Reassembly of extracted keratin from chicken feathers following Pb 2+ adsorption from aqueous solutions

In this research, keratin was extracted from chicken feather waste using potassium sulfide as a reductive agent. By scission of disulfide bonds between two side chains, the pendant sulfide groups were formed that are suitable for pb2+ adsorption. The assembly behavior of extracted molecules before and after Pb2+ adsorption was investigated by Fourier-Transform infrared spectroscopy (FTIR), x-ray powder diffraction (XRD), and Scanning electron microscope -Energy Dispersive Spectroscopy (SEM-EDS). The adsorption ability was examined by UV-Vis analysis and Inductively Coupled Plasma Optical Emission spectroscopy (ICP-OES). The XRD data of the samples showed that the d-spacing of β- crystalline structure shifted to the lower 2θ angle after Pb2+ adsorption. SEM results indicated a feather-like assembly of extracted keratin and tightly packed microparticles before and after Pb2+ adsorption. Increasing the adsorption ability by increasing the absorbent dosage, Pb2+ ion concentration were observed at initial pH of 4.7 (below the zwitterion formation pH). However, by decreasing the solution temperature to 15 °C, the adsorption ability increased due to formation of a secondary crystalline structure at low temperature. The experimental results exhibited the Freundlich isotherm was the well-fitted model and the kinetic data followed the pseudo-second-order model. The adsorption of metal ions mixture indicated the selective adsorption of Pb2+due to complexation mechanism between ion metals and pendant sulfide groups. FTIR and EDS analyses confirmed the structural integrity of the extracted keratin and ion exchange with Na+ after regeneration.