**4.2 Study of the Cu2+ isotherms adsorption on the raw chitin**

**Figure 6a** shows the evolution of the adsorption capacity (Qe) expressed in milligrams of metal per gram of material as a function of the residual content (Ce) of Cu2+ at equilibrium. The results of calculating the average removal percentages for Cu2+ adsorption assays are shown in **Figure 6b**.

Examination of the different isotherms shows that Cu has a high affinity for Clan. For a residual concentration of 1 mg/l, the adsorbed amount reaches 95 mg/g for Clan and 40 mg/g for Ccre. This example proves that the adsorption of Cu2+ depends on the origin of the raw chitin.

From **Figure 4b**, it is clear that Cu2+ shows a particularly great preference for Clan. The percentage of Cu2+ adsorption on Clan varies between 99.07% to 5 mg/l and 93.2% to 100 mg/l, whereas on the Ccre, it varies between 81% to 5 mg/l and 68% at 100 mg/l; this shows that the adsorption of Cu2+ on these supports increases when the concentration decreases, and this is in agreement with the study carried out by Okieimen [60], which found that the percentage of CuCl2 adsorption on the original Arachis Hypogea cellulose varies between 70% to 200 mg/l and 30% to 500 m/l. Likewise, Elliott [61] having studied the adsorption of Cu2+ on Al2O3 has argued that an increase in the ionic strength of the adsorbent-adsorbent system reduces the adsorption of Cu2+ through the effect of the activity coefficients and the double electric surface layer.

#### **Figure 6.**

*(a) Experimental Cu (II) adsorption isotherms on the raw chitin, (b) Effect of the origin of the raw chitin on the Cu (II) elimination efficiency.*


**247**

**Figure 7.**

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

The application of the linearized formula of the Freundlich equation (**Table 5**) in the case of Cu2+ adsorption allows us to say that this model is perfectly applicable. Indeed, the correlation coefficients R (**Table 2**) obtained are very satisfactory. Note that the adsorption capacity of Cu2+ on Clan is greater than that on Ccre and Ccra (**Table 5**). Adsorption capacities deduced from Freundlich prove that copper is more

As with other metals, the kinetic study shows that equilibrium is established rapidly. According to the curves of **Figure 7**, the contact times Ccre-Zn2+, Ccra-Zn2+, and Clan-Zn2+ required to reach equilibrium are around 40, 60, and 50 minutes, respectively. The times are very low in comparison with those necessary to reach equilibrium on mineral surfaces such as on the hydroxide of Fe (III), which requires 48 hours [8] and the goethite, which requires 42 days. Indeed, Balistrieri [58] having studied the adsorption of Zn2+ and Cd2+ on goethite, found that initially, there is a fast adsorption kinetics (a few hours) followed by a very slow diffusion control-

The tendency of surfaces to fix Zn2+ ions decreases with an increase in ion surface charge, since Zn2+ binds rapidly early with high affinity to the surface of the materials, and then slowly to with less activity. In addition, the increase in surface charge may induce some electrostatic repulsion. This effect on surface coverage is less pronounced with Cd2+ and Cu2+. The same remarks were recorded for the kinet-

Monitoring the amount of Zn2+ adsorbed as a function of the residual concentra-

tion (**Figure 8a**) shows that the adsorption phenomenon obeys Henry's law. For Ccra and Clan, isotherms are straight with high slopes. This time, Zn2+ is strongly retained by the Ccra than by the Ccre, the concentration decreases from 100 to 1.85 mg/l by adsorption on the Ccra, which proves a particular affinity of the Zn (II) to the Ccra. This affinity is stronger than that exhibited by mineral surfaces such as illite, montmorillonite, and kaolinite [2]. **Figure 8b** shows the calculation of the

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

**5. Study of the zinc adsorption**

ling the penetration of the metal.

ics of Cu2+ adsorption on algae [60].

**5.2 Study of Zn2+ adsorption isothermals on raw chitin**

average removal percentages for six adsorption tests.

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

**5.1 Kinetic study of the Zn2+ adsorption**

adsorbed by Clan.

#### **Table 5.**

*Values of Freundlich parameters deduced from Cu2+ adsorption isotherms on the raw chitin.*

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

The application of the linearized formula of the Freundlich equation (**Table 5**) in the case of Cu2+ adsorption allows us to say that this model is perfectly applicable. Indeed, the correlation coefficients R (**Table 2**) obtained are very satisfactory. Note that the adsorption capacity of Cu2+ on Clan is greater than that on Ccre and Ccra (**Table 5**).

Adsorption capacities deduced from Freundlich prove that copper is more adsorbed by Clan.
