Blank roasting and bioleaching of stone coal for vanadium recycling

The recovery and utilization of vanadium from stone coal is of great significance because it is an important metal. In the present study, a cleaner metal extraction method to recover vanadium from low-grade stone coal using a novel strain of Bacillus mucilaginosus (BM) and an enhanced bioleaching procedure was explored. The efficient leaching bacteria of BM-5070 were obtained by the atmospheric and room temperature plasma (ARTP)-hydroxylamine hydrochloride compound mutagenesis technique. The results show that BM-5070 had the highest V leaching rate. After a 20-day bioleaching period, the V leaching rate of BM-5070 was 5.5 percentage points higher than that of the original bacteria. Moreover, the pretreatment of stone coal by blank roasting without any additives can further promote the vanadium dissolution, and the V leaching rate reached 85% after bioleaching for 20 days, which was 57 percentage points higher than that of without roasting. This is due to the decrease in the content of V (III) and the increase in the V (V) and V (IV) content after blank roasting, which is beneficial to the leaching of vanadium. The bioleaching behavior was elucidated through the bacteria-mineral contact leaching and non-contact leaching test. The results show that the V leaching rate (81.0%) in the contact mode was much higher than that in the non-contact leaching mode (64.4%), indicating that the bioleaching of vanadium occurs with direct action and indirect action. The results of our study could significantly contribute to a green method for recovering vanadium from stone coal.