Development of Shaped MIL-100(Fe) Granules for High-Performing Adsorption Desalination: From Formulation Optimization...

Adsorption desalination (AD) driven by low-grade renewable energy or waste heat is a sustainable solution to the water crisis. Recently, metal-organic frameworks (MOFs) with excellent water adsorption performances have been recognized as some of the most promising candidates for AD. However, previous studies mainly focused on MOFs in powder form, causing pipe clogging and a drastic pressure drop, which inspire the development of shaped MOFs for industrial use. In this work, MIL-100(Fe) with high water stability, high adsorption capacity, and mild synthesis conditions was chosen, and the optimal formulation of the shaped MIL-100(Fe) granules using different binders was explored. The high-performing MIL-100(Fe)@5PVB granule containing 5% polyvinyl butyral (PVB) with outstanding adsorption performance and mechanical strength was selected and massively prepared for AD system testing. It is found that, although binder content decreased the surface area, pore volume, and water uptake of MIL-100(Fe), the mechanical strength and adsorption kinetics of shaped MIL-100(Fe)@5PVB were enhanced, which favor its performance in an AD system. Moreover, system testing demonstrated that the desalination performance of the AD system based on the adsorption beds of MIL-100(Fe)@5PVB outperformed both silica gel and MIL-100(Fe) powder. The specific daily water production (SDWP) of the AD system based on MIL-100(Fe)@5PVB (28.74 m³/ton/day) is 30% higher than that based on MIL-100(Fe) powder (19 m³/ton/day). Such a phenomenon is mainly contributed by the improved water adsorption dynamics of MIL-100(Fe)@5PVB granules that favors the mass transfer efficiency in the adsorption bed. This work opens up the possibility for the development of high-performing shaped MOFs for adsorption desalination from the perspectives of formulation optimization and system testing.