XANES and EXAFS investigation of uranium incorporation on nZVI in the presence of phosphate

• Published in: Chemosphere (Oxford) Vol. 201; pp. 764 - 771
• Main Authors: Qiu, Muqing, Wang, Min, Zhao, Qingzhou, Hu, Baowei, Zhu, Yuling
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.06.2018
• Subjects: anaerobic conditions; EXAFS; nZVI; Phosphate; phosphates; prediction; Uranium; X-ray absorption spectroscopy; X-ray photoelectron spectroscopy; XANES; Uranium; nZVI; XANES; Phosphate; EXAFS
• ISSN: 0045-6535; 1879-1298; 1879-1298
• DOI: 10.1016/j.chemosphere.2018.03.057

Effect of phosphate on the reduction of U(VI) on nZVI was determined by batch, XPS, XANES and EXAFS techniques. The batch experiments showed that nZVI was quite effective for the removal of uranium under the anaerobic conditions, whereas the addition of phosphate enhanced uranium removal over wide pH range. At low pH, the reduction of U(VI) to U(IV) significantly decreased with increasing phosphate concentration by XPS and XANES analysis. According to EXAFS analysis, the occurrence of UU shell at 10 mg/L phosphate and pH 4.0 was similar to that of U(IV)O2(s), whereas the UP and UFe shells were observed at 50 mg/L phosphate, revealing that reductive co-precipitate (U(IV)O2(s)) and precipitation of uranyl-phosphate were observed at low and high phosphate, respectively. The findings are crucial for the prediction of the effect of phosphate on the speciation and binding of uranium by nZVI at low pH, which is significant in controlling the mobility of U(VI) in contaminated environments. •Phosphate enhanced uranium removal at pH 2.0–11.0•Decreased reduction of U(VI) significantly was observed at high phosphate.•EXAFS analysis demonstrated that uranium removal at low phosphate was reduction.•Uranium removal at high phosphate was uranyl-phosphate precipitation.