Development and characterization of LiCl supported composite sorbents for adsorption desalination

Adsorption desalination (AD) is an emerging technology to reduce risk of freshwater scarcity, able to use renewable energy and applicable in decentralized areas. Only limited sorbents have been tested experimentally for AD systems. This study developed two composite sorbents based on LiCl as embedded salt and two matrices, namely, silica gel (LiCl@SG_30) and expanded vermiculite (LiCl@EVM_45). The performed analysis figured out how the trade-off between high sorption capacity and good mass transfer caused by their different pore structures influences the desalination operations. The results were compared against a standard microporous Siogel. The sorption isobars indicated that the sorption behavior of LiCl@SG_30 is the combination of silica gel and the embedded LiCl crystals, while for LiCl@EVM_45 is mainly the sorption process of the embedded LiCl crystals. LiCl@EVM_45 reached the highest sorption capacity. The Dubinin-Astakhov equation described the equilibrium capacities of the sorbents. The kinetics coefficient (k) was employed to evaluate the sorption rate. Microporous Siogel showed the highest sorption rate, followed by LiCl@SG_30 and LiCl@EVM_45. Finally, predicted specific daily water production (SDWP) were calculated, showing promising features for both LiCl@SG_30 and LiCl@EVM_45, with LiCl@SG_30 achieving SDWP ranging from 43 to 60 m3/tonne/day) for the selected conditions.