Lixin Xing,Ningning Guo,Yatao Zhang,Haoqin Zhang,Jindun Liu
Silica spheres in nanoscale were prepared via sol–gel method and then sodium 4-styrene sulfonate was grafted onto the surfaces of SiO 2 (PSS-SiO 2 ) by surface-initiated atom transfer radical polymerization (SI-ATRP). Then, a negatively charged loose SiO 2 -PSS/polyethersulfone (PES) nanofiltration membrane with high flux was fabricated via phase inversion method. FT-IR and TEM results showed that SiO 2 nanoparticles were synthesized and modified successfully. GPC results further proved the “living”/controlled behavior of SI-ATRP. The morphology, hydrophilicity of the membranes were investigated by SEM, static water contact angle and water ratio. The results revealed that the surface hydrophilicity and water permeability of hybrid membranes were greatly improved after adding SiO 2 -PSS and thus may enhance fouling resistance to a certain extent. The salt permeation and separation of dye/salt mixture of the hybrid membranes were significantly superior to the pure PES membrane, and the order of permeation for different salt solutions was NaCl > MgCl 2 > MgSO 4 > Na 2 SO 4 . When the content of SiO 2 -PSS was 3.0 wt%, the hybrid membrane showed optimal performance with IEC value of 0.07 mmol/g and pure water flux of 269.5 L m −2 h −1 and the rejections for all types of salts declined to under 11%. The above results indicated that SiO 2 -PSS incorporated into PES matrix played an important role in enhancing the performance of NF membranes, which may possess a significant impact on the application in dye purification and desalination.
Yang Liu,Shanshan Liang,Yinghui Qian,Hao-Ran Zuo,Ming Duan
In order to recover dyes from practical dye wastewater through loose nanofiltration (NF) membranes, dyes are supposed to be rejected through synergetic effect of sieving and Donnan repulsion while salts are supposed to permeate through membrane under weakened synergetic effect of sieving and Donnan repulsion. Therefore, redox system initiated interfacial radical polymerization was applied to form an integrated negatively charged separation layer with average pore size of 2.2 nm. The surface potential of −50 mV at pH ≥ 7 was achieved by plenty of –CN, O–C=O, and C–O–C groups. As the results, permeability of 43.1 L/(m 2 h bar) and rejection of 99 % to MB for loose NF membrane (PAN-C) was obtained when treating 50 ppm MB aqueous solution under 2 bar, while only rejection of 5.2 % to MO was obtained, confirming the successful separation of MO from MB. Furthermore, the separation factor of MB over Na 2 SO 4 and MgSO 4 for PAN-C were 261 and 420, respectively, verifying the potential of PAN-C in application to dyestuff effluent treatment. In addition, PAN-C showed excellent anti-fouling performance with FRR of 0.99 against HA. Overall, this work established a new method to fabricate high performance loose NF membranes designed at molecular level, which could be extended to reverse osmosis , forward osmosis, and other membrane processes.
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