**7.1 Removal of cadmium**

Cadmium metal and its ions are the most severe pollutants because they are highly soluble in water as compared to the other toxic metal ions. Therefore, they are easily mobile in soil and have a higher tendency to bioaccumulate. Some of the basic sources that produce cadmium into the environment include solid waste, sewage irrigation, plastics, application of fertilizer, mining, plating on steel, etc. [49]. If the human body is exposed to cadmium for a long time it may result in severe diseases such as bone damage, kidney and lung cancer [50]. Rice husk, rice bran, wheat bran, black gram husk, rice polish, fig leaves, jack fruit, and orange peels, are some of the waste materials that have shown the excellent efficiency towards the removal of Cd. Several studies have been tried using these materials for the eradication of Cd either in their natural form or in the modified form. In addition, potato peels, olive branches, Musa paradisiacal peels, and coconut waste have also been extensively used for the removal of Cd. The adsorption capacity of coconut waste for the removal of Cd (II) was found to be 285.70 mg/g while, the adsorption capacities of other material such as potato peels, olive branches, and Musa paradisiacal peels, were found to be 125, 38.17, 10.0 mg/g, respectively [15]. Therefore, coconut waste has shown the highest adsorption capacity as compared to the potato peels, olive branches, and Musa paradisiacal peels. Some of the waste materials have shown higher adsorption capacity when they were used at acidic pH namely, fig leaves, medlar peels, beans, and jack fruits [51, 52]. Some of the research work that

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*Potential Use of Agro/Food Wastes as Biosorbents in the Removal of Heavy Metals*

has already been done for the removal of Cd using various agricultural wastes is

Chromium is a naturally occurring heavy metal found in the earth's crust. It can be released into the environment either through the natural process or by manmade industrial activities. Industrial activities include wood preservation, tanning, textile manufacturing, pigments, paints, and dyes manufacturing. Chromium is generally found in a number of oxidation states but Cr (III), and Cr (VI) are the largest threat to the environment [42, 84]. In the last two decades, a lot of researches have been done by using various agricultural wastes such as orange, lemon and banana peels, soybean and rice hulls, hazelnut and peanut shells for the removal of chromium metals and ions from different types of wastewater [26, 85]. These waste materials have shown significant chromium removal efficiency as shown in **Table 1**. Other than these waste materials, neem leaves powder, cactus leaves, coconut shell fiber, and pine needles have also shown a promising efficiency in the range 90–100% for the removal of chromium at optimum pH [71]. Wheat brans have showed the highest adsorption capacity for Cr (VI) at 310.58 mg/g whereas, rice bran is a lesser effective adsorbent for the removal of Cr with only up to 50% efficiency [86]. Saw dust, bagasse, rice husk, and mustard oil cake have also been tried by numerous researchers for the removal of chromium and they have reported significant

The removal of nickel is also of great interest due to its high toxicity and its presence in various types of industrial wastewater and effluents. Nickel may enter into the environment by natural and industrial sources. Some of the industrial sources include batteries, coloured ceramics, nickel plating, power plants and trash incinerators [87]. Nickel and its compounds have no taste and odour. Various types of agricultural waste materials such as saw dust of maple, hazelnut and groundnut shell, and waste tea leaves, etc. have been used for the removal of nickel from the effluents either in natural or modified form. These waste materials have shown a very promising and significant efficacy for the removal of nickel. For example, the bagasse of sugarcane showed more than 80% removal efficiency in its natural form for nickel [88]. Similarly, other agro and food wastes such as corncobs, soybeans, cotton seeds, and coir fibers have also been tried by various researchers for the eradication of nickel in their modified form [78, 83]. *Acacia leucocephala*bark has shown the highest adsorption capacity for nickel at 294.10 mg/g and *Cassia fistula* biomass in its natural form has shown the removal efficiency of 99–100% for

Various activities such as finishing of tools, steel and cable reclamation, manufacturing of plastics, formation of cathode ray tubes, ceramics and soldering are the major sources of lead discharge into the environment [89]. Large exposure of lead results in various harmful biological effects and it strongly binds itself with the particles of oil, sediments, and sewage sludge due to which its removal has gained much attention. Various types of agro/food waste materials have been used for the removal of lead such as orange peel, chitosan, rice husk, walnut shells, peanut, lemon grass *(Cymbopogoncitratus)*, groundnut (*Arachishypogaea)*,

*DOI: http://dx.doi.org/10.5772/intechopen.94175*

presented in **Table 1**.

**7.2 Removal of Chromium**

efficiencies in literature [85].

**7.3 Removal of nickel**

nickel [15, 73].

**7.4 Removal of lead**

has already been done for the removal of Cd using various agricultural wastes is presented in **Table 1**.
