Preparation, characterizations and performance evaluations of alumina hollow fiber membrane incorporated with UiO-66 particles for humic acid removal

Humic acid removal requires ceramic membranes incorporated with metal organic framework (MOF) to display remarkable stability over water. Recent work has shown UiO-66, a Zr-based MOF, as an emerging material with the potential to fulfill this requirement. This work investigated the preparation, characterization and performance of UiO-66 particles deposited on alumina hollow fiber membranes. Concentrations of Zr precursors and synthesis period were varied in the preparation of UiO-66 using solvothermal synthesis. The presence of UiO-66 particles was characterized using the field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX) mapping, x-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET) analysis. Pure water flux and humic acid rejection tests were carried out on both pristine alumina hollow fiber membranes and alumina hollow fiber membranes deposited with UiO-66 particles. In the former, a high pure water flux value of 231.24 L m−2 h−1 was recorded, while in the latter the recorded value dropped to 9.36 L m−2 h−1. Pristine ceramic hollow fiber membranes used to separate humic acid (1 g L−1) from an aqueous solution showed a rejection rate of 98%. When UiO-66 particles were deposited on the ceramic membranes, the solute flux of the membranes increased to 68.36 L m−2 h−1. Surprisingly, it was found that 99% humic acid was rejected from a feed solution using the membranes incorporated with UiO-66 particles. Findings showed that the weight loading of the UiO-66 particles on the alumina hollow fiber membranes was very low, showing a reading of only approximately ~ 0.01 g. Based on the adsorption-desorption analysis, at high pH values (≥ 9), UiO-66 particles and humic acid displayed a similar surface charge, creating a repulsion effect during the filtration process. UiO-66 particles on alumina hollow fiber membranes showed excellent stability, making it viable for water purification applications.