Atmospheric-pressure atomic layer deposition (ALD) is an upcoming technology poised to revolutionize the commercial production of large-area substrates and unlock new applications in high-porosity/3D materials.

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.

Sodium hypochlorite (NaClO) is widely used for the chemical cleaning of fouled ultrafiltration (UF) membranes. Various studies performed on polymeric membranes demonstrate that long-term (>100 h) exposure to NaClO deteriorates the physicochemical properties of the membranes, leading to reduced performance and service life. However, the effect of NaClO cleaning on ceramic membranes, particularly the number of cleaning cycles they can undergo to alleviate irreversible fouling, remains poorly understood. Silicon carbide (SiC) membranes have garnered widespread attention for water and wastewater treatment, but their chemical stability in NaClO has not been studied. Low-pressure chemical vapor deposition (LP-CVD) provides a simple and economical route to prepare/modify ceramic membranes. As such, LP-CVD facilitates the preparation of SiC membranes: (a) in a single step; and (b) at much lower temperatures (700–900 °C) in comparison with sol-gel methods (ca. 2000 °C). In this work, SiC ultrafiltration (UF) membranes were prepared via LP-CVD at two different deposition temperatures and pressures. Subsequently, their chemical stability in NaClO was investigated over 200 h of aging. Afterward, the properties and performance of as-prepared SiC UF membranes were evaluated before and after aging to determine the optimal deposition conditions. Our results indicate that the SiC UF membrane prepared via LP-CVD at 860 °C and 100 mTorr exhibited excellent resistance to NaClO aging, while the membrane prepared at 750 °C and 600 mTorr significantly deteriorated. These findings not only highlight a novel preparation route for SiC membranes in a single step via LP-CVD, but also provide new insights about the careful selection of LP-CVD conditions for SiC membranes to ensure their long-term performance and robustness under harsh chemical cleaning conditions.

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.