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核能作为当今新兴清洁能源,在实现“双碳”目标中发挥着不可或缺的作用[1]. 但核能的利用会大量累积高放射性核废物,目前处置高放废物的可行方案是深地质处置,建立高放废物处置库,减缓放射性核素的浸出和迁移[2 − 4],然而高放废物处置库中含有多种放射性核素,如铀、硒、镎、钚及锝等,包装容器在地下水多种作用耦合下易被腐蚀,使得上述放射性核素随地下水流动发生迁移,这些具有放射性和毒性双重污染的核素会严重影响和污染地下水[5 − 11]. 因此,抑制或减缓放射性核素的浸出和迁移对长期安全使用核能具有重要研究意义[12]. 高放废物中的U(Ⅵ)主要以铀酰离子(UO22+)和含铀络合物(UO22+与OH−和CO32−形成的溶解度较高的络合物,如UO2(CO3)22−、UO2OH+等)的形式存在,而长寿命的Se(Ⅳ)通常以SeO32−和H2SeO3(aq)为主要形式存在,以上形式的U(Ⅵ)和Se(Ⅳ)随地下水发生迁移后,会扩大污染范围,因此将U(Ⅵ)和Se(Ⅳ)还原成溶解度极低的UO2和Se(0)、Se(-Ⅰ)及Se(-Ⅱ)[13 − 15],能有效阻止U(Ⅵ)/Se(Ⅳ)在地下水中的迁移,保障地下水安全[16]. 针对高放废物处置库周围地下水开展固定和净化U(Ⅵ)/Se(Ⅳ)污染的研究,成为亟需解决的环境问题[17]. 近年来常用的固化/稳定化技术包括水泥基固化/稳定化技术,地质聚合物基固化/稳定化技术,化学药剂稳定化技术以及微生物诱导矿化稳定化技术等[18]. 已有报道表明[14 − 15],无机、有机、复合/纳米、框架类材料可用于去除U(Ⅵ)/Se(Ⅳ),其中,纳米零价金属材料(铁、镍、铜、铝等)具有无毒无害、还原性好、节能高效、绿色环保等优势,且对废水中的重金属有较好的去除效果而备受国内外学者的广泛关注[19 − 20]. 但传统的纳米金属具有易团聚、沉降、溶解及失活等局限性,且受限于自身理化性质和环境因素[21],严重影响其对污染物的处理效果,而对其改性处理可克服其自身缺陷并增加其对污染物的去除能力. 负载型纳米零价金属可以提高纳米金属自身的活性和回收率,减少对生态环境的二次污染[19 − 20]. 本课题组采用液相还原法制备的纳米零价镍(nZVNi),对U(Ⅵ)的去除率高达98.44%[22]. 维生素B12(VB12)对nZVNi还原重金属具有催化协同作用,VB12的加入增强了nZVNi的电子传递能力,提高了nZVNi对U(Ⅵ)的去除能力,VB12负载nZVNi(VB12@nZVNi)对U(Ⅵ)的去除率提高到98.54%[23].
本研究用液相还原法制备了VB12@nZVNi,并开展VB12@nZVNi固定地下水中U(Ⅵ)/Se(Ⅳ)的动态柱试验研究,该研究对高放废物处置库周围地下水修复具有一定的现实意义和应用价值.
