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<p>Industrial wastewater treatment remains a pressing challenge owing to the coexistence of hazardous heavy metals and persistent organic dye contaminants that resist conventional remediation approaches. In this work, a fibrous silica iron (FSFe) catalyst was successfully incorporated with metal oxides (AgO, ZrO<sub>2</sub>) via a microemulsion-assisted electrolysis method, leading to a uniform dispersion of the metal oxides across the fibrous framework. Among the synthesized composites, AgO/FSFe exhibited superior photocatalytic activity in dual removal of hexavalent chromium (Cr(VI)) and methyl orange (MO) compared to that of ZrO<sub>2</sub>/FSFe and pristine FSFe. Structural characterization confirmed the successful formation of Si–O–M bonds in AgO/FSFe and the electron transfer from AgO to FSFe, indicating strong interfacial interactions. This improvement results from an oxidative shift in the conduction and valence bands, which enables optimal band alignment and a stable <i>p</i>–<i>n</i> heterojunction structure, thereby minimizing electron–hole recombination, as supported by photoluminescence (PL), electrochemical impedance spectroscopy (EIS), and Mott–Schottky analyses. Scavenger experiments revealed that photogenerated electrons were the main contributors to Cr(VI) reduction, whereas ·OH radicals dominated MO degradation. Under optimized conditions (pH 3, catalyst dosage 0.25&#xa0;g&#xa0;L<sup>−1</sup>, initial concentrations of 20&#xa0;mg&#xa0;L<sup>−1</sup> Cr(VI) and 10&#xa0;mg&#xa0;L<sup>−1</sup> MO), the 10AgO/FSFe catalyst achieved simultaneous removal efficiencies of 64.37% for Cr(VI) and 99.45% for MO while maintaining its performance over five successive cycles, outperforming the photolysis and single-pollutant systems. Furthermore, the catalyst demonstrated versatility by effectively degrading additional organic dyes. This structure enhances charge separation and enables the simultaneous removal of heavy metals and organic pollutants, establishing AgO/FSFe as a durable and sustainable wastewater photocatalyst.</p>

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Oxidative Band Alignment Shift in AgO- and ZrO2-Modified Fibrous Silica Iron for Dual-Pollutant Photocatalysis

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年1月5日

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  • Nur Izzati Hannani Hazril,
  • Aishah Abdul Jalil,
  • Nurul Sahida Hassan,
  • Liew Shi Yan,
  • Muhammad Hakimi Sawal,
  • Nik Muhammad Izzudin,
  • Muhammad Hafizuddin Mohd Sofi,
  • Nurfatehah Wahyuny Che Jusoh,
  • Faiz Arith,
  • Sudiyarmanto Sudiyarmanto

摘要

Industrial wastewater treatment remains a pressing challenge owing to the coexistence of hazardous heavy metals and persistent organic dye contaminants that resist conventional remediation approaches. In this work, a fibrous silica iron (FSFe) catalyst was successfully incorporated with metal oxides (AgO, ZrO2) via a microemulsion-assisted electrolysis method, leading to a uniform dispersion of the metal oxides across the fibrous framework. Among the synthesized composites, AgO/FSFe exhibited superior photocatalytic activity in dual removal of hexavalent chromium (Cr(VI)) and methyl orange (MO) compared to that of ZrO2/FSFe and pristine FSFe. Structural characterization confirmed the successful formation of Si–O–M bonds in AgO/FSFe and the electron transfer from AgO to FSFe, indicating strong interfacial interactions. This improvement results from an oxidative shift in the conduction and valence bands, which enables optimal band alignment and a stable p–n heterojunction structure, thereby minimizing electron–hole recombination, as supported by photoluminescence (PL), electrochemical impedance spectroscopy (EIS), and Mott–Schottky analyses. Scavenger experiments revealed that photogenerated electrons were the main contributors to Cr(VI) reduction, whereas ·OH radicals dominated MO degradation. Under optimized conditions (pH 3, catalyst dosage 0.25 g L−1, initial concentrations of 20 mg L−1 Cr(VI) and 10 mg L−1 MO), the 10AgO/FSFe catalyst achieved simultaneous removal efficiencies of 64.37% for Cr(VI) and 99.45% for MO while maintaining its performance over five successive cycles, outperforming the photolysis and single-pollutant systems. Furthermore, the catalyst demonstrated versatility by effectively degrading additional organic dyes. This structure enhances charge separation and enables the simultaneous removal of heavy metals and organic pollutants, establishing AgO/FSFe as a durable and sustainable wastewater photocatalyst.