Chunyu Yang, Rui Huang, Huihui Du
Tungsten (W) mobility in acid mine drainage (AMD) may be strongly influenced by its interactions with schwertmannite (Sch), a metastable sulfate-bearing Fe(III) oxyhydroxide that can effectively scavenge oxyanion-forming contaminants. During aging, Sch gradually transforms into more stable Fe(III) phases, such as goethite, which may substantially alter the mobility and retention of associated contaminants. However, the fate of W during Sch transformation remains unclear. This study investigated W redistribution during Sch aging and examined whether W loading altered the temporal development of Fe mineral phases. Batch aging experiments were conducted at pH 3.5 and 60 ℃ using W-free and W-loaded Sch suspensions. Sch gradually transformed into goethite in both systems. However, W loading altered the transformation in a stage-dependent manner. During the early stage, the W-loaded system exhibited approximately 15% higher sulfate release and earlier development of goethite-related features than the W-free system. During the later stage, the development of crystalline goethite was attenuated. W was initially released into solution and subsequently reassociated with the solid phase. The residual W fraction increased to approximately 38% by day 30. The later redistribution of W coincided with attenuated development of crystalline goethite. Overall, the results reveal a stage-dependent relationship between Sch transformation and W partitioning under accelerated aging conditions and provide a geochemical basis for assessing W retention and mobility in AMD-related systems.