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12 Microbes and Agri-Food Waste as Novel Sources of Biosorbents

properties, targeted metal characteristics of chemical, coordination, and stereo-

chemical, binding sites availability, and sorbent and sorbate concentration [9]. The

agriculture waste enriched with lignin and cellulose content has high efficiency

to bind with the metal as it contains the functional polar groups, which donate

the lone pair to the metal ions and form the complex with them [8]. Agriculture

wastes are readily available and have a unique chemical composition; therefore, it a

feasible option for the removal of heavy metals.

12.3

Application of the Biosorption Processes

12.3.1

Removal of Inorganic Pollutants

Numerous biosorbents have been used in biosorption processes that are utilized

for wastewater treatment and in the removal of harmful heavy metals that became

the subject of focus in the present-day time [9]. Biosorption processes, for instance,

just like electrostatic connections, ion exchange, chelation, immobilization, and

compartmentation of metals, generally rely upon the physicochemical associa-

tion between functional groups on the cell surface and metals [12]. Maximum

biosorption methods have been employed on various microorganisms, primar-

ily microalgae, bacteria, and fungi and with noxious heavy metals [13]. Waste

biomasses of Pseudomonas aeruginosa and Enterobacter cloacae removed around

72% of Pb as biosorbents [14]. Biosorption methods cause the progression of nutrient

independently and quicker, thus correspondingly enhance the metal absorption.

Furthermore, biosorbents such as tannin resins also perform as reducing agents

and are helpful in the accumulation of high content of important metals, such

as gold, platinum, and vanadium, and considerable degradation of anionic water

pollutants, for instance, chromium (Cr⁶⁺) [13]. Bio-Recovery Systems Inc. company

in the United States established a biosorbent Alga SORB^TM from an algal species

Chlorella vulgaris on silica gel polymer matrix, which significantly eliminated metal

ions, being used as an alternative of commercial ion exchange resins. Therefore,

this biosorbent is utilized by several nuclear sites to decontaminate the water from

mercury and uranium [12]. Biosorption method is not only utilized to eliminate

heavy metals but also practised for the heavy metal retrieval and cell walls of

organisms biomass, which are used for biosorption, primarily made up of carbo-

hydrates, lipids, and proteins that have various functional groups, for instance,

aldehyde (–CHO), carboxyl (COOH), sulfate (SO²⁻

4 ^{), phosphate (PO3−}

4 ^{), and amino}

groups for association with these heavy metals [13]. Calcined rice husks exhibited

greater ability for eradicating Pb²⁺ and Cu²⁺, where higher biosorption for these

metals was observed to be 0.0530 and 0.0573 mmol of metal/g in calcined rice

husk, respectively, in batch equilibrium experiments and kinetic sorption method.

The Langmuir model well signified the adsorption isotherms of Pb²⁺ and Cu²⁺.

Biosorption potential of peanut husk charcoal, fly ash, and natural zeolite was

studied for the treatment of wastewater by the exclusion of cationic Cu²⁺ and Zn²⁺

metal ions. It was found that these biosorbents significantly removed Cu²⁺ and