Advancing Water Treatment: Comparing Atomic Layer Deposition and Vapor Phase Infiltration for Polymer Membrane Modification

Clean water is essential for all communities, both for sustenance and energy needs. Membrane technologies are a growing solution for water treatment due to their high separation efficiency and low energy consumption. However, as these technologies evolve, there is still a need for membranes with improved selectivity, reduced fouling, and stability in harsh conditions.

Atomic Layer Deposition (ALD) is a thin-film deposition technique used to generate atomically precise layers of deposited materials. In industry, this method has primarily been used in the semiconductor and energy conversion space. More recently, ALD has been applied to engineer membranes for water treatment. Vapor phase infiltration (VPI), an ALD-derived method, allows materials to infiltrate into polymer chains. As a relatively new technique, its distinction from ALD remains under-defined. So far, VPI has been used to enhance materials’ mechanical strength and fine tune their physical properties (conductivity, internal strain, etc.), and has found success in creating organic-inorganic hybrid materials. However, its use in water treatment membranes remains underexplored. This review seeks to clarify the distinction between ALD and VPI and highlight VPI’s potential benefits for polymer membrane modification in water treatment.

To assess current work done by ALD and VPI for water treatment membranes, we conducted a systematic literature review to research ALD and VPI’s use in modifying polymer membranes. Our search was restricted to polymer membranes specifically as this is an industry standard and is compatible with the described processes. We examine how these techniques enhance membrane properties like flux, hydrophilicity, pore size, and fouling resistance.

ALD has demonstrated efficacy in modifying polymer membranes, particularly through metal oxide coatings that reduce organic fouling and enhance water flow. However, balancing hydrophilicity and pore size with ALD remains a challenge. Specifically, it’s difficult to ensure ALD coatings are thick enough to enhance flux but not so thick that they reduce pore size and water flow. This is one area where VPI could be a promising alternative, as it addresses these challenges by integrating materials into polymer chains, enhancing durability and hydrophilicity without compromising pore size.

Although both ALD and VPI allow for precise membrane modification, ALD’s limitations in long-term membrane durability present challenges. Given VPI’s potential in this area, its use could sustainably enhance clean water access and facilitate broader industry adoption. However, not much work has been done to assess VPI’s utility in this space. We recommend further research on VPI’s use for polymer membranes in order to fully explore the benefits it may offer for sustainable and cost-effective water treatment.