1 Introduction

Hydrazine and its derivatives,which are highly toxic and strong reducing agents,are miscible with water and soluble in most organic solvents.Hydrazine,methylhydrazine,1,1-dimethylhydrazine,phenylhydrazine,2-hydroxyethylhydrazine,and tert-butylhydrazine are the most common hydrazine derivatives.They are important chemical raw materials and widely used in polymers,metallic materials,metallurgy,printing and dyes,textiles,medicine,disease treatment,etc.[1–3].In particular,they are used as propellants for altitude control engines in missiles,satellites,and the aerospace industry because they readily combust to produce hydrogen and nitrogen[4–6].Owing to their strong reduction properties,they have been extensively studied in the Purex process as a support reducing stabilizer for the recovery of Pu(IV)using Fe(II),U(IV),hydroxylamine,and urea.They have also been considered as organic salt-free reductants for Pu(IV)and Np(VI)during the post-treatment of nuclear fuel[7].Accordingly,signi ficant research effort has been targeted at their application as support reducing agents or reducing agents for spent nuclear fuel reprocessing in recent years[8].

A signi ficant amount of hydrazine derivatives are released to the environment as pollutants[9–12].They are strong stimulants and may induce acute poisoning via injection,inhalation,skin poisoning,and gastrointestinal absorption orcausetumorgrowth.Thus,hydrazine derivatives are considered to be very harmful for living organisms and the environment.Once they are released to the environment,they can physically adsorb and interact chemically with the soil,resulting in a polluted environment that is dif ficult to reclaim.Some of the degradation products of hydrazine derivatives are more toxic that the derivatives themselves.Therefore,efficient wastewater disposal and decomposition treatment of ef fluent containing hydrazine derivatives are important.

The stoichiometry,kinetics,and mechanisms of the decomposition of hydrazine and its derivatives have yet to be fully elucidated[13].Currently,the following types of treatment methods for hydrazine compounds are used globally:(1)Physical methods,such as incineration,ion exchange,adsorption,are simple to use but readily produce secondary pollution;also,the regeneration period and lifetime of the ion resin are limited.(2)Biodegradation,which includes activated sludge(microbial)and aquatic plant treatment,is an environmentally friendly method;however,it cannot be applied to non-industrial ef fluent because the pollutants could bioaccumulate in organisms and avoid fundamental degradation[14].(3)Chemical oxidation methods,such as catalytic oxidation,electrolyzed oxidizing water(EOW)oxidation,and photocatalytic oxidation[15],quickly oxidize and remove the organic matter by destroying the organic molecular structure.These methods are suitable for industrial processes;however,they are restricted to wastewater with low pollutant concentrations.(4)Other new processing technologies,such as low temperature plasma technology[16,17],catalyzed supercritical water oxidation[18,19],Fenton oxidation,and membrane bioreactor treatment[20],have also been applied.Fenton’s method has been widely studied because of the high activity of hydroxyl radicals toward the oxidation and decomposition of a variety of organic substances that are typically dif ficult to oxidize.

Radiation technology has been used in the environmental field[21],which is an important aspect of the peaceful use of atomic energy in the twenty- first century,as proposed by the International Atomic Energy Agency.Radiation technology is a non-polluting,inexpensive,simple,and efficient degradation method.The application of beta radiation technology to remove hydrazine pollutants should generate the target outcome with a lower energy consumption and at a faster rate.Hydrazine and its derivatives have been actively researched as support reducing stabilizers and novel salt-free reductants;therefore,their stability under radiation exposure during the post-treatment process is important for the optimal selection of reducing agents for spent fuel reprocessing.

