**7. Comparison with active charcoal powder (CAP)**

The adsorbent supports are numerous and diverse, but in water treatment, activated carbon is used almost exclusively as adsorbent. To value chitin in the treatment of metallic water pollution, we have tried to compare its purification performance with that of CAP. We will then study the kinetics and adsorption isotherms of metals on CAP.

#### **7.1 Kinetic study of adsorption of heavy metals on active coal powder (CAP)**

During the treatment of liquid discharges, processes are always sought which give the maximum of treatment efficiency in a minimum of time. Since then, we have tried to compare the kinetics of adsorption on the studied materials and on the CAP. We have tried to situate ourselves under the same operating conditions as those of the raw chitin. The evolution of the adsorbed quantity as a function of time is reported in **Figure 11**.

From figure above, active carbon rapidly sets a maximum amount of metal. So for the Pb, it takes 60 minutes to reach adsorption equilibrium. Cd requires a time of about 10 minutes, while Cu and Zn only require a few minutes for their concentrations in the solution to stabilize.

Comparing the kinetic curves of the CAP with those obtained for different types of chitin, we find that the raw chitin exhibits identical kinetic behavior to that of the CAP even if the times of the adsorption kinetics on the raw chitin depend on its origin; these times are always close to those observed with the CAP, and sometimes, the equilibrium times are smaller than those of the CAP (case of the Ccre-Zn).

#### **7.2 Comparing isothermals of metals adsorption on CAP and on raw chitin**

To compare the reduction of metallic pollution by crude chitin to that by CAP, we carried out adsorption tests of heavy metals on the CAP under same conditions

**251**

**Table 8.**

for this study.

**Figure 11.**

following **Figure 12**.

capacities of metals on different media.

*Kinetic study of heavy metals adsorption on the CAP.*

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

as those of crude chitin. **Table 8** represents the values of the Freundlich parameters

According to this table, Pb is more adsorbed by CAP than other metals, it is about 10 times more adsorbed than Cu. The retention of Zn and Cu is low, 1 g of CAP retains only 4.35 mg of Cu2+ and 3.38 mg of Zn. The selectivity of CAP toward these metals is as follows Pb > Cd > Cu > Zn. In order to compare these results with those of raw chitin, we have drawn up **Table 9** grouping the maximum adsorption

According to this table, the adsorption capacities of the metals on the CAP are low compared to the raw chitin. There is a difference between the values observed, and this difference is important in the case of Pb. Indeed, the Pb is 58 times retained by the Ccre than by the CAP, it is almost five times more retained by the Ccra than

the Ccre and the CAP, Cd is more than three times retained by the Ccre than by the CAP. For Cu, 1 g of the Ccre retains a quantity of Cu 10 times higher than that retained by the CAP Similarly, Zn is more adsorbed by crude chitin than by CAP The same remarks were made by calculating the elimination percentages for six heavy metal adsorption tests; we have used the example of Cu2+ and Zn, their percentages compared to those observed with the raw chitin are grouped in the

This figure clearly shows that the adsorption of the metals on the raw chitin is much stronger than the adsorption of the metals on the CAP. From this study,

Pb2+ 58.69 1.03 0.98 Cd2+ 9.01 0.56 1.00 Cu2+ 4.35 0.57 1.00 Zn2+ 3.38 0.59 1.00

*Values of the Freundlich parameters deduced from the adsorption isotherms of metal ions on activated carbon.*

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

by the CAP. In the case of Cd2+, the gap exists particularly between

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

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

**Figure 11.** *Kinetic study of heavy metals adsorption on the CAP.*

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

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

adsorbability for Ccra 265.07 mg/g.

initial concentrations.

