12.8 Conclusions

183

recovery of non-destructive products, the immobilization process is the best-suited

technique. The methods such as encapsulation or entrapment are used to immobi-

lize the biosorbent into particles [14].

Several types of matrices have been considered for immobilization of biopoly-

mers, including polysulfone, calcium alginate, sodium alginate, polyurethane, silica,

and polyacrylamide. It is essential to utilize a suitable matrix for immobilization as

it indicates the biosorbent particle’s chemical resistance and mechanical strength

though it should be feasible and cheap [16]. But using the immobilized biosorbents

has some limitations. It reduces the number of binding sites and also affects the

kinetics of mass transfer [17]. From an aqueous solution, copper, lead, and zinc were

removed using the heat and live immobilized beads of Trametes versicolor within

carboxy methylcellulose [27]. The polyurethane immobilized matrix was used to

eradicate the lead, copper, cadmium, nickel, and reactive yellow 2. In contrast, the

polyacrylamide and calcium alginate immobilized matrix was used to remove the

lead, gold, and uranium [28].

The cell wall of bacteria has a complex structure which plays an important role in

selective sorbent [7]. The Gram-positive bacteria show a higher capacity of sorption

due to thick peptidoglycan layer. The teichuronic and teichoic acids in Gram-positive

bacteria are encapsulated, while the Gram-negative bacteria cell wall constitutes a

thin peptidoglycan layer along with lipopolysaccharide phospholipids [12]. In the

continuous and batch system, the biomass of Arthrobacter species is used to remove

Cu(II) ions with polysulfone and inactivated free heat-immobilized biomass [14].

Hence, we can conclude that the microbes have natural potential toward the removal

of heavy metals and can act as promising biosorbents (Table 12.1).

12.8

Conclusions

Microbes and agri-food waste are considered as promising biosorbents for the

removal of both organic and inorganic contaminants in aqueous solutions. These

wastes comprise high cellulose and lignin contents having good sorption capacity.

Presence of various functional groups such as amine, sulfonate, phenolic, phos-

phodiester, carbonyl amide, etc. on their surface has shown a good percentage

of adsorption efficiency. Their use as biosorbents contributes to minimizing the

environmental impact and disposal cost of agricultural biomass. Various factors

characterizing or controlling its mechanism include binding site availability, sor-

bate concentration, sorbent, coordination, stereochemistry, etc. It is a cost-effective

approach for the removal of heavy metal and other contaminants from different

sources. Further study needs to check the assessment of agri-based biosorbents, the

effect of different conditions such as temperature, pH on removal percentage, and

to check the material reusability.