2.4.2 旷场实验 连续注射CORT 21 d后，小鼠禁食不禁水24 h，将动物放入箱内底面中心，试验箱规格为50 cm×50 cm×40 cm。适应30 s后，观察并记录动物在3 min内双后肢跨越方格的个数（水平运动）与前肢腾空或攀爬墙壁的次数（垂直运动）。试验在无明显光源的环境中进行，观察完毕擦拭箱内壁及底面，以免上次动物余留的信息影响下次测试结果。

All chemicals were of analytical grade and used without further puri fication.Hydrazine hydrate(85%)was purchased from Shanghai Hushi Laboratorial Equipment Co.Ltd.(China).tert-butylhydrazine(98%)and 2-hydroxyethylhydrazine(95%)were purchased from Shanghai Macklin Biochemical Co.Ltd.(China).Methylhydrazine,dimethylhydrazine, and p-dimethylaminobenzaldehyde were purchased from Sinopharm Chemical Reagent Co.Ltd.(China).Ethanol,nitric acid,and methane sulfonic acid(MSA)were purchased from Beijing Chemical Works(China).A beta particle accelerator(2 MeV),ion chromatograph(CIC-100),ultraviolet spectrophotometer(Perkin Elmer Lambda 45),and automatic potentiometric titrator(Mettler Toledo G20 compact titrator)were used during the experiment.The beta particle accelerator was rented from the Department of Nuclear Technology Applications in China Institute of Atomic Energy,and the required safety protection was provided.The ion chromatograph was purchased from Qingdao Sheng Han Chromatography Technology Co.Ltd.(China);a CS12A column was used as the cation column,and the baseline noise was stabilized at around 20 mV before detection.

Using methane sulfonic acid as the eluent,the concentrations of the hydrazine,tert-butylhydrazine,1,1-dimethylhydrazine,and 2-hydroxyethylhydrazine solutions were separately determined using ion chromatography.The concentration of methylhydrazine was determined using an ultraviolet visible spectrophotometer with the color rendering of p-dimethylaminobenzaldehyde.The concentrations of the irradiated solutions were determined after the following irradiation durations:0,0.5,1,2,3,4,5,6,7,9,11,13,15,18,and 21 min.Then,the kinetic data for the decomposition of the hydrazine derivatives under beta radiation were obtained.The half-reaction timesof hydrazine and itsderivativesunderβ-radiation are expressed by τ50,which is the time required for the compound to decompose to 50%of the original concentration:A smaller τ50value indicates a faster decomposition rate.The molecular formulas of various hydrazine derivatives and their τ50values are listed in Table 1.

2 Source and structure of the target compound

2.1 Chemicals and equipment

福布斯中文版杂志主编周鹏：商业和关系的问题在中国可以说是经典话题，《青瓷》惟妙惟肖地再现了当代中国商人对关系的顶礼膜拜和娴熟利用，或许中国商人应该从书中得到警示并反思其中利弊，而西方商人则值得去理解其中的联系。

阮小棉把报纸折成飞机，坐在楼顶掷出去。她不相信这样的爱情，那都是作家和剧作家们编出来骗人的东西。楼顶的风很大，把她的裙子鼓起来，袖子也鼓起来，她用手拢一下袖口，扎住，就变成了很复古的宫廷灯笼袖。她小时候就有一件那样的小纱裙，粉红色，大大的裙摆，灯笼袖。每个女孩子都有童年，童年里谁都可以成为公主。

2.2 Experimental method

There are a few published research papers on the stability of hydrazine and its derivatives under radiation.For example,a group at the National Institute of Atomic Energy researched their stability under γ radiation.However,γ rays are dif ficult to use because of their high energy and radiation dose,which makes them unsuitable for largescale industrial applications.There is no suitable kinetic data regarding the β radiation stability of hydrazine and its derivatives.Therefore,in this paper,source data were obtained using experimental and computational methods.The initial solutions of hydrazine and its derivatives were diluted to 0.05 mol/L;then,250 mL aliquots of the solutions were prepared and irradiated using a pulsed electron beam from a beta particle accelerator.The accelerator used a 30 mA current,50 Hz frequency,4 μs pulse width,and 0.25 KGy/s dose.Then,0.1 mL samples of the irradiated solutions were extracted using a syringe after the following irradiation durations:0,0.5,1,2,3,4,5,6,7,9,11,13,15,18,and 21 min.

