Treatment of Seepage Water from a Tailings Pond of Uranium Mining: Column tests with a novel Schwertmannite- Adsorbent
2 G.E.O.S. Ingenieurgesellschaft mbH, Freiberg
3 Wismut GmbH, Chemnitz
P 2.7 in Aquifer systems in Europe and beyond
An agglomerated, filter stable adsorbent was developed based on biotechnologically synthesized schwertmannite (SHM) from iron and sulfate containing lignite mine water. The adsorbent SHM-sorpP’ was obtained by compacting SHM in a briquette press. As investigated by  and , SHM and SHM-based adsorbents offer excellent adsorption properties towards arsenic, respectively.
SHM-sorpP was tested in comparison to the commercially available iron hydroxide adsorbents Ferrosorp®Plus (HeGoBiotec GmbH) and GEH®104 (GEH Wasserchemie & Co KG) to its suitability for the treatment of mine water at the example of seepage water from an uranium tailings pond in column tests (58–148 g adsorbent, filter bed volume 0.078 -0.101 L, flow rate 7.9 – 8.1 L/d) for 177 days. The seepage water was characterized by high pH (8.8–9.0) and significant concentrations of arsenic, molybdenum, phosphate, uranium, carbonate and radium-226. For the tests, an active pretreatment of the seepage water was realized by decreasing its pH to 7 (pH-7-seepage water scenario) and pH 5 (pH-5-seepage water scenario) with a dosage of hydrochloric acid (33%), respectively.
The results of the scenario with pH-7-seepage water (three columns with each of the three adsorbents) showed, that neither uranium nor molybdenum could be adsorbed by Ferrosorp®Plus, GEH®104 and SHM-sorpP. In contrast, all products were able to immobilize more or less arsenic and phosphate and SHM-sorpP offers the most efficient adsorption. In the scenario with pH-5-seepage water (columns with SHM-sorpP or Ferrosorp®Plus), 60 to 80 % of the uranium could be immobilized via precipitation (probably uranyl carbonate) in the inlet tank and in the first part of the flow paths of both adsorbent columns. SHM-sorpP again offered the better performance in the tests: in comparison to Ferrosorp®Plus, about 30% more arsenic and phosphate as well as 100% more molybdenum could be adsorbed.
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