Sophie Cerneaux

Highly Efficient Hydrophobic Titania Ceramic Membranes for Water Desalination

Hydrophobic titania ceramic membranes (300 kD) were prepared by grafting of C6F13C2H4Si(OC2H5)3 and C12F25C2H4Si(OC2H5)3 molecules and thus applied in membrane distillation (MD) process of NaCl solutions. Grafting efficiency and hydrophobicity were evaluated by contact angle measurement, atomic force microscopy, scanning electron microscopy, nitrogen adsorption/desorption, and liquid entry pressure measurement of water. Desalination of NaCl solutions was performed using the modified hydrophobic membranes in air gap MD (AGMD) and direct contact MD (DCMD) processes in various operating conditions. High values of NaCl retention coefficient (>99%) were reached. The permeate fluxes were in the range 231-3692 g·h(-1)·m(-2), depending on applied experimental conditions. AGMD mode appeared to be more efficient showing higher fluxes and selectivity in desalination. Overall mass transfer coefficients (K) for membranes tested in AGMD were constant over the investigated temperature range. However, K values in DCMD increased at elevated temperature. The hydrophobic layer was also stable after 4 years of exposure to open air.

Membrane distillation properties of TiO2 ceramic membranes modified by perfluoroalkylsilanes

Abstract The tubular and planar TiO2 ceramic membranes were modified by grafting with perfluoroalkylsilanes (PFAS) molecules. Two types of PFAS were used for grafting process: 1H,1H,2H,2H-perfluorooctyltriethoxysilane (C6) and 1H,1H,2H,2H-perfluorotetradecyltriethoxysilane (C12). Studies showed that hydrophilic surface of titania ceramic membranes can be efficiently modified as a results of the proposed grafting method. Grafting efficiency of the tubular membranes was determined by measurement of liquid water entry pressure (LEPw), whereas grafting efficiency of planar membranes was verified by contact angle measurement. The contact angle values of the planar membranes are 130 and 140° for grafting with C6 and C12, respectively. The LEPw of the tubular membranes increased from 2 bar to 10 bar after modification by C12, whereas the LEPw values were constant at 2 bar when TiO2 membrane was modified by C6 molecules. It was found that water contact angle, LEPw, and water flux in the membrane distillation (MD)...

How To Functionalize Ceramics by Perfluoroalkylsilanes for Membrane Separation Process? Properties and Application of Hydrophobized Ceramic Membranes

The combination of microscopic (atomic force microscopy and scanning electron microscopy) and goniometric (static and dynamic measurements) techniques, and surface characterization (surface free energy determination, critical surface tension, liquid entry pressure, hydraulic permeability) was implemented to discuss the influence of perfluoroalkylsilanes structure and grafting time on the physicochemistry of the created hydrophobic surfaces on the titania ceramic membranes of 5 kD and 300 kD. The impact of molecular structure of perfluoroalkylsilanes modifiers (possessing from 6 to 12 carbon atoms in the fluorinated part of the alkyl chain) and the time of the functionalization process in the range of 5 to 35 h was studied. Based on the scanning electron microscopy with energy-dispersive X-ray spectroscopy, it was found that the localization of grafting molecules depends on the membrane pore size (5 kD or 300 kD). In the case of 5 kD titania membranes, modifiers are attached mainly on the surface and only partially inside the membrane pores, whereas, for 300 kD membranes, the perfluoroalkylsilanes molecules are present within the whole porous structure of the membranes. The application of 4 various types of PFAS molecules enabled for interesting observations and remarks. It was explained how to obtain ceramic membrane surfaces with controlled material (contact angle, roughness, contact angle hysteresis) and separation properties. Highly hydrophobic surfaces with low values of contact angle hysteresis and low roughness were obtained. These surfaces possessed also low values of critical surface tension, which means that surfaces are highly resistant to wetting. This finding is crucial in membrane applicability in separation processes. The obtained and characterized hydrophobic membranes were subsequently applied in air-gap membrane distillation processes. All membranes were very efficient in MD processes, showing good transport and selective properties (∼99% of NaCl salt rejection). Depending on the membrane pore size and used modifiers, the permeate flux was in the range of 0.5-4.5 kg·m(-2)·h(-1) and 0.3-4.2 kg·m(-2)·h(-1) for 5 kD and 300 kD membranes, respectively.

Effect of hydrophilic modification with nano-titania and operation modes on the oil–water separation performance of microfiltration membrane

AbstractThe tubular Al2O3 microfiltration membranes modified with nano-TiO2 coating were applied in the separation of waste oil-in-water emulsion. The separation performances of the MF membranes with and without nano-TiO2 modification were studied under two different operation modes, i.e. the circulation mode and the concentration mode, respectively. The circulation mode in which the oil concentration in feed keeps constant simulates the condition of the great amount of feed to be treated, while the concentration mode in which the oil concentration in feed increases with the extraction of the filtrate simulates the condition of a small amount of feed to be treated. The results show that the operation mode has a less effect on the flux of the MF membranes, but has an important effect on the oil concentration of filtrate for the unmodified membrane. The oil concentration in filtrate under concentration mode is higher than that of circulation mode. For the modified membrane, the operation mode has a less eff...

Electro-oxidation of organic pollutants by reactive electrochemical membranes

Electro-oxidation processes are promising options for the removal of organic pollutants from water. The major appeal of these technologies is the possibility to avoid the addition of chemical reagents. However, a major limitation is associated with slow mass transfer that reduces the efficiency and hinders the potential for large-scale application of these technologies. Therefore, improving the reactor configuration is currently one of the most important areas for research and development. The recent development of a reactive electrochemical membrane (REM) as a flow-through electrode has proven to be a breakthrough innovation, leading to both high electrochemically active surface area and convection-enhanced mass transport of pollutants. This review summarizes the current state of the art on REMs for the electro-oxidation of organic compounds by anodic oxidation. Specific focuses on the electroactive surface area, mass transport, reactivity, fouling and stability of REMs are included. Recent advances in the development of sub-stoichiometric titanium oxide REMs as anodes have been made. These electrodes possess high electrical conductivity, reactivity (generation of •OH), chemical/electrochemical stability, and suitable pore structure that allows for efficient mass transport. Further development of REMs strongly relies on the development of materials with suitable physico-chemical characteristics that produce electrodes with efficient mass transport properties, high electroactive surface area, high reactivity and long-term stability.