Enhancing desalination efficiency and boron removal through functionalization of layered double hydroxide thin-film nanocomposite membranes

Boron (B) is a micronutrient essential for plant growth, but excessive concentrations can harm ecosystems and human health. Traditional water treatment methods often face challenges in removing boron, particularly in its non-dissociated boric acid form. Reverse osmosis (RO) thin-film nanocomposite (TFN) membranes have shown potential for boric acid removal. However, maintaining high boric acid retention alongside water permeability remains challenging. Layered double hydroxides (LDHs), characterized by their brucite-like layered structures with intercalated anions, have been explored as promising additives in thin-film composite (TFC) membranes. Herein, we introduce a room temperature process for functionalizing LDH with tannic acid (TA) and β-cyclodextrin (β-CD) to form β-CD@TA-LDH, enhancing both cost-effectiveness and separation performance. Our findings show that β-CD@TA-LDH achieved a boron removal efficiency of 80.2% and a salt rejection of 99.25%. The water permeance was measured to be at 2.70 LMH bar⁻¹, indicating improved membrane performance with these modifiers. The long-term stability tests demonstrate consistent separation performance after 96 hr of continuous operation. The incorporation of β-CD@TA-LDH into the polyamide layer results in a thinner layer, enhancing water permeability. Additionally, the presence of free –OH groups on the surface of β-CD@TA-LDH can easily coordinate with boric acid, facilitating boron adsorption. This study highlights advancements in low-cost, easily synthesizable LDH based TFN membranes for boron rejection and contributes to the development of cost-effective nanofillers for efficient water treatment.