Selective removal of lead ions from aqueous solutions using SiO₂–MoO₃: Isotherm, kinetics and thermodynamic studies

This study reveals novel data on adsorptive removal of Pb(II) from single metal solution, as well as from multi-metal solution containing Cd(II), Co(II), Cr(III), Cu(II), Fe(III), Mn(II), Ni(II) and Zn(II) ions along with Pb(II) using inorganic SiO2–MoO3 sorbent in a batch system. The results of multi-metal solution system were strongly pH-depended and due to occurred precipitation of Fe(III) in the form of hydroxide. The parameters affecting the sorption efficiency (contact time, sorbent dosage and initial analyte concentration) were evaluated for single solution system. The optimal conditions for SiO2–MoO3 sorbent indicated high affinity toward Pb(II) ions within following process parameters; pH value 3, sorbent dosage 50 ​mg and contact time 60 ​min for maximum Pb2+ concentration of 100 ​mg/L. The adsorption data for Pb(II) utilizing SiO2–MoO3 best fit to pseudo-second-order kinetic model (R2 ​= ​0.9998) and Langmuir isotherm model (R2 ​= ​0.9320) with an adsorption capacity of 222.20 ​mg/g and Reff >95%. According to thermodynamic study, the adsorption process is feasible, spontaneous and exothermic (ΔG ​= ​−18.6 ​kJ/mol, ΔH ​= ​−7.5 ​kJ/mol and ΔS ​= ​37.32 ​J/mol K). The results of present study demonstrated that SiO2–MoO3 material as a renewable sorbent for Pb(II) removal.