CAJ | 학술논문

采用室内水培和静态吸附实验，研究了水生植物少根紫萍（Landoltia punctata ）活体和干粉对水体中 U（Ⅵ）的吸附能力，并对作用过程和机理进行了初步分析。结果表明：常温下少根紫萍2．5 g·L－1（FW）活体和1．25 g·L－1（DW）干粉在 pH 5下对5 mg·L－1 U（Ⅵ）溶液的去除率分别可达78．70％和95．55％。活体和干粉对 U（Ⅵ）的吸附率随 pH 升高先增大后减小，在 pH 4～5时达到最大，并随投加量的增加而增大；随 U（Ⅵ）初始浓度增加先增大后减小；在作用5 min 时，活体和干粉对水体中 U（Ⅵ）的吸附率分别为13．90％和79．97％，在24 h 时吸附率均达90％以上，吸附逐渐趋于平衡。当 U（Ⅵ）初始浓度增加至250 mg·L－1，活体和干粉对 U（Ⅵ）的吸附量分别达到4．05 mg·g－1（FW）和131．76 mg ·g－1（DW），相比Langmuir 模型，Freundlich 吸附等温方程能较好地描述少根紫萍对 U（Ⅵ）的吸附行为，吸附过程符合准二级吸附动力学方程，r 均在0．99以上。FTIR 分析结果表明：少根紫萍表面含有羟基、羧基、氨基、磷酸基等多种活性基团；SEM-EDS 表明少根紫萍活体与水体中 U（Ⅵ）作用48 h 后，大量片状无机磷酸铀晶体在其根系表面生成，结晶主要由 P，O，U 元素组成，不含 C，其中 P 和 U 的质量百分比分别为8．76％和82．53％，原子百分比分别为25．19％和30．89％，而对照组 P 的质量百分比和原子百分比仅为0．24％和0．11％，干粉未观察到类似晶体存在。XPS 分析结果表明：活体吸附后，部分 U（Ⅵ）被还原为 U（Ⅳ），而干粉吸附的铀主要以 U（Ⅵ）形式存在。由此推断，少根紫萍干粉对 U（Ⅵ）的吸附主要通过静电吸引，离子交换，络合配位等方式实现；活体对 U（Ⅵ）吸附的同时还存在还原和矿化的过程，在 U（Ⅵ）胁迫下活体根系表面会分解释放出无机磷酸根，与吸附的 U（Ⅵ）及部分被还原的 U（Ⅳ）结合矿化为难溶的氢铀云母。採用室內水培和靜態吸附實驗，研究瞭水生植物少根紫萍（Landoltia punctata ）活體和榦粉對水體中 U（Ⅵ）的吸附能力，併對作用過程和機理進行瞭初步分析。結果錶明：常溫下少根紫萍2．5 g·L－1（FW）活體和1．25 g·L－1（DW）榦粉在 pH 5下對5 mg·L－1 U（Ⅵ）溶液的去除率分彆可達78．70％和95．55％。活體和榦粉對 U（Ⅵ）的吸附率隨 pH 升高先增大後減小，在 pH 4～5時達到最大，併隨投加量的增加而增大；隨 U（Ⅵ）初始濃度增加先增大後減小；在作用5 min 時，活體和榦粉對水體中 U（Ⅵ）的吸附率分彆為13．90％和79．97％，在24 h 時吸附率均達90％以上，吸附逐漸趨于平衡。噹 U（Ⅵ）初始濃度增加至250 mg·L－1，活體和榦粉對 U（Ⅵ）的吸附量分彆達到4．05 mg·g－1（FW）和131．76 mg ·g－1（DW），相比Langmuir 模型，Freundlich 吸附等溫方程能較好地描述少根紫萍對 U（Ⅵ）的吸附行為，吸附過程符閤準二級吸附動力學方程，r 均在0．99以上。FTIR 分析結果錶明：少根紫萍錶麵含有羥基、羧基、氨基、燐痠基等多種活性基糰；SEM-EDS 錶明少根紫萍活體與水體中 U（Ⅵ）作用48 h 後，大量片狀無機燐痠鈾晶體在其根繫錶麵生成，結晶主要由 P，O，U 元素組成，不含 C，其中 P 和 U 的質量百分比分彆為8．76％和82．53％，原子百分比分彆為25．19％和30．89％，而對照組 P 的質量百分比和原子百分比僅為0．24％和0．11％，榦粉未觀察到類似晶體存在。XPS 分析結果錶明：活體吸附後，部分 U（Ⅵ）被還原為 U（Ⅳ），而榦粉吸附的鈾主要以 U（Ⅵ）形式存在。由此推斷，少根紫萍榦粉對 U（Ⅵ）的吸附主要通過靜電吸引，離子交換，絡閤配位等方式實現；活體對 U（Ⅵ）吸附的同時還存在還原和礦化的過程，在 U（Ⅵ）脅迫下活體根繫錶麵會分解釋放齣無機燐痠根，與吸附的 U（Ⅵ）及部分被還原的 U（Ⅳ）結閤礦化為難溶的氫鈾雲母。
채용실내수배화정태흡부실험，연구료수생식물소근자평（Landoltia punctata ）활체화간분대수체중 U（Ⅵ）적흡부능력，병대작용과정화궤리진행료초보분석。결과표명：상온하소근자평2．5 g·L－1（FW）활체화1．25 g·L－1（DW）간분재 pH 5하대5 mg·L－1 U（Ⅵ）용액적거제솔분별가체78．70％화95．55％。활체화간분대 U（Ⅵ）적흡부솔수 pH 승고선증대후감소，재 pH 4～5시체도최대，병수투가량적증가이증대；수 U（Ⅵ）초시농도증가선증대후감소；재작용5 min 시，활체화간분대수체중 U（Ⅵ）적흡부솔분별위13．90％화79．97％，재24 h 시흡부솔균체90％이상，흡부축점추우평형。당 U（Ⅵ）초시농도증가지250 mg·L－1，활체화간분대 U（Ⅵ）적흡부량분별체도4．05 mg·g－1（FW）화131．76 mg ·g－1（DW），상비Langmuir 모형，Freundlich 흡부등온방정능교호지묘술소근자평대 U（Ⅵ）적흡부행위，흡부과정부합준이급흡부동역학방정，r 균재0．99이상。FTIR 분석결과표명：소근자평표면함유간기、최기、안기、린산기등다충활성기단；SEM-EDS 표명소근자평활체여수체중 U（Ⅵ）작용48 h 후，대량편상무궤린산유정체재기근계표면생성，결정주요유 P，O，U 원소조성，불함 C，기중 P 화 U 적질량백분비분별위8．76％화82．53％，원자백분비분별위25．19％화30．89％，이대조조 P 적질량백분비화원자백분비부위0．24％화0．11％，간분미관찰도유사정체존재。XPS 분석결과표명：활체흡부후，부분 U（Ⅵ）피환원위 U（Ⅳ），이간분흡부적유주요이 U（Ⅵ）형식존재。유차추단，소근자평간분대 U（Ⅵ）적흡부주요통과정전흡인，리자교환，락합배위등방식실현；활체대 U（Ⅵ）흡부적동시환존재환원화광화적과정，재 U（Ⅵ）협박하활체근계표면회분해석방출무궤린산근，여흡부적 U（Ⅵ）급부분피환원적 U（Ⅳ）결합광화위난용적경유운모。
