Micro-structured Materials for the Removal of Heavy Metals using a Natural Polymer Composite

In this study, a precipitation method was employed to prepare a synthetic hydroxyapatite (HAP)/chitosan (CHN) composite by the modification of synthetic HAP with CHN. The HAP/CHN composite was characterized by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy (SEM-EDX). Furthermore, the HAP/CHN composite in a 1:1 ratio (wt.%) was investigated as an adsorbent for the removal of heavy metals ions (such as Cr⁶⁺, Cd²⁺ and Zn²⁺) from simulated wastewater. Adsorption experiments were conducted in batch mode at room temperature. In addition, the effect of process conditions, such as contact time, was evaluated. Kinetic data were well-described by the pseudo-second-order kinetic model, where adsorption was governed by the intraparticle diffusion model. The HAP/CHN composite demonstrated potential utility as an adsorbent for the removal of heavy metals from an aqueous solution, with the highest maximum adsorption capacities of 39.3, 30.8 and 29.9 mg/g for Cr⁶⁺, Cd²⁺ and Zn²⁺, respectively. The HAP/CHN composite materials with variable structure and composition exhibited remarkably different adsorption properties and potential applicability for industrial applications due to the material cost-effectiveness.