VB12负载纳米零价镍固定地下水中U(Ⅵ)/Se(Ⅳ)的效能研究
Efficacy of VB12 loaded on nano-zero-valent nickel immobilizes U(Ⅵ)/Se(Ⅳ) in groundwater
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摘要: 本研究用液相还原法制备了VB12负载纳米零价镍(VB12@nZVNi)复合材料,通过动态试验探讨了复合材料原位固定地下水中U(Ⅵ)/Se(Ⅳ)的固定效果. 运用Thomas、Yoon-Nelson模型对所得试验数据进行拟合,讨论VB12@nZVNi固定U(Ⅵ)/Se(Ⅳ)的性能. 结果表明,VB12@nZVNi材料对模拟U(Ⅵ)/Se(Ⅳ)污染地下水有着较好的固定效果,对U(Ⅵ)/Se(Ⅳ)的最大吸附量分别为106.96 mg·g−1、103.92 mg·g−1. Yoon-Nelson、Thomas模型符合其动态吸附过程,且理论吸附量和半穿透率与实际值比较接近. 因此,VB12@nZVNi可以作为一种有前景的固定材料,用于含U(Ⅵ)/Se(Ⅳ)地下水的固定和净化处理.Abstract: In this study, a composite material consisting of nano-zero-valent nickel (nZVNi) loaded with VB12 (VB12@nZVNi) was synthesized using the liquid phase reduction method. This composite material was then utilized as a fixed material to investigate its effectiveness in immobilizing U(Ⅵ) and Se(Ⅳ) in groundwater through dynamic testing. The experimental data was analyzed using the Thomas and Yoon-Nelson models to evaluate the effectiveness of VB12@nZVNi in immobilizing U(Ⅵ) and Se(Ⅳ). The results indicate that VB12@nZVNi demonstrates excellent performance in fixing and removing U(Ⅵ) and Se(Ⅳ) from simulated groundwater contaminated with these elements. The maximum adsorption capacities of U(Ⅵ) and Se(Ⅳ) were determined to be 106.96 mg·g−1 and 103.92 mg·g−1, respectively. The Yoon-Nelson and Thomas models demonstrated consistent behavior with the dynamic adsorption process, indicating the accuracy of the models in predicting the theoretical adsorption capacity and semi-penetration rate. These results suggest that VB12@nZVNi holds great promise as an effective material for immobilizing and purifying U(Ⅵ) and Se(Ⅳ)-containing groundwater.
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Key words:
- Vitamin B12 /
- nano zero-valent nickel /
- load /
- U(Ⅵ) /
- Se(IV) /
- groundwater.
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图 2 不同样品的SEM和EDS图 (a)和(b) nZVNi、(c)和(d) VB12@nZVNi、(e)和(f) VB12@nZVNi吸附U(Ⅵ)后、(g)和(h) VB12@nZVNi吸附Se(Ⅳ)后、(i)和(j) VB12@nZVNi吸附U(Ⅵ)/Se(Ⅳ)后
Figure 2. SEM and EDS of different samples (a) and (b) nZVNi, (c) and (d) VB12@nZVNi, (e) and (f) VB12@nZVNi after adsorption U(Ⅵ), (g) and (h) VB12@nZVNi) after adsorption Se(Ⅳ)、(i) and (j) VB12@nZVNi) after adsorption U(Ⅵ)/Se(Ⅳ)
表 1 污染地下水的组成
Table 1. The composition of contaminated groundwater
离子组成
Ionic composition初始浓度/(mg·L−1)
Initial concentration C0Se(Ⅳ) 10.0 U(Ⅵ) 10.0 Na+ 68.5 K+ 50.4 Ca2+ 69.4 Mg2+ 24.0 F− 0.75 NO3− 25.4 CO32− 127.5 SO42− 96.0 表 2 动态吸附试验数据
Table 2. Dynamic adsorption experimental data
污染物
Contaminant进水流速Q/(mL·min−1)
Inlet velocity Q进水浓度C0/(mg·L−1)
Influent concentration C0穿透时间t/h
Penetration time饱和吸附容量
q0,exp/(mg·g−1)
Saturated sorption capacity q0,expU(Ⅵ) 5 10 204 106.96 Se(Ⅳ) 5 10 210 103.92 表 3 Yoon-Nelson模型拟合曲线各参数
Table 3. The Yoon-Nelson model fits the parameters of the curve
污染物
Contaminant进水流速Q/(mL·min−1)
Inlet velocity Q进水浓度C0/(mg·L−1)
Influent concentration C0Yoon-Nelson 相关系数
R2KYN/ min−1 半穿透率τ /h U(Ⅵ) 5 10 0.08625 185.9 0.94291 Se(Ⅳ) 5 10 0.08393 174.4 0.98611 表 4 Thomas模型拟合曲线各参数
Table 4. The Thomas model fits the parameters of the curve
污染物
Contaminant进水流速Q/(mL·min−1)
Inlet velocity Q进水浓度C0/(mg·L−1)
Influent concentration C0Thomas 相关系数
R2KTh/(mL∙min−1∙mg−1) q0/(mg·g−1) U(Ⅵ) 5 10 0.16890 110.444 0.9262 Se(Ⅳ) 5 10 0.14195 104.563 0.9833 -
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