2.3 Analytic procedures

The quantitative structure–activity relationships(QSAR)method[22–24]is widely used during the development of new medicines and is a well-recognized research method.However,it is rarely used in other fields,especially that of radiochemistry.In this study, five hydrazine derivatives,i.e.,hydrazine hydrate,methylhydrazine,dimethylhydrazine,tert-butylhydrazine,and 2-hydroxyethylhydrazine,were irradiated using a pulsed electron beam.The data were then analyzed to establish the QSAR model.This investigation of the radiative stability of hydrazine and its derivatives under β radiolysis expands the fundamental knowledge on the radiochemistry of inorganic compounds and provides abundant theoretical evidence of the degradation of hydrazine.It also provides an important guideline for the degradation of hydrazine and its derivatives in spent nuclear fuel.

3 Calculation methods

It is evident from the data in Table 3 that the correlations between τ50and Etotaland M are signi ficant.G,R,V,ELUMO,HE,A,μ,P,ΔE,and logP also had strong correlations with τ50.However,there was no signi ficant correlation between EHOMOand τ50.

Table 1 Structures of the hydrazine derivatives and time required for 50%degradation using β irradiation

Derivatives τ50(s)Hydrazine,N2H48155.6 Methyl hydrazine,CH3N2H3 6689.2 1,1-Dimethylhydrazine,(CH3)2N2H2 791.6 tert-Butylhydrazine,(CH3)3CHN2H3 426.2 2-Hydroxyethylhydrazine,HOCH2CH2N2H3 204.5

4 Results and discussion

4.1 3D stable molecular structures of the hydrazine compounds

Optimized geometric construction and frequency analysis of the hydrazine derivatives were conducted by adopting the density functional theory B3LYP method of the Gaussian 03 program package with the 6-311+(3d,3p)basis set.No imaginary frequency occurred in the calculation results,indicating that they were reasonable and reliable.This also confirms that the most stable configuration was obtained.The optimized 3D structures are shown in Fig.1.

因此，对于推崇马汉海权论观点的美国来说，虽然自身不是南海问题当事国，但其一旦从地缘政治的视角看待南海争端，南海争端便上升为事关美国全球海权的关键一环，其必将最大限度地确保自己在南海地区的主导权和影响力。

4.2 Values of the quantum chemical parameters

The following parameter values were acquired from the quantum chemical calculations: ELUMO, EHOMO,ΔE(ΔE=ELUMO-EHOMO),μ,and Etotal.In addition,the following parameters were obtained using the molecular simulation software,HyperChem:logP,R,V,molecular super ficial area(A-approx,G-grid),M,P,and HE.The degradation rates of hydrazine and its derivatives under β irradiation are expressed by τ50.The quantum parameter values are shown in Table 2.

4.3 Structure–performance equation for the hydrazine derivatives under β irradiation

In Fig.2,a relationship between the Etotaland τ50of the hydrazine derivatives hydrolysis reaction under beta irradiation is slightly evident.In general,τ50is positively correlated with Etotal;however,the correlation cannot be de fined using a mathematical relationship.Accordingly,we used a multiple linear stepwise regression method to analyze the data.

Fig.1(Color online)Optimized 3D structures of the hydrazine derivatives.a hydrazine,b methylhydrazine,c 1,1-dimethylhydrazine,d tertbutylhydrazine,e 2-hydroxyethylhydrazine

Statistical software,SPSS,was applied to conduct a correlation analysis on the QSAR parameters to obtain the Pearson correlation coefficient matrix(Table 3).

