Nanofiltration Ceramic Membranes as a Feasible Two-Pronged Approach toward Desalination and Lithium Recovery.

Atomic layer deposition (ALD) is known for its unparalleled control over layer thickness and 3D conformality and could be the future technique of choice to tailor the pore size of ceramic nanofiltration membranes. However, a major challenge in tuning and functionalizing a multichannel ceramic membrane is posed by its large internal pore volume, which needs to be evacuated during ALD cycling. This may require significant energy and processing time. This study presents a new reactor design, operating at atmospheric pressure, that is able to deposit thin layers in the pores of ceramic membranes. In this design, the reactor wall is formed by the industrial tubular ceramic membrane itself, and carrier gas flows are employed to transport the precursor and co-reactant vapors to the reactive surface groups present on the membrane surface. The layer growth for atmospheric-pressure ALD in this case proceeds similarly to that for state-of-the-art vacuum-based ALD. Moreover, for membrane preparation, this new reactor design has three advantages: (i) monolayers are deposited only at the outer pore mouths rather than in the entire bulk of the porous membrane substrate, resulting in reduced flow resistances for liquid permeation; (ii) an in-line gas permeation method was developed to follow the layer growth in the pores during the deposition process, allowing more precise control over the finished membrane; and (iii) expensive vacuum components and cleanroom environment are eliminated. This opens up a new avenue for ceramic membrane development with nano-scale precision using ALD at atmospheric pressure.

Textile Industry Wastewater Treatment by Cavitation Combined with Fenton and Ceramic Nanofiltration Membrane

Water scarcity is one of the significant issues many countries face due to the increased demand for freshwater and exhaustion of water resources. Therefore, developing efficient technologies for water purification is anticipated. Nowadays, nanofiltration (NF) separation processes are gaining importance in water purification and pre-treatment for desalination due to their capability in eliminating hardness, salts, and multivalent ions. In addition, NF can be operated under relatively lower pressure than reverse osmosis (RO), where its membrane pore size lies between ultrafiltration (UF) and RO membrane. Polymeric membranes such as polyamide, cellulose acetate, and polyethersulfone are generally used in NF. Many polymeric membranes offer flexibility in the fabrication process and are relatively inexpensive. However, the application of ceramic membranes in water purification has increased hastily due to their beneficial characteristics such as longer life span, fouling resistance, high stability towards corrosive media, and greater mechanical strength. Hence, this chapter discusses the recent signs of progress in ceramic NF membranes for water purification. Various kinds of composite ceramic NF membranes were elaborated in detail, including ceramic-ceramic, ceramic membranes incorporated with nanoparticles and metal–organic frameworks, and ceramic-polymeric membranes. In addition, the implementation of ceramic NF membranes for various water purification methods such as desalination, heavy metal ion removal, removal of dyes, etc., were discussed.

Ceramic membrane technology, whether applied as a stand-alone separation technology or in combination with energy-intensive approaches like distillation, is a promising solution for lower energy alternatives with minimal carbon footprints. To improve the separation of solutes in the nanofiltration range from industrial wastewater streams, ceramic nanofiltration (NF) membranes with reproducible sub-nanometre pore sizes are required. To achieve this, the emerging technique of molecular layer deposition (MLD) is employed to develop ceramic NF membranes, and its efficiency and versatility make it a powerful tool for preparing uniform nanoscale high-porosity membranes. Our work, which involved vapor-phase titanium tetrachloride as a precursor and ethylene glycol as a co-reactant, followed by calcination in air at 350 °C, resulted in NF membranes with pore sizes (radii) around ~0.8 ± 0.1 nm and a demineralized water permeability of 13 ± 1 L·m-2·h-1·bar-1.The high-water flux with >90% rejection of polyethylene glycol molecules with a molecular size larger than 380 ± 6 Dalton indicates the efficiency of the MLD technique in membrane functionalization and size-selective separation processes, and its potential for industrial applications.

Ceramic nanofiltration and membrane distillation hybrid membrane processes for the purification and recycling of boric acid from simulative radioactive waste water

Ionic liquid imbibition of ceramic nanofiltration membranes

One step co-sintering process for low-cost fly ash based ceramic microfiltration membrane in oil-in-water emulsion treatment