**Table 7.**

isotherms of metals on CAP.

is reported in **Figure 11**.

trations in the solution to stabilize.

adsorption capacity according to the Freundlich model is 9266.86 mg/g on the Ccre, it is 35 times greater than that corresponding to the Ccra. There is also a better

Ccre 9266.9 263.98 1.00 Ccra 265.07 1.04 1.00 Clan 3.59 3.69 1.00

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

We compared the rate of fixation of Pb by Ccre with adsorption results on biological surfaces such as 90% algae and rice biomass 99% Hulls [22], adsorption on mineral surfaces such as 35% bentonite and montmorillonite, which retain only 25% of Pb and

to the cellulose for which the percentage of adsorption does not exceed 62.8%. The average reduction percentage of Pb is 95% for the Ccre, and 75% for the Clan. According to the adsorption tests, the percentage of adsorption decreases when the concentration increases, the same observation was recorded for the adsorption of Pb on Kaolinite [13], a significant reduction in Pb is obtained at low

The adsorbent supports are numerous and diverse, but in water treatment, activated carbon is used almost exclusively as adsorbent. To value chitin in the treatment of metallic water pollution, we have tried to compare its purification performance with that of CAP. We will then study the kinetics and adsorption

**7.1 Kinetic study of adsorption of heavy metals on active coal powder (CAP)**

During the treatment of liquid discharges, processes are always sought which give the maximum of treatment efficiency in a minimum of time. Since then, we have tried to compare the kinetics of adsorption on the studied materials and on the CAP. We have tried to situate ourselves under the same operating conditions as those of the raw chitin. The evolution of the adsorbed quantity as a function of time

From figure above, active carbon rapidly sets a maximum amount of metal. So for the Pb, it takes 60 minutes to reach adsorption equilibrium. Cd requires a time of about 10 minutes, while Cu and Zn only require a few minutes for their concen-

Comparing the kinetic curves of the CAP with those obtained for different types of chitin, we find that the raw chitin exhibits identical kinetic behavior to that of the CAP even if the times of the adsorption kinetics on the raw chitin depend on its origin; these times are always close to those observed with the CAP, and sometimes, the equilibrium times are smaller than those of the CAP (case of the Ccre-Zn).

**7.2 Comparing isothermals of metals adsorption on CAP and on raw chitin**

To compare the reduction of metallic pollution by crude chitin to that by CAP, we carried out adsorption tests of heavy metals on the CAP under same conditions

**7. Comparison with active charcoal powder (CAP)**

**250**

as those of crude chitin. **Table 8** represents the values of the Freundlich parameters for this study.

According to this table, Pb is more adsorbed by CAP than other metals, it is about 10 times more adsorbed than Cu. The retention of Zn and Cu is low, 1 g of CAP retains only 4.35 mg of Cu2+ and 3.38 mg of Zn. The selectivity of CAP toward these metals is as follows Pb > Cd > Cu > Zn. In order to compare these results with those of raw chitin, we have drawn up **Table 9** grouping the maximum adsorption capacities of metals on different media.

According to this table, the adsorption capacities of the metals on the CAP are low compared to the raw chitin. There is a difference between the values observed, and this difference is important in the case of Pb. Indeed, the Pb is 58 times retained by the Ccre than by the CAP, it is almost five times more retained by the Ccra than by the CAP. In the case of Cd2+, the gap exists particularly between the Ccre and the CAP, Cd is more than three times retained by the Ccre than by the CAP. For Cu, 1 g of the Ccre retains a quantity of Cu 10 times higher than that retained by the CAP Similarly, Zn is more adsorbed by crude chitin than by CAP The same remarks were made by calculating the elimination percentages for six heavy metal adsorption tests; we have used the example of Cu2+ and Zn, their percentages compared to those observed with the raw chitin are grouped in the following **Figure 12**.

This figure clearly shows that the adsorption of the metals on the raw chitin is much stronger than the adsorption of the metals on the CAP. From this study,


**Table 8.**

*Values of the Freundlich parameters deduced from the adsorption isotherms of metal ions on activated carbon.*


**Table 9.**

*Values of the maximum adsorption capacity K (mg/g) of heavy metals.*

it follows that the CAP can be substituted by the raw chitin for the treatment of the effluents rich in heavy metals.

#### **7.3 Interpretation and comparison of results**

According to this study, we can draw strong conclusions about the existence an affinity between biosorbent materials based on shells of crustaceans and some heavy metals.

