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.
Highlights
With the rapid development of industry, low-carbon renewable energy has attracted considerable interest due to its potential for reduced emissions of greenhouse gases
The analysis described in the present study demonstrates that a poly(vinylidene fluoride) (PVDF) hollow fibre membrane with a superhydrophobic layer has the potential to improve the stability of long-term performance in liquid–gas membrane processes
Superhydrophobic PVDF hollow fibre membranes with a water contact angle of 155° ± 3° were prepared by coating the membranes with a suspension of commercially available hydrophobic SiO2 nanoparticles at room temperature and atmospheric pressure
Summary
With the rapid development of industry, low-carbon renewable energy has attracted considerable interest due to its potential for reduced emissions of greenhouse gases. In addition to being an alternative fuel for large-scale operations, biogas can be used as fuel for vehicles, for which demand has risen significantly over the past few decades [2]. In these applications, purification steps are essential to meet specifications, because the exothermic value of biogas is reduced by the large amount of CO2 present. The conventional pressurized liquid scrubbing process has been considered to be a simple and cheap technology and is applied in more than 53% of biogas purification processes among industrial facilities [6]. Researchers need to develop better processes to remove CO2 from biogas
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