Fabrication of polyvinylidene fluoride blending membranes filled by La-TiO2-reduced graphene oxide with photocatalytic activity
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摘要: 为提高聚偏氟乙烯(PVDF)超滤膜的通量及抗污染性能，首先利用吸附相反应技术耦合乙醇热处理制备La掺杂TiO2-还原氧化石墨烯(La-TiO2-RGO)，再将其与PVDF共混制备La-TiO2-RGO/PVDF抗污染超滤膜。结果表明，均匀分散于PVDF高分子中表面亲水的La-TiO2-RGO增多，La-TiO2-RGO/PVDF共混膜的水通量和抗污染性能也显著提升。当La-TiO2-RGO/PVDF共混膜中出现团聚体，则会削弱其膜通量和抗污染性。在La-TiO2-RGO填充量(与PVDF质量比)为2.0%时，La-TiO2-RGO/PVDF共混膜具有最优纯水通量。La-TiO2-RGO/PVDF共混膜最高纯水通量可达171.5 L·m−2·h−1，是PVDF膜的5倍以上，其通量衰减速率也明显低于PVDF膜。另外，由于La-TiO2-RGO具有可见光催化活性，被污染后的La-TiO2-RGO/PVDF共混膜经过光照处理后用水清洗，其膜通量恢复率较直接用水清洗后的通量恢复率大幅提高；热处理温度升高，La-TiO2-RGO弱可见光活性增强，光照后La-TiO2-RGO/PVDF共混膜通量恢复率变大。但过高热处理温度抑制了La-TiO2-RGO中Ti3+形成，且削弱其光活性，La-TiO2-RGO/PVDF共混膜通量恢复率反而下降；对于La-TiO2-RGO填充量为2.0%的La-TiO2-RGO/PVDF共混膜，被污染后分别采用直接水清洗、仅光照处理2 h、先光照处理2 h后水清洗的膜通量恢复率分别为79.28%、52.42%、90.01%。
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关键词:
- 聚偏氟乙烯(PVDF)共混膜 /
- 抗污染性 /
- 通量恢复率 /
- 弱可见光催化活性 /
- La掺杂TiO2-还原氧化石墨烯
Abstract: To improve the flux and antifouling performance of polyvinylidene fluoride (PVDF) ultrafiltration membrane, La doped TiO2-reduced graphene (La-TiO2-RGO) was first synthesized by the adsorption phase reaction coupled with alcohol solvothermal reduction processes. Followed that, La-TiO2-RGO was blended with PVDF to fabricate a La-TiO2-RGO/PVDF ultrafiltration membrane with high anti-fouling performance. The results show that the water flux and antifouling performance of the La-TiO2-RGO/PVDF blending membrane increase, when more well-distributed La-TiO2-RGO with hydrophilic groups added. The aggregations generate in the La-TiO2-RGO/PVDF blending membranes will depress their water flux and antifouling performance. When the loading content (mass ratio to PVDF) of La-TiO2-RGO is 2.0%, the La-TiO2-RGO/PVDF blending membrane has the best pure water flux. The optimum pure water flux of the La-TiO2-RGO/PVDF blending membrane reaches 171.5 L·m−2·h−1, which is 5 times as high as that of the PVDF membrane. And the flux decay rate of the La-TiO2-RGO/PVDF blending membrane is significantly lower than that of the PVDF membrane. The flux recovery of the contaminated La-TiO2-RGO/PVDF blending membrane treated by illumination then washing is obviously higher than that just treated by washing, due to the addition of La-TiO2-RGO with photocatalytic activity. The increase in the solvothermal temperature enhances the photocatalytic activity of La-TiO2-RGO, thus improving the flux recovery rate of the La-TiO2-RGO/PVDF membranes after light irradiation. However, too high solvothermal temperature inhibites the formation of Ti3+ in La-TiO2-RGO, which weakens its photoactivity and decreases the flux recovery rate of the resulting La-TiO2-RGO/PVDF blending membranes. For the La-TiO2-RGO/PVDF blending membrane filled with La-TiO2-RGO loading of 2.0%, the flux recovery rates of contaminated membrane are 79.28%, 52.42% and 90.01%, respectively, after washing, illumination for 2 h and illumination for 2 h then washing. -
图 1 不同温度热处理后La-TiO2-RGO的HRTEM图像(内插图为TEM图像)
Figure 1. HRTEM images of La-TiO2-RGO treated by solvothermal reduction under different temperatures (Inset are TEM images)
图 2 不同温度热处理后La-TiO2-RGO的XRD图谱
Figure 2. XRD patterns of La-TiO2-RGO treated by solvothermal reduction under different temperatures
