Microbial Production of Schwertmannite: Development from Microbial Fundamentals to Marketable Products

摘要

Pumped groundwater in the lignite open-cast mines in Lusatia, Germany, contains a high level of ferrous iron (up to 1000 mg/L) at an initial pH of about 5. In recent R&D projects G.E.O.S. developed an innovative water treatment process for ferrous iron oxidation using the autochthonous microbial consortium in the mine water. The pilot plant is operated in the Nochten open-pit mine in cooperation with the LEAG and produces 5 - 10 t of schwertmannite per year. Extensive research work was carried out in parallel to utilize the produced schwertmannite. Pigment production proved to be technically feasible but difficult due to economic and market constraints. However, the high affinity of schwertmannite to oxy-anions provides the suitability for utilization as adsorbent to remove arsenate, antimonate, chromate, molybdate, vanadate or phosphate from mine water or industrial effluents. In the R&D project SURFTRAPII two kinds of filter-stable sorption materials were developed 1) by compacting schwertmannite or 2) by adhesive curing using an organic polymer, respectively. The produced filter-stable adsorbents were tested under technical conditions in cooperation with potential end users to remove arsenate, molybdate and phosphate from mine and industrial water and to concentrate valuable metals. The results showed a better performance of the material compared to other commercially available iron hydroxide adsorbents.