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<p>The discharge of synthetic dyes into industrial wastewater poses serious environmental concerns due to their toxicity and persistence in aquatic systems. In this study, activated carbon (ZSAC) was successfully prepared from <i>Ziziphus lotus</i> seeds through chemical activation using sodium hydroxide (NaOH) and evaluated for the removal of Congo Red (CR) dye from aqueous solutions. Fourier-transform infrared (FTIR) analysis confirmed the presence of functional groups such as hydroxyl (–OH), carbonyl (C = O), and aromatic (C = C), which play an important role in the adsorption process, and the point of zero charge (pHpzc) of the adsorbent was determined to be 7. A Box–Behnken design (BBD) was applied to optimize the adsorption process by investigating the effects of adsorbent dose, initial dye concentration, and contact time. The developed quadratic model showed a high coefficient of determination (R<sup>2</sup> = 0.9963, <i>p</i> &lt; 0.0001), indicating the reliability of the statistical model. The optimal operating conditions predicted by the model were 3&#xa0;g/L adsorbent dose, 50&#xa0;mg/L dye concentration, and 120&#xa0;min contact time, corresponding to a predicted removal efficiency of approximately 71.92%. Equilibrium data were best described by the Langmuir isotherm model with a maximum adsorption capacity of 40.29&#xa0;mg/g, while the adsorption kinetics followed the pseudo-second-order model. Regeneration experiments demonstrated that the adsorbent maintained satisfactory performance over repeated adsorption–desorption cycles, confirming its stability and reusability. These results indicate that ZSAC is a promising, low-cost, and sustainable adsorbent for dye removal from wastewater.</p> Graphical Abstract <p></p>

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Optimizing Congo Red Removal Using a Novel Ziziphus Lotus (l.) Seed-based Activated Carbon: box–behnken Design, Isotherm, and Kinetic Studies

  • 期刊论文

  • 发表日期：

    2026年5月18日

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  • Amira Ouakkaf,
  • Sahnoune Derradji,
  • Fatiha Benmahdi,
  • Fatiha Chelgham,
  • Mounira Chelgham,
  • Hafssa Chetteh

摘要

The discharge of synthetic dyes into industrial wastewater poses serious environmental concerns due to their toxicity and persistence in aquatic systems. In this study, activated carbon (ZSAC) was successfully prepared from Ziziphus lotus seeds through chemical activation using sodium hydroxide (NaOH) and evaluated for the removal of Congo Red (CR) dye from aqueous solutions. Fourier-transform infrared (FTIR) analysis confirmed the presence of functional groups such as hydroxyl (–OH), carbonyl (C = O), and aromatic (C = C), which play an important role in the adsorption process, and the point of zero charge (pHpzc) of the adsorbent was determined to be 7. A Box–Behnken design (BBD) was applied to optimize the adsorption process by investigating the effects of adsorbent dose, initial dye concentration, and contact time. The developed quadratic model showed a high coefficient of determination (R2 = 0.9963, p < 0.0001), indicating the reliability of the statistical model. The optimal operating conditions predicted by the model were 3 g/L adsorbent dose, 50 mg/L dye concentration, and 120 min contact time, corresponding to a predicted removal efficiency of approximately 71.92%. Equilibrium data were best described by the Langmuir isotherm model with a maximum adsorption capacity of 40.29 mg/g, while the adsorption kinetics followed the pseudo-second-order model. Regeneration experiments demonstrated that the adsorbent maintained satisfactory performance over repeated adsorption–desorption cycles, confirming its stability and reusability. These results indicate that ZSAC is a promising, low-cost, and sustainable adsorbent for dye removal from wastewater.

Graphical Abstract