Abstract:

Using an tubular Al₂O₃ ultrafiltration membrane with an average pore diameter of 20 nm as the carrier, after modified by dopamine, a pressure-driven deposition method was used to successfully prepare a GO/Al₂O₃ composite nanofiltration membrane that can be stable in aqueous solution for a long time. The thickness of GO layer can be controlled by changing the loading amount. The results showed that the pure water permeability of all GO/Al₂O₃ composite nanofiltration membranes decreased and then reached a steady state during the cross-flow filtration. In addition, the pure water permeability of GO/Al₂O₃ composite nanofiltration membranes decreased as the GO loading amount increased. The permeability and rejection of GO/Al₂O₃ composite nanofiltration membranes remained stable when GO loading amount was greater than 90 mg/m². As the storage time (in pure water) extended, the cross-linking of GO sheets caused by residual salt ions during tests led to a higher rejection of GO/Al₂O₃ composite nanofiltration membranes towards monovalent and divalent salts. After being immersed in pure water for 680 h, the GO/Al₂O₃ composite nanofiltration membrane with GO loading amount of 140 mg/m² showed the highest Na₂SO₄ rejection of 91.0%. The rejections of GO/Al₂O₃ composite nanofiltration membranes towards four salt solutions were as follows: R(Na₂SO₄) > R(MgSO₄) > R(NaCl) > R(MgCl₂).

Key words: graphene oxide, tubular Al₂O₃ membranes, dopamine, loading amount, nanofiltration, stability

摘要：

以平均孔径为20 nm的Al₂O₃管式超滤膜为载体，经多巴胺改性后，利用压力驱动沉积法成功制备出能在水溶液中长期稳定的GO/Al₂O₃复合纳滤膜，并通过改变负载量实现了对GO层厚的调控。结果表明，随错流时间的延长，不同GO负载量下GO/Al₂O₃复合纳滤膜的纯水渗透系数均呈现先降低后稳定的趋势。且随着GO负载量的增加，稳态纯水渗透系数逐渐降低；当GO负载量增加到90 mg/m²后，GO/Al₂O₃复合纳滤膜对一二价盐的渗透系数与截留率均无显著变化。同时，由于盐测试过程中残余的盐离子在GO片层间产生了交联作用，从而导致随着在纯水中存放时间的延长，不同GO负载量的GO/Al₂O₃复合纳滤膜对一二价盐的截留率均呈上升趋势。GO负载量为140 mg/m²的GO/Al₂O₃复合纳滤膜在水中浸泡680 h后对1 mmol/L Na₂SO₄的截留率可达到91.0%。GO/Al₂O₃复合纳滤膜对四种一二价盐的截留率满足：R(Na₂SO₄) > R(MgSO₄) > R(NaCl) > R(MgCl₂)。

关键词: 氧化石墨烯, Al₂O₃管式膜, 多巴胺, 负载量, 纳滤, 稳定性