Abstract
Thin-film nanocomposites (TFN) functionalized with tunable molecular-sieving nanomaterials have been employed to tailor membranes, with an enhanced permeability and selectivity. Herein, water-soluble hollow cup-like macrocyclic molecules, sulfothiacalix[4]arene (STCAss) and sulfocalix[4]arene (SCA), are ionically bonded into the polyamide network to engineer the molecular-sieving properties of TFN membranes for organic solvent forward osmosis (OSFO). Introducing both STCAss and SCA into the polyamide network not only increases the free volume, but also reduces the thickness of the TFN layers. Combining with their molecularly tunable size of the lower cavities, both STCAss and SCA enable the TFN membranes to size exclusively reject the draw solutes, but only STCAss-functionalized membrane has an ethanol flux doubling the pristine one under the FO and PRO modes in OSFO processes; leading the functionalized polyamide network with remarkable improvements in OSFO performance. This study may provide insights to molecularly functionalize TFN membranes using multifunctional nano-fillers for sustainable separations.
Highlights
Thin-film nanocomposites (TFN) functionalized with tunable molecular-sieving nanomaterials have been employed to tailor membranes, with an enhanced permeability and selectivity
Since the sulfonate and sulfonic acid groups in STCAss and SCA may interact with MPD, their presence interferes the interfacial polymerization process[26]
The proton dissociated from the sulfonic acid groups would inhibit the HCl generation during the interfacial polymerization because it shifts the reaction equilibrium backward
Summary
Thin-film nanocomposites (TFN) functionalized with tunable molecular-sieving nanomaterials have been employed to tailor membranes, with an enhanced permeability and selectivity. Water-soluble hollow cup-like macrocyclic molecules, sulfothiacalix[4]arene (STCAss) and sulfocalix[4]arene (SCA), are ionically bonded into the polyamide network to engineer the molecular-sieving properties of TFN membranes for organic solvent forward osmosis (OSFO). Introducing both STCAss and SCA into the polyamide network increases the free volume, and reduces the thickness of the TFN layers. Thiacalix[n]arene is a subgroup of calix[n]arene where the methylene bridge between each phenolic block is replaced by sulfur atoms, which may alter the lower-rim dimension and the size-sieving properties Since both STCAss and SCA have multifunctionalities, they may interact with the polyamide layer closely and affect its formation and separation performance. The objectives of this work are to (1) functionalize the polyamide network by incorporating close-loop size-selective macrocyclic molecules, and (2) simultaneously improve the permeability and selectivity of the TFN membranes for OSFO processes
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