*2.1.1 Preparation of adsorbent carriers*

Our study focused on an economic and abundant adsorbent, the raw chitin. This polymer exists at concentrations ranging between 20% and 50% in the skeletons of arthropods and more than 60% in the skeletons of crabs and shrimp [53, 54]. The studied crustaceans [crabs, lobsters, and shrimps (**Figure 1**)] belong to the phylum of the arthropods, it is the most important branch of the animal kingdom (75%) about 1 million species, are invertebrate animals metazoans, triploblastics, acoelomates, protostomials with metamerized body, bilateral symmetry and heteronome segmentation, covered by a protective epicuticle serving as external skeleton/exoskeleton, rigid but flexible in some places, and very rich in chitin. This richness is relative to each species. The systematics of these crustaceans is summarized **Table 1**.

The selected species, Squinado, Panulirus, and Kerathurus (**Figure 1**) are the most abundant species in Moroccan markets. Their carapaces consist of an external epicuticle followed inward by a pigmented zone, a calcified layer, another noncalcified, and an epidermis.

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

The raw chitin of shrimp origin (Ccre), crab origin (Ccra), and lobster origin (Clan) is extracted from the shells of these crustaceans according to the following mode: the shells are isolated from their soft parts containing the proteins, washed with bidistilled water, dried in an oven at 100°C for 48 hours, and finally they are

For each metal, a stock solution of 1 g/l [expressed in (g) metal cations per liter of test solution] was prepared using the metallic substances used in the most soluble

and Cd (x = 4)]. For each adsorption test, the solution containing the metals to be

Adsorption is a surface phenomenon and to evaluate the adsorption of a com-

The adsorption kinetics was established by stirring for varying periods of time, the M2+ solutions introduced into 250 ml Erlenmeyer flasks and added to constant amounts of the adsorbent. After a determined contact time of each suspension, they are filtered; the amount of M2+ not removed by the support is subsequently assayed.

The adsorption mechanism can be described using an adsorption isotherm. An adsorption isotherm is the curve, which represents the variation of the adsorbed quantity "Qe" as a function of the equilibrium concentration "Ce" with Eq. (1)

where, C0: initial concentration of adsorbate (mg/l); m: mass of adsorbent used (mg); v: volume of the solution (ml); and ma: mass of retained adsorbate (mg). The adsorption can be studied, either by examining the decrease of the concentration of the adsorbate in the solution, or by a direct determination of the amount fixed on the solid; the second case requires a washing of the solid in order to remove all the unadsorbed molecules, which can cause destruction in the case of the reversible process, and thus leads to erroneous results, and for these reasons, we opted for

To obtain an adsorption isotherm for a solute on an adsorbent, a constant temperature was used, by mixing a determined quantity of the adsorbent with a solution whose solute concentration is known. After vigorous stirring (500 rpm) and prolonged, the equilibrium time between the solid and liquid phases is determined. The mixture is filtered, and by appropriate dosage, the residual concentration of the solute in the solution is measured. This equilibrium concentration will be noted Ce (mg/l). The amount fixed on the adsorbent is deduced, by difference with the initial concentration. This quantity will be symbolized by Qe (mg/g): amount of solute adsorbed per unit mass of the adsorbent. The measurement is repeated several times using solutions of different concentrations, which allow us to draw the isothermal curve. The operating conditions are summarized in **Table 2**. The supernatant is filtered and the equilibrium

(1)

<sup>−</sup>) × H2O with [M = Zn (x = 6), Pb (x = 0), Cu (x = 3),

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

crushed and sieved at particle size well defined.

studied is obtained from the daughter solutions.

**2.2 Experimental study of the adsorption phenomenon**

pound on an adsorbent, it is necessary to start the following studies:

*2.1.2 Preparation of synthetic wastewater*

mineral form (M2+, 2NO3

*2.2.1 Adsorption kinetics*

*2.2.2 Adsorption isotherm*

the first possibility.
