本文選題：反滲透 + 放射性廢水�。� 參考：《武漢大學(xué)》2014年博士論文

【摘要】：核設(shè)施在運行、維修和退役階段會產(chǎn)生大量含硼放射性廢水,此類廢水必須經(jīng)除放射性并分離硼酸后才能向環(huán)境排放。目前采用的蒸發(fā)處理方法存在系統(tǒng)工藝復(fù)雜、能耗高的缺點。本文在在深入調(diào)研含硼放射性廢水處理方法的基礎(chǔ)上,對苦咸水反滲透膜分離硼酸的特性進(jìn)行全面研究,并提出采用多羥基化合物絡(luò)合強(qiáng)化的方法改善反滲透膜分離硼酸的性能。采用人工配制的模擬廢水和實際放射性廢水進(jìn)行了含硼廢水的處理實驗,并基于不可逆熱力學(xué)模型對反滲透分離硼酸的機(jī)理及性能進(jìn)行了分析,為反滲透方法用于處理含硼放射性廢水打下了技術(shù)基礎(chǔ)。 不同條件下反滲透膜對硼酸分離特性實驗結(jié)果表明,影響反滲透除硼率最重要的因素是進(jìn)水pH,隨著進(jìn)水pH的上升反滲透除硼率不斷提高,pH為10.31時CPA2膜和BW30膜對硼酸的截留率分別達(dá)到了91%和92.1%。反滲透除硼率隨著操作壓力的增大和水溫的降低而提高,膜元件的回收率和進(jìn)水含鹽量對反滲透除硼率也有一定影響,而進(jìn)水硼濃度對除硼率幾乎沒有影響。 硼酸絡(luò)合實驗結(jié)果表明,多羥基化合物對硼酸絡(luò)合作用由強(qiáng)到弱的排列順序為：山梨醇甘露醇果糖≈木糖醇葡萄糖。通過多羥基化合物的絡(luò)合強(qiáng)化,可以明顯提高反滲透過程的除硼效果。在pH為8.5以上時,經(jīng)過甘露醇按2：1的絡(luò)合比進(jìn)行絡(luò)合強(qiáng)化后,兩種反滲透膜的除硼率均分別提高7～10個百分點；按5：1的絡(luò)合比進(jìn)行絡(luò)合強(qiáng)化后,除硼率提高12～18個百分點。山梨醇和甘露醇絡(luò)合強(qiáng)化反滲透正交實驗結(jié)果表明,pH對絡(luò)合強(qiáng)化反滲透除硼效率的影響最大,水溫次之,回收率和壓力相對來說影響程度較小。絡(luò)合強(qiáng)化反滲透可以在相對低的pH條件下實現(xiàn)較高的硼酸去除率,反滲透膜在相對低的pH下運行可以降低膜結(jié)垢風(fēng)險,延長使用壽命,這對于含硼廢水的處理具有實際意義。 模擬含硼放射性廢水反滲透處理實驗結(jié)果顯示,在pH為9.13時,經(jīng)山梨醇按5：1的摩爾比絡(luò)合后,CPA2和BW30兩種膜對硼酸的去除率分別處于96.60%～98.49%和97.32%～99.21%的范圍內(nèi),比直接反滲透的除硼率有顯著提高。在模擬含硼廢水處理過程中,脫鹽率隨著操作壓力的提高、回收率的下降而上升。在同樣的進(jìn)水壓力和回收率下,脫鹽率隨著進(jìn)水pH的提高明顯上升。另外,經(jīng)反滲透膜處理后,透過水中鈷濃度降低到檢測限以下。對銫的去除效果與pH、操作壓力和回收率有關(guān),在pH為9.13時,銫的去除率可達(dá)到95%以上。 實際含硼放射性廢水反滲透處理實驗結(jié)果表明,在進(jìn)水壓力1.0MPa、回收率約為25%的條件下,直接反滲透對硼酸的去除率僅為51.12%,山梨醇絡(luò)合強(qiáng)化反滲透(絡(luò)合摩爾比5：1)對硼酸的去除率為89.68%,比直接反滲透下的去除率提高了約75%。絡(luò)合強(qiáng)化反滲透對實際含硼廢水中硼酸有非常好的截留效果。實際含硼放射性廢水的絡(luò)合強(qiáng)化反滲透濃縮處理實驗結(jié)果顯示,反滲透膜在除硼的同時,還對廢水中的鹽分和放射性核素保持了比較好的去除效果,對硼酸的去除率保持在86.78%～89.21%之間,脫鹽率則在94.0%-94.8%之間變化,對廢水中54Mn、60Co和137Cs的去污因子最高可達(dá)934。 將反滲透過程中硼酸的傳質(zhì)過程分解成H3B03和H2BO3-兩種組分進(jìn)行討論,并根據(jù)實驗數(shù)據(jù),運用不可逆熱力學(xué)模型,計算出了CPA2膜和BW30膜對兩種組分的反射系數(shù)以及兩種組分在反滲透膜中的透過系數(shù)。并由組分的反射系數(shù)和透過系數(shù),計算出了反滲透過程中的硼反射系數(shù)和硼透過系數(shù)。并根據(jù)反射系數(shù)和透過系數(shù)的變化,合理解釋了反滲透過程中除硼率的變化機(jī)理。采用不可逆熱力學(xué)模型,計算預(yù)測了25℃時CPA2和BW30兩種反滲透膜在不同進(jìn)水壓力和pH條件下的除硼率,預(yù)測結(jié)果與實驗數(shù)據(jù)相吻合。
[Abstract]:A large amount of radioactive waste water containing boron is produced in the stage of operation, maintenance and decommissioning. This kind of waste water must be discharged to the environment after radioactive removal and separation of boric acid. The current evaporation treatment method has the disadvantages of complex system technology and high energy consumption. This paper is based on the deep study of the treatment of boron containing radioactive waste water. The characteristics of boric acid separation by the reverse osmosis membrane of bitter salt water are studied comprehensively, and the method of complex strengthening of polyhydroxy compounds is proposed to improve the performance of boric acid separation by the reverse osmosis membrane. The experiment of treating boron containing wastewater with artificial wastewater and actual radioactive waste water is carried out, and the reverse osmosis is based on the irreversible thermodynamic model. The mechanism and properties of boric acid separation were analyzed, which laid a technical foundation for RO treatment of boron containing radioactive waste water.
