Hierarchical ZnO/ZnFe2O4 yolk-shell adsorbent as a promising material for phosphate recovery and adsorption of organic pollutants from the simulated wastewater

Mitigation of phosphate contamination is essential to preserve the health and integrity of the water ecosystem. Therefore, to prevent eutrophication and preserve water resources, it is essential to establish an effective and long-lasting phosphate removal process. Herein, a highly efficient and eco-friendly ZnO/ZnFe2O4 (ZZFO) yolk-shell microsphere was designed by the glycothermal method followed by calcination for phosphate removal and adsorption of Congo red (CR) organic dye aqueous solution. ZZFO demonstrated an outstanding Langmuir hypothetical optimum phosphate adsorption ability of 103.2 mg-P/g in batch phosphate adsorption studies. This value is 5.54 and 8 times higher than that of pristine ZnO and Fe2O3, respectively, and the adsorbent was readily removed with the use of an external magnetic field. The anions experiments showed that, except chlorine and fluoride ions, other regular anions have a slight influence on the phosphate adsorption process. The Langmuir and pseudo-second-order model showed excellent correlation constants. Moreover, ZZFO exhibited the capability to adsorb CR aqueous solution, which is a significant finding for aquatic remediation. Our experimental findings have significant implications for the fabrication of sustainable adsorbents for the treatment of wastewater.