Isolation and identification of a high-efficiency hexavalent uranium adsorption strain and preliminary study of the influencing factors and adsorption mechanism

In this study, a bacterial strain WK-3 with high adsorption efficiency of hexavalent uranium U(VI) was isolated from the rhizosphere soil of a uranium (U) tailings in southern China, with an adsorption rate of 92.3%, and was identified as Chryseobacterium bernardetii . The influence of different environmental conditions on the adsorption rate of Chryseobacterium bernardetii was investigated, and the adsorption mechanism was preliminarily discussed by scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS). The results showed that: 1) The optimal adsorption conditions for Chryseobacterium bernardetii were pH = 5, temperature 30 ℃, NaCl concentration 1%, and inoculation volume 10%; 2) Under the condition of initial concentration of 50 mg/L U(VI), the maximum adsorption rate of Chryseobacterium Bernardetii was reached and maintained in equilibrium within 24 h; Under the condition of initial concentration of 50 ~ 150 mg/L U(VI), the time for Chryseobacterium bernardii to reached its maximum adsorption rate and maintained equilibrium was extended to 48 h; 3) Under the condition of initial concentration of ≥ 200 mg/L U(VI), Chryseobacterium bernardii did not grow and had no adsorption capacity; 4) Under the condition of coexistence of 2 mmol/l Zn(II) and 50 mg/L U(VI), the adsorption of Chryseobacterium bernardii to U(VI) was significantly inhibited. ESM-EDS results show that phosphorus in cells participates in the interaction of uranyl ions, which may indicate that phosphate is produced during cell metabolism and is further combined to form U(VI)-phosphate minerals. Meanwhile, the possibility of complexation between cell surface groups and U(VI) cannot be ruled out.