Boron Removal Using Membranes

Boron is an important micronutrient for humans, animals, and plants, although the range between deficiency and excess is narrow. The use of desalinated water and the reuse of treated wastewater for irrigation may result in excess boron. In aqueous environments boron is mainly present as boric acid, which at natural pH of water is mostly undissociated and insufficiently rejected by desalination membranes.The main methods applied nowadays for removing boron are based on ion exchange resins and multistage-stage reverse osmosis (RO) membranes. In particular, dense seawater RO membranes have a baseline rejection for boric acid of approximately 70-90% at the natural pH, so only increased level, at pH. ≥. 10, may ensure adequate removal of boron from permeate.This chapter reviews and discusses the use of membranes for the removal of boron in desalination systems employing RO membranes as direct treatment at elevated pH. Ultrafiltration and microfiltration membranes are used when boron complexation/adsorption hybrid processes are applied. The principles of electrodialysis, a third membrane-based process for boron removal is described. The mechanism of boron rejection by commercial RO membranes as well as novel modified desalination membranes with improved trade-off between permeability and boron rejection are also discussed.