Adsorption of Cd²⁺ Ions by Modified Chitosan with 3, 4-Dihydroxy Benzoyl Groups

Rapid Communication

In recent years, much attention has been focused on the contamination of aquatic media by heavy metals; because heavy metals are highly toxic even at low concentrations and can accumulate in living organisms, causing various disorders and diseases [1]. Several methods have been attempted to remove heavy metals from waste water such as chemical precipitation, filtration, membrane separation, electrochemical treatment, ion exchange, and adsorption [2–4]. Chitosan (CS) is well known as an excellent natural biosorbent of heavy metal ions, dyes and proteins because its amino and hydroxyl groups may serve as coordination sites to form complexes with various heavy metal ions such as Cu(II), Ni(II), Pb(II), Cr(IV) [5,6]. Considering the interaction of chitosan with metals the reaction may be described by:

Chitosan + Mⁿ⁺ →( Complex) ⁿ⁺

The amino and hydroxyl groups of chitosan can act as a reactive site for chemical modification. In order to increase the adsorption capacity of chitosan, and to improve the adsorption selectivity of metal ions, several chemicals with certain functional groups have been loaded on chitosan such as isatin, diacetylmonoxime, thiourea and maleic anhydride [7-9]. previously, N-di and trihydroxy benzoyl chitosan nanoparticles were prepared and studied theirs capability in the removal of Cu²⁺, Zn²⁺, Pb²⁺ and Ca²⁺ ions from aqueous solution [10].

Cadmium is one of the heavy metals, which is highly toxic to humans, plant and animals. The metal is of special concern because it is non-degradable and therefore persistent. It was found that the adsorption capacity of Cd²⁺ from aqueous solutions on N-Dihydroxy Benzoyl chitosan (CS-DHBA) nanoparticles are higher than that on CS at different initial Cd²⁺ concentrations.

Figure 1:  CS-DHBA