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<p>In this study, synthesized trifunctional c-PDDA/Fe<sub>3</sub>O<sub>4</sub>-PES microcapsule was studied for the removal of methyl orange (MO). The trifunctional microcapsule offered excellent adsorptive ability, catalytic activity and being magnetic responsive. The removal of MO was achieved through destructive adsorption process and was proven through kinetic studies. In the single adsorption process (without presence of H<sub>2</sub>O<sub>2</sub>), the adsorption kinetic fitted to Langmuir isotherm with <i>k</i> value of 0.5801&#xa0;min<sup>−1</sup>. Intraparticle diffusion model confirmed the rate limiting step of the adsorption was the diffusion of MO into the pores of microcapsule. However, in the presence of H<sub>2</sub>O<sub>2</sub>, the destructive adsorption of MO fitted well with the pseudo-second-order kinetic model with <i>k</i> value of 1.2198&#xa0;min<sup>−1</sup>. Through optimization study, an optimum MO removal of 94.52 ± 0.48% could be obtained under the following conditions: microcapsule dosage of 24&#xa0;g/L, initial MO concentration of 22&#xa0;mg/L, H<sub>2</sub>O<sub>2</sub> concentration of 0.58&#xa0;mol/L, contact time of 230&#xa0;min and pH of 4.32. High dosage of microcapsule could provide greater surface area for the adsorption of MO, at the same time carrying more Fe<sub>3</sub>O<sub>4</sub> NPs for degradation reaction. It was discovered that higher H<sub>2</sub>O<sub>2</sub> concentration did not lead to significant increase in MO removal as excessive generation of ·OH will result in recombination of ·OH and reduce the free radicals for degradation. The destructive adsorption removal of MO was favorable under acidic pH as H<sub>2</sub>O<sub>2</sub> becomes unstable at elevated pH, which it decomposed into water and oxygen. Furthermore, ·OH will become less active under alkaline conditions due to the reaction to form ferrous/ferric hydroxide complexes and conjugate base, thereby reducing the degradation removal of MO.</p>

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Destructive adsorption of methyl orange using engineered trifunctional c-PDDA/Fe3O4-PES microcapsules: an insight into process, mechanism, and kinetics

  • 期刊论文

  • 发表日期：

    2025年8月30日

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  • W. Y. Tan,
  • S. H. Shuit,
  • S. Lim,
  • S. F. Tee,
  • Y. L. Pang,
  • Q. H. Ng,
  • W. Y. Wong

摘要

In this study, synthesized trifunctional c-PDDA/Fe3O4-PES microcapsule was studied for the removal of methyl orange (MO). The trifunctional microcapsule offered excellent adsorptive ability, catalytic activity and being magnetic responsive. The removal of MO was achieved through destructive adsorption process and was proven through kinetic studies. In the single adsorption process (without presence of H2O2), the adsorption kinetic fitted to Langmuir isotherm with k value of 0.5801 min−1. Intraparticle diffusion model confirmed the rate limiting step of the adsorption was the diffusion of MO into the pores of microcapsule. However, in the presence of H2O2, the destructive adsorption of MO fitted well with the pseudo-second-order kinetic model with k value of 1.2198 min−1. Through optimization study, an optimum MO removal of 94.52 ± 0.48% could be obtained under the following conditions: microcapsule dosage of 24 g/L, initial MO concentration of 22 mg/L, H2O2 concentration of 0.58 mol/L, contact time of 230 min and pH of 4.32. High dosage of microcapsule could provide greater surface area for the adsorption of MO, at the same time carrying more Fe3O4 NPs for degradation reaction. It was discovered that higher H2O2 concentration did not lead to significant increase in MO removal as excessive generation of ·OH will result in recombination of ·OH and reduce the free radicals for degradation. The destructive adsorption removal of MO was favorable under acidic pH as H2O2 becomes unstable at elevated pH, which it decomposed into water and oxygen. Furthermore, ·OH will become less active under alkaline conditions due to the reaction to form ferrous/ferric hydroxide complexes and conjugate base, thereby reducing the degradation removal of MO.