含氟、铀废水深度净化处理方法研究

发布时间：2018-09-01 20:07

【摘要】：随着核工业的发展,产生了一批难于处理的含氟、铀废水。本研究以含氟、铀废水为研究对象,采用生物沉降、化学沉降以及离子交换纤维(IEF)技术,分别实现了对氟和铀的深度净化要求,并以此提出了一条较为经济可行的含氟、铀废水深度净化工艺。生物沉降采用固定化活体耐辐射奇球菌(IDR)进行,结果表明,菌含量2.5%的IDR颗粒对铀的沉降性能良好,p H=3.5,铀初始浓度50mg/L,去除率最高可达95%以上,最大吸附量达103.82 mg/g(DW)。IDR的动态柱吸附实验表明,其去除铀的稳定性较好,吸附后铀易通过0.1 mol/L HCl再生,解吸率达90%以上,也可作为固定床填料考虑。经SEM/EDS、XRD等分析可知,铀在IDR颗粒表面以片状铀的磷酸盐形式存在。经过灰化处理后,减重比为254;灰分中铀以Ca(UO2)(PO4)·3H2O和(Ca,U)(PO4)·2H2O的形式赋存。化学沉降铀试验结果表明,优选组合为p H=9,添加10%乙醇,磷酸二氢钙用量为3g,铀去除率达95%以上。经SEM/EDS分析,沉淀是5~10μm片层状堆积的颗粒,由Ca、P、U、O四种元素组成的混合物。在p H=9,加10%乙醇,投加磷酸二氢钙3g条件下,易生成U(HPO4)2·6H2O;而p H=7,加30%乙醇,投加磷酸二氢钙3g条件下易生成(UO2)3(PO4)2·8H2O。化学沉淀氟采用钙盐进行,废水氟离子浓度控制在130%理论值的钙盐投加量条件下,除氟效果达到最佳,氟离子浓度可以降到30mg/L左右,进一步处理首先调节p H=11左右,按照2:1的磷酸盐:氟离子的比例投加磷酸盐,可以使废水中氟离子浓度降至5mg/L左右,达到可排放的水平。IEF筛选优化静态除铀试验结果表明,纯铀体系下,强碱型纤维(SAIEF)处理效果最优,预处理采用酸碱洗的方式进行,接触时间在15~30 min内,其对铀的去除率可达90%以上;p H最佳范围为9.5~11,于10.5处最佳,投加量以1.5g/100mL为宜,铀初始浓度20~100mg/L为宜;恒定投加量梯度递降3次可使50mg/L的铀降至0.05mg/L以下;采用0.1M盐酸作为解吸剂效果较佳,10%的氯化钠也可;解吸后浓水可采用化学沉降的方式回收利用。氟铀体系下,设定氟离子浓度5g/L、10g/L、15g/L条件下,分别对应5mg/LU和50mg/LU,SAIEF基本保持了在纯铀体系下对铀的吸附性能,且几乎对氟离子不去除。结合SEM/EDS、FTIR表征和模拟分析,SAIEF的主要离子交换方程如下:P-CH2N+(CH3)3Cl-+(UO2)2CO3(OH)3-→[P-CH2N+(CH3)3](UO2)2CO3(OH)3 + Cl-(pH 8~11.5)P-CH2N+(CH3)3Cl-+ UO2(OH)3-→[P-CH2N+(CH3)3]UO2(OH)3+ Cl-(p H 10~14)SAIEF动态柱试验结果表明,纯铀体系下,流速10~20mL/min,SAIEF对铀的饱和吸附量约为426.7mg/g;单级填料10~20 g、填料密度=0.1g/mL;填料高度10~20 cm;径高比=1:3~6;进水浓度2~50mg/L铀时,进入量:30-60个柱体积;可保证出水维持10 h左右持续出水铀浓度在0.05g/L以下,符合深度净化要求。且该流速下高径比对铀去除的影响不大,动态解吸流速减半,采用3倍柱体积的0.1M盐酸或10%氯化钠可完成。流速25ml/min时,三级串连,填料密度0.1g/mL;填料高度20 cm;径高比=1:7.6条件下,进水50mg/L U,出水维持10 h左右持续出水铀浓度0.05mg/L以下,此时进水总体积为120个柱体积;当进水5mg/L U时,出水维持28 h左右持续出水铀浓度0.05mg/L以下,此时进水总体积为1050个柱体积。吸附后纤维的灰化产物主要成分为UO4·4H2O,减重比为6.5左右。氟铀体系下,流速10~20mL/min时,两级串连,填料密度=0.1g/mL;填料高度10 cm;径高比=1:6,进水50mg/L U、10g/L F,通水体积4.5L左右可保持出水铀浓度在0.05mg/L以下,氟浓度维持在10g/L左右。流速25ml/min时,三级串连,填料密度0.1g/mL;填料高度20 cm;径高比=1:7.6条件下,进水50mg/L U、10g/L F,5mg/L U、10g/L F条件下,均可保证至少8 h持续出水铀浓度0.05mg/L以下,氟离子浓度维持进水浓度左右。在纯铀体系下对SAIEF单元进行小试和中试试验,结果表明,设定浓度5~100mg/L,流速5~100L/h,高径比4:1,单级纤维填充密度为0.1g/mL,3~4级串连条件下,对各初始浓度各流速条件下,均可完成对废水中铀的深度净化,去污因子最高达3.762×105。同时,对长期使用后SAIEF进行SEM分析,结果表明,纤维在反复多次使用后结构完好,未有解体现象。从EDS结果可以看出,Cl含量增加,说明纤维的功能基团正常,在反复使用过程中,其交换能力得到了进一步优化。结合以上研究,本文提出一条以沉降方法配合SAIEF技术的较经济可行的含氟、铀废水深度净化工艺,为核工业含氟、铀废水的处理提供一定的参考。
[Abstract]:With the development of nuclear industry, a number of wastewater containing fluorine and uranium are produced which are difficult to be treated. In this study, biological sedimentation, chemical sedimentation and ion exchange fiber (IEF) technology are used to purify fluorine and uranium, and a more economical and feasible method is proposed to purify fluorine and uranium wastewater. Biological sedimentation was carried out by immobilized in vivo Mycoccus radiodurans (IDR). The results showed that the