Abstract

Electric arc furnace slag (EAF) and argon oxygen decarburization slag (AOD) were investigated in column experiments to determine the effect of mineralogical composition on their P removal performance and lifespan. Polyethylene glycol (PEG) and NaOH solutions were used for pretreatment of the slags to adjust their dissolution properties. The modified slags exhibited better P removal performance at the beginning of the experiment, but had shorter lifespan than the unmodified slags. AOD and EAF modified with PEG and NaOH achieved 100% P removal during the first 84 and 60 pore volumes, respectively, which were >= 20 pore volumes longer than virgin AOD and EAF. However, virgin EAF and AOD both had a P removal efficiency above 90% during the first 280 pore volumes. Possibly, soluble minerals such as free lime are lost during the modification step, causing a decreased long-term P removal capacity. The XRD results showed that the high P removal ability of AOD and EAF was attributed to the dissolution of beta dicalcium silicate (beta-C-2) and gamma dicalcium silicate (gamma-C2S), which were dominant mineral phases in the slags. Results from SEM-EDS analysis revealed significant P accumulation on the slag surface. Cracks on the EAF slag surface contributed to its longer lifespan. Analysis with P Kedge XANES spectroscopy showed that the P retained on the slag surface was dominated by amorphous calcium phosphate, with a substantial amount of carbonate apatite (around 30%). Amorphous calcium phosphate was transformed to crystalline apatite as the slag aged with column operating time.

Keywords

Slag mineralogy; Dicalcium silicate; Calcium phosphate; Apatite; P speciation

Published in

Journal of water process engineering
2018, Volume: 25, pages: 105-112
Publisher: ELSEVIER SCIENCE BV

SLU Authors

• Gustafsson, Jon-Petter

  • Department of Soil and Environment, Swedish University of Agricultural Sciences
    
  • Royal Institute of Technology (KTH)

Sustainable Development Goals

SDG6 Ensure availability and sustainable management of water and sanitation for all


UKÄ Subject classification

Water Treatment


Publication identifier

DOI: https://doi.org/10.1016/j.jwpe.2018.07.003

Permanent link to this page (URI)

https://res.slu.se/id/publ/96552