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<p>In this study, alginate beads encapsulating natural marl clay (Alg@M) were successfully prepared using Ca<sup>2+</sup>, Cu<sup>2+</sup>, and Fe<sup>3+</sup> as crosslinkers. The materials were characterized by XRD, SEM, EDS, and FTIR, and their physical properties (water content, bead diameter, density, and point of zero charge) were measured. The beads were tested as adsorbents for removing the antibiotic oxytetracycline hydrochloride (OTC) from water. Cu-Alg@M beads exhibited superior OTC removal efficiency compared to Fe-Alg@M and Ca-Alg@M. Under optimal conditions (90&#xa0;min, 0.5&#xa0;g beads, pH 4.3, 100&#xa0;rpm, 50&#xa0;mg/L OTC), the removal efficiency exceeded 96%. The amount of marl clay had only a slight effect on performance. Co-existing ions did not significantly affect adsorption, while CO<sub>3</sub><sup>2-</sup> reduced capacity by about 11% at concentration 0.001&#xa0;mol/L. In the presence of organic compounds, even in complex mixtures (chlortetracycline hydrochloride (CTC) + paracetamol (PC) + diclofenac sodium (DF)), a moderate efficiency reduction of 7% was observed. Kinetic data fitted both pseudo-first-order and pseudo-second-order models, indicating that both physical and chemical mechanisms were involved. Furthermore, the equilibrium data fitted both Freundlich and Langmuir isotherm models, with a maximum Langmuir adsorption capacity of 194.91&#xa0;mg/g at 298&#xa0;K. Thermodynamic parameters confirmed spontaneous, exothermic, and chemisorption-driven adsorption. The beads exhibited excellent reusability over eleven cycles, and microbiological tests confirmed reduced antibacterial activity after OTC removal. Cu-Alg@M beads represent a low-cost, environmentally friendly solution for removing antibiotic pollutants from aquatic systems. Despite these promising results, this study is limited to batch-mode experiments with spiked urban wastewater, and the long-term stability and continuous-flow performance of the beads remain to be investigated before large-scale application.</p>

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Eco-Friendly Copper-Alginate/Marl Clay Composite Beads for Efficient Oxytetracycline Hydrochloride Removal from Water: Preparation, Isotherms, Kinetics, and Microbiological Assay

  • 期刊论文

  • 发表日期：

    2026年7月25日

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  • Cherifi Souad,
  • Fizir Meriem,
  • Touil Sami,
  • Richa Amina,
  • Djafer Abderrahmane,
  • El Alia Zineb,
  • Sidi Othmane Imane,
  • Lekhal Nadia,
  • Zemmache Safia

摘要

In this study, alginate beads encapsulating natural marl clay (Alg@M) were successfully prepared using Ca2+, Cu2+, and Fe3+ as crosslinkers. The materials were characterized by XRD, SEM, EDS, and FTIR, and their physical properties (water content, bead diameter, density, and point of zero charge) were measured. The beads were tested as adsorbents for removing the antibiotic oxytetracycline hydrochloride (OTC) from water. Cu-Alg@M beads exhibited superior OTC removal efficiency compared to Fe-Alg@M and Ca-Alg@M. Under optimal conditions (90 min, 0.5 g beads, pH 4.3, 100 rpm, 50 mg/L OTC), the removal efficiency exceeded 96%. The amount of marl clay had only a slight effect on performance. Co-existing ions did not significantly affect adsorption, while CO32- reduced capacity by about 11% at concentration 0.001 mol/L. In the presence of organic compounds, even in complex mixtures (chlortetracycline hydrochloride (CTC) + paracetamol (PC) + diclofenac sodium (DF)), a moderate efficiency reduction of 7% was observed. Kinetic data fitted both pseudo-first-order and pseudo-second-order models, indicating that both physical and chemical mechanisms were involved. Furthermore, the equilibrium data fitted both Freundlich and Langmuir isotherm models, with a maximum Langmuir adsorption capacity of 194.91 mg/g at 298 K. Thermodynamic parameters confirmed spontaneous, exothermic, and chemisorption-driven adsorption. The beads exhibited excellent reusability over eleven cycles, and microbiological tests confirmed reduced antibacterial activity after OTC removal. Cu-Alg@M beads represent a low-cost, environmentally friendly solution for removing antibiotic pollutants from aquatic systems. Despite these promising results, this study is limited to batch-mode experiments with spiked urban wastewater, and the long-term stability and continuous-flow performance of the beads remain to be investigated before large-scale application.