**6.1 Kinetic study of the Pb2+ adsorption**

The evolution of equilibrium concentration as a function of time is shown in **Figure 9**. The kinetic study of the adsorption has shown that more than 50% of the initial amount of Pb2+ is absorbed on the Ccre before the time is reached 5 minutes. The concentration of Pb2+ decreases rapidly in a few minutes, from 100 mg/l to a concentration of less than 1 mg/l for the Ccre. A pseudo-equilibrium with the surface of the supports appears to be reached, the equilibrium times are estimated at about 18 minutes for the Ccre, 30 minutes for the Clan, and 60 minutes for the Ccra.

The study conducted by Melchor [39] on the adsorption of Pb2+ on chitin extracted from crabs has shown that this is a reaction of the first order and gives an equilibrium time t = 44 minutes relatively low compared to the time found for the raw chitin 60 minutes; this implies that the mineral part plays a role in adsorption kinetics.

**249**

**Figure 10.**

*removal efficiency of Pb (II).*

*Sustainable Treatment of Heavy Metals by Adsorption on Raw Chitin/Chitosan*

After equilibrium, more than 80% of the initial amount of Pb2+ (100 mg/l) is adsorbed on the Ccra, whereas only 41% of the initial amount of Pb2+ is adsorbed on pure chitin [39]; this shows that the mineral part of the crab shells plays a role in the retention of Pb2+. The percentages of adsorption as a function of time are in good

According to **Figure 10a**, the curve representing the variation of the quantity of Pb2+ adsorbed on the Ccra as a function of residual concentration is linear up to 80 mg/g, whereas for Ccre and Clan, the adsorption obeys Henry's law in the range

Pb adsorption on the Ccre is peculiar, which is a very important slope that shows

The calculation of the percentage of average abatement of Pb2+ (**Figure 10b**), for several adsorption tests confirms these results. So Pb is more retained by the Ccre. The concentration of Pb from 100 mg/l to only 0.37 mg/l for 10 minutes is a remarkable retention with a yield of 99.63%. From **Table 7**, the maximum

*(a) Experimental isotherms of Pb (II) adsorption on raw chitin, (b) effect of the origin of crude chitin on the* 

Ccre exhibits a strong affinity toward this metal. This feature was also noticed during the adsorption of Pb2+ on the zeolites [63, 64] and during adsorption on clinoptilolite [65]. Pb adsorption on all three supports perfectly the Freundlich model in comparison with the adsorption of Pb on activated carbon [66], which

*DOI: http://dx.doi.org/10.5772/intechopen.88998*

agreement with the results obtained by Yang [37].

*Kinetic study of Pb (II) adsorption on raw chitin.*

(10–100 mg/l).

**Figure 9.**

gives a capacity of 1.046 mg/g.

**6.2 Study of Pb2+ adsorption isothermals on raw chitin**

*Sustainable Treatment of Heavy Metals by Adsorption on Raw Chitin/Chitosan DOI: http://dx.doi.org/10.5772/intechopen.88998*

#### **Figure 9.**

*Trace Metals in the Environment - New Approaches and Recent Advances*

Elimination percentages reach 98% for Ccra and 97% for Clan. These results are compared to those found for mineral surfaces such as Al2O3, zeolite, and albeit

*(a) Experimental isotherms of Zn (II) adsorption on raw chitin (b) Effect of the origin of raw chitin on the* 

Ccre 10.82 0.63 0.99 Ccra 23.74 1.72 0.99 Clan 11.49 1.99 0.99

Linear adsorption transforms according to the Freundlich model—**Table 6** show that Zn has a great affinity for hard shells. The Freundlich model makes it possible

The perfectly applicable Freundlich model shows that the adsorption capacity of

According to the isotherms of **Figure 8a**, the percentage of adsorption decreases when the concentration of Zn2+ increases, the same remark was recorded by Spark and Bourg [17, 62] during the study of Zn adsorption on kaolinite and clay mineral.

The evolution of equilibrium concentration as a function of time is shown in **Figure 9**. The kinetic study of the adsorption has shown that more than 50% of the initial amount of Pb2+ is absorbed on the Ccre before the time is reached 5 minutes. The concentration of Pb2+ decreases rapidly in a few minutes, from 100 mg/l to a concentration of less than 1 mg/l for the Ccre. A pseudo-equilibrium with the surface of the supports appears to be reached, the equilibrium times are estimated at about 18 minutes for the Ccre, 30 minutes for the Clan, and

The study conducted by Melchor [39] on the adsorption of Pb2+ on chitin extracted from crabs has shown that this is a reaction of the first order and gives an equilibrium time t = 44 minutes relatively low compared to the time found for the raw chitin 60 minutes; this implies that the mineral part plays a role in adsorption kinetics.

> 0.95. In this case, the adsorption is hydropho-

**Kf mg/g 1/n R**

whose percentages of elimination do not go beyond 30% [10].

Zn2+ on the Ccra is twice as large as that on the Ccre (**Table 6**).

bic in nature through Van Der Waals interaction and hydrogen bonds.

*Values of Freundlich parameters deduced from Zn2+ adsorption isotherms on the raw chitin.*

to describe the adsorption of Zn: R<sup>2</sup>

**Figure 8.**

**Table 6.**

*elimination efficiency of Zn.*

**6. Study of the lead adsorption**

60 minutes for the Ccra.

**6.1 Kinetic study of the Pb2+ adsorption**

**248**

*Kinetic study of Pb (II) adsorption on raw chitin.*

After equilibrium, more than 80% of the initial amount of Pb2+ (100 mg/l) is adsorbed on the Ccra, whereas only 41% of the initial amount of Pb2+ is adsorbed on pure chitin [39]; this shows that the mineral part of the crab shells plays a role in the retention of Pb2+. The percentages of adsorption as a function of time are in good agreement with the results obtained by Yang [37].
