Rare earth elements recovery and sulphate removal from phosphogypsum waste waters with sulphate reducing bacteria

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Abstract

Phosphogypsum waste, originating from phosphoric acid production from apatite ores, is well known for its high production rate and possible release of sulphate-rich seepage waters. In addition to negative environmental impacts, phosphogypsum waste heaps are also remarkable secondary sources of rare earth elements (REE); in the phosphoric acid production process a majority of REE, occurring in apatite, are precipitated to the phosphogypsum waste. Therefore, a method treating both sulphate-rich waters and recovering REE from phosphogypsum heaps and seepage waters would offer both economic and environmental benefits. In this ongoing study, seepage waters from a phosphogypsum heap are treated with sulphate reducing bacteria (SRB) and ethanol as a substrate. Sulphate is first reduced to hydrogen sulphide, which is then assumed to precipitate REE as sulphides. The main challenge, low concentration of REE in seepage waters (e.g. 2.87 µg/l La, 5.13 µg/l Ce, 0.67 µg/l Y and 3.32 µg/l Nd), is overcome by utilizing continuous mode, semi-passive and cost effective column apparatus, requiring no agitation and performing both sulphate reduction and REE recovery in a single reactor. The SRB method results in a sulphate reduction rate of 40-80 % (from app. 1400 mg/l to 276-844 mg/l sulphate in the effluent) and efficient REE recovery from seepage water. The concentrate obtained from the column consists of a mixture of anaerobic sludge and precipitated REE, with respective REE concentrations of 202 mg/kg La, 477 mg/kg Ce, 49 mg/kg Y and 295 mg/kg Nd.

Original languageEnglish
Title of host publication22nd International Biohydrometallurgy Symposium
EditorsWolfgang Sand, Kathrin Rubberdt, Franz Glombitza, Wolfgang Sand, Mario Vera Veliz, Sabine Willscher, Sabrina Hedrich, Axel Schippers
PublisherTrans Tech Publications
Pages573-576
Number of pages4
ISBN (Print)978-3-0357-1180-6
DOIs
Publication statusPublished - 1 Jan 2017
MoE publication typeA4 Article in a conference publication
Event22nd International Biohydrometallurgy Symposium - Freiberg, Germany
Duration: 24 Sep 201727 Sep 2017

Publication series

SeriesSolid State Phenomena
Volume262 SSP

Conference

Conference22nd International Biohydrometallurgy Symposium
CountryGermany
CityFreiberg
Period24/09/1727/09/17

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Keywords

  • apatite
  • phosphogypsum
  • rare earth element
  • sulphate
  • sulphate reducing bacteria

Cite this

Mäkinen, J., Bomberg, M., Salo, M., Arnold, M., & Koukkari, P. (2017). Rare earth elements recovery and sulphate removal from phosphogypsum waste waters with sulphate reducing bacteria. In W. Sand, K. Rubberdt, F. Glombitza, W. Sand, M. V. Veliz, S. Willscher, S. Hedrich, & A. Schippers (Eds.), 22nd International Biohydrometallurgy Symposium (pp. 573-576). Trans Tech Publications. Solid State Phenomena, Vol.. 262 SSP https://doi.org/10.4028/www.scientific.net/SSP.262.573