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<p>Reuse and recycle of the large quantities of solid waste generated during steel production can enhance the environmental sustainability of the process. Reuse of the basic oxygen furnace (BOF) slag is however restricted, due to the simultaneous presence of various metals in the slag. Leaching of the metals from the insoluble matrix in soluble form with the help of chemical or biological agents can facilitate metal recovery. However, the alkaline pH of BOF slag is detrimental for leaching. A water washing protocol based on 5 washing cycles with reused water could reduce the pH of BOF slag from 13.44 to 8.35. Metal dissolution and reprecipitation (primarily as calcite), change in slag mineralogy, and filtration followed by drying of the slag after each cycle were possibly responsible for pH lowering, as revealed through alkalinity, hardness, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and analysis of residual metals through sequential extraction process (SEP). Breakdown of the calcium aluminium silicate minerals also contributed to the pH reduction. Studies on inorganic acid leaching of 1% slag with 0.1&#xa0;M acid showed that higher leaching was attained for the prewashed slag. The water washing pretreatment also reduced the time required for maximum leaching from 120 to 90&#xa0;min for most metals for all the acids used for leaching. Bacterial leaching using <i>Acidithiobacillus ferrooxidans</i> also showed significant increase in metal removal due to pre-washing of BOF slag. The time required for bioleaching for 1% BOF slag was reduced from 30 to 21&#xa0;days.</p>

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Pretreatment of Basic Oxygen Furnace (BOF) Slag using Water Washing and its Effect on Acid Leaching and Bioleaching of Metals

  • 期刊论文

  • 发表日期：

    2025年6月3日

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  • Neha Garg,
  • Suparna Mukherji

摘要

Reuse and recycle of the large quantities of solid waste generated during steel production can enhance the environmental sustainability of the process. Reuse of the basic oxygen furnace (BOF) slag is however restricted, due to the simultaneous presence of various metals in the slag. Leaching of the metals from the insoluble matrix in soluble form with the help of chemical or biological agents can facilitate metal recovery. However, the alkaline pH of BOF slag is detrimental for leaching. A water washing protocol based on 5 washing cycles with reused water could reduce the pH of BOF slag from 13.44 to 8.35. Metal dissolution and reprecipitation (primarily as calcite), change in slag mineralogy, and filtration followed by drying of the slag after each cycle were possibly responsible for pH lowering, as revealed through alkalinity, hardness, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and analysis of residual metals through sequential extraction process (SEP). Breakdown of the calcium aluminium silicate minerals also contributed to the pH reduction. Studies on inorganic acid leaching of 1% slag with 0.1 M acid showed that higher leaching was attained for the prewashed slag. The water washing pretreatment also reduced the time required for maximum leaching from 120 to 90 min for most metals for all the acids used for leaching. Bacterial leaching using Acidithiobacillus ferrooxidans also showed significant increase in metal removal due to pre-washing of BOF slag. The time required for bioleaching for 1% BOF slag was reduced from 30 to 21 days.