Ceramic nanofiltration (NF) is a newly-developed technology for water recycling, but is still limited to pilot-scale applications. Lacking efficient and eco-friendly strategies for cleaning ceramic NF membrane impedes its scaling-up in industries. Forward flush, backwash and acidic/caustic cleaning are not efficient enough. In this work, a novel oxalic acid-aided Fenton process was proposed for synergistic relaxation/oxidation of persistent Ca2+-mediated gel-like fouling of ceramic NF membrane. A reactive catalyst layer was online pre-coated on top of the membrane via a pressure-driven cross-flow pre-filtration of Fe3O4 hydrosols. The gel-like fouling was simulated by alginate in the presence of Ca2+ ions. Results show that the Fe3O4 loading could be readily tuned from 0.16 to 1.34 g m−2 by altering the permeate flux during the pre-coating. The membrane permeability loss due to the pre-coating was minimal (<10%). The combination of oxalic acid chelation and Fenton-based oxidation resulted in high flux recovery (85.07%) for the iron-oxide pre-coated membrane, whereas the single treatment by hydrogen peroxide (H2O2) or oxalic acid was inefficient. This synergistic effect was attributed to relaxation of the Ca2+-mediated gel layer via oxalic acid/Ca2+ chelation, which presumably facilitated H2O2 diffusion at the Fe3O4/foulant interface. The iron-oxide pre-coated membrane maintained stable initial normalized fluxes (83.33–90.15%) through the oxalic acid/H2O2 cleaning over five cycles, with no need of refreshing the iron-oxide pre-coat. Additionally, the leaching of iron from the iron-oxide pre-coat by oxalic acid was suppressed by the oxalic acid/H2O2 combination, owing to a reactive shielding by competitive sorption of H2O2 onto the Fe3O4 surface. Overall, the synergistic relaxation/oxidation method, demonstrated in this study, provides new insights into improving reactivity of Fenton-based processes on hybrid catalytic ceramic membranes for water treatment or fouling control.

Performance of ceramic nanofiltration membrane for desalination of dye solutions containing NaCl and Na2SO4

Ceramic membrane with double catalytic layer for efficient peroxymonosulfate activation and dissolved organic matter (DOM) membrane fouling control

Ceramic membranes have become one of the most rapidly developing and promising membrane materials owing to their excellent properties. Compared with other membrane materials, ceramic membranes are widely used in the wastewater and water treatment fields owing to their advantages, including higher chemical stability, stronger mechanical strength, longer service life, and better water filtration performance. In this paper, the sources of raw materials and their preparation for the production of ceramic membranes are briefly introduced. The methods for preparing ceramic membranes are described in detail, including the role of ceramic membranes in water treatment applications, the preparation methods of the membranes, and the latest progress in this area, along with a review of the applications of ceramic membranes in wastewater and water treatment. Simultaneously, this study also evaluates which preparation method is the most advantageous and the aspects of its advantages. The raw materials used in the ceramic membrane preparation and the types of water treatment suitable for this method were studied. The results showed that the phase-conversion sintering technique has multiple advantages, and the generated asymmetric structure with finger- and sponge-like voids can further improve the flux and separation abilities, which are attractive for scientific researchers. Finally, the development trends in the inorganic ceramic membrane market were surveyed. This work can help beginners understand the preparation procedures employed to produce ceramic membranes for water treatment; compare the porosity, mechanical strength, permeation flux, and chemical and thermal stability of the resulting membranes; and reasonably select the appropriate preparation method for the relevant water treatment type.

Feasibility and challenges of low-cost ceramic membranes in water treatment applications

Efficiently mitigating permeability-reactivity trade-off and membrane fouling on Cu-N-C functionalized ceramic catalytic membrane for enhanced water treatment.

&lt;p&gt;The application of ceramic Nanofiltration (NF) membrane in brackish water treatment is increasing due to strict water quality standards. Ceramic NF is a widely used membrane process and has replaced reverse osmosis (RO) membranes in many applications due to lower energy consumption and higher flux rates. This work aims to study the separation performance of tubular ceramic TiO2 Nanofiltration membrane at low-pressure (2 bar) for single and tertiary salt mixture separation. The results showed that the rejection of ions is ordered as follows: R (Cl1-) ion size &amp;gt; R calcium (Ca2+) ion size &amp;gt; R sodium (Na1+) ion size &amp;gt; R magnesium (Mg2+) ion size. Moreover, the highest Cl1- rejection was about 46%, the highest Ca2+ and Mg2+ rejection was about 44%, and the highest Na1+ rejection was about 37%. The pure water flux through the investigated ceramic NF membrane for distilled water was calculated to be 5.29 x 10-7 m3 s-1 m-2 bar-1, and this flux was dropped down for the salt mixture feed to 2.56 x 10-7 m3 s-1 m-2 bar-1 due to the presence of salt particles in the feed.&lt;/p&gt;&#x0D;

Application of ZnO nanostructures in ceramic and polymeric membranes for water and wastewater technologies: A review