| Reducing the migratory ability of uranium via reduction,coprecipitation or immobilization is the widely used technology for remediation of uranium contaminated groundwater.However,the longterm effect of groundwater remediation is restricted due to uranium rerelease caused by environmental alterations such as oxidation,acid dissolution,or microbial decomposition.Electrochemical mineralization does not require the addition of reagents and can directly dope uranyl ions into inorganic minerals formed by the self-crystallization of metallic and non-metallic ions,removing uranium from groundwater in an efficient and stable manner,and the mineralization products can be stored underground environment for a long time without dissolving.However,most of current studies have focused on the construction of electrochemical systems in simulated aqueous solutions,the modification of electrodes or the optimization of electrochemical parameters.However,the application of electrochemical mineralization remediation at the site scale should consider process variables including site characteristics,such as hydrogeological environment,electrode configuration and secondary release of contamination,which are crucial for future site applications.In view of this,a novel solar-powered electrochemical mineralization(SPEM)system was proposed for persistent remediation of uraniumcontaining groundwater by incorporating uranium into magnetite crystal to achieve the long-term stability of uranium.The simulated groundwater environment was built using one-and two-dimensional simulated tank experiments,with the emphasis on the effects of photoelectric conversion,simulated complex hydrogeological conditions,continuous remediation,and electrode configuration methods on uranium mineralization;the stability of remediation products was evaluated,and the effectiveness of the method on actual wastewater was initially investigated.The main conclusions are as follows:(1)The feasibility of using solar energy as a DC power source to power to the electrochemical mineralization system was investigated.The results showed that this process can not only produce magnetite stably but also remove uranium from groundwater efficiently by immobilizing uranium in the magnetite lattice with stable structure,and the removal rate of uranium can reach over 90.0%.(2)The adaptability of the solar-driven electrochemical mineralization system to different water percolation rates,media voids and continuous treatment experiments,and the resistance to impurity ions were investigated;the uranium-doped magnetite produced by the reaction is mainly concentrated near the cathode which is conducive to further recycling after magnetic separation at a later stage.(3)The proposed hexagonal two-dimensional electrode configuration(1A6C)was able to reduce the effluent uranium concentration from 6.00mg/L to 0.25 mg/L in situ after 12 h of continuous treatment;the mineralized uranium was not re-released by continuous flushing of the simulated ore layer with an acidic solution of p H=3.0 for 370 h,indicating that the uranium-doped magnetite has a strong stability.(4)Using this system to treat actual uranium-bearing groundwater,the removal rate was as high as about 80.0% within 6 h,indicating that this method can effectively remediate actual uranium-bearing groundwater and the complex water quality environment does not affect the remediation process.This study proposes a new strategy for the long-term effectiveness and continuous remediation of uranium-contaminated groundwater,as well as provides a theoretical foundation for its wide application in deep groundwater remediation. |
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