<p>In this study, CuZnAl layered double hydroxide (LDH) adsorbents were synthesized via a facile co-precipitation method and evaluated for the removal of methyl orange (MO), a model anionic azo dye. Comprehensive characterization using XRD, FTIR, BET, and SEM confirmed the successful formation of phase-pure carbonate-type LDHs with ordered layer stacking, mesoporous texture, and plate-like morphology. Among the samples tested, CuZnAl exhibited the highest BET surface area (45 m<sup>2</sup> g<sup>−1</sup>) and the largest total pore volume (0.432 cm<sup>3</sup> g<sup>−1</sup>), facilitating superior adsorption performance. Batch experiments revealed that all adsorbents achieved maximum removal at acidic pH, with CuZnAl reaching ≈ 100% MO removal at pH 3. Adsorption kinetics followed the pseudo-second-order model (<i>R</i><sup>2</sup> &gt; 0.99), indicating that chemisorption and interlayer ion exchange were the dominant mechanisms. The Langmuir isotherm model provided excellent fits (<i>R</i><sup>2</sup> &gt; 0.96), with the highest maximum monolayer adsorption capacity (<i>qₘ</i>) observed for CuZnAl (392.2 mg g<sup>−1</sup>), followed by CuAl (293.3 mg g<sup>−1</sup>) and ZnAl (235.3 mg g<sup>−1</sup>). Reusability studies demonstrated robust cycling performance for CuZnAl, which retained ≈ 95% of its initial removal capacity after five cycles, whereas ZnAl suffered the greatest decline.</p> Graphical Abstract <p></p>

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Durable CuZnAl Layered Double Hydroxides for Robust Removal of Methyl Orange from Water

  • Shen-Wei Yu,
  • Chia-Hsiang Yang,
  • Chen-Bin Wang

摘要

In this study, CuZnAl layered double hydroxide (LDH) adsorbents were synthesized via a facile co-precipitation method and evaluated for the removal of methyl orange (MO), a model anionic azo dye. Comprehensive characterization using XRD, FTIR, BET, and SEM confirmed the successful formation of phase-pure carbonate-type LDHs with ordered layer stacking, mesoporous texture, and plate-like morphology. Among the samples tested, CuZnAl exhibited the highest BET surface area (45 m2 g−1) and the largest total pore volume (0.432 cm3 g−1), facilitating superior adsorption performance. Batch experiments revealed that all adsorbents achieved maximum removal at acidic pH, with CuZnAl reaching ≈ 100% MO removal at pH 3. Adsorption kinetics followed the pseudo-second-order model (R2 > 0.99), indicating that chemisorption and interlayer ion exchange were the dominant mechanisms. The Langmuir isotherm model provided excellent fits (R2 > 0.96), with the highest maximum monolayer adsorption capacity (qₘ) observed for CuZnAl (392.2 mg g−1), followed by CuAl (293.3 mg g−1) and ZnAl (235.3 mg g−1). Reusability studies demonstrated robust cycling performance for CuZnAl, which retained ≈ 95% of its initial removal capacity after five cycles, whereas ZnAl suffered the greatest decline.

Graphical Abstract