Fabricating ultrafine zirconium oxide based composite sorbents in “soft confined space” for efficiently removing fluoride from environmental water

• Ultrafine Zirconium Oxide Based Composite Sorbents were prepared in “Soft Confined Space” • Covalently attached lipases resulted in excellent interfacial stability, even after several regeneration cycles. • E-ELP-Zr possessed excellent fluorine uptake capacity, quick binding kinetics and superior selectivity. • The actual application performance validated the treated ability of fluorinated wastewater with low level of fluoride. The fluoride pollution in environmental water can cause serious health problems, and the fluoride removal by sorbent is an effective strategy, and challenges by its poor selectivity and low capacity. Herein, we reported a new insight into the fabricating ultrafine zirconium oxide (ZrO 2 ) based composite sorbents (E-ELP-Zr) in “soft confined space” and efficient fluoride removal from water. It relies on the confined aqueous phase of Oil-in-Water (O/W) high internal phase emulsions (HIPEs) as droplet reactor, and ultrafine ZrO 2 particles (<10 nm) were achieved via the controllable in situ growth onto lipase immobilized poly(styrene-co-glycidyl methacrylate) nanospheres. E-ELP-Zr exhibited outstanding capacity for defluorination (135.8 mg g −1 at 298 K), quick adsorption rate in the first 10 min, and the superior selectivity against co-occurring anions (Cl - , SO 4 2− , NO 3 – and CO 3 2– ). The adsorption mechanism of fluoride on E-ELP-Zr was strong electrostatic attraction as well as the specific affinity of zirconium. After five regeneration cycles, the adsorption capacity of E-ELP-Zr slightly decreases to 88.55% of the initial value, and the excellent interfacial stability was benefited from covalently attached lipases. More importantly, this hybrid sorbent can be successfully applied for low level (7.15 mg L -1 ) of fluoride decontamination from actual sample of fluorinated wastewater, which endowed a distribution coefficient ( K d ) as high as 6.3 L g −1 .