Development and characterization of biopolymer-hydroxyapatite composites for efficient lead removal

Abstract

Heavy metals in wastewater require special attention due to their toxic effects on humans. The removal of these metals can be costly and challenging. Biosorption is an alternative removal method using biological materials with metal-sequestering properties. This study investigates the biosorption process using sodium alginate (SA), biological agar (BA), and hydroxyapatite (Hap) in two different shapes: beads and noodles. The Hap/SA/BA solution was added into a CaCl2 solution, forming a Hap/SA/BA composite through coagulation. The adsorbents were characterized using Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscope (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS). Atomic absorption analysis was performed to determine the residual lead concentrations. The results indicated that the adsorption process for all samples fitted the pseudo-second-order kinetic model. The maximum sorption capacity of the sample was 98.5 mg of Pb2+/g. Noodle-shaped samples exhibited faster adsorption kinetics than bead-shaped ones; however, the final amount of Pb2+ removed was nearly identical across all samples. This study provides valuable evidence for the ongoing development of different shapes of ceramic/polymer composites for environmental applications.