Highly efficient P uptake by Fe3O4 loaded amorphous Zr-La (carbonate) oxides: Electrostatic attraction, inner-sphere complexation and oxygen vacancies acceleration effect

• Published in: Journal of environmental sciences (China) 2022-10, Vol.120, p.18-29
• Main Authors: Liu, Chenyang, Wang, Yili, Li, Xiaolin, Li, Junyi, Dong, Shuoxun, Hao, Haotian, Tong, Yao, Zhou, Yanqing
• Format: Article
• Language: English
• Subjects: Fe3O4 loaded amorphous Zr-La (carbonate) oxides; Mechanism; Phosphate adsorption performance; Real water treatment; Regeneration
• ISSN: 1001-0742; 1878-7320
• DOI: 10.1016/j.jes.2022.01.003

•A novel composites MZLCO was developed by a one-pot solvothermal method.•MZLCO exhibited high phosphate adsorption capacity of 96.16 mg P/g.•MZLCO showed fast adsorption kinetics and strong phosphate selectivity.•Electrostatic attraction and inner-sphere complexation dominated the adsorption.•Oxygen vacancies could accelerate the chemisorption rate. Bimetallic oxides composites have received an increasing attention as promising adsorbents for aqueous phosphate (P) removal in recent years. In this study, a novel magnetic composite MZLCO was prepared by hybridizing amorphous Zr-La (carbonate) oxides (ZLCO) with nano-Fe3O4 through a one-pot solvothermal method for efficient phosphate adsorption. Our optimum sample of MZLCO-45 exhibited a high Langmuir maximum adsorption capacity of 96.16 mg P/g and performed well even at low phosphate concentration. The phosphate adsorption kinetics by MZLCO-45 fitted well with the pseudo-second-order model, and the adsorption capacity could reach 79% of the ultimate value within the first 60 min. The phosphate adsorption process was highly pH-dependent, and MZLCO-45 performed well over a wide pH range of 2.0-8.0. Moreover, MZLCO-45 showed a strong selectivity to phosphate in the presence of competing ions (Cl−, NO3−, SO42−, HCO3−, Ca2+, and Mg2+) and a good reusability using the eluent of NaOH/NaCl mixture, then 64% adsorption capacity remained after ten recycles. The initial 2.0 mg P/L in municipal wastewater and surface water could be efficiently reduced to below 0.1mg P/L by 0.07 g/L MZLCO-45, and the phosphate removal efficiencies were 95.7% and 96.21%, respectively. Phosphate adsorption mechanisms by MZLCO-45 could be attributed to electrostatic attraction and the inner-sphere complexation via ligand exchange forming Zr/La-O-P, -OH and CO32− groups on MZLCO-45 surface played important roles in the ligand exchange process. The existence of oxygen vacancies could accelerate the phosphate absorption rate of the MZLCO-45 composites. [Display omitted]