Feasibility Study on Phytoremediation of Malachite Green Dye from Contaminated Aqueous Solutions Using Watercress (Nasturtium Officinale)

Malachite green dye is used in many industries including textile industries. Disposal of wastewaters containing the dye to the environment, can lead to many environmental problems. Currently, many physico-chemical approaches are used for wastewater treatment. Because of limitations and difficulties of these methods, biological treatment is considered as an economic and effective treatment method. The aim of the present study was to study the feasibility of phytoremediation of malachite green dye using watercress and investigate the effect of some environmental factors in removal efficiency.
After collection, the plants were kept in the laboratory, and they were treated with different concentrations of malachite green. During the experiments, decolorization extent was determined by UV-Vis spectrophotometry. Intermediate compounds generated during the biodegradation of the pollutant were identified using GC-MS method.
After 7 days, the ability of watercress in removal and biodegradation of 10 mg/L of malachite green solution was more than 90%. Five intermediate compounds were identified in the biodegradation pathway of the pollutant. It was also found that increasing dye concentration up to 20 mg/L led to the increase of the plant photosynthetic pigment contents and activities of antioxidant enzymes.
Our results showed that watercress has high ability in the dye removal of malachite green. The reusability of the plant for decolorization confirmed the biological degradation process. Moreover, an increase in the plant biomass, temperature and pH led to the increased decolorization efficiency.