【作者】 张长平；

【导师】 顾平；

【作者基本信息】 天津大学 ， 环境工程， 2009， 博士

【摘要】 微滤工艺和传统工艺相结合处理放射性废水能获得较高的去污因数和浓缩倍数。本文开发了吸附-微滤工艺、混凝共沉淀-微滤工艺分别处理含铯、锶的废水,对混凝-微滤工艺处理锕系元素废水的操作参数进行了优化。以亚铁氰化钾锌为吸附剂,进行了吸附-微滤工艺处理低浓度含铯废水的冷试验研究,试验中制备的亚铁氰化钾锌的分子式为K₂Zn₃[Fe（CN）₆]₂,结构致密,粒径为0.275¹7.4μm,对铯具有较好的吸附性能,对铯的吸附行为符合Freundlich等温式和拟二级动力学模型。静态试验表明,吸附剂的投加量为0.330 g/L时,对铯的去污因数为75.8,去除率达到了98.7%,而相同参数下的小试规模冷试验对铯的去除效果要好于静态吸附试验,主要原因是曝气过程使吸附剂表面不断更新,从而使旧吸附剂具有持续的吸附能力。吸附剂用量越大,去污因数越大,浓缩倍数越小,吸附剂投加量分别为0.330 g/L、0.165 g/L、0.083 g/L,进水铯浓度为100μg/L左右时,去污因数分别为208.7、128.8、77.2,浓缩倍数分别为539、1218、2306。出水无色透明,浊度最低为0.05 NTU,最高为0.10 NTU。出水中金属元素钙、镁基本不被截留,铁被全部截留。毒性很强的CN-浓度小于0.002 mg/L,达到了《污水综合排放标准》（GB8978-1996）。以蒙脱石为吸附剂,由于吸附剂投量过高,无法满足工程要求,因而采用吸附-微滤工艺处理含锶废水是不可行的。以Na₂CO₃为沉淀剂,以FeCl₃为混凝剂,采用混凝共沉淀-微滤工艺处理含锶废水是可行的。序批式运行方式中,当Na₂CO₃投加量为2000 mg/L,FeCl₃投加量为10 mg/L,进水锶浓度为10 mg/L左右时,去污因数达到458,但膜污染严重,限制了工艺的应用范围。在连续式运行方式中,当进水锶浓度为5.3 mg/L,Na₂CO₃投加量为2000 mg/L,FeCl₃投加量为20 mg/L时,平均去污因数为183.6,浓缩倍数达到249。该工艺出水水质较好,浊度小于0.10 NTU。铁基本被全部去除,钙的去除率达到88%以上,镁的去除率较低,水的软化有利于锶的去除。混凝-微滤工艺处理锕系元素废水的应用规模冷试验运行效果良好,无论主膜组件出水期间,还是辅助膜组件进行浓缩期间,出水的浊度正常。当浓缩倍数为565时,污泥流动性较好,能顺利排出反应器。参考处理含裂片核素废水和锕系元素废水的试验结果,进行了处理同时含铯、锶混合废水工艺的初步设计,原水首先以Na₂CO₃为沉淀剂,以FeCl₃为混凝剂采用混凝共沉淀-微滤工艺去除锶,然后以亚铁氰化钾锌为吸附剂采用吸附-微滤工艺去除铯。更多还原

【Abstract】 Microfiltration process combined with traditional process for the treatment of liquid radioactive waste can obtain higher decontamination factor and concentration factor. An adsorption-microfiltration process and a coagulating coprecipitation-microfiltration process were developed to treat the wastewater containing cesium and strontium respectively and the operating parameters of the coagulation-microfiltration process for the treatment of actinide elements wastewater were optimized as well in this paper.The adsorption-microfiltration process was researched to treat the low level cesium wastewater with the potassium zinc hexacyanoferrate as the adsorbent. The molecular formula of the adsorbent was K₂Zn₃[Fe（CN）₆]₂, and its structure was compacted with particle size of 0.275¹7.4μm. Its adsorption ability for cesium was good and the adsorption behavior was in accordance with the Freundlich type sorption isotherm and the pseudo-second order kinetics model. The results of the jar test showed that the decontamination factor was 75.8 and the removal reached 98.7% when the dose of the adsorbent was 0.330 g/L, whenas, the results of the lab-scale test with the same parameters showed that the effect of cesium removal was better than that of the jar test, which resulted from the continuous renewal of the adsorbent surface by which the adsorption capacity of the old adsorbent was improved. The more the adsorbent dose, the largerer the decontamination factor was while the smaller the concentration factor was. When the dose of the adsorbent was 0.330 g/L, 0.165 g/L, 0.083 g/L respectively and the cesium concentration of the raw water was about 100μg/L, the decontamination factor was 208.7, 128.8, 77.2 and concentration factor was 539, 1218, 2306 respectively. The effluent was colorless and transparent, the lowest turbidity was 0.05 NTU and the highest was 0.10 NTU. The calcium and the magnesium were not rejected while iron was rejected all and the concentration of CN- in the effluent, whose toxicity was serious, was lower than 0.002 mg/L and met the Integrated Wastewater Discharge Standard （GB8978-1996）.The adsorption-microfiltration process with the montmorillonite as the adsorbent was not feasible because of the adsorbent does being too high to satisfy the engineering requirement.The coagulating coprecipitation-microfiltration process was feasible to treat wastewater containing strontium with Na₂CO₃ as the precipitant and FeCl₃ as the coagulant. In the batch operation mode, the decontamination factor reached 458 when the Na₂CO₃ dose was 2000 mg/L, the FeCl₃ dose was 10 mg/L and the strontium concentration in the raw water was about 10 mg/L, but the membrane fouling was serious which limited the application of the process. In the continuous operation mode, the mean decontamination factor was 183.6 and the concentration factor was 249 when the Na₂CO₃ dose was 2000 mg/L, the FeCl₃ dose was 20 mg/L and the strontium concentration in the raw water was 5.3 mg/L. The effluent quality was good with the turbidity being smaller than 0.10 NTU. The iron was removed all, the removal of the calcium was higher than 88% and that of the magnesium was lower, the softening of the water was favorable to the strontium removal.The operation effect of the full-scale cold test of the coagulation-microfiltration process for the treatment of actinide elements wastewater was good and the turbidity of the effluent was normal no matter the main or the auxiliary membrane worked. When the concentration factor was 565, the fluidity of the sludge was good and discharging from the membrane reactor was feasible.With reference to the results of the treatment of fission produce nuclides wastewater and actinide elements wastewater, a process for the treatment of mixed wastewater containing strontium and cesium simultaneously was designed preliminarily by which the strontium was removed first by coagulating coprecipitation-microfiltration with Na₂CO₃ as the precipitant and FeCl₃ as the coagulant, and then the cesium was removed by adsorption-microfiltration with the potassium zinc hexacyanoferrate as the adsorbent.更多还原