Photodegradation of malachite green and malachite green carbinol under irradiation with different wavelength ranges

A. R. Fischer, P. Werner, K. U. Goss

Research output: Contribution to journalArticlepeer-review

37 Citations (Scopus)


The dye malachite green (MG) is used worldwide as a fungicide in aquaculture. It is a toxic substance which in aqueous solutions is partly converted into its non-ionic colorless form (leucocarbinol). The equilibrium between these two forms is pH-dependent (pK=6.9). To assess the photodegradation of MG under sunlight conditions, both species were irradiated separately in aqueous solutions with different pH values (4.0 and 12.0) using various ultraviolet and visible wavelength ranges (UV/VIS). A 700W high-pressure mercury lamp with special filters was used. No artificial photooxidizers such as H2O2 or TiO2 were added. MG leucocarbinol proved to be much more sensitive to irradiation than the dye form. Quantum yields Φ were calculated for some wavelength ranges as follows: MG carbinol: Φ(280-312nm) is 4.3×10-3, Φ(313-410nm) is 5.8×10-3, and MG dye: Φ(280-312nm) is 4.8×10-5, Φ(313-365nm) is 1.1×10-5, and Φ(>365nm) is 0, respectively. Therefore, the solar photolysis of MG is an important sink and primarily depends on the photodegradation of the colorless leucocarbinol. During the irradiation of MG leucocarbinol with wavelengths >365nm, an intermediate was formed which has photocatalytical properties.

Original languageEnglish
Pages (from-to)210-214
Number of pages5
Issue number2
Publication statusPublished - Jan 2011
Externally publishedYes


  • Malachite green
  • Photocatalyst
  • Photodegradation
  • Quantum yields
  • Wavelength ranges

ASJC Scopus subject areas

  • Environmental Engineering
  • Environmental Chemistry
  • General Chemistry
  • Pollution
  • Health, Toxicology and Mutagenesis


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