Modeling and simulation of CO2 capture in aqueous ammonia with hollow fiber composite membrane contactors using a selective dense layer

Surface modification of polypropylene hollow fiber membranes using fluorosilane for CO2 absorption in a gas-liquid membrane contactor

Conventional methods for improving the hydrophobicity of polypropylene (PP) membranes to prevent wetting phenomena require complex pretreatment procedures in order to activate the surface for enabling the reaction with fluorosilane (FS)-based materials. This study successfully prepared PP membrane contactors with enhanced hydrophobicity through a simple single-step dip-coating method using perfluoroether-grafted silanes for CO2 capture. The FS coating layer on the PP membrane surface was confirmed through ATR-FTIR spectroscopy, XPS, FE-SEM, and EDS. Furthermore, the evaluation of the CO2 absorption performance and long-term stability of the FS-coated PP membrane according to the variation of the gas flow rate (50, 100, 200, 400, and 800 mL/min) confirmed the superior chemical stability and durability of our membranes to those of previously reported hydrophobic membranes. The as-prepared FS-coated PP membrane expands the application scope of gas-liquid membrane contactors for CO2 capture from the flue gas of coal-fired power plants.

Superhydrophobic Surface-Constructed Membrane Contactor with Hierarchical Lotus-Leaf-Like Interfaces for Efficient SO2 Capture

An organic-inorganic polyvinylidene fluoride/polyvinylidene fluoride-silica (PVDF/PVDF-SiO₂) mixed matrix membrane contactor is fabricated via a facile and efficient hydrophobic modification method. The solubility parameters of the PVDF particle are precisely regulated, the PVDF particles are blended with SiO₂ nanoparticles to form PVDF-SiO₂ suspension, and then the suspension is introduced onto the surface of the PVDF substrate by an in situ spin coating strategy. The PVDF particles are partly etched and incorporated to construct the adhesive PVDF-SiO₂ core-shell layer on the PVDF substrate, which results in a more stable PVDF-SiO₂ coating layer on the substrate. The surface structure is precisely regulated by changing the etching morphology of PVDF particles and amount of doped PVDF and SiO₂ particles, forming an integrated porous PVDF-SiO₂ layer and constructing hierarchical lotus-leaf-like interfaces. The resultant PVDF/PVDF-SiO₂ membrane contactors display the relatively regular distribution of pore size with ∼420 nm and excellent hydrophobic property with a water contact angle of ∼158°, which noticeably lightens wetting phenomena of membrane contactors. The SO₂ absorption fluxes can reach as high as 1.26 × 10^-3 mol·m^-2·s^-1 using 0.625 M of ethanolamine (EA) as liquid absorbent. The high stability of the SO₂ absorption flux test indicates the excellent interface compatibility between the PVDF-SiO₂ coating layer and the PVDF substrate. The versatile organic-inorganic layer exhibits super hydrophobic property, which prevents wetting of membrane pores. In addition, the membrane mass transfer resistance (H/K_m) and membrane phase transfer coefficient (K_m) are explored.

Hollow Fiber Membrane Contactors for Post-Combustion Carbon Capture: A Review of Modeling Approaches

Hollow fiber membrane contactors (HFMCs) can effectively separate CO2 from post-combustion flue gas by providing a high contact surface area between the flue gas and a liquid solvent. Accurate models of carbon capture HFMCs are necessary to understand the underlying transport processes and optimize HFMC designs. There are various methods for modeling HFMCs in 1D, 2D, or 3D. These methods include (but are not limited to): resistance-in-series, solution-diffusion, pore flow, Happel’s free surface model, and porous media modeling. This review paper discusses the state-of-the-art methods for modeling carbon capture HFMCs in 1D, 2D, and 3D. State-of-the-art 1D, 2D, and 3D carbon capture HFMC models are then compared in depth, based on their underlying assumptions. Numerical methods are also discussed, along with modeling to scale up HFMCs from the lab scale to the commercial scale.

Mixed matrix membrane contactor containing core-shell hierarchical Cu@4A filler for efficient SO2 capture

Achieving high flux membrane contactor is significantly important for hazardous gas removal. In this study, we prepared poly(vinylidene fluoride) (PVDF)-based mixed matrix membrane contactor (MMMC) that contained a core-shell hirarchical Cu@4A composite filler (Cu@4A). On one hand, the Cu@4A regulated the physical structure of MMMC, which enhanced gas permeation and thus resulted in the increment of physical SO₂ absorption flux. On the other hand, Cu@4A changed the chemical environment of MMMC by remarkably increased SO₂ facilitated transport sites, which elevated SO₂ concentration around Cu@4A by the enhancement of adsorption and oxidation of SO₂, resulting in the increase of chemical SO₂ absorption flux. Moreover, the copper nanosheets on 4A helped to construct facilitated transport pathways along the Cu@4A fillers at polymer-filler interface. The results showed that Cu@4A loaded MMMC exhibited increased SO₂ removal efficiency and SO₂ absorption flux compared with PVDF control membrane. Specifically, the M₁₀⁴⁰ MMMC loaded with 40 wt% Cu@4A and PVDF concentration 10 wt% exhibited the highest SO₂ removal efficiency and SO₂ absorption flux, which was up to 73.6% and 9.1 × 10^-4 mol·m^-2·s^-1 at the liquid flow rate of 30 L/h. Besides, the overall SO₂ mass transfer coefficient (K_o) and membrane mass transfer resistance (H/K_m) were investigated.