Guanhua Liu

Embedding dopamine nanoaggregates into a poly(dimethylsiloxane) membrane to confer controlled interactions and free volume for enhanced separation performance

In this study, a series of hybrid membranes with high separation performance and superior swelling-resistance were fabricated by incorporating metal ion-chelated dopamine nanoaggregates into a poly(dimethylsiloxane) (PDMS) bulk matrix membrane. The concomitant hydrogen bond, metal-organic coordination and π-complexation interactions render the synergy of a favorable free volume property, reinforced chain rigidity and facilitated transport function within the membranes. The membranes displayed simultaneously enhanced permeation flux and enrichment factors when utilized for model gasoline separation. Especially, when the weight fraction of dopamine/Cu reached 5.0 wt%, the membrane displayed an optimum separation performance with a permeation flux of 7.42 kg m−2 h−1 (2.7 times as much as that of the PDMS control membrane) and an enrichment factor of 4.81 (11% more than that of the PDMS control membrane). Thanks to the elevated cohesive energy and the chain extension effect, the swelling degree of the PDMS-dopamine/Cu membranes decreased remarkably with the dopamine/Cu content. This study may provide a novel route to the design and fabrication of robust, high-performance hybrid membranes to meet diverse energy and environment-related application requirements.

Enhanced desulfurization performance of PDMS membranes by incorporating silver decorated dopamine nanoparticles

Dopamine–silver (DAAg) nanoparticles were synthesized in aqueous solution via bioinspired adhesion and redox reaction, and they were then incorporated into poly (dimethyl siloxane) (PDMS) matrix to prepare PDMS–DAAg hybrid membranes for pervaporative desulfurization of model gasoline. The loading content of Ag(I) in DAAg nanoparticles could reach as high as 54.03 wt%. The polymer chain flexibility and membrane swelling properties were mediated by DAAg nanoparticles. The hybrid membrane with 5.0 wt% of DAAg nanoparticles displayed an optimum separation performance with permeation flux of 8.22 kg m−2 h−1 (3-fold higher than that of PDMS control membrane) and enrichment factor of 5.03 (50% higher than that of PDMS control membrane). The enhancement of separation performance was mainly due to the facilitated transport of thiophene by reversible interaction between Ag(I) and thiophene molecules, and the moderate fractional free volume tuned by DAAg nanoparticles. Moreover, effects of operation parameters such as temperature, thiophene concentration in the feed, and feed Reynolds number on the permeation flux and enrichment factor were investigated.

Enhancing the permeation selectivity of sodium alginate membrane by incorporating attapulgite nanorods for ethanol dehydration

Hybrid membranes for ethanol dehydration were fabricated by blending sodium alginate with natural hydrophilic attapulgite nanorods, which contained plentiful selective channels and hydrophilic –OH groups. With the incorporation of attapulgite nanorods, the crystallinity of hybrid membranes was gradually decreased and the content of non-freezable water in hybrid membranes was increased, facilitating the solution-diffusion process of water molecules by forming hydration layers along the nanorods. The water uptake of hybrid membranes was ∼10% higher than the pristine alginate membrane while the swelling degree in feed solution was only increased by ∼1%, exhibiting good structural stability in ethanol dehydration. The optimum separation performance with a permeate flux of 1356 g m−2 h−1 and a separation factor of 2030 for dehydration of a 90/10 wt% ethanol/water feed was achieved using the hybrid membrane with 2 wt% of attapulgite nanorods. Moreover, the influences of feed temperature and feed composition on separation performance were investigated.

Creation of hierarchical structures within membranes by incorporating mesoporous microcapsules for enhanced separation performance and stability

In this study, we present a novel approach for fabricating hybrid membranes with superior separation performance and physicochemical stability by incorporating multifunctional dopamine mesoporous microcapsules upon CaCO3 template. The microcapsules are synthesized via the synergy of surface segregation, metal–organic coordination and biomimetic mineralization. The micro-scale hollow lumen and the mesoporous wall decrease diffusion resistance of the membranes by endowing smaller effective membrane thickness and introducing additional shorter permeation pathways for the penetrants, which lead to a faster mass transfer within the membranes. Meanwhile, the microcapsules bridge the polymer chains mainly owing to the numerous mesopores and unique bio-adhesion, which render the optimal polymer–microcapsule interface. Due to the hierarchical structures spanning from microscale, nanoscale to molecular-scale within the membranes, the membranes display remarkably enhanced permeation flux and desired enrichment factor when utilized for model gasoline separation. In addition, due to the elevated cohesive energy and reinforced chain rigidity, the membranes display higher thermal and mechanical stability. This study can identify a facile, generic, and efficient route to design and fabricate a variety of robust, high-performance hybrid membranes for a broad range of energy and environment-related applications.

Functionally graded membranes from nanoporous covalent organic frameworks for highly selective water permeation

Natural materials are often arranged in intricate gradient architectures to implement specific functionalities. Implanting such an exquisite prototype into synthetic membranes remains a grand challenge in real-world applications. In this study, functionally graded membranes are fabricated through a surface segregation method using 2D nanoporous COF TpHZ and poly(ether sulfone) as composite building blocks. During the membrane formation, the COF nanosheets can spontaneously migrate from the membrane bulk to the membrane surface to form a gradient distribution, which can be varied by manipulating the COF addition content and phase inversion temperature. The highest COF content on the membrane surface can be up to 50.90 vol%. Due to the formation of a graded structure, the membranes are endowed with remarkably increased hydrophilicity and free volume characteristics. Accordingly, the optimized membrane exhibits a permeation flux of 2.48 kg m−2 h−1 and a high separation factor of 1430, and remains robust during a stability test for 320 h, and is one of the most efficient mixed matrix membranes for water/ethanol separation. The separation factor is two orders of magnitude more than that of existing commercial membranes. The concept of functionally graded membranes can be applicable to the development of a broad range of high-performance materials.