第45卷第3期原子能科學(xué)技·術(shù)Vol 45, No. 32011年3月Atomic Energy Science and TechnologyMar.2011氨基羥基脲與Pu(Ⅳ)的還原動(dòng)力學(xué)研究肖松濤,葉國安,劉協(xié)春,羅方祥,蘭天,李峰峰中國原子能科學(xué)研究院放射化學(xué)研究所,北京102413)摘要:研究了氨基羥基脲(HSC)與Pu(Ⅳ)的還原反應(yīng)動(dòng)力學(xué),其動(dòng)力學(xué)方程式為:-d(Pu(Ⅳ))/dr=kc(Pu(Ⅳ)(HSC)c(H+)c05(NO3),在22.1℃時(shí)反應(yīng)速率常數(shù)k=(1.8±1.1)(molL)046:s-1,活化能為(71.0±1.0)kJ/mol研究了氨基羥基脲濃度、H+濃度、硝酸根濃度、Fe3+濃度、UO濃度對(duì)氨基羥基脲與Pu(Ⅳ)還原反應(yīng)速率的影響,增加氨基羥基脲濃度,降低H+濃度、硝酸根濃度,Pu(Ⅳ)還原速度增加;UO濃度和Fe3濃度對(duì)Pu(Ⅳ)還原速度基本無影響關(guān)鍵詞:Pu(Ⅳ);氨基羥基脲;還原反應(yīng);反應(yīng)速率中圖分類號(hào):TQ031.6文獻(xiàn)標(biāo)志碼:A文章編號(hào):1000-6931(2011)03-0277-05Kinetics of Reaction Between Pu(l) and Hydroxysemicarbazidein Nitric Acid SolutionXIAO Song-tao, YE Guoan, LIU Xie-chun, LUO Fang-xiangLI Feng-fengChina Institute of Atomic Energy, P. O. Box 275-26, Beijing 102413, China)Abstract: The kinetics of reaction between Pu(Nv)and hydroxysemicarbazide(HSC)innitric acid solution was studied. the rate equation is found to be: -dc(Pu(iv)) dt=ke(Pu(Ⅳ))c°(HSC)c4(H+)c-05(NO3), where k=(11.8±1.1)(mol/L)-s at 22. 1 C and the activation energy E,=(71.0+1. 0)kJ/mol. Effects of c(HSC)c(H+), c(Fe+), c(UO2+), ionic strength and temperature on reduction rate of Pu(Nv)were investigated. The results show that Pu(l)can be rapidly reduced to Pu(l )byHSC under normal conditions. The reaction rate can be accelerated by increasing con-entration of hydroxysemicarbazide or temperature, and decreasing concentration ofHNO, or ionic strength. The influence of UO2+ and Fe+ on reaction rate is negligible.Key words: Pu(N); hydroxysemicarbazide: reduction reaction; reaction ratePurex流程是核燃料后處理水法的主要流程,其利用TBP對(duì)不同價(jià)態(tài)的Pu的萃取行為收稿日期:201001-26;修回日期:20100309基金項(xiàng)目:中國核工業(yè)集團(tuán)公司武器裝備預(yù)先研究基金項(xiàng)目(616010904作者簡介:肖松濤(1975一),男,北京人,工程師核燃料后處理專業(yè)yhA中國煤化工CNMHG278原子能科學(xué)技術(shù)第45卷差異,以達(dá)到U、Pu分離和純化的目的們。通液中Pu(Ⅳ)的吸光度,以吸光度時(shí)間曲線確常Pu(Ⅳ)到Pu(Ⅲ)的價(jià)態(tài)轉(zhuǎn)換采用試劑還原定反應(yīng)進(jìn)程。和電解還原,其中新型有機(jī)試劑被認(rèn)為是高效1.3動(dòng)力學(xué)數(shù)據(jù)處理方法的、應(yīng)用前景廣闊的試劑,因此,新型無鹽有機(jī)首先設(shè)立氧化還原反應(yīng)動(dòng)力學(xué)的方程,然還原劑一直是改進(jìn) Purex流程的一重點(diǎn)研究方后依次改變其中一個(gè)條件,其余條件不變,求表向(2。