图 3 不同温度热处理后La-TiO2-RGO的FTIR图谱
Figure 3. FTIR spectra of La-TiO2-RGO treated by solvothermal reduction under different temperatures
图 4 不同温度热处理后La-TiO2-RGO的XPS图谱
Figure 4. XPS spectra of La-TiO2-RGO treated by solvothermal reduction under different temperatures
图 5 不同温度热处理后La-TiO2-RGO可见光激发光电流响应曲线
Figure 5. Visible light excitation photocurrent response curves of La-TiO2-RGO treated by solvothermal reduction under different temperatures
图 6 PVDF膜和La-TiO2-RGO/PVDF共混膜表面的SEM图像
Figure 6. SEM images of surface of PVDF membrane and La-TiO2-RGO/PVDF blending membranes
图 7 PVDF膜和La-TiO2-RGO/PVDF共混膜断面的SEM图像
Figure 7. SEM images of cross-section of PVDF membrane and La-TiO2-RGO/PVDF blending membranes
图 8 光照对PVDF膜和La-TiO2-RGO(170)/PVDF-2混合膜通量衰减过程的影响
Figure 8. Effect of irradiation on flux decay process of PVDF membrane and La-TiO2-RGO(170)/PVDF-2 blending membrane
图 9 PVDF膜和及La-TiO2-RGO/PVDF共混膜的抗污染性能
Figure 9. Anti-fouling performance of PVDF membrane and La-TiO2-RGO/PVDF blending membranes
表 1 La-TiO2-还原氧化石墨烯(RGO)/聚偏氟乙烯(PVDF)共混膜各组分含量
Table 1. Contents of components of La-TiO2-reduced graphene oxide(RGO)/ polyvinylidene fluoride(PVDF) blending membranes
Membrane La-TiO2-RGO VDMAc/
mLMass of
PVDF/gMass of
PEG2000/gMass ratio of La-TiO2-
RGO to PVDF/%Emax/
MPaPVDF — 50 7.5 2.5 0 75.3 La-TiO2-RGO(160)/PVDF-1 La-TiO2-RGO(160) 50 7.5 2.5 1.0 86.7 La-TiO2-RGO(160)/PVDF-2 La-TiO2-RGO(160) 50 7.5 2.5 2.0 98.9 La-TiO2-RGO(160)/PVDF-3 La-TiO2-RGO(160) 50 7.5 2.5 3.0 88.1 La-TiO2-RGO(170)/PVDF-1 La-TiO2-RGO(170) 50 7.5 2.5 1.0 87.2 La-TiO2-RGO(170)/PVDF-2 La-TiO2-RGO(170) 50 7.5 2.5 2.0 101.1 La-TiO2-RGO(170)/PVDF-3 La-TiO2-RGO(170) 50 7.5 2.5 3.0 89.5 Notes: Emax—Maximum tensile strength of membrane; La-TiO2-RGO(160)/PVDF-(1/2/3)—Blending membrane in which mass ratio of La-TiO2-RGO(160) to PVDF is 1%, 2%, 3%, respectively, La-TiO2-RGO(170)/PVDF-(1/2/3) is also understood like this; VDMAc—Volume of N,N-dimethyl acetamide. 
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表 2 PVDF膜和La-TiO2-RGO/PVDF共混膜的孔隙结构、表面亲水角和膜通量
Table 2. Porosities, mean pore sizes, water contact angles and flux of PVDF membrane and La-TiO2-RGO/PVDF blending membranes
Membrane Porosity/% Mean pore size/nm Water contact angle/(°) Jw/(L·m−2·h−1) Jp/(L·m−2·h−1) PVDF 30.2 35.1 91.3 37.9 7.4 La-TiO2-RGO(160)/PVDF-1 61.3 51.5 66.7 145.3 31.5 La-TiO2-RGO(160)/PVDF-2 71.1 62.3 65.3 169.2 39.6 La-TiO2-RGO(160)/PVDF-3 68.8 49.7 61.2 119.1 22.4 La-TiO2-RGO(170)/PVDF-1 65.3 57.2 56.4 149.2 33.4 La-TiO2-RGO(170)/PVDF-2 70.7 65.3 55.8 171.5 42.8 La-TiO2-RGO(170)/PVDF-3 69.7 59.7 58.9 155.1 38.7 Notes: Jw—Water flux; Jp—Bull serum albumin (BSA) flux.
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表 3 PVDF膜和La-TiO2-RGO/PVDF共混膜的抗污染性能
Table 3. Anti-fouling performance of PVDF membrane and La-TiO2-RGO/PVDF blending membranes
Membrane R/% RE/% REr/% PVDF 32.65 14.19 34.86 La-TiO2-RGO(160)/PVDF-1 77.40 34.70 82.22 La-TiO2-RGO(160)/PVDF-2 79.79 48.47 84.51 La-TiO2-RGO(160)/PVDF-3 63.69 33.55 72.09 La-TiO2-RGO(170)/PVDF-1 78.59 43.78 86.00 La-TiO2-RGO(170)/PVDF-2 79.28 52.42 90.01 La-TiO2-RGO(170)/PVDF-3 66.12 40.87 72.81 Notes: R—Flux recovery rate of contaminated membrane after washing; RE—Flux recovery rate after illumination for 2 h; REr—Flux recovery rate after illumination for 2 h then washing.
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