Removal of Pb(II) from Aqueous Solutions with Manganese Oxide-Modified Diatomite

In the present work, natural diatomite modified with manganese oxide (MnO₂) was prepared via direct redox reaction with KMnO₄ and HCl. The product was characterized by using X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray, and nitrogen adsorption-desorption isotherms. It was found that the nanorod manganese oxide was highly dispersed onto the diatomite porous matrix. The specific surface area of the obtained manganese oxide/diatomite () is larger than that of natural diatomite (). It was utilized to remove Pb(II) in aqueous solutions. It exhibits an excellent Pb(II) adsorption capacity. The adsorption data fits well with the pseudo-second-order kinetics model, and the adsorption process is endothermic and spontaneous with an activation energy of 41.56 kJ mol⁻¹ and follows the Freundlich isotherm model. The Mn/diatomite adsorption capacity for Pb(II) is 81.42 mg g⁻¹, calculated with the Langmuir model. In addition, the adsorption mechanism of Pb(II) onto Mn/diatomite is also addressed.