**6.2. Agricultural waste materials**

• high affinity for metals (biosorption capacity)

The use of different materials as biosorbents is explained in detail:

**Biosorbate Biosorption** 

Cd (II), Fe (II)

Cationic dye (Basic blue 41)

(II), Pb (II), Cd (II)

**Table 2.** Use of industrial byproducts for biosorption of metal ions.

**capacity/ efficiency (mg/g or %)**

Cr (VI) 54.65 mg/ga\* Langmuir -OH, -SO<sup>3</sup>

13.7, 13.9, 14.1, 14.8 mg/ga\*

• easy desorption of the adsorbed metal ions and possible multiple reuse of the biosorbent

Low-cost materials from different industries have been used for the treatment of wastewater. Many industries, especially food industries, dispose large quantities of waste and byproducts. The cost for disposal is sometimes challenging. Using these zero-cost industrial wastes as effective biosorbents for treating wastewater effluents can solve the dual problem (waste disposal and effluent treatment) [57]. Waste byproducts produced from different industries, that is, steel, aluminum, paper, fertilizer, food, mining, and pharmaceuticals, can be used as biosorbents. It is estimated that the use of biosorbents from industrial waste will grow at an annual rate of 5% [58]. **Table 2** summarizes the type and source of the biosorbent, type of biosorbate targeted, and maximum biosorption capacity/biosorption efficiency of various

> **Isotherm model**

Pb (II) 97.64%, 93%a\* Langmuir [61]

111 mg/ga\* Freundlich Ion

Zn (II) 10.0 mg/ga\* Freundlich [64]

Pb 22 mg/ga\* Precipitation [65]

Indicates batch biosorption experiments at laboratory scale.

**Functional groups involved**

C-O, -CN

Freundlich Ion exchange

96.4%, 93.8%a\* [60]

,

**Mechanism Reference**

exchange or complexation

and physicchemical adsorption

[59]

[62]

[63]

• low economic values (low cost) • availability in large quantities

**6.1. Industrial byproducts**

industrial biosorbents.

**Source of biosorbent**

Local tea factory

Juice and jam industry

Antibiotic production complex

Sludge Paper mill Ni (II), Cu

Iron foundry industry

Indicates the dry weight of the biosorbent, \*

industry

Food canning processes

**Type of biosorbent**

78 Biosorption

Tea industry waste

Sugar industry waste (bagasse)

Peach and apricot stones

Antibiotic waste

Waste green sands

a

Fly ash Cement

A great deal of interest in the removal of pollutants from wastewaters has focused on the use of agricultural waste/byproducts as biosorbents. Agricultural wastes especially those with high percentage of cellulose and lignin contains polar functional groups like amino, carbonyl, alcoholic, phenolic, and ether groups having high potential for metal binding [66]. These groups donate a lone pair of electrons and form complexes with metal ions in the solution [67]. Due to their unique chemical composition (the presence of hemicellulose, lipids, lignin, water hydrocarbons, simple sugars, and starch having a variety of functional groups) and availability, the use of agro-wastes seems to be a viable option for heavy metal remediation. Grapefruit peel was reported to biosorb cadmium and nickel with a biosorption capacity of 42.09 and 46.13 mg/g from aqueous solutions. Equilibrium data showed the better fit with the Freundlich isotherm model with the ion exchange mechanism. FTIR analysis showed that the carboxyl and hydroxyl groups are mainly involved in the biosorption of metal ions [68]. The bark powder of *Acacia leucocephala* was used as a low-cost biosorbent for the removal of Cu (II), Cd (II), and Pb (II) with the biosorption capacity of 147.1, 167.7, 185.2 mg/g, respectively, from the aqueous solution. The biosorption mechanism involved is physico-chemical adsorption involving carboxyl, hydroxyl, and amine groups present on the surface of the biosorbent for biosorption. The Langmuir model shows the best fit than the Freundlich model [69]. **Table 3** summarizes the type of the biosorbent, biosorbate, and maximum biosorption capacity of the different agriculture wastes as biosorbents.

