Zeolite-A deposited on glass/yttria stabilized zirconia forward osmosis membrane for desalination application

Abstract

The global water scarcity is now a major concern, which made recovering fresh water from seawater is the best alternative. Membrane-based technologies have been widely adopted in desalination, performed using reverse osmosis (RO) and forward osmosis (FO). Zeolite membrane showed great potentials for desalination due to the chemical and thermal stabilities. Zeolite membrane is generally developed by depositing zeolite onto a support material. However, there is a great tendency for delamination to occur. Unsupported zeolite membrane was developed as an alternative to overcome the cracking problem, but the unsupported zeolite membrane transforms into a glass membrane during sintering process. The glass membrane produced have a dense structure, which increased the water resistance pathway in the membrane, and resulted in low flux. Hence, in this study yttria-stabilized zirconia (YSZ) particles were added to increase the flux. Zeolite membrane was developed by depositing zeolite onto glass/YSZ hollow fibre, using the hydrothermal method, to improve the performance of the membrane. Thus, this study aims to i) fabricate glass hollow fibre using zeolite as a starting material, ii) investigate the effects of YSZ particles addition on the membrane performances and iii) evaluate zeolite deposition parameters on the glass/YSZ hollow fibre performances. The glass membrane was fabricated using a phase inversion and sintering technique, by a transformation of zeolite to glass during the sintering process. The YSZ was added into the glass hollow fibre through the same method of the aforementioned glass hollow fibre. The zeolite was deposited onto the glass/YSZ hollow fibre through a hydrothermal method, in an autogenous condition at 120 °C for various synthesis time. Zeolite transformed into glass due to the changed in the arrangement of the molecular structure. Zeolite, a crystalline phase changed to glass, an amorphous phase, when exposed to high temperature. The addition of the YSZ particles improved the permeation by reducing the pathway resistance through the void formed during the sintering process but gave low rejection. To improve the rejection, zeolite was deposited onto the membrane at different concentration and synthesized time. It was found that the suitable conditions were at 0.66 M concentration, and synthesis for 18 hours. The zeolite deposited on glass/YSZ membrane was able to perform sodium chloride (NaCl) rejection thus gave 62.25 L m-2 hr-1 and 0.11 kg m-2 hr-1 for solute flux and reverse solute flux, using FO water filtration system. It can be concluded that the zeolite membrane on glass hollow fibre was capable for desalination application with high flux and low reverse solute flux. A further investigation on the zeolite membrane deposited on glass hollow fibre i.e., to control the zeolite layer and a study to reduce the risk of delamination of the zeolite layer should be conducted.