直接接触式膜蒸馏技术处理模拟放射性废液
Treatment of Simulated Radioactive Wastewater by Direct Contact Membrane Distillation
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摘要: 采用聚丙烯中空纤维膜开展直接接触式膜蒸馏（DCMD）过程处理模拟放射性废液的研究，主要考察了料液温度、冷却水温度、料液流速以及冷却水流速的变化对膜通量和目标元素（Sr(Ⅱ)、Co(Ⅱ)和Cs(Ⅰ)）截留效果的影响，并探讨了DCMD过程的传质传热机理。考察的四个运行参数中，料液温度的变化对膜通量的影响最大，料液温度由40 ℃增加至80 ℃，膜通量由2.7 L/(m2•h)增加至29.2 L/(m2•h)。此DCMD过程中，水蒸气在膜孔内的传质机理以努森-分子扩散为主，传质阻力主要来自于膜本身。在考察的料液温度（40～80 ℃）、冷却水温度（10～30 ℃）、料液流速（425～1450 mL/min）和冷却水流速（75～600 mL/min）范围内，DCMD过程对Sr(Ⅱ)、Co(Ⅱ)和Cs(Ⅰ)的去污因子（DF）均保持在105以上。结果表明：DCMD过程对模拟放射性废液具有良好的处理效果，可作为一种新的放射性废液处理技术。Abstract: The treatment of simulated radioactive wastewater by direct contact membrane distillation(DCMD) process with polypropylene hollow fibers was conducted to estimate the effect of feed temperature, cooling water temperature, feed velocity, and cooling water velocity on the permeation flux and rejection of objective elements(Sr(Ⅱ), Co(Ⅱ) and Cs(Ⅰ)). Simultaneously, the mechanism of mass transfer and heat transfer was investigated. Among the four operation parameters, the variation of feed temperature shows the highest influence on the permeation flux. The permeation flux increases from 2.7 L/(m2•h) to 29.2 L/(m2•h) when feed temperature varies from 40 ℃ to 80 ℃. In this DCMD process, the mass transfer of vapor in membrane pores is dominated by the Knudsen-molecule diffusion, and the main resistance of mass transfer is derived from membrane itself. In the investigated conditions, i.e., feed temperature(40-80 ℃), cooling water temperature(10-30 ℃), feed velocity(425-1450 mL/min), and cooling water velocity(75-600 mL/min), the decontamination factors(DF) of Sr(Ⅱ), Co(Ⅱ) and Cs(Ⅰ) in the DCMD processes are higher than 105. The experimental results reveal that DCMD process shows excellent treatment effici-ency on the simulated radioactive wastewater, and it can potentially serve as a new method to treat radioactive wastewater.
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