近些年研究的主要無鹽有機(jī)還原劑有單觀速率常數(shù)k’,具體方法參見文獻(xiàn)[7羥基脲、乙醛肟、NN乙基羥乙基羥胺等,它們還原Pu(Ⅳ)到Pu(Ⅲ)遠(yuǎn)快于羥胺,快速還原2結(jié)果與討論Np(Ⅵ)到Np(V)而不生成可被萃取的Np(Ⅳ),2.1反應(yīng)對(duì)Pu(N)級(jí)數(shù)的確定使U/Pu分離時(shí)Np隨Pu液流走,減輕U線在22.1℃,c(H+)=1.0mol/L,c(NO萬)負(fù)擔(dān),提高Np的凈化系數(shù)。但他們各自存在2.5mo/L,p(Pu(Ⅳ)=1.0g/L,氨基羥基脲些獨(dú)特特點(diǎn):有些脲還原產(chǎn)物較復(fù)雜,且會(huì)濃度分別為0.022、0.040、0.050、0.061、產(chǎn)生大量不利于 Purex流程的NH';有些會(huì)0.071、0.085mol/L條件下,進(jìn)行了氨基羥基導(dǎo)致有機(jī)相和水相產(chǎn)生界面污物;有些胺分脲與Pu(Ⅳ)的反應(yīng),記錄反應(yīng)體系在不同時(shí)間解太快12.因此,開展新型還原劑的研究,下的吸光度數(shù)據(jù)A.以ln[(A,-A)/(A0以期能尋找到綜合性能更優(yōu)越的新型無鹽有A)]對(duì)t作圖。可看出,ln[(A,-A。)/(A機(jī)還原劑是一項(xiàng)非常有意義的工作A)]與t之間呈良好的線性關(guān)系,這表明反應(yīng)氨基羥基脲是一種的弱堿性的有機(jī)還原對(duì)Pu(Ⅳ)是一級(jí)反應(yīng)(圖1)。劑,它不僅可快速還原Pu(Ⅳ)到Pu(Ⅲ),而且可快速還原Np(Ⅵ)到Np(V),并基本上不生c(HSC), mol/L成Np(Ⅳ);它是弱堿性試劑(pH=8.0),只需很少量的硝酸中和,因此可降低鹽析效應(yīng)對(duì)Pu(Ⅲ)萃取分配的影響;它符合C、H、N、O無鹽原則,減少最終固體廢物量,降低核燃料后處R2099理對(duì)環(huán)境的影響R2=0.991實(shí)驗(yàn)1.1試劑與儀器氨基羥基脲,純度大于99%,實(shí)驗(yàn)室合成;圖1反應(yīng)對(duì)Pu(Ⅳ)為一級(jí)反應(yīng)的驗(yàn)證Pu(Ⅳ)溶液系Fe(Ⅱ)還原、HNO2氧化、2606Fig 1 First order plot for reaction陰離子交換樹脂純化所得,以K邊界法及aof Pu( N) with HSC計(jì)數(shù)法測定其濃度,其H+濃度用pH滴定法測定;硝酸和硝酸鈉,分析純,北京化學(xué)試劑2.2反應(yīng)對(duì)氨基羥基脲級(jí)數(shù)的確定公司。在22.1℃,c(H)=1.0mol/L,c(NO3)=S600型紫外可見分光光度計(jì),德國耶拿2.5molL,p(Pu(Ⅳ))=1.0g/L,氨基羥基公司DC1020型低溫恒溫水浴槽寧波新芝生脲濃度分別為0.040、0.050、0.061、0.071物科技公司;PHs3C型酸度計(jì),上海雷磁儀0.085mol/L條件下,進(jìn)行了氨基羥基脲與器廠。Pu(Ⅳ)的反應(yīng)。以ln[(A,-A.)/(A12實(shí)驗(yàn)方法A)]對(duì)t作圖,所得直線的斜率為表觀速率取(Pu)=2.0g/L、c(HN()=1.0moLk,不同氨基羥基脲濃度下的表觀速率常數(shù)k的溶液1mL及其它調(diào)節(jié)各種物質(zhì)濃度的溶液列中國煤化工圖,可求得斜1mL置于1cm比色皿中,快速加入0.1mL.率nCNMHG級(jí)數(shù)為1.06氨基羥基脲的硝酸溶液,于476m處測定溶(圖第3期肖松濤等:氨基羥基脲與Pu(Ⅳ)的還原動(dòng)力學(xué)研究表1不同氨基羥基服濃度下的表觀速率常數(shù)2.4反應(yīng)對(duì)NO級(jí)數(shù)的確定Table 1 Influence of HSC concentration在22.1℃時(shí),c(HSC)=0.051mol/L、on apparent rate constantP(Pu(Ⅳ)=1.0g/L、c(H+)=1.0mol/L,c(HSC)/(mol·L-1)NO3濃度分別為1.0、1.5、2.0、2.5、3.0mol/L0.0400.249條件下,求出不同NO3濃度下反應(yīng)的k,以nc(NO萬)對(duì)lnk’作圖得圖4。圖4即為反應(yīng)對(duì)NO3級(jí)數(shù)的驗(yàn)證。結(jié)果表明:在NO3離子濃度較高情況下,部分Pu(Ⅳ)離子與NO3形0.543成絡(luò)合物,減少了參與氧化還原反應(yīng)Pu(Ⅳ)的量,從而降低了反應(yīng)速率。lnc(NO3)與lnk呈線性關(guān)系,直線的斜率是-0.58,即反應(yīng)對(duì)0NO3的反應(yīng)級(jí)數(shù)為-0.58。