sedimentation performance of uranium by 2.5% IDR particles was good, P H=3.5, the initial concentration of uranium was 50mg/L. The removal rate of uranium was up to 95%, and the maximum adsorption capacity was 103.82 mg/g (DW). The dynamic column adsorption experiment of IDR showed that the removal stability of uranium was better. Good, uranium can be easily regenerated by 0.1 mol/L HCl after adsorption, and the desorption rate is over 90%. It can also be considered as a fixed bed packing. The results of chemical precipitation uranium test show that the optimum combination is p H=9, 10% ethanol is added, the dosage of calcium dihydrogen phosphate is 3 g, and the uranium removal rate is more than 95%. When the concentration of fluoride in wastewater is controlled at 130% of the theoretical value of calcium salt, the effect of fluoride removal is the best. The concentration of fluoride ion can be reduced to about 30mg/L. The further treatment is first regulated about P H = 11 according to the 2. Phosphate: 1. Phosphate: The proportion of fluoride ions added to phosphate can reduce the concentration of fluoride ions in wastewater to about 5 mg / L, reaching the level of discharge. IEF screening and optimization of static uranium removal test results show that under the pure uranium system, strong alkali fiber (SAIEF) treatment effect is the best, the pretreatment is carried out by acid-alkali washing, contact time is 15-30 minutes, and its contact time is within 15-30 minutes. The removal rate of uranium can reach more than 90%; the optimum range of P H is 9.5-11 and 10.5, the optimum dosage is 1.5 g/100 mL, and the initial concentration of uranium is 20-100 mg/L; the constant dosage gradient three times can reduce uranium to less than 0.05 mg/L; 0.1M hydrochloric acid as a desorbent, 10% sodium chloride can also be used; after desorption, concentrated water can be used. Under the condition of 5 g/L, 10 g/L, 15 g/L fluoride ion concentration, 5 mg/LU and 50 mg/LU respectively, SAIEF basically maintains the adsorption performance of uranium in the pure uranium system, and almost does not remove fluoride ions. Combined with SEM/EDS, FTIR characterization and simulation analysis, the main ion exchange equations of SAIEF are as follows: H2N + (CH3) 3Cl - + (CH3) 3Cl - + (UO2) 2CO3 (OH) 3 - 85 [[P - CH2N + (CH3) 3 3] (UO2) 2CO3 (OH) 3 + Cl - (pH 8 ~ 11.5) P - CH2N + (CH3) 3Cl - + UO2 (OH) 3 (OH) 3 (OH 3) 3 - 85 85 [P - CH2N + (CH3) 2SAN + (CH3) 3) 3] UO2 (OH) 3 + Cl - (p H 10 ~ 14) IEF dynamic column test results showed that in the pure uransystem, the flow rate of pure uransystem, flow rate of 20 mIEL / min, 20 m IEL / min, SAIEL / The saturated adsorption capacity of F to uranium is about 426.7 mg/g, the single stage packing is 10-20 g, and the packing density is 0.1 g/mL. The packing height is 10-20 cm, the ratio of diameter to height is 1:3-6, the inlet concentration is 2-50 mg/L uranium, the inlet volume is 30-60 column volume, and the effluent can be maintained for about 10 hours at a consistently effluent uranium concentration below 0.05 g/L, which meets the requirements of deep purification. 