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<p>This study investigates the valorization of Brazil nut shell agro-industrial waste into a potent, low-cost biosorbent (CAS) for the removal of the cationic dyes crystal violet (CV) and methylene blue (MB) from aqueous solutions. CAS was prepared and extensively characterized via SEM, XRD, N<sub>2</sub> physisorption, FTIR, and pH<sub>pzc</sub> analysis. Characterization revealed a highly irregular, macroporous, and predominantly amorphous structure with an exceptionally low <i>S</i><sub>BET</sub> of 0.941 m<sup>2</sup>g<sup>−1</sup>. Despite this, CAS showed excellent maximum adsorption capacities (<i>Q</i><sub>max</sub>) of 511.3&#xa0;mg&#xa0;g<sup>−1</sup> for CV and 490.0&#xa0;mg&#xa0;g<sup>−1</sup> for MB, as determined by the best-fitting Liu isotherm model, at 25&#xa0;°C. A predominantly chemical-surface-interaction mechanism resolves this paradox of high capacity in a low-surface-area material. The process is driven by strong electrostatic attraction between the cationic dyes and the negatively charged biosorbent surface (pH<sub>pzc</sub> 7.261) rich in accessible hydroxyl and carboxyl functional groups. Adsorption kinetics were rapid, best described by fractional-order models consistent with surface heterogeneity. Thermodynamic analysis confirmed the process is spontaneous (Δ<i>G</i>° &lt; 0), endothermic (Δ<i>H</i>° &gt; 0), and entropy-driven (Δ<i>S</i>° &gt; 0). CAS maintained ~ 70% removal efficiency after six regeneration cycles and achieved &gt; 99% dye removal from spiked river water. This work establishes CAS as a highly effective material for wastewater treatment, highlighting its potential as a sustainable and low-cost solution. Its alignment with circular bioeconomy principles is demonstrated by transforming an abundant agro-industrial waste into a high-value environmental remediation tool using a simple preparation method and offering good reusability.</p>

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Removal of crystal violet and methylene blue dyes from aqueous effluents using Brazil nut (Bertholletia excelsa) wastes as a potent biosorbent from Amazonia

  • 期刊论文

  • 发表日期：

    2025年10月1日

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  • Júlia Cristina Diel,
  • Matias Schadeck Netto,
  • Isaac dos Santos Nunes,
  • Luis Felipe Oliveira Silva,
  • Tito José Crissien,
  • Glaydson Simões dos Reis,
  • Eder Cláudio Lima,
  • Guilherme Luiz Dotto

摘要

This study investigates the valorization of Brazil nut shell agro-industrial waste into a potent, low-cost biosorbent (CAS) for the removal of the cationic dyes crystal violet (CV) and methylene blue (MB) from aqueous solutions. CAS was prepared and extensively characterized via SEM, XRD, N2 physisorption, FTIR, and pHpzc analysis. Characterization revealed a highly irregular, macroporous, and predominantly amorphous structure with an exceptionally low SBET of 0.941 m2g−1. Despite this, CAS showed excellent maximum adsorption capacities (Qmax) of 511.3 mg g−1 for CV and 490.0 mg g−1 for MB, as determined by the best-fitting Liu isotherm model, at 25 °C. A predominantly chemical-surface-interaction mechanism resolves this paradox of high capacity in a low-surface-area material. The process is driven by strong electrostatic attraction between the cationic dyes and the negatively charged biosorbent surface (pHpzc 7.261) rich in accessible hydroxyl and carboxyl functional groups. Adsorption kinetics were rapid, best described by fractional-order models consistent with surface heterogeneity. Thermodynamic analysis confirmed the process is spontaneous (ΔG° < 0), endothermic (ΔH° > 0), and entropy-driven (ΔS° > 0). CAS maintained ~ 70% removal efficiency after six regeneration cycles and achieved > 99% dye removal from spiked river water. This work establishes CAS as a highly effective material for wastewater treatment, highlighting its potential as a sustainable and low-cost solution. Its alignment with circular bioeconomy principles is demonstrated by transforming an abundant agro-industrial waste into a high-value environmental remediation tool using a simple preparation method and offering good reusability.