Oriented Clay Nanotube Membrane Assembled on Microporous Polymeric Substrates

Abstract

Organized arrays of halloysite clay nanotubes have great potential in molecular separation, absorption, and biomedical applications. A highly oriented layer of halloysite on polyacrylonitrile porous membrane was prepared via a facile evaporation-induced method. Scanning electronic microscopy, surface attenuated total reflection Fourier transform infrared spectroscopy, and energy dispersive X-ray spectroscopy mapping indicated formation of the nanoarchitecture-controlled membrane. The well-ordered nanotube coating allowed for the excellent dye rejection (97.7% for reactive black 5) with high salt permeation (86.5% for aqueous NaCl), and thus these membranes were suitable for dye purification or concentration. These well-aligned nanotubes' composite membranes also showed very good fouling resistance against dye accumulation and bovine serum albumin adsorption as compared to the pristine polyacrylonitrile or membrane coated with disordered halloysite layer.

Strategic Design of Clay‐Based Multifunctional Materials: From Natural Minerals to Nanostructured Membranes

“…The commonality of casting, dip coating, and spray coating is evaporation‐induced assembly. Some nonvolatile solutes such as polymers and dispersed particles such as clay nanosheets can lead to inconsistencies in an ordered structure during evaporation . Thus, in order to take the extreme simplicity of the top‐down technique to its full potential and obtain a regular structure, the choice of solvent and solution concentration, the control of evaporation flux and interfacial interaction are the most important considerations .…”

Heteroepitaxial growth of vertically orientated zeolitic imidazolate framework‐L (Co/Zn‐ZIF‐L) molecular sieve membranes

“…The gradual evaporation of PVA solution containing PSS‐HNTs not only enables a highly oriented HNTs layer (Figure S2a) but also boosts the interfacial stability significantly. This ordered arrangement of HNTs is closely associated with the hydrophilic surface of support, high axis ratio of nanotubes with high free volume, and capillary flow direction during a slow evaporation process, which is discussed in detail in our previous study 33 …”

“…Figure 1 illustrates heteroepitaxial grown Co‐ZIF‐L with a vertical orientation on a Zn‐ZIF‐L seeded layer by employing well‐aligned, functionalized nanotubes as a substrate. Our group has previously reported the assembly of well‐aligned halloysite nanotubes (HNTs: [Al 2 Si 2 O 5 (OH) 4 ·2H 2 O]) onto a PAN substrate via an evaporation‐induced method 33 . We postulated that the large surface area, high hydrophilicity, and organized arrays of modified nanotubes facilitated the uniform heterogeneous nucleation of ZIF‐L atop a modified polymeric substrate.…”

“…This ordered arrangement of HNTs is closely associated with the hydrophilic surface of support, high axis ratio of nanotubes with high free volume, and capillary flow direction during a slow evaporation process, which is discussed in detail in our previous study. 33 It was observed that, through a secondary growth, a layer of Zn-ZIF-L with a series of staggered vertical nanosheets orderly was stacked on PSS-HNTs functionalized surface ( Figure S2b). Despite the presence of macrovoids among the aligned nanosheets, there were no apparent defects such as pinholes or cracks.…”

Suppressing Salt Transport through Composite Pervaporation Membranes for Brine Desalination

“…During the formation of PVA-GO surface coating, the gradual evaporation of the solvent (water) allowed the cross-linking of the PVA chains, forming the final coating layer of 0.5-1 µm. In terms of the GO, the evaporation-induced capillary flow during the drying process, together with the viscous PVA solution, disrupted the entropy-driven phase transition of GO, leading to the formation of surface protrusions [44]. The XRD pattern can reveal the GO nanosheets arrangement within the hybrid coating layer.…”