Treatment Of Simulated Radioactive Wastewater Containing Co²⁺in Nuclear Power Plant By In-situ Synthesis Process Of MnO_x

With the rapid development of nuclear power technology and the conotinuous increase of nuclear power percentage,the radioactive waste continues to increase which causes serious damage to the environment and human health.Manganese oxide as a special adsorbent,shows great application value in heavy metal wastewater treatment.In this paper,the in-situ synthesis process of MnOx(Mn3O4 process and Birnessite process)was used to remove Co2+ which was the common nuclide in radioactive wastewater.Optimal reaction parameters,water quality influence and removing mechanism were studied.Experimental results were as follows:(1)The study showed that Mn3O4 process could remove Co2+ effectively in the simulated radioactive wastewater.When the wastewater contained 10mg/L Co2+ and 1000mg/L boric acid(as B),the effluent concentration of Co2+ was 5.68ng/L,the removal efficiency was more than 99.99%and DFCo reached 1.761×106 under the optimal condition;Moreover,when boric acid concentration was 0?3000 mg/L and the influent Co2+ concentration was 0.01?25mg/L,the process of Mn3O4 also could remove Co2+ effectively and the removal efficiency was higher than 99.00%.(2)The study of Co2+ removing mechanism by Mn3O4 process showed that:ORP varied obviously during the feeding stage and the trend of viriation conformed to the results of AOS analysis while Mn3O4 was forming continually.The stage of Mn3O4 formation started mainly after the alkali titration process,and then cobalt element replaced mangese element forming CoMn2O4.XRD?FTIR and precipitation-dissolution analysis showed that Co2+ was removed in three ways:hydroxide precipitation(0.03%),adsorption(16.59%)and entering the crystal(83.38%).(3)The study of Birnessite could move Co2+ effectively in the simulated radioactive wastewater.When the wastewater contained 10mg/l Co2+ and 1000mg/L boric acid(as B),the effluent concentration of Co2+ was 43.05ng/L,the removal efficiency was more than 99.99%and DFCo reached 5.465×105 under the optimal congdition;Moreover,when boric acid concentration was 0?3000mg/L and the influent Co2 +concentration was 0.01?25mg/L,the process of Birnessite also could remove Co2+ effectively and the removal efficiency was higher than 98.90%.(4)The study of Co2+ removing mechanism by Birnessite showed that:ORP varied obviously during the feeding stage of Birnessite and the trend of viriation conformed to the results of AOS analysis while Birnessite was forming continually.It could be obtained that Birnessite was almost generated within 30 mins and and XRD?FTIR and EDS showed that Co2+ was mainly removed by adsorption hereafter.Precipitation-dissolution analysis showed that Co2+ was removed in three ways:hydroxide precipitation(0.36%),adsorption(4.70%)and ion-excnange or entering the crystal(94.94%).(5)The comparative study of in-situ synthesis of MnOx showed that:Mn3O4 process had slower sedimentation efficiency,smaller precipitate size,lighter sediment quality than Birnessite process;Under certain water condition,the treatment of Mn3O4 was more stable,higher removal efficiency;However,the sediment of Birnessite prosess was more stable and Co2+ wasn't easy to dissolve.(6)All in all,both in-situ synthesis process of MnOx had their advantages,they could be applied to treat the wastewater containing radioactive Co2+ from nuclear power plant.