Optimization of the adsorption of lead (II) by hydroxyapatite using a factorial design: Density functional theory and molecular dynamics

• Published in: Frontiers in environmental science Vol. 11
• Main Authors: El Hammari, L., Hamed, R., Azzaoui, K., Jodeh, S., Latifi, S., Saoiabi, S., Boukra, O., Krime, A., Boukra, A., Saoiabi, A., Hammouti, B., Khan, M. M., Sabbahi, R., Hanbali, G., Berisha, A., Taleb, M., Dagdag, O.
• Format: Journal Article
• Language: English
• Published: Lausanne Frontiers Research Foundation 02.03.2023; Frontiers Media S.A
• Subjects: Adsorbates; Adsorbents; Adsorption; Aqueous solutions; Chemical synthesis; Chemisorption; Density functional theory; Environmental science; Equilibrium; Factorial design; Fourier transforms; Hydroxyapatite; Infrared analysis; Lead; lead (II); Metals; Molecular dynamics; Optimization; Pollutants; pollution; Regression coefficients; Scanning electron microscopy; Spectrum analysis; Temperature effects; Water treatment; X-ray diffraction
• ISSN: 2296-665X; 2296-665X
• DOI: 10.3389/fenvs.2023.1112019

Hydroxyapatite (HAp) synthesized through a wet chemical procedure was used to adsorb lead (II) from an aqueous solution. HAp was characterized using Fourier transform infrared, X-ray diffraction, Brunauer–Emmett–Teller analysis, and scanning electron microscopy. The removal of Pb +2 was investigated using the factorial design approach to investigate the efficiency of different Pb +2 concentrations, adsorption contact time, and HAp mass. The greatest Pb +2 removal (98.94%) was obtained at a starting concentration of 50 mg/L, a contact period of 15 min, and a pH of 8. At 323 K, the isothermal adoption module was fitted to the Langmuir isotherms with a regression coefficient ( R 2 ) of 0.96. The thermodynamic calculations revealed that the adsorption process was exothermic, spontaneous, and predominantly dominated by chemisorption. Furthermore, the maximum adsorption capacity ( Q max ) at equilibrium was 90.18 mg/g, and the adsorption kinetics was specified by a pseudo-second-order kinetic model. Density functional theory and theoretical studies showed that the results of the experiment were correlated by the observation of a much higher negative E ads value for the lead ion adsorbate molecules as they attached to the surface of the adsorbent.