Preparation And Properties Of Intelligent Forward Osmosis Agent Sludge Ash-Thermosensitive Hydrogel

Forward osmosis（FO）technology is a kind of membrane separation water solution desalination technology with low energy consumption,low pollution and low cost.In recent years,intelligent hydrogels,especially thermosensitive hydrogels,as a new type of forward osmotic agents,are easy to recover water resources,avoid salt reverse osmosis,and can rapidly absorb water and dehydrate water resources under the influence of external temperature stimulation.However,intelligent thermosensitive hydrogels generally have less water flux.Therefore,this paper focuses on the optimization of thermosensitive hydrogels and the modification of sludge ash（SSA）in order to improve the performance of thermosensitive hydrogels,and to explore their characteristics and the performance of FO process.（1）Using N-isopropyl acrylamide（NIPAM）,different dosage of acrylic acid（AA,0～200wt%（relative to NIPAM）,the same below）as monomer,a series of thermosensitive hydrogel samples A0,A5,A10,A15,A50,A100 and A200 were successfully prepared by aqueous solution free radical polymerization.The scanning electron microscope（SEM）chart of the hydrogel sample A0～A200 showed that the number of pores increased and the pore size decreased after the addition of AA,indicating that A5～A200 enhanced the crosslinking strength of hydrogels effectively compared with the sample A0 without AA addition.It was observed from the infrared spectrum（FTIR）that AA and NIPAM were successfully copolymerized.The swelling and deswelling tests of samples A0～A200 show that sample A0has excellent temperature sensitivity,but the swelling property is general;comprehensive comparison of samples A5～A200 shows that sample A5 has strong swelling property,excellent temperature sensitivity,p H response,salt resistance,and good cyclic water carrying capacity.（2）Physical and chemical characterization of sludge（SS）and SSA were carried out.From SEM,it can be seen that SS has a dense surface,while SSA has a loose porous surface.From solubility test,it can be seen that the dissolved inorganic salt and organic matter in SSA may not affect the quality of recycled water.From FTIR,it can be seen that both of them have the characteristic peak of Si O₂,and after high temperature incineration,the intensity of characteristic peaks of organic matter in SS weakens or even disappears.From XRD,it can be seem that the main mineral composition of inorganic components in SS and SSA is quartz crystal.（3）SSA-thermosensitive hydrogel was prepared by adding different amounts of SSA（0～4.5wt%）with NIPAM and AA（5wt%）as monomers,and T0（A5）,T0.5,T1.5,T2.5,T3.5and T4.5 were finally prepared.From SEM,it can be observed that the number of micropores increased and pore size decreased after adding SSA,indicating that SSA provided a binding site in the process of hydrogel copolymerization.From FTIR,the characteristic peaks of SSA in T0.5～T4.5 were observed,and the characteristic peaks of AA and NIPAM were also observed,indicating that SSA was successfully involved in the copolymerization of monomers.After comprehensive comparison of swelling and deswelling test results of sample T0（A5）～T4.5,it is found that sample T2.5 has the strongest swelling property,excellent temperature sensitivity,p H response,salt resistance,and good circulating water carrying capacity.（4）Samples T0（A5）and T2.5 were used as agents for FO test.The results showed that the water flux of group T2.5 was stable at 2.15 LMH,which was significantly higher than that of group T0（1.05 LMH）.In FO process,T2.5 showed higher reuse rate（more than 94.4%）than T0 after 4 times recycling.This proves that SSA modified smart-thermosensitive hydrogel has better water flux and regeneration performance.