Extraction of Ge and synchronous activation of humic acid in germanium bearing lignite via oxidation leaching

Germanium-bearing lignite was a crucial source for Ge extraction; however, existing methods focus on extracting Ge from lignite by-products, which overlooked its abundant organic matters. Effectively extracting valuable elements from lignite and fully utilizing its organic resources are still significant challenges. In this study, a novel processing of recovering Ge and synchronous extracting humic acids in germanium-bearing lignite via oxidation leaching was proposed. A Ge extraction recovery of 73.93 % was achieved using a L/S ratio of 10 and 5 % nitric acid at 90 °C for 30 min. The effects of nitric acid on the activation and depolymerization of lignite samples were also analyzed. The results demonstrated that HNO 3 pretreatment significantly enhanced humic acid yield, increasing it from 28.73 % to 71.32 % in lignite. The mechanism of Ge oxidation leaching in lignite was investigated, which could be divided into four stages due to the migration and transformation behavior of germanium. In addition, a new technical route for the efficient and high recovery of strategic rare metals Ge and organic resources humic acid in lignite was proposed. The research establishes a foundation for the extraction of valuable metal elements and the efficient utilization of organic resources in lignite. • A novel method to recover Ge and organic matters in lignite was proposed. • Both Ge extraction and humic acid activation were achieved via oxidation leaching. • Migration and transformation of Ge and humic acid in lignite were analyzed.