The initial structures of the hydrazine compounds were generated using ChemOf fice software,and geometric preoptimization was conducted using built-in molecular mechanics MM2 modules in Chem3D Ultra.The minimum energy conformation of the hydrazine derivative was obtained after optimization.Geometric optimization and energy calculations were conducted on a variety of target compounds by applying the density functional theory B3LYP method of the Gaussian 03 program package with a 6-311+(3d,3p)basis set.The vibration frequencies calculated for all of the molecular structures did not have imaginary frequencies, which indicate that theconfiguration obtained from the calculation was the most stable.Using the HyperChem software package,calculations were conducted on the optimized molecules and the physicochemical parameters were obtained;these included the total energy(Etotal),highest occupied molecular orbital energy(EHOMO),lowest unoccupied molecular orbital energy(ELUMO),molecular orbital transition energy(ΔE),molecular dipole moment(μ),hydrophobic parameter(logP),molecular refractivity(R),molecular volume(V),molecular super ficial area(A),molecular molar mass(M),molecular polarizability(P),and hydration energy(HE).Mathematical statistical software,SPSS,was applied to perform a correlation analysis and stepwise regression analysis on the τ50and physicochemical parameters of the selected hydrazine derivatives.Finally,a QSAR equation with suf ficient correlation was obtained.The convergence precision of the quantum chemical calculations is a default value.

选取2017年1月～2018年1月在本院手术室进行手术的患者80例作为研究对象，按照随机分组的方式将其分为观察组与对照组，各40例。其中，对照组男22例，女18例，平均年龄（32.4±11.3）岁；观察组男23例，女17例，平均年龄（34.5±10.3）岁。给予对照组患者常规手术护理措施，而观察组患者则实施手术室风险护理管理方案。两组患者在一般资料方面比较，差异无统计学意义（P＞0.05）。

Before a QSAR regression equation was established,the quantum chemical parameters adopted were applied forpreprocessing.The Pearson correlation coefficient analysis parameters that were signi ficantly related to the β irradiation half-reaction time were obtained to facilitate elucidation of the relationship between the parameters of each structure and the degradation rate of the target compound.

The Pearson correlation analysis shows that there is a close relationship between the total energy of the molecules and τ50of the hydrazine compounds radiolysis reaction under beta irradiation;their relationship diagram was established,as depicted in Fig.2.

4.4 QSAR equation for the hydrazine derivatives under β irradiation

The QSAR equation for the hydrazine derivatives(i.e.,hydrazine,methylhydrazine,1,1-dimethylhydrazine,tertbutylhydrazine,and 2-hydroxyethylhydrazine)under β irradiation was established using a multiple linear stepwise regression method,and the results are shown in Tables 4,5,6 and 7.

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The stepwise regression analysis results suggest the following:(1)Signi ficant correlation exists between Etotal and τ50as well as Etotaland ΔE,as shown in Tables 4 and 5.The square root of the determination coefficient,determination coefficient,and adjusted determination coefficient were 0.995,0.989,and 0.979,respectively;these values indicate that the equations could account for 97.9%of the change in the τ50and that the correlations between independent and dependent variable are evident.(2)The square of the equation,residual sum of the squares,total sum of the squares,F-statistics value,and signi ficance were 5.858×107, 0.955, 6.264×105, 93.481, and 0.011＜0.05,respectively,indicating that a signi ficant linear relationship exists between the dependent and independent variables.(3)From Table 7,it is evident that the QSAR equation for the hydrazine derivatives and τ50of the hydrazine derivatives hydrolysis reaction under beta radiation was Y=-7583.464+54.687X1+94333.586X2,where X1and X2represent Etotaland ΔE,respectively.The signi ficance levels of the regression coefficients are 0.006 and 0.031;these values are less than 0.05.This model fully represents the relationship between the hydrazine derivatives and β radiolysis stability.