The experimental results of boric acid separation under different conditions show that the most important factor affecting the rate of boron removal is influent pH. With the increasing of the influent pH, the rate of boron removal is increasing. When the pH is 10.31, the retention of boric acid to the CPA2 film and the BW30 film is up to 91%, and the rate of the reverse osmosis removal is increased with the increase of the operating pressure. With the increase of water temperature, the recovery rate of the membrane elements and the salt content of the influent also have some influence on the rate of boron removal, while the concentration of influent boron has little effect on the boron removal rate.
The results of boric acid complexation showed that the arrangement sequence of polyhydroxy compounds for boric acid collaterals from strong to weak is: sorbitol mannitol fructose and xylitol glucose. Through the complexation of polyhydroxy compounds, the effect of boron removal in the reverse osmosis process can be obviously improved. When pH is more than 8.5, the complexation ratio of mannitol to 2:1 is obtained. The boron removal rate of the two kinds of reverse osmosis membranes increased by 7~10 percentage points, respectively, and the boron removal rate increased by 12~18 percentage points after complexing with the complexing ratio of 5:1. The orthogonal experimental results of sorbitol and mannitol complexation enhanced reverse osmosis showed that pH had the greatest influence on the efficiency of boronide removal by complexing enhanced reverse osmosis. The ratio of yield and pressure is relatively small. Complex enhanced reverse osmosis can achieve high removal rate of boric acid at relatively low pH conditions. The operation of reverse osmosis film under relatively low pH can reduce the risk of fouling and prolong the service life, which is of practical significance for the treatment of boron containing wastewater.
The experimental results of reverse osmosis treatment of simulated boron containing radioactive waste water show that the removal rate of two kinds of CPA2 and BW30 membranes to boric acid is in the range of 96.60% to 98.49% and 97.32% to 99.21%, respectively, after the pH is 9.13, and the rate of boron removal is significantly higher than that of direct reverse osmosis. The desalination rate increases with the increase of operating pressure and the decrease of recovery rate. Under the same influent pressure and recovery rate, the desalination rate increases obviously with the increase of the influent pH. In addition, the cobalt concentration in the water is reduced to below the detection limit after the reverse osmosis membrane treatment. The removal effect of cesium is related to the pH, operating pressure and recovery rate, at pH 9 At.13, the removal rate of cesium can reach more than 95%.
The experimental results of reverse osmosis treatment of actual boron containing radioactive waste water show that the removal rate of boric acid by direct reverse osmosis is only 51.12% under the condition of inlet pressure 1.0MPa and the recovery rate is about 25%, and the removal rate of boric acid by sorbitol complexing enhanced reverse osmosis (complex molar ratio 5:1) is 89.68%, which is about 75%. collaterals higher than that of direct reverse osmosis. The experimental results show that the reverse osmosis membrane has a good removal effect on the salt and radioactive nuclides in the wastewater, and the removal rate of boric acid remains at 86.7. Between 8% and 89.21%, the desalination rate changes between 94.0%-94.8%, and the decontamination factor for 54Mn, 60Co and 137Cs in wastewater is up to 934..
The mass transfer process of boric acid in the process of reverse osmosis is decomposed into two components of H3B03 and H2BO3-. According to the experimental data, the reflection coefficient of the two components and the transmittance coefficient of the two components in the reverse osmosis membrane are calculated by using the irreversible thermodynamic model, and the reflection coefficient and the transmission coefficient of the components are obtained. The boron reflection coefficient and boron transmission coefficient in the process of reverse osmosis are calculated. According to the change of reflection coefficient and transmission coefficient, the mechanism of the change of boron removal rate in the process of reverse osmosis is reasonably explained. Using an irreversible thermodynamic model, the prediction of the removal of two kinds of CPA2 and two kinds of reverse osmosis membranes at 25 degrees C under the conditions of different influent pressure and pH is calculated. The results are in good agreement with the experimental data.
【學(xué)位授予單位】：武漢大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2014
【分類號】：X771

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