3D printed photocatalytic feed spacers functionalized with β-FeOOH nanorods inducing pollutant degradation and membrane cleaning capabilities in water treatment

• Novel photocatalytic 3D printed feed spacers developed for (waste)water treatment. • β-FeOOH nanorods were mineralized on PDA/PEI-coated polyamide spacer. • The spacers degraded methylene blue and 4-nitrophenol in the feed during filtration. • Photocatalytic spacer also cleaned the organic foulants deposited on the membrane. • New approach enables a shift to spacer-centered photocatalytic membrane systems. A novel 3D printed photocatalytic feed spacer was developed for use in membrane-based water and wastewater filtration systems. The spacer fulfilled two new functions; degradation of membrane-permeating pollutants in the feed and membrane cleaning, in addition to its basic role as membrane support. The spacer, designed based on a triply periodic minimal surface architecture, was coated with polydopamine-polyethyleneimine, on which a photocatalytic layer of β-FeOOH nanorods was mineralized. The photocatalytic performance of the spacer was demonstrated through the degradation of methylene blue and 4-nitrophenol, both in batch and crossflow ultrafiltration (UF) modes. The spacer also exhibited the ability to clean the membrane surface of three organic foulants (humic acid (HA), sodium alginate (SA) and bovine serum albumin (BSA)), with a flux recovery ratio of 92 %, 60 %, and 54 % achieved for SA, HA, and BSA, respectively. This enables a shift to spacer-centered photocatalytic membrane system approach in water and wastewater treatment.