Iron acetylacetonate additive improves the water permeance and fluoride/phosphate selectivity of polyamide nanofiltration membrane for phosphorus recovery

Industrial wastewater often contains significantly high concentrations of phosphorus, suggesting the potential for efficient phosphorus recovery. Nanofiltration (NF), with the ability to precisely separate different components, can be a promising strategy for this resource recovery. However, existing literature generally used the commercial polyamide NF membrane for phosphorus recovery, and demonstrated limited separation performance (e.g., low selectivity). In this regard, we developed highly selective NF membranes through interfacial polymerization (IP) with iron acetylacetonate as an additive. Compared to the control membrane, the tailored membranes showed higher water permeance up to 23.8 L m −2 h −1 bar −1 thanks to the formation of crumpled surface morphology and larger pore size of polyamide. This high permeable nature can reduce energy consumption and improve the quantity of product water for the phosphate recovery process. Additionally, the tailored membrane simultaneously demonstrated the improved phosphate rejection and the reduced fluoride rejection due to the combined effects of its enhanced surface negative charge and larger pore size of polyamide. This allowed the tailored membrane achieved significantly higher fluoride/phosphate selectivity at either single-salt or mixed-salt feed conditions. Such high selectivity values implied the potential of the tailored membrane as a promising candidate for the selective separation of phosphate from wastewater. Our findings give important implications for the development of highly selective polyamide membrane toward the selective separation and recovery of phosphorus from industrial wastewater.