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

showed a higher capacity of sorption, while in contrast, algal species were widely

reported for the removal of metal cations [3]. The process of biosorption could reduce

the costs of total treatment, operating cost, and capital cost by 28%, 36%, and 20%,

respectively, compared to the exchange system of convenient ion. In 1990, various

biosorbents at commercial scale were anticipated for removing the heavy metal ions,

namely, AlgaSORB, AMTIBIOCLAIM, and BIOFIX [4].

The heavy metals are considered to be major pollutants in the waste effluents

discharged by the various industries [3]. Heavy metal pollutants cause toxicity

to humans as well as to the ecosystem as they are non-biodegradable. The lead,

chromium, zinc, mercury, and cadmium metals are the majorly used compounds

by the industries, and according to United States Environmental Protection Agency

(USEPA), they are toxic (EPA). Since, these pollutants can lead to many diseases

in living beings and affects the cardiovascular system, central nervous system,

and gastrointestinal tract [3]. Hence, it is essential to regulate pollutants discharge

by treating industry effluents. There are several ways to use biological wastes,

i.e. byproducts of agriculture and urban area, to adsorb these heavy metals [4].

For the purification of water, lignocellulosic biomass is considered as a potential

adsorbent as well as their raw materials produce the carbons in the activated form

[5]. Generally, the byproducts of the vegetables such as cauliflower and broccoli

from the agri-food industries offer to be significant biomass for preparing low-cost

adsorbents [6]. A substantial amount, around 37.2 million tons of agri-waste

biomass, is annually generated worldwide. A probable alternate to adjust these

aggravated agri-food industry byproducts can be to use them as raw adsorbents

and their transformation into carbon-based materials to control environmental

pollution and other applications. This approach could contribute to a reduction in

the disposal costs and environmental impact of vegetable waste management [7].

The advantages of using these agri-wastes for the biosorption process include

multiple benefits. Along with the treatment of wastewater in large volumes by

rapid kinetics, it offers the cheap natural biomaterials with high selectivity for the

recovery and removal of heavy metals, along with capabilities to manage the wastes

including numerous heavy metals, less requirement of additional reagents, and

inexpensive operation cost. Various isotherms are used to describe the kinetics

of biosorption. It determines the adsorbent feasibility and also represents the

relationship of equilibrium [8].

The agri-food waste-based adsorbents are characterized by their good uptake

capacities in many studies. The textile dye RR198 was removed using the pomace

residues of untreated olive from the wastewater effluents. The solid residues of

olive oil adsorb the zinc ion from the aqueous solution. For the removal of this

dye, biosorption method was endothermic and spontaneous [9]. The biosorption

capacity of heavy metals using the banana peels was observed to show adsorption

efficiency of copper and lead ions, 2.18 and 5.71 mg/g, respectively [10]. The

cauliflower leaves were used to produce the magnetic composite of clay biochar

and used for the removal of oxytetracycline from the aqueous medium with the

33.31 mg/l capacity of adsorption [11].