y=1.059x1.951R=0970.58r-0.74n(c(HSC)(mol-L-))圖2反應(yīng)與氨基羥基脲級(jí)數(shù)的關(guān)系Fig 2 Relationship between In k' and In c(HSC)In(c(NO, (molL)2.3反應(yīng)對(duì)H濃度的確定圖4反應(yīng)與NO7級(jí)數(shù)的關(guān)系在22.1℃,c(HSC)=0.051mol/LFig 4 Relationship between In k" and In c(NO,)p(Pu(Ⅳ)=1.0g/L、c(NO5)=2.5mol/L,H+濃度分別為0.65、1.0、1.5、2.0、2.5mol/L綜上所述,可得到氨基羥基脲還原Pu(Ⅳ)條件下,求出不同H濃度下反應(yīng)的k,以的動(dòng)力學(xué)速率方程為:nc(H+)對(duì)lnk'作圖。圖3即為反應(yīng)對(duì)H+級(jí)dc(Pu(Ⅳ))/dt=kc(Pu(Ⅳ))數(shù)的驗(yàn)證。結(jié)果表明,隨酸度增加,氨基羥基脲c.06(HSC)c0.43(H*)c-0S(NO:在22.1℃時(shí),k=(11.7±1.1)(mol/與Pu(Ⅳ)反應(yīng)速度減慢。Inc(H+)與lnk'呈L)6·s-1。線性關(guān)系,直線的斜率是一0.43,即反應(yīng)對(duì)H+表2列出本實(shí)驗(yàn)條件下部分氨基羥基脲與的反應(yīng)級(jí)數(shù)為-0.43Pu(Ⅳ)氧化還原反應(yīng)的k和k值2.5Fe濃度對(duì)Pu(N)還原速率的影響043x1.19后處理過程中,由于設(shè)備的腐蝕,料液中有Fe3存在。實(shí)驗(yàn)測得的不同F(xiàn)e3濃度下氨基羥基脲還原Pu(Ⅳ)的表觀速率常數(shù)列于表3可見,Fe3+的存在對(duì)氨基羥基脲還原Pu(Ⅳ)→Pu(Ⅲ)的反應(yīng)無明顯影響。26UO+濃度對(duì)Pu(Ⅳ)還原速率的影響1.0-050.00.51.0伴隨在一起的中國煤化工的影響涉圖3反應(yīng)與H級(jí)數(shù)的關(guān)系及CNMHGUOE濃度Fig 3 Relationship between In k and In c(H+)下,氨基羥基脲還原Pu(Ⅳ)的反應(yīng)速率,所對(duì)280原子能科學(xué)技術(shù)第45卷表2實(shí)驗(yàn)條件下部分氨基羥基脲與Pu(N)氧化還原反應(yīng)的k和kTable 2 k and k of reaction between HSC and Pu( N)in HNO, solutionsc(H+)/(mol·L-1)c(HsC)/(mol·L-1)c(NO)/(mol·L-1)k/((mol·L-1)-06·s-1)0.04010.05070.06120.07140.08490.610.0507-0.970.0507-1.2511.42.500.05070.05072.511.90,050710.80.050711.70.05071.2511.40.05071.4310.6注;反應(yīng)溫度為22.1℃應(yīng)的表觀速率常數(shù)相近(表4)?？梢?UO2+的Pu(Ⅳ)的反應(yīng)速率的影響。隨著溫度升高存在對(duì)氨基羥基脲還原Pu(Ⅳ)的反應(yīng)速率基Pu(Ⅳ)的還原速度明顯加快,溫度每升高本上無影響。10℃,氨基羥基脲還原Pu(Ⅳ)的反應(yīng)速率增加約10倍。根據(jù) Arrhenius定理,以lnk’對(duì)表3不同F(xiàn)e濃度下k1/T作圖,求得反應(yīng)過程的活化能E=(71.0士Table 3 Influence of Fe+ concentration on k1. 0)kJ/molFe14)/(mol·L1)k'/s-1k/((mol·L-1)-.04·s-1)y=5l10x+17270.00112.20.00511.2Table 4 Effect of UO+ concentration on k1037-Kp(UⅥ)/(g·L1)k/s-1k/(mol·L-1)-0ms·s-1)圖5反應(yīng)與溫度的關(guān)系Fig 5 Relat3結(jié)論27溫度對(duì)Pu(Ⅳ)還原速率的影響對(duì)同樣的反應(yīng)物濃度和介質(zhì)條件,改變反中國煤化工的動(dòng)力學(xué)基應(yīng)體系的溫度,研究溫度對(duì)氨基羥基脲還原礎(chǔ)研CNMHG羥經(jīng)基脲還原Pu(Ⅳ)的動(dòng)力學(xué)速率方程為一d(Pu(Ⅳ)/dt=第3期肖松濤等:氨基羥基脲與Pu(Ⅳ)的還原動(dòng)力學(xué)研究c(Pu(Ⅳ)c6(HSC)c04(H+)c0(NO),在Japan,2002:355-35821℃時(shí)k=(17+1.14)(ml/1·s-1,反[7]章英杰,范顯華,曾繼述,等.H1O2對(duì)Pu(N)自應(yīng)過程的活化能E=(71,0±1.0)kJ/mol;酸還原動(dòng)力學(xué)研究[].核化學(xué)與放射化學(xué),2006度、NO3濃度升高,其反應(yīng)速率降低;升高溫28(2):72-79.度,其反應(yīng)速率加快;Fe3+、UO濃度對(duì)反應(yīng)ZHANG Yingjie, FAN Xianhua, ZENG Jishuet al. 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