Research On The Distribution Law Of Riot Control Agents In Gas-liquid

In the past few decades,the world is not peaceful,ethnic conflicts,social conflicts,religious conflicts,and class conflicts have deepened,civilization,conflicts have intensified,domestic and international anti-terrorism and anti-riot actions have increased significantly,and riot control agents have been used more frequentiy.The environmental behavioral and impact of riot control agents also received widespread attention.The study of the migration,diffusion and distribution of riot control agents in the gas-liquid system is conducive to predicting the distribution situation between the liquid phase and gas phase when the system is in an equilibrium state,and can be used to deduce the transmission rate of the system toward the equilibrium direction,and help people understand the transformation of trace riot control agents in the atmosphere.Such data is essential for modeling the environmental behavior of pollutants nakebuand formulating wastewater treatment strategies.This paper uses differential scanning calorimetry(DSC)single peak method to analyze the four types of riot control agents(CN、CS、CR and OC)purity:and combine with high performance liquid chromatography(HPLC),gas chromatography-mass spectrometry(GC-MS)method and nuclear magnetic resonance(1H NMR)method to compare the measurement results.The study have solved sample’s quality problem,eliminating the influence of the impurities,and then use numerical calculation methods to complete the calculation and comparison of Henry’s law constants of riot control agent in the gas-liquid system by simulated water and atmospheric environment in the laboratory.As shown in the restult:(1)By optimizing the experimental conditions of DSC.a purity analysis method for riot control agents were constructed and obtained the best experimental conditions for the purity determination of four types of riot control agents.The DSC purity analysis results of CN、CS、CR and OC were 99.89%、99.89%、99.35%and 98.88%,respectively.The measurement results of this method are close to those of HPLC and GC-MS methods,but are quite different from the results of 1H NMR method.The reasons for the deviation are discussed.Moreover,the DSC single-peak method is simple to operate,with only a little sample used,and has high precision.It does not need to introduce standard reference materials,and does not need to separate the sample form impurities,and it will avoid the introduction of the other impurity.It fills the technical gaps in related fields and provides quality assurance for the research of the subject.(2)Henry’s law constant(KH)is an important parameter for estimating the exchange of semivolatile organic compounds between air and water.The KH of the four types of riot control agents in different aqueous solutions was determined using air stripping technology.Henry’s constants under standard conditions are:272.68 kg·mol-1·atm-1(CN)、28.06kg·mol-1·atm-1(CS)、1120.62 kg-mol-1·atm-1(CR)、and 151.77 kg·mol-1·atm-1(OC).In addition,in the temperature range of 278.15～318.15K,the experimentally measured KH value of each substance in pure water can be obtained by the following equation:lnKH=(4529.45/T(K))-9.39(CN),lnKH=(6495.05/T(K))-18.38(CS),lnKH=(3894.51/T(K))-6.08(CR)and lnKH=(4974.01/T(K))-11.67(OC),KH value decreases with the increase of temperature.From this,the enthalpy and entropy of the gas-liquid transfer of each substance in the aqueous solution can be obtained.The results show that at the same temperature,with the larger the KH value,the enthalpy and entropy values will be less.(3)Control the temperature,solution volume,and gas flow rate unchanged.The range of KH measured in artificial brine with different salt content(<40‰)is 380.49～511.28 kg·mol-1·atm-1(CN)、23.37～32.73 kg·mol-1·atm-1(CS)、1460.89～1636.11 kg-mol-1·atm-1(CR)and 109.17-166.28·kg·mol-1·atm-1(OC),which are all higher than the value in pure water.Due to the salting-out effect,KH increases with the increase of salinity.In addition,the KH of four types of riot control agents besides CN measured in seawater and river water have no difference,the relation of CS、CR、OC’s the KH is KH(0‰)<KH(river)<KH(10‰)<KH(20‰)<KH(seawater)<KH(40‰),which is consistent with the change of the solution salinity.(4)The gas stripping experiment of CN in the sulfuric acid system shows:at the temperature of 298.15K,when the sulfuric acid.solutions concentration in aqueous are10%、20%and 40%,the KH are:296.34、322.78 and 940.03 kg·mol-1·atm-1,respectively.Compare with the value of KH in pure water,It was found that in the low-concentration(0%～20%)acid solution,CN is slightly dependence on acidity.The KH have more than doubled after the acid concentration increased to 40%.It shows that,with high acidity,the transmission rate of CN in the equilibrium direction of the atmosphere-water system will be changed.