Surface modification of poly(vinylidene fluoride) hollow fibre membranes for biogas purification in a gas–liquid membrane contactor system

Abstract

The wetting of hollow fibre membranes decreases the performance of the liquid–gas membrane contactor for CO2 capture in biogas upgrading. To solve this problem, in this work, a poly(vinylidene fluoride) (PVDF) hollow fibre membrane for a liquid–gas membrane contactor was coated with a superhydrophobic layer composed of a combination of hydrophobic SiO2 nanoparticles and polydimethylsiloxane (PDMS) by the method of spray deposition. A rough layer of SiO2 deposited on the PVDF membrane resulted in an enhanced surface hydrophobicity. The surface structure of the pristine PVDF significantly affected the homogeneity of the generated SiO2 layer. A uniform surface coating on the PVDF upper layer resulted from the presence of micrometre and nanometre-sized roughness on the surface of the PVDF membrane, which was achieved with a SiO2 concentration of 4.44 mg ml−1 (0.2 g/45 ml) in the coating solution. As a result, the water contact angle of the modified surface was recorded as 155 ± 3°, which is higher than that of the pristine surface. The high contact angle is advantageous for reducing the wetting of the membrane. Additional mass transfer resistance was introduced by the superhydrophobic layer. In addition, continuous CO2 absorption tests were carried out in original and modified PVDF hollow fibre membrane contactors, using monoethanolamine (MEA) solution as the absorbent. A long-term stability test revealed that the modified PVDF hollow fibre membrane contactor was able to outperform the original membrane contactor and demonstrated outstanding long-term stability, suggesting that spray deposition is a promising approach to obtain superhydrophobic PVDF membranes for liquid–gas membrane absorption.

Comparison of separation performance of absorption column and membrane contactor system for biohydrogen upgraded from palm oil mill effluent fermentation

“…Evaluation of gas–liquid membrane contactor performance in separating H 2 /CO 2 mixtures was performed by using PVDF hollow fiber membranes as the physical barrier between the gases to be separated and the liquid absorbent. PVDF hollow fiber membranes were selected because of their satisfactory characteristics, which meet the criteria for H 2 /CO 2 separation 14,15,33 . Before evaluating the separation performance of gas–liquid membrane contactor, the characteristics of the hollow fiber membranes used with this unit were analyzed in terms of their morphology and physical and chemical properties.…”

“…According to the contact angle value of the membranes, presented in Figure 5c, the hollow fiber membrane has a hydrophobic surface with a contact angle value of 96.6 ± 1.89°. It might have less tendency to allow liquid to pass through its layer 15,33 . The characteristics of PVDF hollow fiber membrane presented here are essential for maintaining the separation performance of the system.…”

“…Numerous established gas upgrading methods, such as absorption, adsorption, and membrane technology, have been reportedly used for purifying valuable/energy gases 13‐15 . Of these, the most preferred approach for CO 2 removal is chemical absorption because of its high reactivity 12,16 .…”

Large-scale fabrication of porous YBO 3 hollow microspheres with tunable photoluminescence

“…[4,9,24–31]. Thus, much attention has been devoted to synthesizing hollow structures of various functional materials.…”

“…As a unique family of functional materials, hollow structure materials possess a large fraction of empty space and high surface area which endow them with broad applications in gas sensors, drug delivery, biomaterials, water treatment, supercapacitors, dye-sensitized solar cells, heterogeneous catalysts, fuel cells, etc. [4,9,[24][25][26][27][28][29][30][31]. Thus, much attention has been devoted to synthesizing hollow structures of various functional materials.…”