| Forward osmosis（FO）is a new membrane separation technology driven by osmotic pressure difference,which is spontaneous,low energy consumption and relatively simple to operate.It has been successfully applied in the fields of seawater desalination,sewage treatment and resource utilization,food concentration and so on.Absorption agent is one of the key factors for the smooth progress of FO process and has become a research hotspot.In recent years,stimulus-responsive hydrogels,as a new forward osmosis absorbent,have attracted extensive attention because of their reversible contraction-swelling properties to achieve low energy dewatering regeneration.However,there are some disadvantages such as low water flux performance or poor regeneration performance.In order to overcome the above problems,electro-sensitive hydrogel absorbent with superabsorbability was prepared and used to study forward osmosis desalination performance.The main research work and results are as follows:（1）In the first work of this paper,acrylic acid（AA）and acrylamide（AM）were used as monomers and sodium carboxymethyl cellulose（CMC）was used as the main chain,through the approach of grafting copolymerization to synthesize CMC-g-poly（AA-co-AM）superabsorbent hydrogels with different cross-linking degrees.The morphology was characterized by scanning electron microscopy（SEM）,the chemical structure was characterized by Fourier transform infrared spectroscopy（FTIR）,and the swelling properties were characterized by swelling test.The properties of swelling,electrical stimulation,water flux and regeneration of superabsorbent hydrogels were tested with different cross-linking ratios.The dehydration mechanism and potential mechanisml under electric field were analyzed.The results showed that the swelling behavior of hydrogels fit to the second-order swelling dynamics model,and the optimal theoretical equilibrium swelling rate of hydrogels was 399.52 g/g,which only decreased by 7.2%after three cycles in the reswelling test.In the FO test,0.25g of dried hydrogel could provide 0.89L/m-2h-1water flux.The swollen hydrogel after FO could effectively release about 80.71%liquid water when electrically stimulated for 40 min at 15V.In addition,it also produced the water flux of 0.43 L/m-2 h-1 and kept the water retention rate of 67.51%after five cycles of regeneration.（2）In the second work of this paper,P（AA-co-AM）NC superabsorbent hydrogels was synthesized by radical polymerization with inorganic nanoparticles vinyl hybrid silica（VSNPs）as the cross-linking agent and with AA and AM as monomers.The particles’size and external morphology of VSNPs and P（AA-co-AM）NC hydrogels were characterized by scanning electron microscopy（SEM）.The main chemical bonds of VSNPs and NC gel were characterized by Fourier transform infrared spectroscopy（FTIR）to prove the correct preparation.Swelling test was used to characterize the swelling kinetics.The results showed that the swelling behavior of hydrogels was fit the second-order swelling dynamics model,and the hydrogels with the best swelling performance showed a swelling rate of 1708.47g/g.After five cycles of electric stimulation-reswelling test,the average swelling performance of each cycle only decreased by 1.72%.In the FO test,0.25g dried hydrogel could provide 1.23L/m-2h-1 water flux,which was about 27.6%higher than the FO performance of the superabsorbent hydrogels in the first work.After five cycles of FO-electrical stimulation test,the liquid water recovery performance of P（AA-co-AM）NC superabsorbent hydrogels decreased by only 1.16%per cycle.After five cycles of regeneration,it still produced a water flux of 0.38 L/m-2h-1 and provided the water recovery of 76.51%,which increased 9%compared with the material in the first work. |