10% NaCl can be completed. When the flow rate is 25 ml/min, the three stages are connected in series, the packing density is 0.1 g/mL; the packing height is 20 cm; the diameter-to-height ratio is 1:7.6, the inlet water is 50 mg/L U, and the outlet water is maintained below 0.05 mg/L for about 10 hours, the total volume of the inlet water is 120 columns; when the inlet water is 5 mg/L U, the outlet water is maintained at 0.05 mg/L for about 28 hours. The main component of ashing product after adsorption is UO4.4H2O, and the weight loss ratio is about 6.5. In uranium fluoride system, when the flow rate is 10-20 mL/min, the two stages are in series, the packing density is 0.1 g/mL, the packing height is 10 cm, the diameter-height ratio is 1:6, the influent water volume is 50 mg/L, 10 g/L F, and the outlet water volume is about 4.5 L. Under the condition of 0.05 mg/L, fluorine concentration maintained at about 10 g/L, flow rate 25 ml/min, three stages in series, packing density 0.1 g/mL, packing height 20 cm, diameter-to-height ratio = 1:7.6, influent 50 mg/L U, 10 g/L F, 5 mg/L U, 10 g/L F, the influent concentration of uranium can be maintained at least 8 hours under 0.05 mg/L, fluoride ion concentration maintained at about the influent concentration. The results of pilot and pilot tests on SAIEF unit show that the deep purification of uranium in wastewater can be achieved under the conditions of setting concentration 5-100mg/L, flow rate 5-100L/h, height-diameter ratio 4:1, single-stage fiber packing density 0.1g/mL, 3-4 stages in series, and each initial concentration and flow rate. The maximum decontamination factor is 3.762 65507 The results of SEM analysis by post-SAIEF show that the structure of the fibers is intact after repeated use, and there is no disintegration. From the EDS results, it can be seen that the content of Cl increases, indicating that the functional groups of the fibers are normal. In the process of repeated use, the exchange capacity of the fibers is further optimized. SAIEF is an economical and feasible advanced purification process for fluorine-containing and uranium-containing wastewater, which provides a certain reference for the treatment of fluorine-containing and uranium-containing wastewater in nuclear industry.
【学位授予单位】：西南科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X703

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