Nanofiltration (NF)
membranes have attracted significant attention
owing to their widespread applications in water treatment and seawater
desalination. However, challenges still remain in improving their
antifouling performance and water permeation. Here, a sulfobetaine-based
zwitterion with polyhydroxy groups was designed and synthesized successfully.
Then, the NF membranes were modified by the reaction of the hydroxyl
group of the zwitterion and the acid chloride group on the surface
of the initial NF membrane. Hence, the hydrophilicity of the NF membrane
was significantly enhanced and resulted in the high promotion of nanofiltration
performance and antifouling property. Besides, the flux of the modified
NF membrane (A2) reached 9.28 L m–2 h–1 bar–1, which was 2.2 times higher than the flux
of pristine NF membrane (A0). Nevertheless, the rejection showed a
slight decrease. Also, the modified NF membrane possessed excellent
fouling resistance to protein; the flux recovery ratio was nearly
98% after the membrane was treated with bovine serum albumin for 2.5
cycles. The excellent water flux and fouling resistance of this NF
membrane advanced its application in wastewater treatment.
Selectivity and antifouling of ultrafiltration (UF) membranes
are major challenges in the separation and purification of biological
proteins. This work reported that full-coverage spongy poly(ether
sulfone) (PES) ultrafiltration membranes assisted by the self-cross-linking
of N-hydroxyethyl acrylamide (HEAA) were fabricated
via a phase inversion method at room temperature. The pore structure
of the UF membrane from finger-like to coverage of the spongy structure
occurred by increasing the content of HEAA, which is beneficial for
size-selective separation of biomolecules. The optimized M4 membrane
showed a high surface porosity with a uniform pore size of 30 nm,
resulting in more than 99% protein rejection rate for immunoglobulin
G (IgG) but less than 20% rejection for bovine serum albumin, confirming
that the molecular weight cutoff is 100k Da. Furthermore, the fabricated
PES composite ultrafiltration membranes showed excellent antifouling
performance and flux recovery efficiency for proteins due to the hydrophilic
group of HEAA. This study provides an intelligent strategy for fouling
prevention and selective isolation of proteins.
The single crystal form and uncontrollable topography of CaCO3 in nature severely restrict its product grade and application. Meanwhile, lignin is still not utilized efficiently. In order to improve this, three types of lignin monomer model compounds as p‐coumaric acid (PCA), ferulic acid (FA), and sinapic acid (SA) are employed to induce the growth of CaCO3 to investigate the relationship between lignin structure and CaCO3 crystallization. The synthesized PCA and CaCO3 composite crystals (PC‐ACCs), FA and CaCO3 composite crystals (F‐ACCs), and SA and CaCO3 composite crystals (S‐ACCs) are characterized by field emission scanning electron microscope (FESEM), X‐ray diffraction (XRD), and Fourier transmission infrared spectroscopy (FTIR) to ascertain their molecular structures and crystal information. The growth rule of the acid and CaCO3 composite crystals (ACCs) induced by the three units is also explored. The results show that the vaterite and calcite of ACCs can be formed selectively. In the presence of PCA, FA, and SA, pH is the key factor on the phase selection of ACCs. The temperature and organic acid type also play important roles on the formation of CaCO3. The ACCs present distinguishing surface topographies at different temperatures. The number of methoxyl in the PCA, FA, and SA decides the phase ratio of vaterite and calcite in the ACCs.
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