Simultaneous dealkalization of red mud and recovery of valuable metals by a novel marine fungus tolerating high alkalinity and salinity

Abstract

Red mud is a highly saline and alkaline solid waste generated in alumina refinery, which entails dealkalization for safe disposal and valorization. Herein, Trichocomaceae sp. K-2, a novel fungus isolated from marine sediment, was used for the simultaneous dealkalization of red mud and recovery of valuable metals. The fungus demonstrated robust growth at high salinity (45 g/L NaCl), good tolerance to high pH (up to 12), and capability of utilizing low-cost substrates derived from lignocellulosic biomass. Both structural and free alkali can be removed by Trichocomaceae sp. K-2 to achieve a significantly lower minimum pH (<4) in a considerably short timeframe (<16 days), and the alkali removal efficiency as high as 94% was attained. Moreover, concomitant leaching of valuable Nd, Sc and Y from red mud during dealkalization was feasible. Physical disintegration and chemical erosion by the secreted organic acids were responsible for the effective dealkalization, as well as leaching of valuable metals. This study sheds lights on how marine microorganisms can be harnessed to the green disposal of red mud, and provokes the exploration of more robust and versatile marine microbes for the sustainable and cost-effective management of other highly saline and alkaline solid waste.