Preparation and performance of electrocatalytic carbon membranes for treating micro-polluted water
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摘要: 以椰壳活性炭为原料，设计制备一种具有吸附、电催化氧化、膜过滤三重功能的电催化炭膜（TCM），通过调节原料配比、炭化温度以及原料活性炭的粒径实现对TCM性能的调控。采用SEM、XRD、拉曼和氮吸附等技术对TCM的形貌与结构进行表征，并以TCM为阳极构建电催化膜反应器（ECMR），考察其水处理性能。结果表明，TCM具有发达的孔道结构和较高的比表面积，整体呈现出大孔-介孔-微孔的多级孔道结构，并具有良好的机械强度与导电性；改变活性炭的粒径可以有效调控TCM的孔道结构。TCM对水中微污染有机物和重金属离子均具有较高的吸附量；在外加2 V电压电场下，对水中亚铁氰化钾的氧化率为98.4%，表现出良好的电催化氧化活性；在低压电场的作用下处理真实微污染水时，炭膜的三重功能协同作用使其展现出优异的综合处理性能，其中COD、UV254、浊度以及细菌的去除率分别达到了94.3%、90.5%、96.3%和100%，重金属离子几乎完全去除，出水水质得到显著地改善，并且水渗透通量有所提升，具有良好的抗污染性能。Abstract: Porous carbon membranes (PCMs) with three functions of adsorption, electrocatalytic oxidation and membrane filtration were prepared from coconut shell activated carbon using carboxymethyl cellulose (CMC,10 wt%) and benzoxazine resin (BR, 10 wt%-40 wt%) as the binder components. The morphology and microstructure of PCMs were characterized by SEM, XRD, Raman and nitrogen adsorption. An electrocatalytic membrane reactor (ECMR) was constructed using PCMs as the anode materials to investigate their water treatment performance. Results show that the PCMs have well-developed hierarchical macro, meso and micropores, whose macropore size decreases with the particle size of the activated carbon. The mechanical strength and electrical conductivity of the PCMs increased with BR content and carbonization temperature. The water flux decreased as the average particle size of the activated carbon decreased and the iodine value decreased with decreasing BR content. The PCM performed best with an excellent comprehensive performance in adsorption, electrocatalytic oxidation and filtration when it was prepared from an activated carbon of average particle size of 37.9 μm using a BR content of 30 wt% and a carbonization temperature of 950 ℃. For the micro-polluted Lingshui River water in Dalian, the removal of COD, UV254, turbidity and bacteria with the ECMR reached 94.3%, 90.5%, 96.3% and 100%, respectively, and heavy metal ions (Pb2+, Cu2+, Zn2+, Ni2+ ) were removed to levels below the detection limits, and the anti-fouling performance was good. The excellent performance in treating micro-polluted water is ascribed to the combined effects of adsorption, electrocatalytic oxidation and filtration.
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图 2 不同BR添加量TCMs的机械强度与电阻率
Figure 2. Mechanical strength and resistivity of TCMs with different BR dosages.
图 3 不同炭化温度TCMs的机械强度与电阻率
Figure 3. Mechanical strength and resistivity of TCMs at different carbonization temperatures.
图 4 不同粒径活性炭制得TCMs的SEM照片：（a，c）TCM-1的表面和断面；（b，d）TCM-4的表面和断面
Figure 4. SEM images of TCMs sprepared by AC with different particle sizes: (a, c) surface and section of TCM-1; (b, d) surface and section of TCM-4.
图 5 不同粒径活性炭制得TCMs的孔径分布
Figure 5. Pore size distributions of TCMs prepared by AC with different particle sizes.
图 6 不同粒径活性炭制得TCM的机械强度与电阻率
Figure 6. Mechanical strength and resistivity of TCMs prepared by AC with different particle sizes.
图 7 活性炭与TCM的（a）拉曼光谱与（b）XRD谱图
Figure 7. (a) Raman spectra and (b) XRD spectra of AC and TCM.
图 8 活性炭与TCM的（a）N2吸附/脱附等温线与（b）微介孔孔径分布（DFT）
Figure 8. (a) N2 adsorption/desorption isotherm and (b) micropore and mesopore size distribution (DFT) of AC and TCM.
图 9 （a）有机物的穿透曲线（C0：200 mg·L−1），（b）金属离子在TCM上的吸附量
Figure 9. (a) Breakthrough curve of organics (C0: 200 mg·L−1) and (b) sorption capacity of metal ions on TCM.
图 10 （a）TCM的CV曲线，（b）K4Fe(CN)6的氧化率（C0: 0.005 mol·L−1），内嵌图为原液与渗透液的紫外吸收光谱
Figure 10. (a) CV curve of TCM, (b) oxidation efficiency of K4Fe(CN)6 (C0: 0.005 mol·L−1), inset graph is the UV absorption spectrum of the feed and the penetrating fluid.
图 11 TCM在静态与流通模式下的计时电流法测试曲线
Figure 11. Chronoamperometry measurements of TCM in batch mode and flow-through mode.
图 12 不同电压下（a）渗透液中COD、浊度、UV254、细菌以及重金属离子的去除率；（b）渗透通量随时间的变化
Figure 12. (a) Removal rate of COD, turbidity, UV254, bacterial and heavy metal ions in the penetrating fluid and (b) the relation of permeability flux with time under different voltages.
图 13 TCM处理微污染水的机理示意图
Figure 13. Schematic diagram of the mechanism of micro-polluted water treatment with TCM.
表 1 不同BR添加量TCMs的孔结构性能与碘值
Table 1. Pore structure and Iodine absorb of TCMs with different BR dosages.
BR dosage Average pore size/μm Porosity Water flux (L·m−2·h−1·MPa−1) Iodine absorb /mg·g−1 0% - - - 803.2 10% - 62.7% 11431 696.9 20% 1.19 60.5% 9931 585.7 30% 1.08 58.7% 9448 526.7 40% 1.00 58.3% 9012 342.1 
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表 2 不同炭化温度TCMs的孔结构性能与碘值
Table 2. Pore structure and Iodine absorb of TCMs at different carbonization temperatures.
Temper-atur (°C) Average pore size (μm) Porosity Water flux (L·m−2·h−1·MPa−1) Iodine absorb (mg·g−1) 750 0.99 56.6% 9118 474.2 850 1.03 57.0% 9283 481.0 950 1.08 58.7% 9448 526.7 1050 1.12 59.4% 9899 551.4
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表 3 不同粒径活性炭制得TCMs的孔结构性能与碘值
Table 3. Pore structure and Iodine absorb of TCMs prepared by AC with different particle sizes.
Sample Average pore size (μm) Porosity Water flux (L·m−2·h−1·MPa−1) Iodine absorb (mg·g−1) TCM-1 1.08 58.7% 9448 526.7 TCM-2 0.87 58.4% 5923 480.9 TCM-3 0.75 58.2% 5073 483.8 TCM-4 0.54 57.9% 1536 461.5
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表 4 AC与TCM的微介孔结构性能
Table 4. Micropore and mesopore structure properties of AC and TCM.
Sample SBET (m2·g−1) Smicro (m2·g−1) Vtotal (mL·g−1) Vmicro (mL·g−1) Vmeso (mL·g−1) AC 860.8 574.3 0.677 0.388 0.295 TCM 517.7 312.4 0.309 0.223 0.120
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