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<p>The discharge of heavy metals such as chromium ions into the rivers has caused a serious threat to the environment. This paper reports the reduction of Cr<sup>6+</sup> ions in the presence of a visible light source using eggshells-integrated graphitic carbon nitride. By optical investigations, the band gap of g-C<sub>3</sub>N<sub>4</sub> was found to have a value of 2.72&#xa0;eV. It was narrowed down to 2.62&#xa0;eV at the optimum composition of ES/g-C<sub>3</sub>N<sub>4</sub>. XRD confirmed the hexagonal structure of the composite. XPS and EDS confirmed the presence of C, N, Ca, and O elements, resulting in the successful preparation of ES/g-C<sub>3</sub>N<sub>4</sub>. The effects of several reaction parameters, such as the catalyst dosage, Cr<sup>6+</sup> ions concentration, and the solution pH, on the photoreduction rate were investigated. The results showed that the catalyst reduced around 81.3% of the chromium ions in 120&#xa0;min under optimized conditions. The kinetic data analysis deduced a pseudo-first-order model, and ES /g-C<sub>3</sub>N<sub>4</sub>&#xa0;has a higher rate constant compared to bare g-C<sub>3</sub>N<sub>4</sub>. The k value of ES/g-C<sub>3</sub>N<sub>4</sub> is 2.3 times greater than g-C<sub>3</sub>N<sub>4,</sub> signifying the photoreduction efficiency is high for the composite. The R<sup>2</sup> of g-C<sub>3</sub>N<sub>4</sub>, ES, and ES/g-C<sub>3</sub>N<sub>4</sub> was found to be 0.909, 0.895, and 0.981, respectively. The pseudo-first-order model has a higher R<sup>2</sup> than the second-order model, proving that the process is likely physisorption. The crystalline structure of the photocatalyst was stable for up to 4 cycles. Hence, ES/g-C<sub>3</sub>N<sub>4</sub> has the characteristics of acting as a viable and sustainable material for heavy metal reduction.</p>

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Photocatalytic reduction of Cr (VI) ions using eggshells/graphitic carbon nitride composite

  • 期刊论文

  • 发表日期：

    2025年6月1日

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  • J. Ambigadevi,
  • P. Senthil Kumar,
  • B. Chitra,
  • G. Rangasamy

摘要

The discharge of heavy metals such as chromium ions into the rivers has caused a serious threat to the environment. This paper reports the reduction of Cr6+ ions in the presence of a visible light source using eggshells-integrated graphitic carbon nitride. By optical investigations, the band gap of g-C3N4 was found to have a value of 2.72 eV. It was narrowed down to 2.62 eV at the optimum composition of ES/g-C3N4. XRD confirmed the hexagonal structure of the composite. XPS and EDS confirmed the presence of C, N, Ca, and O elements, resulting in the successful preparation of ES/g-C3N4. The effects of several reaction parameters, such as the catalyst dosage, Cr6+ ions concentration, and the solution pH, on the photoreduction rate were investigated. The results showed that the catalyst reduced around 81.3% of the chromium ions in 120 min under optimized conditions. The kinetic data analysis deduced a pseudo-first-order model, and ES /g-C3N4 has a higher rate constant compared to bare g-C3N4. The k value of ES/g-C3N4 is 2.3 times greater than g-C3N4, signifying the photoreduction efficiency is high for the composite. The R2 of g-C3N4, ES, and ES/g-C3N4 was found to be 0.909, 0.895, and 0.981, respectively. The pseudo-first-order model has a higher R2 than the second-order model, proving that the process is likely physisorption. The crystalline structure of the photocatalyst was stable for up to 4 cycles. Hence, ES/g-C3N4 has the characteristics of acting as a viable and sustainable material for heavy metal reduction.