Synthesis of phosphorylated raw sawdust for the removal of toxic metal ions from aqueous medium: Adsorption mechanism for clean approach

In this work, phosphorus oxychloride was grafted onto the surface of raw sawdust (RSD) particles to get effective adsorbent for capturing Cd(II), Cr(III), and Pb(II) metal ions from aqueous medium. Phosphorylated raw sawdust (RSD@P) was characterized by FTIR, TGA, SEM-EDX, TEM, BET, and XPS analyses. Various experimental conditions of adsorption viz. pH, contact time, temperature, and initial concentration were optimized. The adsorption behavior of RSD@P concerning adsorption kinetics, isotherms and thermodynamics was also studied. The values of qe for Cd(II), Cr(III), and Pb(II) metal ions onto RSD@P was found to be 244.3, 325, and 217 mg/g, respectively at 298 K according to monolayer Langmuir adsorption. The adsorption kinetics data revealed that Cd(II), Cr(III), and Pb(II) metal ions were well fitted to pseudo- second-order kinetic model. The thermodynamic results demonstrated that adsorption was spontaneous and exothermic. The mechanisms of interactions was also discussed for the adsorption of Cd(II), Cr(III), and Pb(II) metal ions over RSD@P. The obtained results showed that RSD@P was an auspicious adsorbent which showed outstanding reusability for the removal of metal ions from aqueous medium.