Although MIL-101(Fe) has a homogeneous distribution of active metal sites, the relatively low stability of its coordination bonds limits its potential for application, especially in harsh environments. Here, a novel lanthanum-doped MIL-101(Fe)-NH 2 @mesoporous SiO 2 yolk-shell (LMFN-YS) material, synthesized by green water-etching, has effectively improved the adsorption capacity and stability of MIL-101(Fe)-NH 2 . Compared to traditional acid-base etching methods, water etching offered a more co-friendly and cost-effective approach to producing yolk-shell structures. Due to the mesoporous protective shell of mesoporous SiO 2 and more exposed active sites, the yolk-shell materials showed a faster adsorption rate (30 min) and a larger uptake capacity (240.0 mg P/g) than those of MIL-101. The material also exhibited broad range of pH stability from 2 to 10 and displayed good cyclic regeneration ability, with a removal efficiency of 75.9 % after three cycles. Additionally, it demonstrated excellent selectivity towards various coexisting anions such as Cl − , NO 3 − , SO 4 2− , CO 3 2− and HCO 3 − at diverse ionic strengths ranging from 0.001 to 1 M. The superior performance of L 1 MFN-YS (yolk-shell materials of La: Fe = 1:1) was attributed to a combination of factors, including ligand exchange between La(Fe)-OH and phosphates, Lewis acid-base interaction and electrostatic attraction. Additionally, high phosphate removal performance was observed in the real petrochemical wastewater (initial concentrations of 5.48 mg P/g) with a residual effluent concentration of 0.05 mg P/L, which was below the A-level standard of phosphate effluent in China (0.5 mg/L). This work provides a green method for preparing yolk-shell materials with improved ability to treat phosphate wastewater.
Yingqi Xia,Lijia Liu,Yudan Wang,Chunhong Zhang,Yawen Liu
CH 3 Hg + in water is a neurotoxin that is difficult to eliminate and is readily absorbed by the human body through food chains. In this study, thioctic acid was grafted onto the surface of NH 2 -MIL-101 via an amidation reaction to prepare an adsorption material for the rapid and effective removal of CH 3 Hg + , which is designated as LA-MIL-101.The synthesis of LA-MIL-101 was confirmed through analyses including FT-IR, XRD, SEM, TGA, and XPS. BET results indicate that the specific surface area of LA-MIL-101 is 464.92 m 2 ·g −1 . The ideal conditions for CH 3 Hg + adsorption were explored by varying environmental factors such as pH, contact time, and temperature. Furthermore, the introduction of sulfur significantly enhanced the adsorption capacity for CH 3 Hg + . Batch adsorption experiments demonstrate that LA-MIL-101 exhibits an exceptionally rapid adsorption rate, achieving over 88.3 % of the total removal rate within just one minute. Additionally, LA-MIL-101 shows remarkable adsorption efficacy across a broad pH range. The adsorption behavior of LA-MIL-101 for CH 3 Hg + aligns with the Elovich and Langmuir models, with a maximum adsorption capacity reaching 1391.77 μg·g −1 . LA-MIL-101 also displays a strong anti-interference capability in environments containing humic acid or Na + . Notably, it maintains high removal efficiency under conditions involving coexisting cations, as well as in simulated surface water, simulated groundwater, and natural seawater. Moreover, LA-MIL-101 demonstrates good stability and recyclability, retaining effective adsorption after five adsorption/desorption cycles. XPS results elucidate the adsorption mechanism of CH 3 Hg + , highlighting interactions with sulfur (S) and nitrogen (N) atoms. Overall, LA-MIL-101 exhibits high practicality and significant potential for application in the emergency treatment of CH 3 Hg + in aquatic environments.
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