State Key Laboratory of Environmental Aquatic Chemistry Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
J Environ Sci (China). 2010;22(12):1860-7. doi: 10.1016/s1001-0742(09)60332-6.
The direct contact membrane distillation applied for fluoride removal from brackish groundwater was investigated. The self-prepared polyvinylidene fluoride membrane exhibited high rejection of inorganic salt solutes. The maximum permeate flux 35.6 kg/(m2 x hr) was obtained with the feed solution at 80 degrees C and the cold distillate water at 20 degrees C. The feed concentration had no significant impact on the permeate flux and the rejection in fluoride. The precipitation of CaCO3 would clog the hollow fiber inlets and foul the membrane surface with increasing concentration factor when natural groundwater was used directly as the feed, which resulted in a rapid decline in the module efficiency. This phenomenon was diminished by acidification of the feed. The experimental results showed that the permeate flux and the quality of obtained distillate kept stable before concentration factor reached 5.0 with the acidified groundwater as feed. The membrane module efficiency began to decline gradually when the feed continued to be concentrated, which can be mainly attributed to the formation of CaF2 deposits on the membrane surface. In addition, a 300 hr continuous fluoride removal experiment of acidified groundwater was carried out with concentration factor at 4.0, the permeate flux kept stable and the permeate fluoride was not detected.
采用直接接触式膜蒸馏技术从微咸地下水中除氟。自制的聚偏氟乙烯膜对无机盐溶质具有较高的截留率。在 80°C 的进料溶液和 20°C 的冷蒸馏水条件下，获得了 35.6 kg/（m2·h）的最大渗透通量。进料浓度对氟的渗透通量和截留率没有显著影响。当直接使用天然地下水作为进料时，随着浓缩因子的增加，CaCO3 的沉淀会堵塞中空纤维入口并污染膜表面，从而导致模块效率迅速下降。酸化进料可以减轻这种现象。实验结果表明，在用酸化地下水作为进料时，在浓缩因子达到 5.0 之前，渗透通量和获得的蒸馏水的质量保持稳定。当进料继续浓缩时，膜组件效率开始逐渐下降，这主要归因于膜表面形成了 CaF2 沉积物。此外，在浓缩因子为 4.0 的条件下进行了 300 小时的酸化地下水连续除氟实验，渗透通量保持稳定，未检测到渗透氟。