#### **6.3. Microbial biosorbents**

Microorganisms capable of tolerating unfavorable conditions evolved their use as biosorbents in the removal of metal ions from wastewaters. They include bacteria, yeast, algae, and fungi. Experiments focused on the use of dead and or living microorganisms offer options for the type of remediation to perform [82]. However, the use of dead microbial biomass for the binding of metal ions has been preferred over living biomass because of the absence of the requirement of nutrients and monitoring BOD and COD in effluents. Hence, the use of dead biomass is economical [83]. These biosorbents can effectively sequester metal ions in the solution and decrease the concentration from the ppm to ppb level efficiently; therefore, they are considered as ideal candidates for the treatment of complex wastewaters with high volume and low concentration of metal ions [84]. A large quantity of materials of microbial origin has been investigated as biosorbents for the removal of metal ions extensively [85]. Reports do not include the use biomass of any pathogens for water treatment. Most of the microbial groups are composed of a large number of functional groups which indicate their potential as biosorbents. Some studies which identified the functional groups involved in the biosorption of metal ions are given in **Table 4**.

#### *6.3.1. Algae as biosorbents*

The use of algae as a biosorbent has received focus due to the scarce requirement of nutrients, high sorption capacity, plentiful availability, high surface area to volume ratio, less volume of sludge to be disposed, and the potential for metal regeneration and recovery. They are considered as both economic and ecofriendly solutions for wastewater treatment [92]. Different groups of algae differ in the composition of the cell wall. The cell wall of brown algae mainly contains three components: cellulose (structural support), alginic acid (a polymer of mannuronic and


**Biosorbent Biosorbate Functional groups Reference** *Mucor rouxii* Cu (II) Amino, carboxyl, phosphate [86] *Streptomyces rimosus* Pb (II) –COO, –C–O, –NH, –C=O, –OH [87] *Maugeotia genuflexa* As (III) Carboxyl, hydroxyl, amide [88] *Rhizopus cohnii* Cd (II) Carboxyl, amino, hydroxyl [89] *Oedogonium hatei* Ni (II) Carboxyl, phosphate, amide, hydroxide, thiol [90] *Bacillus subtilis* Au (III) Amino, carboxyl, hydroxyl [91]

> **Isotherm model**

*Spirulina platensis* Cu (II) 90.6%a\* [99]

Ar (III) 57.48 mg/ga\* Langmuir Carboxyl,

and Freundlich

*Spirulina platensis* Cu 67.93 mg/ga\* [100]

*Laminaria japonica* Zn (II) 91.5 mg/g\* [37]

Cr (VI) 32.63 mg/ga\* Freundlich Ion exchange [97]

**Functional groups involved**

Application of Biosorption for Removal of Heavy Metals from Wastewater

http://dx.doi.org/10.5772/intechopen.77315

81

hydroxyl, C=O, C–O

–OH, –CH, C=O, –CN, =C–N

hydroxyl, amide

C–O, –S=O

50, 32.5, 46.2 mg/ga\* Freundlich [102]

amino, amide, hydroxyl

carboxyl

Indicates batch biosorption experiments at laboratory scale.

46.51, 14.71 mg/ga\* Langmuir Physical adsorption

**Mechanism Reference**

chemisorption [98]

Ion exchange [88]

Ion exchange and complexation

or ion exchange

Chemisorption and Ion exchange

[90]

[101]

[95]

[103]

[51]

**Table 4.** Functional groups of microbial biomass involved in biosorption of metals.

**capacity/efficiency (mg/g or %)**

*Ulva lactuca* sp. Cd (II) 35.72 mg/ga\* Langmuir Amido,

*Palmaria palmate* Cr (VI) 33.8 mg/ga\* Langmuir –NH, C=O,

*Spirogyra* sp Pb (II) 140 mg/ga\* Langmuir Carboxyl,

*Ecklonia* sp Cr (VI) 60%a\* Amino and

*Oedogonium hatei* Ni 40.9 mg/ga\* Langmuir

**Biosorbent type Metal ion Biosorption** 

*Fucusvesiculosus* 42.6 mg/ga\*

(II)

Indicates the dry weight of the biosorbent, \*

**Table 5.** Algal biomass used for biosorption of metals.

(II), Cd (II)

*Enterobacter* sp. Pb (II), Cu

*Cladophora* spp Pb (II), Cu

*Stoechospermum marginatum*

*Maugeotia genuflexa*

a

a Indicates the dry weight of the biosorbent, \* Indicates batch biosorption experiments at laboratory scale.

