Simultaneous removal of copper and zinc ions by low cost natural snail shell/hydroxyapatite/chitosan composite

In this work, the snail shell/hydroxyapatite/chitosan composite was prepared as adsorbent. The adsorption potential of the composite was studied for simultaneous sorption behavior of Zn (II) and Cu (II) ions in a batch system. Chitosan and hydroxyapatite (HAP) were extracted from shrimp shell and bone ash, respectively, so this is a low cost natural composite. To prepare the composite, chitosan was dissolved in acetic acid, then HAP and snail shell powders were added to the chitosan solution. The morphology and characterization of the composite was studied by SEM and EDX analysis. Atomic adsorption was used to measure the amount of the ions. Experimental parameters were optimized with Design Expert Software and five parameters such as the concentration of ions, pH, adsorbent amount and contact time were studied at room temperature. Optimized value for the parameters of Zn (II) and Cu (II) concentrations, pH, adsorbent dose, and contact time were 3.01 mg·L^-1, 5.5, 0.02 g and 95 min, respectively. The adsorption isotherms for Zn (II) and Cu (II) showed Langmuir and Tempkin, respectively. Kinetic and equilibrium studies showed the experimental data of Zn (II) and Cu (II) ions were best described by the pseudo-second-order model. Studies on thermodynamic show the adsorption process were physical and spontaneous.