Raw shrimp chitin exhibits a strong affinity for Pb. The adsorption capacity of zinc on the raw chitin of crabs is twice as great as that on the raw chitin of shrimp. The selectivity of the metal for each of these materials was defined by the plot of the adsorption isotherms. The metal ions are retained by these materials in the following order:

Lead: Ccre > Ccra > Clan Cadmium: Ccre > Clan > Ccra Copper: Clan > Ccre > Ccra Zinc: Ccra > Clan > Ccre

The kinetic study has shown that the adsorption process is relatively fast compared to the adsorption on the supports described in the bibliography (of mineral origin). More than 50% of these ions are adsorbed before equilibrium is reached (20 minutes). The adsorption kinetics has also shown that the mineral part of the raw chitin is partly responsible for the retention of heavy metals. The hardness of the shells has a negative effect on the kinetics of the adsorption process, given the time required for equilibrium. Indeed, the adsorption of Pb on the raw chitin shrimp requires only 30 minutes; while the raw chitin lobsters the equilibrium time is 60 minutes.

Studies cited in the literature have shown that to obtain a given abatement, it is necessary to introduce a sufficient quantity of the material. Thus, our treatment tests have shown that to achieve a removal rate of 99% copper contained in

**253**

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

increase when the concentration of these ions decreases.

by raw chitin according to the following sequences:

[21] found the affinities of the following heavy metals:

metals in the following order: Cu > Cd > Pb.

**8. Test of metallic ion adsorption in series**

be compared to FAO standards.

shown in **Table 10**.

a synthetic release with an initial concentration of 100 mg/l, it is necessary to add 1 g of raw chitin. The adsorption percentages of the metal ions on the raw chitin

The comparative study with activated carbon powder (CAP) indicates that the substitution of the latter by chitin may be possible. However, chitin can be coupled to CAP during a chain of treatment of industrial discharges of various loads. As a result, the quantity of heavy metals not retained by the CAP will be retained by the raw

**7.4 Comparative study of the selectivity of heavy metals adsorption on raw** 

From the previous results, we can classify the retention capacity of heavy metals

Ccre Pb > Cu > Cd > Zn Ccra Pb > Zn > Cu > Cd Clan Cu > Cd > Zn > Pb

Zn > Cu = Ni > Cd (pyrophosphates +61 mg/g polysaccharides) Cu = Ni > Cd > Zn (pyrophosphates +222 mg/g of proteins)

Melchor [38, 39] showed that pure chitin crabs exhibits affinity vis-à-vis heavy

In general, the chitin selectivity sequence depends, on the one hand, on the origin of this chitin (algae, fungi, crustaceans, etc.) and on the other hand, on the nature of the ions, in particular the 3d orbitals. It does not depend in any case on their Cu 0.72 Å, Pb 1.2 Å, Cd 0.97 Å, and Zn 0.74 Å sizes. However, the adsorption selectivity of metal ions on mineral surfaces varies greatly from one medium to another. We give the following sequences as an example: Pb > Cu > Zn = Cd and

In order to study the effect of the number of treatments on the percentages of elimination of metal ions and to solve the problem of competitive adsorption, we proceeded to a series treatment starting with an initial concentration of 100 mg/l from M2+. After each adsorption test, the measured filtrate is again adsorbed on the material. This operation is repeated four times for the four metals. In parallel, we do a simple treatment using the same quantity used previously. The results found will

The results of the monitoring of the evolution of the metal ion contents during the series treatment and after the simple treatment of the synthetic rejection are

This table shows that the equilibrium concentration decreases after each adsorption test. Thus, we go from 100 to 0.032 mg/l after the first test and from 0.032 to only 0.002 mg/l after second test for Pb. This value is 25 times lower than the FAO

standard of 0.050 mg/l; it is a remarkable reduction of the Pb ion.

Pb > Cd > Zn > Cu respectively for montmorillonite and Kaolinite [68].

These results are in agreement with some studies, indeed Haug et al. [67] showed that the addition of metal ions to a solution of Na alginate prepared from *Laminaria digitata* leads to the order of the next affinity: Pb > Cu > Cd > Zn. Nicolas

**chitin in relation to other adsorbent cited in the literatures**

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

chitin.

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

a synthetic release with an initial concentration of 100 mg/l, it is necessary to add 1 g of raw chitin. The adsorption percentages of the metal ions on the raw chitin increase when the concentration of these ions decreases.

The comparative study with activated carbon powder (CAP) indicates that the substitution of the latter by chitin may be possible. However, chitin can be coupled to CAP during a chain of treatment of industrial discharges of various loads. As a result, the quantity of heavy metals not retained by the CAP will be retained by the raw chitin.
