Preparation Of Multiporous Polymer Hydrogels Draw Agents And Study On Their Forward Osmosis Properties

With the development of forward osmosis technology, a wide variety of drawagents in forward osmosis had been prepared. But they all had their own drawbacks.Recently, hydrogels had been widely concerned as new draw agents in forwardosmosis. But the draw agents present poor performance in forward osmosis whichneed to be modified with other methods. However, traditional methods for modifyinghad drawbacks of lower water fluxes or nonrenewable property. Therefore, researchworks had been focused on preparing hydrogels which could solve these problems.In order to prepare the hydrogels with higher water fluxes and renewableproperty, with pore-forming agents method, multiporous poly(N-isopropylacrylamide)-poly(sodium acrylate)(PNIPAM-PSA) hydrogels draw agents were prepared byincorporating into multiporous structure. PNIPAM-PSA hydrogels were prepared byfree-radical polymerization method. The preparing method of the hydrogels wasoptimized to determine the optimum reaction conditions, which was evaluated byswelling ratio, dehydration ratio and forward osmosis water fluxes. On this basis, theinfluence of PEG400as pore-forming agents dosage on the forward osmosisperformance of hydrogels was also investigated. In addition, the different hydrogelswere characterized by the techniques such as Fourier transform infraredanalysis(FT-IR) and Scanning electron microscope(SEM). Finally, the hydrogels withdifferent PEG400dosage were choosed to test the renewable property.The results showed that PNIPAM-PSA hydrogels draw agents showed bestperformance in forward osmosis when the molar ratio of monomer was1:1, themolar ratio of monomer to crosslinkers was50:1, the molar ratio of monomer to initiator was100:1. In this moment, swelling ratio was61.31g/g, dehydration ratio was76.83%, water fluxes within the first hour were0.63LHM. In the course ofpreparation of the multiporous hydrogels, the results showed that the hydrogelsexhibited best performance in forward osmosis when the molar ratio of PEG400tomonomer was1:2. Compared with PNIPAM-PSA hydrogels, the swelling ratio,dehydration ratio and forward osmosis water fluxes of the multiporousPNIPAM-PSA hydrogels were increased by162.26%,15.08%and144.44%respectively.The characterization results of FT-IR showed that amide group-CONH2ashydrophilic groups and isopropyl-CH (CH3)2as hydrophobic groups appeared indifferent hydrogels, and the obvious characteristic absorption peak of PEG didn’tappear in the multiporous hydrogels, which meant that PEG had been removed in thewashing process.The characterization results of SEM showed that the obvious porous structuredidn’t appear in the hydrogels without adding PEG400. But, more obvious porousstructure appeared in the hydrogels with the increasing of PEG400dosage.The regeneration performance of the hydrogels with different PEG400dosagehad been tested. The results showed that the water fluxes of the hydrogels had smallchange and good stability, the regeneration performance of the hydrogels was well.