No abstract

No abstract

Porous membranes as gas-liquid contactors are widely used in carbon dioxide (CO2) absorption systems. It provides larger mass transfer area and excellent operational flexibility. Membrane contactors have been considered as alternative to conventional approaches in removing CO2. In spite of its advantages over conventional technologies, membrane wetting is a major problem which reduces performance of CO2 absorption. This paper explains the concept of membrane wetting phenomenon and its influence on the CO2 mass transfer through the membrane and absorption performance. The factors that cause membrane wetting were presented including hydrophobicity of membranes surfaces, membrane pore size, liquid entry pressure and properties of absorbent liquid. Current proposed methods to alleviate the membrane wetting were reviewed and discussed. Development of mathematical model was presented for all types of membrane wetting modes, as well as its validity for CO2 physical and chemical absorption.

No abstract

The hydrophobic membranes have been widely explored to meet the membrane characteristics for the membrane distillation (MD) process. Inorganic metal oxide nanoparticles have been used to improve the membrane hydrophobicity, but limited studies have used nano clay particles. This study introduces halloysite nanotube (HNT) as an alternative material to synthesis a hydrophobic poly(vinylidene fluoride) (PVDF)-HNT membrane. The PVDF membranes were fabricated using functionalized HNTs (e.g., carnauba wax and 1H,1H,2H,2H-perfluorooctyl-trichlorosilane (FOTS)). The results were determined by Fourier transform infrared-attenuated total reflection, scanning electron microscope, goniometer and porometer to determine the desired hydrophobic membrane for direct contact membrane distillation (DCMD). The addition of FOTS-HNT (fs-HNT) and carnauba wax-HNT (fw-HNT) in the PVDF membrane enhanced the water contact angle (CA) to 127° and 137°, respectively. The presence of fw-HNT in the PVDF membrane exhibited higher liquid entry pressure (LEP) (2.64 bar) compared to fs-HNT in the membrane matrix (1.44 bar). The PVDF/fw-HNT membrane (Pfw-HNT) obtained the highest flux of 7.24 L/m2h with 99.9% salt removal. A stable permeability in the Pfw-HNT membrane was obtained throughout 16 h of DCMD. The incorporation of fw-HNT in the PVDF membrane had improved the anti-wetting properties and the membrane performance with the anti-fouling effect.

No abstract

No abstract

Shear rate is proven in many studies to be playing an important role in reducing the concentration polarization and membrane fouling. This paper investigates the effect of rotation speed of corrugated spacer on the shear rate using computational fluid dynamics (CFD). Two small channels with the inner membrane (IM) 39 mm from the axis of rotation and outer membrane (OM) with 41.5 mm were used for the studies. The inlet pressure is set as 100 kPa and water is used to study the shear stress on the rotating membrane. The average surface shear rate between the two membranes is found out to be increasing with the rotation. The average shear rate on stationary membrane is 25,645 s -1 and increased to 46,961 s -1 at rotation speed of 250 rad/s. The shear rate of OM is larger than IM when the rotation speed is lower than 75 rad/s but the shear rate on IM is larger when rotation speed is higher than 75 rad/s. The rotation of corrugated spacer can be applied to the spiral wound membrane module to increase the shear rate and thus increase the permeate flux and reduce the concentration polarization.