Accelerated alkalinity regulation and long-term dry-wet aging durability for bauxite residue remediated with biomass pyrolysis

Biomass fermentation provides a potential route toward the ecological disposal for the bauxite residue (BR) with high alkalinity issues.However,how to accelerate the remedia-tion of the alkaline problem with a long-term durability is still a big challenge.Herein,we investigated the acceleration of the decomposition of straw toward organic acid species via a pyrolysis strategy as well as the pH stability during long-term dry-wet aging for the treated BR.The pH of pyrolytic BR at 300 ℃ is stabilized at around 8.90 after 70 days' dry-wet aging.During the aging,the main Ca-contained alkaline minerals of calcite and cancrinite are dis-solved and the content of exchangeable Na+ is reduced.This pyrolysis process can decom-pose straw quickly and produce more organic matters that are easily degraded to fulvic and humic acid as evidenced by 3D fluorescence spectrum analysis.Compared to the fermen-tation with straw under natural conditions,the alkalinity regulation of BR after pyrolysis is featured with shorter period and lower pH as well as long-term pH stability.Therefore,the synergistic pyrolysis of BR with straw provides an alternative method to address the alkaline issues,which is conducive to promoting the soil formation of BR.