Search

This study investigates the efficacy of activated carbon-nano-hydroxyapatite (AC-nHAP) gel microspheres, composed of sodium alginate and AC-nHAP, as permeable reactive barrier (PRB) fillers for electrokinetic remediation of uranium-contaminated soil. The optimum configuration with 3 g each of AC and nHAP achieved a uranium removal efficiency of 82.31%, surpassing pure electrokinetic remediation by 18.15%. The porous structure of the microspheres facilitated uranium immobilization via complexation, precipitation, and adsorption mechanisms, effectively reducing the leaching toxicity to 0.068 mg/L. These findings underscore the potential of AC-nHAP gel microspheres as PRB fillers in enhancing the efficacy of EK remediation for heavy metal-contaminanted soil. [ABSTRACT FROM AUTHOR]

One of the more concerning issues in the world today is that radioactive uranium contaminates the soil and threatens the organisms. The focus of contaminated soil remediation is to immobilize the uranium in the soil and reduce its leaching. Nano-hydroxyapatite (nHAP) and nano-hydroxyapatite/nano-zero-valent iron mixture (nHAP/nZVI) are used as immobilizer to remediate uranium-contaminated soil. The leaching characteristics and morphological changes of uranium before and after immobilization were studied by using Toxicity Characteristic Leaching Procedure (TCLP) and Tessier stepwise chemical extraction method. The results show that the leaching concentration of uranium in the soil was 0.005 mg/L when nHAP was added alone, and the leaching rate was 9.14%. The leaching concentration of uranium in the soil was only 0.004 mg/L when adding nHAP/nZVI, and the leaching rate was reduced to 8.57%. U (VI) not only reacts with nHAP to form a stable complex but also is reduced by nZVI to insoluble U (IV) when nHAP/nZVI is added. As a result, both nHAP/nZVI and nHAP can effectively immobilize uranium in the soil, and nHAP/nZVI can better promote the immobilization of the uranium in the soil. [ABSTRACT FROM AUTHOR]

• The EK technology coupled with ZVI/AC-PRB technology was first applied to the remediation of uranium-contaminated soil. • The effects of the type, location and quantity of PRB on the removal of uranium from soil were studied. • The effect of AC on ZVI activity and the removal mechanism of U(VI) on mixture ZVI/AC were investigated. Zero-valent iron/activated carbon (ZVI/AC) particles can promote the reduction of U(VI) by micro-electrolysis. Therefore, they can be used to develop materials for permeable reactive barrier (PRB). In this study, citric acid (CA) mixed with ferric chloride (FeCl 3) was selected as composite electrolyte, and we investigated the feasibility of electrokinetic (EK) coupled with Fe/C-PRB on the remediation of red soil artificially contaminated with U(VI). Seven EK experiments were conducted to study the effect of the type, location, and amount of PRB media on the removal of U(VI) in soil by the EK-PRB system. The results showed that the ZVI/AC mixture is superior to the single ZVI or AC as the PRB medium. For the EK-PRB system, a moderate increase in the number of PRBs and decrease in the thickness of the PRB in soil chamber can enhanced the removal of U(VI) from the contaminated soil. Under optimized conditions, after the 120 h remediation experiment obtained the maximum removal efficiency (80.58 ± 0.99%) of U(VI). Scanning electron microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDS), infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) were used to study the surface properties of the ZVI/AC mixture before and after the reaction. The results demonstrated that the soluble U(VI) was reduced to the insoluble U(IV) in the ZVI/AC mixture, or adsorption of activated carbon or iron corrosion products regardless of the pH distribution. This work provides a green efficient technology for the recovery of U(VI) from contaminated soil, waste slag or solid waste. [ABSTRACT FROM AUTHOR]