Metal organic frameworks (MOFs) for the removal of dissolved silica before reverse osmosis desalination

Abstract

Freshwater scarcity in many arid regions necessitates brackish water desalination via reverse osmosis (RO). One of the key obstacles to lowering the cost of RO freshwater is scaling or fouling on the RO membrane caused by dissolved silica in the brackish water. Herein, a robust metal organic framework (MOF) material was produced with green production methods. During column tests, the MOF demonstrates a high and selective affinity toward silicic acid from the dominant species in brackish water (e.g., Cl-, SO42-, HCO3-, Ca2+, Mg2+). Further lab-scale desalination tests showed over 80% of the 10–15 µm sized stone-like scales on the membrane were reduced while a 28.1% increase in the permeate flux was observed compared to the RO membrane without MOF treatment. Plus, two regeneration methods based on the properties of the selected MOFs were developed and evaluated.