| Summary: | Background. Works aimed at finding ecological and energy-saving technologies
for water purification from heavy metals are very relevant. The purpose of this work is to
study the methods of enhancing the completeness of copper, nickel and iron ions extraction
from the aquatic environment of Lemna minor L. under the influence of EMP EHF, as well
as its regeneration after the phytoremediation process in the presence of calcium cation additives
in solutions. Materials and methods. A G4-142 high-frequency signal generator was
used to study the processes of removing heavy metal ions (ITM) from model solutions
using an electromagnetic field (EMP) with a frequency of 65 GHz. After EMP irradiation,
Lemna minor L. plants were placed in model solutions based on settled tap water, simulating
waste water containing heavy metal ions (ITM). The residual amount of ITM after phytoremediation
was determined by voltammetric and photometric methods using a robotic
complex “Expertise VA – 2D” with an electrode “3 in 1” and KFK-3. Histochemical methods
were used in experiments on the regeneration of Lemna minor L. The statistical significance
of the differences was carried out according to the medians in the samples, calculating
the Kruskal – Wallis H-test. Results. As a result of the research, it was found that the
efficiency of cleaning model solutions from copper ions by irradiated Lemna minor L. was
85–90 %. This indicator is slightly lower than the efficiency of cleaning the solution with
Lemna minor L. not exposed to irradiation. The processes of copper extraction from solutions
were influenced by the nature of the anion. Copper cations were better extracted from
sulfate solution. The extraction of nickel ions by irradiated Lemna minor L. was more intense
than by unirradiated Lemna minor L., but in both cases at low rates. The extraction
efficiency of iron cations was 52–75 %. Experiments on regeneration of duckweed after
phytoremediation showed that mother and daughter cells are more resistant to heavy metals
than vegetative ones. Such resistance may be associated with the selectivity of the sensitivity
of various plant organs to chemical agents. Conclusions. It was found that under the action of EHF EMR of the 65 GHz range, the process of extraction by duckweed cations of
copper, iron and nickel proceeded more intensively. The efficiency of water purification
from ITM reached 75–90 %. The influence of the radius of the cation and the size of the
salt anion on the extraction rate of duckweed ITM was revealed. The positive effect of sulfate
ions on the process of penetration of metals into the volume of duckweed phytomass is
shown. The possibility of regeneration of duckweed after extraction of Ni2+ and Cu2+ ions
(C = 1 and 10 mg/L) with or without the addition of calcium ions is shown. At the same
time, duckweed fronds, after exposure to solutions with a copper cation content of 1 mg/l,
with subsequent planting on a nutrient medium, retained the ability to produce buds and
multiply. When the duckweed was kept in more concentrated media (Cu2+ 10 mg/l), even in
the presence of calcium, the plants died, that is, no regeneration took place. With the content
of nickel cation in the solution at concentrations of 1 and 10 mg/l, regeneration of
duckweed was achieved in the presence of calcium ions. The regeneration of duckweed did
not occur without calcium supplements.
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