The biosorption and biomineralization characteristics of uranium by the duckweed Landoltia punctata was investigated in aqueous solutions enriched with 1 to 250 mg·L-1 of U(Ⅵ)supplied as uranyl nitrate [UO2 (NO3 )2 ·6H2 O].The maximum uranium removal for the plant cultivar occurred at pH 4~5 of solution and their uranium removal efficiencies exceeded 90% after 24 h.In kinetics studies,the dried powder of duckweed can finished nearly 80% adsorption within 5 min,the batch adsorption equilibrium can be reached within 24 h for the living and dried powder of duckweed,Both for the living and dried powder of duckweed,the experimental data were well fitted by the pseudo-second-order rate model with the degree of fitting (r)higher than 0.99.The adsorption isotherms could be better described by the Freundlich model than the Langmuir model.In addition, Fourier transform infrared spectroscopy (FTIR)revealed that the surface of Landoltia punctata possess many active groups such as hydroxyl,carboxyl,phosphate and amide groups,the hydroxyl,amino groups involved in adsorption of U(Ⅵ)by living and dried powder of Landoltia punctata ,and the phosphate groups also participated in the adsorption behavior of U(Ⅵ)by the liv-ing Landoltia punctata .The living Landoltia punctata reduction part of U(Ⅵ)to U(Ⅳ)was observed by XPS analysis.SEM and energy dispersive X-ray spectroscopy (EDS)of duckweed from 10 ~200 mg·L-1 uranium treatments indeed showed root surface of living Landoltia punctata formed a significant portion of U precipitates with nanometer sized schistose structures that consisted primarily U and P,not containing C.Inorganic phosphate was released by the root cells of Landoltia punctata during the experiments providing ligands for formation of insoluble U(Ⅵ)and U(Ⅳ)phosphates.The distinct uranium peaks in the EDS spectra of the cluster on the root surface can be observed after biosorption and the uranium and phosphorus mass ratio of the cluster spot was measured to be 82.5% and 8.76% of the total component weight,respectively,and the atomic percentage of 30.89% and 25.19%,respectively.It is worth noting that the phosphorus mass ratio and the atomic rate of the control group is only 0.24% and 0.11%,respectively.But there was no similar crystals observed on the surface of dried powder of Landoltia punctata after biosorption.The present work suggests that living and dried powder of Landoltia punctata can remove more than 90% U(Ⅵ)from solution simultaneously precipitated together with phosphate by the living Landoltia punctata ,and the dried powder of Landoltia punctata adsorption U(Ⅵ)is mainly through the effect of electrostatic attraction,ion exchange and compl-exation coordination,etc.Here,for the first time,the presence of U immobilization mechanisms within one aquatic plant is re-ported using Landoltia punctata .