Modification of Adansonia digitata Cellulose by Hydroxamic Acid: a Promising Resource for Removing Pb (II) Ions from Water

Abstract

Developing cheap and affordable materials for the removal of toxic heavy metal ions such as Pb (II) ions from water is a challenge. In response to this, this work evaluated the synthesis and use of hydroxamic acid modified Adansonia digitata cellulose (ADHX) as a useful resource for the removal of Pb (II) ions from water. ADHX was characterized using Fourier Transform Infrared spectrometry (FTIR), Thermogravimetric analysis (TGA), X-ray Diffraction analysis (XRD), zeta potential, Particle Size Dispersion (PSD), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). The sorption of Pb (II) ions on ADHX follows the pseudo-second order model, intra-particle diffusion and Liquid film diffusion kinetic models. The adsorption capacity of ADHX was found to be 18.00 mg g−1, which fitted well for Langmuir, Temkin and Freundlich isotherms. PSD revealed ADHX to be monomodal while Gibb’s free energy change (∆Go) suggests a non-spontaneous process. The negative nature of enthalpy change (∆Ho, −69.774 kJ mol−1) shows that the process is exothermic while entropy change (∆So, −0.214 kJ mol−1) suggests a stable configuration of Pb (II) ions on the surface of ADHX. However, the desorption studies revealed a possible regeneration of ADHX with a desorption capacity of 68.75% in 0.01 M NaNO3 while quantum chemical computation using Density Functional Theory (DFT) revealed the mechanism of sorption to be via ionic interaction. This study revealed ADHX to be a promising resource for removing Pb (II) ions from water. Graphical abstract