Electrolysis with ultrafiltration membrane as a pretreatment for seawater desalination

The work explores the feasibility of applying membrane electrolysis incorporated with a low-cost ultrafiltration (UF) membrane as an alternative seawater pretreatment process. For the first time, this study evaluates the potential of replacing anolyte Na 2 SO 4 with seawater in both UF membrane electrolysis chamber, eliminating chemical anolyte requirement, paving the way for a chemical-free pretreatment. Likewise, the novel approach of incorporating activated carbon (AC) submerged in the electrolysis chamber as a supplementary flow electrode material is examined. The combination of dual chamber seawater UF membrane electrolysis incorporated with AC removed up to 99% of Ca 2+ and Mg 2+ , while also efficiently removing boron and bromide. Dispersed AC provides high-surface-area adsorption sites and functions as a network of conductive micro-electrodes. This adsorption-electrochemical interaction synergy enabled 60% boron removal in the catholyte, against 38% without AC. AC also improved anode-side bromide oxidation, attaining 99.5% removal while inhibiting the chlorine evolution reaction (CER), increasing selectivity and overall process efficiency. Operating at a reduced current density of 4 mA cm −2 resulted in comparable seawater ion removal efficiency within 5 h as that at 8 mA cm −2 , with 51% lower energy consumption. Also, Ca and Mg can be recovered as Ca(OH) 2 and Mg(OH) 2 , providing a low-carbon route to raw limestone mining for cement feedstock production. These findings establish that AC-assisted UF membrane electrolysis as an alternative low chemical and scalable pretreatment platform for seawater pretreatment.