**Table 3.** Use of agricultural wastes for biosorption of metal ions.

guluronic acid with its corresponding salts), and sulfated polysaccharide with high contents of carboxyl groups that are involved in the process of the biosorption of metals. Red algae have received attention for biosorption due to the presence of sulfated polysaccharide made of galactans (having high contents of hydroxyl and carboxyl groups). Green algae contain cellulose with a high percentage of protein bound to polysaccharides which contain many functional groups like amino, sulfate, hydroxyl, and carboxyl [93]. Hence several authors focused on the removal of metal ions using algal biomass from contaminated water resources. It has been reported that algae can biosorb about 15.3–84.6% which is higher compared to the other microbial biosorbents [94]. The biosorption capacity of green algal species, *Spirogyra* sp. and *Cladophora* sp. for the removal of Pb (II) and Cu (II) from aqueous solutions, was studied. The capacity of *Spirogyra* was 87.2 and 38.2 mg/g and for that of *Cladophora* was 45.4 and 13.7 mg/g


**Table 4.** Functional groups of microbial biomass involved in biosorption of metals.


a Indicates the dry weight of the biosorbent, \* Indicates batch biosorption experiments at laboratory scale.

**Table 5.** Algal biomass used for biosorption of metals.

guluronic acid with its corresponding salts), and sulfated polysaccharide with high contents of carboxyl groups that are involved in the process of the biosorption of metals. Red algae have received attention for biosorption due to the presence of sulfated polysaccharide made of galactans (having high contents of hydroxyl and carboxyl groups). Green algae contain cellulose with a high percentage of protein bound to polysaccharides which contain many functional groups like amino, sulfate, hydroxyl, and carboxyl [93]. Hence several authors focused on the removal of metal ions using algal biomass from contaminated water resources. It has been reported that algae can biosorb about 15.3–84.6% which is higher compared to the other microbial biosorbents [94]. The biosorption capacity of green algal species, *Spirogyra* sp. and *Cladophora* sp. for the removal of Pb (II) and Cu (II) from aqueous solutions, was studied. The capacity of *Spirogyra* was 87.2 and 38.2 mg/g and for that of *Cladophora* was 45.4 and 13.7 mg/g

**Type of biosorbent**

80 Biosorption

Cabbage, cauliflower waste

Sugarcane bagasse

Green coconut shell (powder)

Papaya wood Cd (II), Cu

Iris peat Cu (II), Ni (II)

Date pit Cu (II),Cd (II)

> Cu (II), Cd (II)

Indicates the dry weight of the biosorbent, \*

**Table 3.** Use of agricultural wastes for biosorption of metal ions.

Cassava peelings

a

(II), Zn (II)

Cr (III), Cr (VI), Cd (II),

**Biosorbate Biosorption** 

Rice husk Ni (II) 51.8%a\* Langmuir

**capacity/efficiency (mg/g or %)**

**Isotherm model**

Pb (II) 60.57, 47.63 mg/ga\* Langmuir -OH, C=O chemisorption [71]

Ni (II) 2 mg/ga\* Langmuir Ion exchange [72]

97.8%, 94.9%, 66.8%a\* Langmuir [73]

90%, 86%, 99%a\* Freundlich Ion exchange [74]

N–H, C–N, C–O, S–O

17.6, 14.5 mg/ga\* Langmuir [79]

127.3, 119.6 mg/ga\* Langmuir Ion exchange [81]

Indicates batch biosorption experiments at laboratory scale.

35.9, 39.5 mg/ga\* Freundlich –C=C, –C=N Hydrogen bonding

and Freundlich

Wheat shell Cu 99%a\* Langmuir [75] Peanut hull Cu 12 mg/ga\* Langmuir Ion exchange [76]

Barley straws Cu, Pb 4.64, 23.20 mg/ga\* Langmuir Chemisorption and

Neem bark Pb 86.7%a\* Freundlich O–H, C–O,

**Functional groups involved**

–OH, C=O, C–H

**Mechanism Reference**

ion exchange

and electrostatic attraction

Ion exchange [78]

[70]

[77]

[80]

for Pb (II) and Cu (II), respectively. The biosorption process showed the better fit with the Langmuir model, and the mechanism involved for biosorption is physical or ion exchange [95]. A marine algae *Sargassum filipendula* was used as a biosorbent for Cu (II) and Ni (II) ions with biosorption capacity of 1.324 and 1.070 mmol/g. An ion exchange mechanism was involved in biosorption with the Langmuir isotherm model showing the better fit [96]. **Table 5** summarizes some more examples of algae as biosorbents.
