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<p>Conventional leaching processes for recycling spent hydroprocessing catalysts (SPHCs) are highly toxic and cause serious environmental pollution. Herein, we propose the direct use of nature-derived organic acids in ‘<i>Citrus limon’ (C. limon)</i> as an environmentally friendly method to extract valuable nickel (Ni), molybdenum (Mo), and vanadium (V) from SPHCs. The analysis of <i>C. limon</i> juice using high-performance liquid chromatography (HPLC) confirmed that it contained citric acid (&gt; 0.35 molar), and other minute organic acids (malic acid and tartaric acid). The <i>C. limon</i> juice reaction with decoked SPHCs (DSHPCs) led to highly efficient leaching of metals (Ni: 94.7%, Mo: 92.7%, and V: 84.6%) under optimum conditions (<i>C. limon</i> juice concentration: 40%, temperature: 60&#xa0;°C, mixing speed: 150&#xa0;rpm, and DSHPCs concentration: 25&#xa0;g/L). The dissolution of the metals was explained through a mixed kinetic model (Avrami equation), which suggested that diffusion control is the dominant leaching mechanism. After leaching, the residue (LR) showed significantly lower toxicity and improved surface textural properties (specific surface area − 236.25 m<sup>2</sup>/g). The improved textural properties of LR allow its potential reuse for preparing fresh hydroprocessing catalysts. Compared to current hazardous processes, this leaching process demonstrates a green and sustainable recycling solution for SHPCs.</p>

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Bio-based leaching of Ni, Mo and V from spent petroleum hydroprocessing catalysts (SPHCs) using citrus limon juice

  • 期刊论文

  • 发表日期：

    2025年11月25日

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  • Ashish Pathak,
  • Mohan S. Rana,
  • Hanadi Al-Sheeha,
  • R. Navvamani,
  • Sakeena Al-Sairafi

摘要

Conventional leaching processes for recycling spent hydroprocessing catalysts (SPHCs) are highly toxic and cause serious environmental pollution. Herein, we propose the direct use of nature-derived organic acids in ‘Citrus limon’ (C. limon) as an environmentally friendly method to extract valuable nickel (Ni), molybdenum (Mo), and vanadium (V) from SPHCs. The analysis of C. limon juice using high-performance liquid chromatography (HPLC) confirmed that it contained citric acid (> 0.35 molar), and other minute organic acids (malic acid and tartaric acid). The C. limon juice reaction with decoked SPHCs (DSHPCs) led to highly efficient leaching of metals (Ni: 94.7%, Mo: 92.7%, and V: 84.6%) under optimum conditions (C. limon juice concentration: 40%, temperature: 60 °C, mixing speed: 150 rpm, and DSHPCs concentration: 25 g/L). The dissolution of the metals was explained through a mixed kinetic model (Avrami equation), which suggested that diffusion control is the dominant leaching mechanism. After leaching, the residue (LR) showed significantly lower toxicity and improved surface textural properties (specific surface area − 236.25 m2/g). The improved textural properties of LR allow its potential reuse for preparing fresh hydroprocessing catalysts. Compared to current hazardous processes, this leaching process demonstrates a green and sustainable recycling solution for SHPCs.