Study On Combined Treatment Method And Effcet Of Simulated Radioactive Wastewater

With the development of China's economy,nuclear energy has become an inevitable choice.Meanwhile,radionuclides are increasingly used in scientific research in military,industrial,agricultural,energy,and medical sciences,which will inevitably produce radioactive liquid waste.Therefore,the demand for efficient and economical radioactive waste liquid treatment technologies is ever more urgent.Since the reverse osmosis membrane has a very small pore size,it can remove most of the substances in the water.Reverse osmosis has a high retention efficiency for most ions having a small particle size in the aqueous solution and the decontamination factor is good.Although reverse osmosis has a good application prospect in the treatment of radioactive wastewater,it requires high quality of raw water,so it needs to be pretreated with raw water.Therefore,it is combined with other methods.This paper adopts flocculation-microfiltration-reverse osmosis combination process to treat the simulated radioactive wastewater,and focus on the conductivity of the effluent at all levels and the removal efficiency of the nuclides.In the light of the ¹⁰⁹Cd,¹⁴⁴Ce,¹⁴¹Ce,¹⁰⁷Pb,⁵¹Cr,⁶³Ni,⁶⁰Co and ⁵⁶Mn radionuclides,the nuclides have the same chemical properties and different physical properties.This paper uses non-radioactive Cd²⁺,Ce⁴⁺,Pb²⁺,Cr⁶⁺,Ni²⁺,Co²⁺and Mn²⁺to replace radionuclides for experimental studies.Cd²⁺and Ce⁴⁺are analysed by UV-visible spectrophotometry.Pb²⁺,Cr⁶⁺,Ni²⁺,Co²⁺and Mn²⁺are determined by flame atomic absorption spectrometry?FAAS?.In the process of ion competitive flocculation and combined treatment,Inductively Coupled Plasma Mass Spectrometry?ICP-MS?is used.The Cd²⁺is tested by UV-visible spectrophotometry.And the effects of buffer solution dosage,emulsifier dosage,color developer dosage,pH value and standing time on the Cd²⁺test results are discussed.Under the optimal conditions,the chelate is stable and has a high linear correlation coefficient.When Ce⁴⁺is tested,the color development system is stable under the combined action of 4.5 mol/L H₂SO₄ solution and 0.1%methyl green solution.And the linear correlation coefficient?R²?is above 0.99.The results of the FAAS and ICP-MS methods are accurate and reliable,and the linear correlation coefficient and sensitivity are high.On the basis of establishing a more accurate test method,polyacrylamide is used for organic flocculation experiments.The results show that the flocculation effect of other ions can be maintained above 80%except for Cr⁶⁺,and the optimal flocculation experimental conditions are determined.When discussing the competitive flocculation relationship of ions by orthogonal test,the order of selective flocculation of PAM on ions is Pb²⁺>Ce⁴⁺>Mn²⁺>Ni²⁺>Co²⁺>Cd²⁺>Cr⁶⁺,and the experimental factors are not obvious influences on Pb²⁺,Ce⁴⁺and Cr⁶⁺.The flocculation-microfiltration-reverse osmosis combined treatment experiment under the optimal flocculation conditions showed that the conductivity of the effluent gradually decreased with the deepening of the treatment depth,and finally maintained at about 1.00?S/cm;The removal rate is as high as 99.58%for Cr⁶⁺,and other ions are above 99.99%.The influence of ion coexistence leads to a certain degree of pollution of the microfiltration membrane and the reverse osmosis membrane,and the interception performance has a decreasing trend.As the ion concentration increases,the trend is more obvious,but overall,the combined treatment capacity does not decrease significantly.The overall removal rate is above 98.15%.The experimental error and membrane performance degradation are reduced by adjusting the pH of the filtrate to neutral,deionized water membrane cleaning,secondary filtration,low pressure operation and the like.The flocculant can purify the water by itself and interact with the suspended particulate matter in the solution.The purpose of removing the suspended particulate matter in the solution and purifying the water body is obtained by physical and chemical actions.The filtration mechanism of microfiltration includes screening,deep filtration and cake layer filtration.When wastewater passes through the microfiltration membrane,because of the mechanical interception,internal interception and bridging of particles,particles with a larger radius than the microfiltration membrane cannot be intercepted through the membrane to form filter cake.And the formation of filter cake will lead to more adequate filtration.Under the actuation of static pressure difference,particles with a radius less than the filter aperture pass through the filter membrane,while particles with a radius larger than the filter aperture are intercepted on the membrane surface.Thus,components of different sizes can be separated,purified and concentrated.Depending upon the dissolution-diffusion theory,the reverse osmosis process is that the feed solution first dissolves or selectively adsorbs on the membrane surface of the feed solution.When pressure greater than osmotic pressure is applied on one side of the concentrated solution,the solvent on the other side of the concentrated solution will pass through the reverse osmosis membrane and resolve into the dilute solution on the other side.