The As behavior of natural arsenical-containing colloidal ferric oxyhydroxide reacted with sulfate reducing bacteria

- Naturally formed arsenic-containing ferric colloidal ferric oxyhydroxide was characterized.
- As(III) species was observed when sulfate reducing bacteria acted with these colloidal sediments.
- Arsenic transformation in tailing ponds is described.

The extensive mining activities in Shimen realgar mine have generated large amounts of secondary arsenical ferric oxyhydroxides. The reductive dissolution of these tailing sediments at the soil/water interface influences the behavior of arsenic (As). Here, the dynamics of As in these flooded high arsenic tailing sediments at circumneutral pH conditions were investigated by employing a pure culture of a sulfate reducing bacteria (SRB). Changes in Eh, pH, aqueous Fe(II) and As speciation were monitored over 6 days in batch experiments. Our results demonstrated that SRB was able to reductive dissolve high levels of arsenical ferric oxyhydroxide. The results showed that reactions with aqueous As(III) and As(V) presented different trends, with As(III) (80-100% of total As) being the dominant arsenic species. Aqueous As behavior showed two distinct stages, firstly, the As(V) was released and immediately reduced to As(III) by biogenic sulfide. Next, the released As was removed from the solution by adsorption onto newly formed nano-Fe sulfides (e.g. FeS, FeS2) or co-precipitation with S(-II) to produce nano arsenic sulfide (As3S2). In addition, the addition of sulfate, calcium and sodium lactate played different roles in the release of As. Addition of sulfate and sodium lactate can trigger the release of arsenic, while calcium caused the opposite effect.

Collection of arsenical sediment from Shimen Realgar Mine, Changde City, Hunan province, China, September 2016.81