Composite Christian Albrecht University-1 membrane on alumina hollow fiber for desalination applications

Abstract

Depletion of fresh water sources seems to be concerning as a lot of factors lead to it such as population growth, urbanization, industrialization and climate change. Membrane technology seems to be the key to save the sources from continuingly depleting. This study was aimed to develop metal organic framework (MOF) based membrane for desalination process. Christian-Albrechts-University-1 (CAU-1) is an excellent choice of MOF as it is water stable and can be utilized in desalination application. It was synthesized using solvothermal technique by differentiating the precursor concentration (0.05 M, 0.1 M, 0.5 M) and further post-treatment process using methanol was carried out to remove guest molecules. The problem with CAU-1 is to produce defect-free layer on alumina support. Perfluorinated polymer (PF) layer need to be added to improve the surface as well as the permeation performances. Series of characterization and performance tests were conducted to evaluate the parameter effects. Field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), atomic force microscopy (AFM) and contact angle were performed to achieve better understanding in changes that occur to CAU-1 membrane properties. FESEM images showed that CAU-1 membrane was successfully produced on alumina hollow fiber support with thicknesses ranging from 1.3 – 2.7 µm. FTIR and XRD results showed that the presence of guest molecules does really gives significant effect to the CAU-1 framework. Guest molecules in CAU-1 framework interrupts the amine peak that should be presence in range 3500 – 3300 cm-1. The removal of guest molecules does help in defining the peak in XRD. Forward osmosis (FO) performance of untreated 0.5 M CAU-1 (M6) membrane manage to achieve water flux of 18 L m-2 h-1 and reverse solute of 0.0792 kg m-2 h-1. The configuration of the FO process was changed by facing the active layer towards the draw solution. Results obtained were surprisingly different than it should be as it follows reverse osmosis concept. The water molecules flows from higher concentration gradient to lower concentration gradient. M6 membrane possesses flux value of 4.05 L m-2 h-1 and salt rejection of 75% for sodium chloride. The addition of PF layer does significantly improve the structural integrity of CAU-1 framework as it heals micro-defect present in CAU-1. In FO performance, treated 0.5 M CAU-1 (M5) membrane with PF layer showed the highest flux of 11.15 L m-2 h-1 and the reverse solute of 0.00084 kg m-2 h-1. For the active layer facing draw process, M5 membrane with PF layer managed to get flux up to 5.16 L m-2 h-1 and salt rejection up to 95.98%. It can be concluded that the presence of guest molecules and addition of polymer layer can improve the performance of CAU-1 membrane.