图1 用于膜结晶的典型中空纤维膜结构SEM图[24]

Fig.1 SEM images of typical hollow fiber membrane structures used for membrane crystallization[24]

图2 空心钇稳定氧化锆(YSZ)管表面上制备的C-D35-2膜的SEM图(a)，YSZ和碳层之间界面的FIB-SEM图,即图（a）中方框区域放大图（碳和YSZ之间的界面清晰可见。碳纤维-陶瓷界面附近的孔径被认为是最小的，通过气体渗透确定约为31 nm）(b)，C-D35-2膜中典型的单碳纳米纤维的HRTEM图（箭头指向碳纤维内部的“竹节状”结构，该结构将内部空间划分为多个隔室，1 ? =0.1 nm）(c)[31]

Fig.2 SEM image of C-D35-2 film prepared on the surface of hollow yttrium-stabilized zirconia (YSZ) tube (a); FIB-SEM image of the square in Fig.2(a)（The clear interface between carbon and YSZ is clearly visible. You can also see the nanopores on the carbon side. The pore size near the carbon fiber-ceramic interface is considered to be the smallest, which is determined to be about 31 nm by gas penetration） (b); HRTEM image of typical single carbon nanofibers in C-D35-2 film (The arrow points to the “slubby” structure inside the carbon fiber, which divides the internal space into multiple compartments) (c)[31]

图3 在T = 70°C(343.15 K)和S = 1.01时KNO3在不同膜材料和孔隙率的膜蒸馏结晶中成核功W对比[32]

Fig.3 Comparison of nucleation work W of KNO3 in membrane distillation crystallization of different membrane materials and porosities at T = 70℃ (343.15 K) and S = 1.01[32]

图4 MDC过程中溶液在膜表面非均相成核、生长及脱附的示意图[33]

Fig.4 Schematic diagram of solution heterogeneous nucleation, growth and detachment on the membrane surface during MDC[33]

图5 膜蒸馏装置：直接接触膜蒸馏(DCMD)、渗透膜蒸馏(OMD)、吹扫气膜蒸馏(SGMD)、气隙膜蒸馏(AGMD)和真空膜蒸馏(VMD)[34]

Fig.5 Membrane distillation unit: direct contact membrane distillation (DCMD), osmotic membrane distillation (OMD), sweep gas membrane distillation (SGMD), air gap membrane distillation (AGMD) and vacuum membrane distillation (VMD)[34]

图6 各种进料温度下SMDC中的渗透通量[42]

Fig.6 Permeation flux in SMDC at various feed temperatures[42]

图7 通过膜结晶得到的LiCl晶体的形态：斜方多晶型(a),立方多晶型(b); 各种进料温度和流速下立方和斜方晶型的分布[(c)~(e)][47]

Fig.7 Morphology of LiCl crystals obtained by film crystallization: orthogonal polymorph (a), cubic polymorph (b); distribution of cubic and orthogonal structures at various feed temperatures and flow rates[(c)—(e)][47]

图8 自然冷却结晶，冷却速率为0.1 K/min下的膜蒸馏耦合冷却结晶(KNO3)不同结晶时间的CSD（柱形图）(a)，晶体的光学显微镜图[放大100倍(b),放大40倍(c)]；膜辅助结晶，冷却速率为0.2 K/min下的膜蒸馏耦合冷却结晶(KNO3)的温度曲线及不同结晶时间的CSD(d)，晶体的光学显微镜图[放大100倍(e),放大40倍(f)]；快速冷却结晶，冷却速率为0.33 K/min下的膜蒸馏耦合冷却结晶(KNO3)的温度曲线及不同结晶时间的CSD(g)，晶体的光学显微镜图[放大100倍(h),放大40倍(i)] (图中虚线表示由MATLAB编程建立粒数衡算方程得出的动力学模拟结果，Ni/Ntotal表示不同尺寸晶体数占晶体总数百分比，峰值数字为变异系数，lˉ表示晶体平均尺寸)[32]

Fig.8 Under natural cooling and cooling rate of 0.1 K/min, CSD (bar graph) of different crystallization time of membrane distillation coupled cooling crystallization (KNO3) (a), optical microscope image of the crystal [magnification 100 times (b), magnification 40 times (c)]; under membrane assisted crystallization and cooling rate of 0.2 K/min, CSD of different crystallization time of membrane distillation coupled cooling crystallization (KNO3) (d), optical microscope image of the crystal [magnification 100 (e), magnification 40 times (f)]; under rapid cooling crystallization and cooling rate of 0.33 K/min, CSD of different crystallization time of membrane distillation coupled cooling crystallization (KNO3) (g),the optical microscope image of the crystal [magnification 100 times (h), magnified 40 times (i)] （The dot line in the figure: the kinetic simulation results obtained by the MATLAB programming to establish the particle number balance equation; Ni/Ntotal: the percentage of the number of crystals of different sizes; the number marked at the peak: C.V.; lˉ: the average crystal size）[32]

图9 快速冷却方式下晶体的粒度分布和显微镜照片（插图，×200）[49]

Fig.9 Crystal particle size distribution and microscope photo (inset，×200) in rapid cooling model [49]

图10 高盐废水的膜蒸馏结晶基本流程[42]

Fig.10 Basic process of membrane distillation crystallization of high-salt wastewater[42]

图11 在MDC中同时进行EG、有机含盐废水的回收和结晶控制：实验装置(a)；重复实验下渗透通量、EG和NaCl截留率(b)；通过MDC和真空蒸发结晶(VEC)获得的晶体颗粒性质的比较(c)[58]

Fig.11 Simultaneous recovery and crystallization control of EG and organic saline wastewater in MDC: experimental device (a); permeation flux, EG and NaCl rejection rate under repeated experiments (b); comparison of the properties of crystal particles obtained by MDC and vacuum evaporation crystallization (VEC) (c)[58]

图12 水凝胶复合膜调控生成的不同CaCO3晶体SEM图[11]

Fig.12 SEM images of different CaCO3 crystals generated by hydrogel composite membrane[11]

图13 HCMs膜结晶流程示意图(a)；膜组件单元分解示意图(b)；多通道连续实验平台(c)；PEGDA-NIPAM HCMs的晶体成核调控及高选择性生长机理与实验结果(d) [69]G*nucleation—临界成核能； Tfeed—进料结晶溶液的温度； vflow—进料流动的速度； Cs—晶体组分的浓度

Fig.13 Schematic diagram of HCMs membrane crystallization process(a); schematic diagram of membrane module unit decomposition(b); multi-channel continuous experiment platform(c); crystal nucleation regulation and highly selective growth mechanism and experimental results of PEGDA-NIPAM HCMs(d) [69]

图14 膜蒸馏结晶研究的重要进展和未来发展方向

Fig.14 Important progress and further directions of membrane distillation crystallization research