Chemical surface mechanisms in rapid solid-liquid separation of sludge from HD-sludge recycling of AMD (Horobetsu)

G. C. Badulis*, C. Tokoro, H. Sasaki

*Corresponding author for this work

Research output: Contribution to conferencePaperpeer-review


A disadvantage of the continuous recycling process of high density (HD) sludge in the treatment of Acid Mine Drainage (AMD) from Horobetsu is the formation of ultra fine solid particles (UFP) in a low concentration. These suspended particles complicate the rapid separation. This article analyses a batch-type recycling process for the HD-sludge. Experiments were conducted with various neutralizers at pH 7 and the separation of suspended ultra fine particles was done by means of ferro-nickel slag (FS) fibers in a glass column. Different phenomena were analysed: the iron-sludge density and composition, the influence of electrocinetic surface phenomena in the generated sludge and the separation of the suspended UFP in a FS-fiber-bed. The neutralizers increase the density of the iron sludge, yet irregularly with the progression of the recycling. A MgO-based neutralizer provided the densest sludge followed by a two-step neutralizer, while Ca(OH)2 and NaOH provided the least dense sludge. The strong effect of MgO is due to the large negative minimum potential energy (Vtmin) from Fe(OH)3 as basic ferric sulphate and undissolved MgO. Also the sludge from the two-step-method has large negative Vtmin from Fe(OH)3 and undissolved CaCO3. The difference to MgO can be explained by a smaller negative Vtmin caused by heterocoagulation with other sludge materials, and by the sludge composition and concentration. The Fe(OH)3- and CaSO4-sludge from the Ca(OH)2-neutralization and the Fe(OH)3-sludge as basic ferric sulphate from the NaOH-neutralization have smaller Vtmin, resulting in low iron density. FS-fibers are very effective media to separate suspended UFP. The separation process is controlled by the Vtmin from the heterecoagulation of the UFP and the FS followed by the homocoagulation of UFP. As a result, the utilization of FS-fibers in the column bed improved the continuous-type HD-sludge recycling process.

Original languageEnglish
Number of pages17
Publication statusPublished - 2005
EventEuropean Metallurgical Conference, EMC 2005 - Dresden, Germany
Duration: 2005 Sept 182005 Sept 21


ConferenceEuropean Metallurgical Conference, EMC 2005


  • Acid mine drainage
  • Coagulation
  • Filtration
  • High density sludge
  • Recycling
  • Solid-liquid separation
  • Waste effluent treatment

ASJC Scopus subject areas

  • Metals and Alloys


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