Synthesis of mesoporous cerium–zirconium binary oxide nanoadsorbents by a solvothermal process and their effective adsorption of phosphate from water

• Cerium–zirconium binary oxide nanoparticles synthesized by a solvothermal process.
• Ce0.8Zr0.2O2 nanoparticles with the desirable structure and surface properties.
• The phosphate adsorption capacity of Ce0.8Zr0.2O2 nanoparticles reached ∼ 112.23 mg/g.
• The phosphate adsorption follows the inner-sphere complexing mechanism.
• Easy phosphate desorption by NaOH solution washing.

Cerium–zirconium binary oxide nanoparticles were synthesized by a simple and low-cost solvothermal process without templates, and their phosphate removal performance was investigated in batch studies. Through careful modulation of the Ce/Zr ratio, Ce/Zr binary oxide nanoparticles were created with different structure, crystal size, surface properties, and phosphate adsorption performance. It was found that Ce0.8Zr0.2O2 nanoparticles had the best phosphate adsorption performance among these Ce/Zr binary oxide nanoparticles, which could be attributed to their desirable structure and surface properties. The phosphate adsorption capacity of Ce0.8Zr0.2O2 nanoparticles was determined at ∼ 112.23 mg/g, the highest among various adsorbents reported in literature. The adsorption of phosphate onto Ce0.8Zr0.2O2 nanoparticles followed the inner-sphere complexing mechanism, and the surface OH groups played the major role. Commonly coexisting anions showed no or moderate effect on the phosphate adsorption onto Ce0.8Zr0.2O2 nanoparticles, and little pH dependence was observed for their phosphate adsorption in the range from pH 2 to 6. After adsorption, phosphate adsorbed on these Ce0.8Zr0.2O2 nanoparticles could be easily desorbed by NaOH solution washing.

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