁺ with the highest

absorbance ability of 9.10 mg g^–1 and 15.85 mg g^–1, respectively (Ojha et al. 2015). Aspergillus

niger can eliminate Pb and Cu with the greatest uptake of 34.4 mg g^–1 and 15.6 mg g^–1, respectively

(Srichandan et al. 2015).

13.2.3 Bioleaching

The bioleaching process is also called bio-hydrometallurgy or microbial leaching. The process in

which solubilization of metals occurs from some ores that are not soluble is called bioleaching.

Microorganisms are also used in this process as reducing agents (Mishra et al. 2005). These methods

include membrane separation, solvent extraction, adsorption, ion exchange, selective precipitation

and electrowinning.

Microbial bioleaching is used for the solubilization of various metals viz. cobalt, nickel copper,

zinc and uranium (Rohwerder et al. 2003). For example, in the bioleaching process of arsenopyrite,

the sulfides of arsenic and iron are dissolved. The endured gold is recuperated by the procedure

known as cyanidation.

decreasing amount of biological sludge