Key Takeaways & Executive Findings
- •• • Ce-FMSY achieved 86.2% F− removal within 30 min at Ce/Fe mass ratio 2:1 and Ce loading 1.0%, with a maximum adsorption capacity of 4.139 mg·g−1, demonstrating rapid kinetics suitable for continuous flow treatment. • • The adsorbent exhibited a saturated magnetization of 13.4 emu·g−1, enabling efficient magnetic separation, which addresses the common bottleneck of adsorbent recovery in slurry reactors. • • Over an initial pH range of 3–9, Ce-FMSY maintained a stable fluoride removal rate of 77.1%–96.8%, indicating robustness against pH fluctuations in real wastewater streams. • • After five adsorption-desorption cycles, the adsorbent retained approximately 72.3% of its initial F− removal efficiency, showing good reusability and potential for cost-effective operation.
Abstract
With increasingly stringent discharge standards for fluoride-containing wastewater, there is an urgent need for cost-effective, easily operable adsorbents capable of rapid adsorption and separation for deep defluorination. In this study, a novel adsorbent, Ce-FMSY, was successfully prepared by co-precipitation of cerium (Ce) and Fe3O4 onto Y-type molecular sieve (MSY). The effects of Ce/Fe mass ratio, adsorption time, initial solution pH, and coexisting anions on adsorption performance were systematically investigated. Results showed that at a Ce loading of 1.0% and Ce/Fe mass ratio of 2:1, Ce-FMSY rapidly adsorbed 86.2% of F− within 30 min, with a maximum adsorption capacity of 4.139 mg·g−1. The saturated magnetization of Ce-FMSY was 13.4 emu·g−1, enabling rapid solid-liquid separation. The adsorbent maintained a stable fluoride removal rate of 77.1%–96.8% over an initial pH range of 3–9. Adsorption kinetics and isotherm fitting indicated that F− adsorption onto Ce-FMSY followed pseudo-second-order kinetics and the Freundlich model, suggesting chemisorption as the dominant mechanism, involving rapid diffusion, surface complexation, and valence transformation reactions. After five adsorption-desorption cycles, the adsorption capacity slightly decreased and then stabilized, with F− removal efficiency maintained at approximately 72.3% of the initial value. This study provides data support and theoretical reference for deep fluoride removal from wastewater.
1. Introduction
The discharge of fluoride-laden wastewater from industries such as chemical, electronics, photovoltaic, and smelting poses severe risks to ecosystems and human health. Chronic exposure to excess fluoride can cause dental and skeletal fluorosis, and long-term ingestion of contaminated water may damage the nervous system and liver/kidney functions. Regulatory limits are stringent: China's drinking water standard sets a maximum fluoride concentration of 1.0 mg·L−1, and surface water quality standards for Class I–III bodies limit F− to 1.0 mg·L−1, with Class IV–V at 1.5 mg·L−1. Conventional treatment methods, including precipitation, membrane separation, ion exchange, and electrochemical processes, have limitations: precipitation typically leaves residual F− around 5 mg·L−1, failing deep treatment requirements; membrane processes are costly; ion exchange demands high pretreatment and operational expenses. Adsorption is considered a promising technology due to its simplicity, efficiency, and low cost, yet existing adsorbents suffer from complex preparation, high cost, slow kinetics, or difficult separation.
To address these bottlenecks, this study develops a novel composite adsorbent by loading cerium (Ce) and magnetite (Fe3O4) onto Y-type molecular sieve (MSY) via co-precipitation. MSY offers high specific surface area and uniform pore structure, serving as a stable substrate; Ce exhibits strong affinity for fluoride through coordination; and Fe3O4 imparts magnetic properties for rapid separation. This synergistic combination aims to achieve fast adsorption kinetics, high capacity, and easy recovery, which are critical for practical deep defluorination of wastewater. The study systematically evaluates the adsorbent's performance under various conditions and elucidates the adsorption mechanisms, providing a foundation for engineering applications.
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FANG Wanrong, QIU Zhaofu, WANG Yuan, LI Shangshu, JIN Xibiao (2026). Cerium-Based Magnetic Y-Type Molecular Sieve for Deep Removal of Fluoride Ions from Water. Chinese Journal of Environmental Engineering. https://doi.org/10.12030/j.cjee.202512064
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Frequently Asked Questions
What is the maximum adsorption capacity of Ce-FMSY and under what conditions is it achieved?
The maximum adsorption capacity of Ce-FMSY is 4.139 mg·g−1, achieved at a Ce/Fe mass ratio of 2:1 and Ce loading of 1.0%, with an initial F− concentration of 100 mg·L−1 and pH 7.0±0.1, at 25°C.
How does the adsorbent perform over repeated use, and what regeneration method is employed?
After five adsorption-desorption cycles using 0.01 mol·L−1 HCl with ultrasonic assistance, the F− removal efficiency stabilizes at approximately 72.3% of the initial value, indicating good reusability.
What is the effect of coexisting anions on fluoride adsorption by Ce-FMSY?
The study examined six common anions (Cl−, NO3−, SO4^2−, CO3^2−, H2PO4−, HCO3−). While specific data are not detailed in the abstract, the adsorbent maintained stable performance over pH 3–9, suggesting moderate interference; however, further details are in the full text.
What are the adsorption kinetics and isotherm characteristics of Ce-FMSY for fluoride?
The adsorption follows pseudo-second-order kinetics and the Freundlich isotherm model, indicating chemisorption as the rate-limiting step and heterogeneous surface binding, with mechanisms involving rapid diffusion, surface complexation, and valence transformation.
How does the magnetic property of Ce-FMSY facilitate separation, and what is its saturation magnetization?
Ce-FMSY exhibits a saturation magnetization of 13.4 emu·g−1, which allows rapid solid-liquid separation using an external magnetic field, overcoming the separation difficulty common in powdered adsorbents.
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