Studies have shown that the use of chelating compounds in directed phytoextraction significantly increases the uptake of heavy metals by plants . In the course of this study, laboratory experiments were carried out to obtain results on the possibility of using Eichhornia crássipes with the chelating phosphorus-containing agent of disameted potassium salt of oskietilidene diphosphonic acid (K2HEDP) to purify various heavy metal compounds Cd, Hg, Cu, Ni, Cr and Co from water . For the intensification of cleaning processes artificial roots from polymeric materials are used, which create a considerable surface area. In particular, artificial roots contribute to the acceleration of biological decomposition through increased activity of micro-organisms settling on the surface of fibre .
The experimental installation is a simulation of a closed water body consisting of 7 water-filled containers with a capacity of 40 litres each. Mat platforms with higher aquatic plants planted in them are placed in the tanks. Air temperatures and water are 26℃ and 18℃, respectively. Heavy metal salts at different concentrations were included in some containers: 60 mg/l (ZnSO4) and 60 mg/l (NiSO47H2O). Nanocarbon fibers were also added to honor the containers. Above containers there is a lighting system consisting of light-emitting diode phytolamps, which emit a sufficient amount of light for 16 hours a day.
The main element of the bioplato is the higher aquatic plants of aquatic Eichhornia crássipes. Plants are not intricate in their care: they prefer sunlit areas or semi-shadows and high moisture levels. These plant species regenerate contaminated water bodies due to the good absorption capacity of the root system . They are also uncomfortable in continental climates, grow relatively quickly (1,5-2 weeks) and have high aesthetics (they are also used for decorating water bodies) .
The experiment consists of experience with the dissolution of heavy metal salts in water and further observation of the hypoacumulation capacity of plants depending on the presence or absence of an artificial root system, soaked in disubstituted potassium salt of osietilidene diphosphonic acid. The experiment was conducted over 18 days. The sampling was carried out in accordance with GOST 31861-2012 «Water. General sampling requirements». To determine the heavy metal content of all experiments, the samples were analysed using an atomic emission spectrometer with inductively bound plasma iCAP6300 Duo.
The data obtained showed that the use of a double mass of carbon fiber to increase the absorption surface of the root zone in comparison with a single mass does not significantly affect the absorption of Zn ions. However, for Ni ions, an increase in the mass of carbon fiber had an effect increased the absorption capacity of the roots of Eichhornia crássipes by 5%. Soaking artificial carbon fiber in a K2HEDP solution showed the opposite result. Phytoextraction is much worse. Moreover, a decrease in the mass of carbon fiber and, accordingly, the amount of a K2HEDP increase phytoextraction by 4-9% for Zn ions and by 12-24% for Ni ions. Thus, it can be concluded that the most effective use of a double mass of carbon fiber without soaking in the disubstituted potassium salt of osietilidene diphosphonic acid.
This study is funded by the Russian Foundation for Basic Research under research project № 18-29-25068 and MUCTR project № 3-2020-039.
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|Publication||IOP Conference Series: Earth and Environmental Science|
|Affiliation of speaker||Tatyana Avdeenkova|