Yufen Kong,Hongdan Wu,Zhihui Zhou,Xianyuan Fan,Ming Li
To address the long-standing trade-off between flux and selectivity, as well as the structural instability of conventional nanofiltration (NF) membranes, this study proposes a novel intercalation strategy for constructing two-dimensional laminar NF membranes based on MXene for efficient dye/salt separation. Spherical Fe 3 O 4 nanoparticles were functionalized with amino groups using 3-aminopropyltriethoxysilane (APTES) to impart positive surface charges, and subsequently assembled onto hydrophilic MXene (Ti 3 C 2 T x ) nanosheets via electrostatic self-assembly, forming a structurally stable MXene/NH 2 -Fe 3 O 4 composite membrane. The surface functionalization of Fe 3 O 4 plays a critical role in regulating the interlayer structure of MXene, thereby enhancing membrane stability and selective transport performance. At a mass ratio of MXene to NH 2 -Fe 3 O 4 of 1:6, the membrane exhibited a pure water flux of 136.6 L/(m 2 ·h) and rejection rates of up to 99.9 % for Congo Red (CR) and Evans Blue (EB). In contrast, the rejection rates for NaCl, MgSO 4 , and Na 2 SO 4 were 7.0 %, 15.4 %, and 26.4 %, respectively. In mixed dye/salt systems, the membrane exhibited excellent selectivity, with separation factors of 839 for CR/NaCl, 704 for CR/MgSO 4 , and 566 for CR/Na 2 SO 4 , attributed to synergistic contributions of size exclusion, electrostatic repulsion, and the Donnan exclusion effect. Furthermore, the composite membrane demonstrated outstanding dye removal efficiency, acceptable salt rejection, and robust structural integrity under prolonged operation, wide pH variations, and challenging conditions involving organic foulants and surfactants, offering a practical strategy for developing advanced NF membranes for complex wastewater treatment.
A novel adsorbent, aminated Fe 3 O 4 (Fe 3 O 4 -NH 2 )/graphite oxide (GO)/carboxylated cross-linked β-cyclodextrin polymer (CDP-COOH) composite, was fabricated for influential removal of various types of dyes from waters. The morphology and structure of resulting Fe 3 O 4 -NH 2 /GO/CDP-COOH composite was studied by SEM, two-dimensional EDS map, FTIR, WAXD, XPS, TGA, and zeta potential meter, and its saturation magnetization was determined to be 46.3 emu/g by VSM. The maximal sorption capacities of Fe 3 O 4 -NH 2 /GO/CDP-COOH composite for methylene blue (MB, as a model of cationic dyes) and Congo red (CR, as a model of anionic dyes) at 303 K were 201.75 mg/g and 2211.05 mg/g, respectively, which can be mainly assigned to multiple adsorptive forces like electrostatic attractions, hydrogen bonds, host–guest self-assembly interactions, π-π electron cloud interactions, and Lewis acid-base interactions. The dye sorption by the Fe 3 O 4 -NH 2 /GO/CDP-COOH composite had a spontaneous nature according to the sorption thermodynamic calculation and can be well explained by pseudo-second-order model. The Langmuir and Freundlich models could explain the sorption isotherms of Fe 3 O 4 -NH 2 /GO/CDP-COOH composite for MB and GO, respectively. The Fe 3 O 4 -NH 2 /GO/CDP-COOH composite possessed many other advantages including the good sorption capability for different heavy metal ions (like Pb 2+ , Ni 2+ , and Cu 2+ ) and organic compounds (like dichlorophenol and propranolol) as well as the good recyclability and reusability.
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