采用气相色谱法分析了两个实际天然气样品，常量组分采用GB/T 13610-2014，延伸组分采用GB/T 17281-2016。其中，对于各组分的定量，分别采用气体标准物质中n-C4架桥定量分析(方法一)和样品气中n-C5架桥定量分析(方法二)，表1为延伸组分采用两种定量分析方法获得的结果。

4.5 The relationship between the hydrazine derivative structure and half-reaction time for β irradiation

In the structural activity equation,the τ50for hydrazine compound radiolysis relates closely with Etotaland ΔE.A diagram of their relationship is shown in Fig.3.

The analysis results indicate the following:(1)The relationship between the structure ofthe hydrazine derivative and reaction time can be described quantitatively by the QSAR equation even for complex hydrazine derivative structures.(2)The decomposition rate under β irradiation and structure of the hydrazine derivatives are negatively correlated and can be described quantitatively by Etotaland ΔE.(3)The relationship between the decomposition rate under β irradiation and structure of the hydrazine derivatives can be described quantitatively by the QSAR equation,which simpli fies the complex problem and provides direction for the subsequent study of hydrazine and its derivatives.

5 Conclusion

Fig.2 Relationship between the molecular total energy and halfreaction time under β irradiation

Table 4 Variables entered/removed

Dependent variable:half-reaction time

Model Variables entered Variables removed Method 1 Molecule total energy – Stepwise 2 Orbital transition energy – Stepwise

In this work,the relationship between the structure of hydrazine derivatives and β radiolysis stability was studied resulting in a quantitative structure–activity relationship equation.The most stable configurations of the five hydrazine derivativeswere obtained by geometrical optimization and energy calculations.The relationships between the half lifetimes of radiolysis and structural parameters of the hydrazine derivatives were analyzed using the Pearson correlation coefficient,and there was signi ficantcorrelation between the total energy and molecular mass.There was also strong correlation with the molecular super ficial area,molecular refractivity,molecular volume,lowest unoccupied molecular orbital energy,orbital transition energy,etc.The 3D-QSAR structure equations between the structure and rate of radiolysis were also established using SPSS software.According to the model equation,the total energy of the molecule and orbital transition energy are the main factors that affect the stability of hydrazine derivatives under beta radiolysis,and the correlation is negative.In other words,the physicochemicalparametersthatdescribe thepropertiesof hydrazine derivatives were obtained using quantitative calculations and related chemistry software.It can be concluded that the hydrazine derivatives with higher total molecularand orbitaltransition energies are more stable under beta irradiation,as evidenced by the slower β radiolysis rate.

Table 5 Model summary

Dependent variable:half-reaction time aPredictors:(Constant):molecule total energy bPredictors:(Constant):molecule total energy,orbit transition energy

Model R R2 Adjusted R2 Standard error of the estimate 1 0.909a 0.827 0.769 1848.089752 2 0.995b 0.989 0.979 559.650556

Table 6 Analysis of variance (ANOVA)

Dependent variable:half-reaction time aPredictors:(Constant):molecule total energy bPredictors:(Constant):molecule total energy,orbital transition energy

Model Sum of squares df Mean square F Signi ficance 1 Regression 4.894×107 1 4.894×107 14.329 0.032a Residual 1.025×107 3 3.415×106 Total 5.918×107 4 2 Regression 5.856×107 2 2.928×107 93.481 0.011b Residual 6.264×105 2 3.132×105 Total 5.918×107 4

Table 7 Coefficients

Dependent variable:half-reaction time

Model Unstandardized coefficients Standardized coefficients t Signi ficance B SE Beta 1 (Constant) 13205.114 2755.880 4.792 0.017 Total energy 50.326 13.295 0.909 3.785 0.032 2 (Constant) -7583.464 3842.799 -1.973 0.187 Molecule total energy 54.687 4.102 0.988 13.331 0.006 Orbital transition energy 94333.586 17021.516 0.411 5.542 0.031

Fig.3 Relationships between the half-reaction time and molecular total energy and orbital transition energy of the hydrazine derivatives

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