Controllable Preparation Of Polysulfonamide Composite Separation Membrane And Its Performance Study

Industries such as fermentation,pulp,mining,metal surface treatment often produce a large number of acidic wastewater that poses threat to both environment and public health.Membrane separation technology can achieve the separation and recovery of acid and metal salt,which can be used to treat acidic saline wastewater.Traditional reverse osmosis and nanofiltration membranes with polyamide as the separation layer have been widely developed and applied in recent decades.However,the vulnerability of the chemical structure,such as poor acid-base stability and poor oxidation resistance,limits their application in the field of acid-containing wastewater treatment.Polysulfonamide is a kind of polymer which is connected by sulfonamide bond.Its specific sulfonamide bond gives it high acid stability and chemical stability.However,due to the low reaction activity of sulfonyl chloride monomers and the relatively long film-forming time,the prepared polysulfonamide composite membrane usually has a poor retention of inorganic salts and a low flux,affecting its further application.To solve this,we first focus on monomer structure selection,and synthesized the monomer 2,4,6-tris（chlorosulfonyl）phenol.The sulfonyl chloride was then used to react with different multi-functional amine monomer to form polysulfonamide membrane via two different methods,i.e.interfacial polymerization（IP）and spinning-assist multi-layer interfacial polymerization（s MIP）.The influence of preparation parameters was well investigated,and the physiochemical properties of the membranes were characterized.The acid stability was studied and the separation performance towards a simulated acidic wastewater was evaluated.The experimental results show that the prepared polysulfonamide composite membrane exhibited promising desalination performance.The two IP technique prepared polysulfonamide membrane show a Na Cl rejection of more than 85%,whereas the rejections for magnesium sulfate,sodium sulfate and calcium chloride are greater than 95%.The s MIP method can successfully control the growth of the thickness of skin layer and the surface roughness.Moreover,when the number of repeated layer is 5,the rejection of the membrane towards Na₂SO₄ and Mg SO₄ can reach more than 99%,while maintaining a water flux at 35 L m^-2 h^-1.Acid stability test showed that the membranes prepared herein maintain a high desalination performance after treated with 20 wt%sulfuric acid at 90°C for 24 h.The ATR-IR spectra show no significant changes in the chemical structure of the separation layer before and after acid treatment,proving its high stability.In addition,the membranes exhibit preferable performance when treating Cu SO₄/H₂SO₄ mixture,with high salt rejection while maintaining the structure integrity.The findings of this thesis will likely have practical value in the field of acidic wastewater treatment.