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<p>Hexavalent chromium (Cr(VI)) is a highly toxic and carcinogenic pollutant widely discharged from tannery industries and poses serious environmental and public health risks when released into aquatic ecosystems. In this study, a sustainable and low-cost approach was developed for the efficient removal of Cr(VI) from real tannery wastewater using carbonized chicken eggshell, a readily available biowaste material. Eggshells were carbonized at 800 °C for 2 h, yielding a material with improved physicochemical properties and a surface area of 68.01 m<sup>2</sup>/g. The material was characterized using FTIR, XRD, proximate analysis, and BET surface area analysis. Optimization of adsorption parameters was conducted using Response Surface Methodology with a Central Composite Design employed to statistically evaluate the individual and interactive effects of key adsorption parameters. The developed quadratic model showed high statistical significance (P &lt; 0.0001, R<sup>2</sup> = 0.9776). The effects of pH, adsorbent dosage, initial Cr(VI) concentration, and contact time were systematically evaluated. The optimal conditions for maximum Cr(VI) removal (99.63%) were pH 7, adsorbent dose 1.5 g, initial concentration 80 mg/L, and contact time 120 min. Adsorption data were best described by the Langmuir isotherm model (R<sup>2</sup> = 0.990), indicating monolayer adsorption, while kinetic studies followed the pseudo-second-order model (R<sup>2</sup> = 0.993), suggesting chemisorption. This study demonstrates the effective application of carbonized eggshells for Cr<sup>6+</sup> removal from tannery wastewater, offering a cost-effective, eco-friendly solution for industrial effluent treatment.</p>

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Response surface optimization of hexavalent chromium removal from real tannery wastewater using carbonized eggshells

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年3月25日

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  • Berihu Gebrecherkos Gebretsadkan,
  • Desbelom Welegebrial Hagos,
  • Mebrahtom Gebresemati Weldehans,
  • Birhane Ekubay Teweldebrhan,
  • Maebele Gereziher Zegeye

摘要

Hexavalent chromium (Cr(VI)) is a highly toxic and carcinogenic pollutant widely discharged from tannery industries and poses serious environmental and public health risks when released into aquatic ecosystems. In this study, a sustainable and low-cost approach was developed for the efficient removal of Cr(VI) from real tannery wastewater using carbonized chicken eggshell, a readily available biowaste material. Eggshells were carbonized at 800 °C for 2 h, yielding a material with improved physicochemical properties and a surface area of 68.01 m2/g. The material was characterized using FTIR, XRD, proximate analysis, and BET surface area analysis. Optimization of adsorption parameters was conducted using Response Surface Methodology with a Central Composite Design employed to statistically evaluate the individual and interactive effects of key adsorption parameters. The developed quadratic model showed high statistical significance (P < 0.0001, R2 = 0.9776). The effects of pH, adsorbent dosage, initial Cr(VI) concentration, and contact time were systematically evaluated. The optimal conditions for maximum Cr(VI) removal (99.63%) were pH 7, adsorbent dose 1.5 g, initial concentration 80 mg/L, and contact time 120 min. Adsorption data were best described by the Langmuir isotherm model (R2 = 0.990), indicating monolayer adsorption, while kinetic studies followed the pseudo-second-order model (R2 = 0.993), suggesting chemisorption. This study demonstrates the effective application of carbonized eggshells for Cr6+ removal from tannery wastewater, offering a cost-effective, eco-friendly solution for industrial effluent treatment.