Modeling chromium dissolution and leaching from chromite ore-processing residue


Yalcin S., Unlu K.

ENVIRONMENTAL ENGINEERING SCIENCE, cilt.23, ss.187-201, 2006 (SCI İndekslerine Giren Dergi) identifier identifier

  • Cilt numarası: 23 Konu: 1
  • Basım Tarihi: 2006
  • Doi Numarası: 10.1089/ees.2006.23.187
  • Dergi Adı: ENVIRONMENTAL ENGINEERING SCIENCE
  • Sayfa Sayıları: ss.187-201

Özet

Chromium has been widely used in many industrial applications. As a result of chromite ore processing, large amounts of chromite ore processing residue (COPR) material that can be classified as hazardous have been produced and released into the environment. Therefore, knowledge of migration behavior and leaching rates of chromium through waste materials are of primary concern for environmentally sound management of hazardous wastes. Leaching rates of total Cr and Cr(VI) were studied experimentally using laboratory columns packed with COPR material produced by a sodium chromite plant. Based on the experimental results, the present study alms, through mathematical modeling, to understand the dissolution kinetics of chromium during leaching of COPR material and to investigate the effectiveness of intermittent leaching, which involves a sequence of batch (dissolution) and mass flushing (leaching) operational modes. Modeling results show that a coupled system of two first-order differential equations was able to capture the essential characteristics of leaching behavior of COPR material. In addition, the kinetics of chromium dissolution from COPR appeared to be controlled by the difference between aqueous phase concentration and saturation concentration (effective solubility), by the mass fraction of dissolvable chromium remaining in the solid phase, and finally, by the contribution of a constant dissolution rate manifested as a steady-state tailing behavior. As a result of performed simulations it was seen that intermittent leaching could be 65 and 35% more effective than continuous leaching for total Cr and Cr(VI) removal, respectively.