聚乙烯醇包埋奥奈达希瓦氏菌还原铀的试验研究

发布时间：2018-12-06 08:57

【摘要】：在铀矿开采及生产过程中,产生了大量放射性含铀废水,对生态环境和人类健康构成严重威胁。如何采用经济有效的方法处理放射性废水,甚至对废水中的铀等其他重金属,进行资源回收利用,是目前面临且亟待解决的核环境与安全问题。传统的物理化学处理方法,对废水中铀的去除有一定效果,但也存在如投加的化学药剂成本高,容易造成二次污染等问题;生物处理方法,具有原料充足且成本低廉、处理效率高且无二次污染等优势,成为近年来的研究热点。希瓦氏菌能有效去除废水中的重金属Cr(VI)、Hg(II)等以及放射性金属U(VI)、Tc(VII)等,因此希瓦氏菌在重金属离子以及放射性金属的微生物修复领域拥有广阔的前景。课题组前期研究了奥奈达希瓦氏菌还原铀的特性,本研究在此基础上采用奥奈达希瓦氏菌为还原微生物,以聚乙烯醇为包埋材料,用聚乙烯醇包埋奥奈达希瓦氏菌,制备微球,探讨微球制备的最佳试验条件,以及研究包埋微球对铀的还原性能。以包埋微球的成球难易、稳定性能和传质性能等为指标,通过试验确定了制备聚乙烯醇包埋奥奈达希瓦氏菌微球的最佳组合条件,即聚乙烯醇浓度为10%,氯化钙浓度为4%,交联时间为4h。试验中加入浓度为0.5%的海藻酸钠有利于包埋微球的制备。p H=7.0时,U(VI)初始浓度为15mg/L,奥奈达希瓦氏菌投加量为6m L,且奥奈达希瓦氏菌与聚乙烯醇按1:2的比例进行包埋后,包埋微球还原U(VI)的去除率最高,达96.22%。扫描电镜分析,包埋微球还原U(VI)后,表面出现破损,U(VI)对奥奈达希瓦氏菌具有毒害作用,且微球表面和内部均有晶体沉积;电子能谱分析,包埋微球还原U(VI)后,能谱图中出现铀的吸收峰,结合能为3~4ke V。结合分析包埋微球中沉积的晶体为铀的沉积物,U(VI)被包埋微球还原,沉积下来。共存金属离子对包埋微球还原U(VI)有不同的影响,2mmol/L的Ca2+对包埋微球还原U(VI)具有微弱的促进作用;2mmol/L Mn2+和2mmol/L Cu2+对包埋微球还原U(VI)具有明显抑制作用。
[Abstract]:In the process of uranium mining and production, a large amount of radioactive uranium-bearing wastewater is produced, which poses a serious threat to the ecological environment and human health. How to use economic and effective methods to treat radioactive wastewater, and even to recycle uranium and other heavy metals in the wastewater, is a nuclear environmental and safety problem that needs to be solved. The traditional physicochemical treatment method has certain effect on the removal of uranium in wastewater, but there are also some problems such as the high cost of adding chemicals, which are easy to cause secondary pollution and so on. Biological treatment, with the advantages of abundant raw materials, low cost, high treatment efficiency and no secondary pollution, has become a research hotspot in recent years. Shiva's bacteria can effectively remove heavy metal Cr (VI), Hg (II) and radioactive metal U (VI), Tc (VII) in wastewater. Therefore, Shiva has a broad prospect in the field of heavy metal ions and microbial remediation of radioactive metals. The study group studied the characteristics of reducing uranium by Alneda-Shiva 's bacteria. On this basis, the microspheres were prepared by using Alneda-Shiva bacteria as reducing microorganism and polyvinyl alcohol as the entrapment material, and the microspheres were prepared by using polyvinyl alcohol as the entrapment material, and the microspheres were prepared by using polyvinyl alcohol as the entrapment material. The optimum experimental conditions for the preparation of microspheres and the reduction properties of the encapsulated microspheres to uranium were studied. Taking the encapsulated microspheres as indexes, such as easy to form, stability and mass transfer, the optimum conditions for the preparation of polyvinyl alcohol encapsulated Alnaida Shiva microspheres were determined, that is, the concentration of polyvinyl alcohol was 10, the concentration of calcium chloride was 4 times, and the optimum conditions of preparing the microspheres were as follows: the concentration of polyvinyl alcohol was 10, and the concentration of calcium chloride was 4%. The crosslinking time is 4 h. The addition of 0.5% sodium alginate was beneficial to the preparation of encapsulated microspheres. The initial concentration of, U (VI) was 15 mg / L at pH 7.0, and the dosage of Alnaida Shiva was 6 mL. The removal rate of U (VI) by encapsulated microspheres was the highest (96.2222) after the embedding of Alneda-Shiva and polyvinyl alcohol at 1:2. Scanning electron microscopy (SEM) analysis showed that the appearance of damaged, U (VI) on the surface of the microspheres after the reduction of U (VI) was toxic to Alnaida Shiva, and crystal deposition was found on the surface and inside of the microspheres. After the reduction of U (VI) by embedded microspheres, the absorption peak of uranium appears in the spectrogram, and the binding energy is 3~4ke V. The crystal deposited in the encapsulated microsphere is the uranium deposit, which is reduced and deposited by, U (VI) embedded microsphere. Coexisting metal ions have different effects on the reduction of U (VI) by encapsulated microspheres, and Ca2 of 2mmol/L has a weak promoting effect on the reduction of U (VI) by embedded microspheres. 2mmol/L Mn2 and 2mmol/L Cu2 inhibited the reduction of U (VI) by encapsulated microspheres.
【学位授予单位】：南华大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X753

【相似文献】