Insight into efficient removal of Cr(VI) by magnetite immobilized with Lysinibacillus sp. JLT12: Mechanism and performance

In this work, Lysinibacillus sp. JLT12 was used to remove the Cr(VI)-induced passive layer on the magnetite. Mechanism study via dynamic kinetics, X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy analyses revealed that Lysinibacillus sp. JLT12 could remove the passive layer (lepidocrocite and goethite) to facilitate the further Cr(VI) reduction by magnetite. For large-scale applications, porous ceramsite (PC) was prepared with magnetite, kaolin, and fallen leaves. Lysinibacillus sp. was then immobilized on the holes in PC. Slow-released nutrients were added to immobilized porous ceramsite (IM-PC) at a ratio of 1.5:10 (g/g) to supply carbon, nitrogen, and phosphorus to Lysinibacillus sp. JLT12 with low secondary pollution. The performance of IM-PC was evaluated via a column experiment. The results indicate that, in the presence of Lysinibacillus, the break-through time and maximum adsorption ability of IM-PC were 11.67 h and 121.47 mg/g, respectively. These values are higher than those of PC. Additionally, break-through curves detected at 5, 10, and 15 days demonstrated that the usage life of IM-PC was significantly longer than that of PC. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

This study utilized Lysinibacillus sp. to remove the passive layer induced by Cr(VI) on magnetite, facilitating further Cr(VI) reduction. Immobilizing Lysinibacillus sp. in porous ceramsite extended its lifespan and enhanced adsorption capacity.