Diatomite-Based Adsorbent Decorated with Fe₃O₄ Nanoparticles for the Removal of Hazardous Metal Ions

Diatomite has been verified as an economical adsorbentto treatwastewater. Unfortunately, limited by poor regeneration and an inertsurface with less active silanol groups, the retrievable and efficientdiatomite-based adsorbent needs to be further explored. Here, on thebasis of the thorough activation treatments of the raw diatomite,we developed a diatomite-based adsorbent with a uniform assembly ofFe(3)O(4) nanoparticles on the surface. The nanocompositepossesses a high specific surface area, the trait of magnetic separation,and more functional groups for adsorption. The maximum adsorptioncapacities of Pb2+, Ni2+, and Cd2+ at 314 K reached 0.97, 1.18, and 0.88 mmol/g, respectively, whichwere more competitive than those of previously reported diatomite-basedadsorbents. The experimental data fitted well with the pseudo-second-orderkinetic model and Freundlich isotherm model, demonstrating that theadsorption was mainly derived from the electrostatic interaction andchelation between the hydroxyl/carboxyl groups on multilayer surfacesand the hazardous metal ions. According to the analytical resultsof the adsorption isotherms and response surface optimization, theremoval efficiency can exceed 94%, obtained by increasing the pH andreaction temperature. The activation-enhanced surface engineeringcan arouse the adsorption potential of a diatomite-based adsorbentand provide universal perspectives into the concept design of a nanocompositeadsorbent with lower cost recovery and higher adsorption efficiency.