Chromium Ion Accumulations from Aqueous Solution by the Eichorinia crassipes Plant and Reusing in the Synthesis of Cr-Doped ZnO Photocatalyst

TLDR: The Cr-doped ZnO photocatalysts were synthesized through the chromium ion accumulations by water hyacinth (Eichhornia crassipes) in the preparation process, the plant tissues were immersed in different sample flasks containing chromium precursors for 1, 2, 4, 6, and 8 days as discussed by the authors .

Abstract: The Cr-doped ZnO photocatalysts were synthesized through the chromium ion accumulations by water hyacinth (Eichhornia crassipes). In the preparation process, the plant tissues were immersed in different sample flasks containing chromium precursors for 1, 2, 4, 6, and 8 days. The plant tissue containing chromium ion was mixed with zinc precursor followed by calcinations. For simplicity, the prepared Cr-doped ZnO samples with the plant immersed for 1, 2, 4, 6, and 8 days were abbreviated as D1, D2, D4, D6, and D8, respectively. Moreover, pure ZnO was also prepared without the water hyacinth plant accumulated with chromium ion for comparison purposes. The powder sample characterizations were performed and evaluated in the degradation of methylene blue (MB). The Cr-doped ZnO sample (D1) degrades 80% of MB dye while the D2, D4, D6, D8, and pure ZnO samples degrade only 74, 76, 79, 73, and 25%, respectively. On the other hand, without the addition of catalysts (blank), there was no significant degradation of MB dye within 90 min irradiation. Therefore, the degradation performance of Cr-doped ZnO in the presence of optimum amount of chromium dopant and water hyacinth is highly improved than that of pure ZnO. The catalytic improvement may be as a result of reducing the photogenerated electron and hole recombination rates due to the presence of dopants. Moreover, the presence of the Eichhornia crassipes plant in the synthesis of Cr-doped ZnO could also prevent further aggregations and particle size growth and enhance the porosity after calcination.