New easily recycled carrier based polyurethane foam by loading Al-MOF and biochar for selective removal of fluoride ion from aqueous solutions.

The production of Integrated circuits (ICs) generates wastewater with a high concentration of residual fluoride ions, necessitating highly efficient fluorine removal methods. In this study, a novel composite carrier was developed using a hydrothermal synthesis method to load Al-MOF and biochar (BC) onto polyurethane foam (PUF), resulting in the composite foam of Al-MOF-PUF@BC. The results showed that the composite carrier exhibited a stable fluoride removal effect, with a maximum adsorption capacity of 16.52 mg/g at room temperature. The adsorption isotherm curves were consistent with the Langmuir isotherm model, and the adsorption kinetics were well-described by the pseudo-first-order model. The mechanism of fluorine adsorption on Al-MOF-PUF@BC was ligand exchange with hydroxyl groups and the formation of FAl bonds. Density functional theory (DFT) calculations revealed that the adsorption energy reached -246.7 eV, indicating stable adsorption for fluoride ions. The composite foam demonstrated excellent regenerative properties and was effective for fluoride removal in actual IC wastewater.