An international team of scientists, in which researchers from the
University of Barcelona (UB) have participated, has applied ultrasound
treatment that enables ibuprofen to be eliminated from waters polluted
with this drug. This method could be used in water purification plants,
which would avoid the emission of pharmaceutical pollutants into rivers,
lakes, seas and other surface waters.
The team of scientists at the laboratories of the Federal Polytechnic
School in Lausanne, Switzerland has developed a novel method for
eliminating pharmaceutical products from water. The substance chosen for
the study was ibuprofen, as it is one of the drugs that appears with the
most frequency in the analyses of waste waters due to its high consumption
as an anti-inflammatory and analgesic.
"Pharmaceutical compounds are pollutant substances from the moment in
which they maintain their pharmacological activity outside the environment
for which they were designed", Fabiola Méndez-Arriaga explains to SINC.
She is the co-author of the study and a researcher at the Department of
Chemical Engineering in the University of Barcelona (UB).
The new technique consists of subjecting water polluted with ibuprofen
to ultrasonic waves that are generated by a piezoelectric generator, which
converts electrical energy into mechanical energy and is located at the
bottom of the reaction tank. In this way the drug is totally eliminated.
During the application of ultrasonic waves to the polluted liquid a
physical and chemical reaction is generated known as "sonolysis", in which
water (H2O) is disassociated in highly oxidant radicals such as hydroxyl
(-OH). This radical facilitates the oxidation and breaking down of
ibuprofen into other low-molecular mass compounds.
How is this drug eliminated?
In this process, during which carbon dioxide (CO2) is produced,
"cavitation bubbles" are generated. These bubbles look similar to those
generated in boiling water, but they are microscopic in size, and a large
quantity of energy accumulates inside the bubbles (up to a pressure of 200
bar and 2,000 oC in temperature).
"Ultrasonic waves are applied for half an hour and this enables up to
98% of ibuprofen to be broken down and after two hours of irradiation the
drug is eliminated completely and transformed into biodegradable
substances which can be removed or eliminated in a conventional
purification plant", states Méndez-Arriaga.
"Although this is not the case with ibuprofen", remarks the researcher,
"sometimes during the breaking down process of the pharmaceutical
compounds, substances more toxic than the original compound itself are
produced. For this reason the evolution of this toxicity has been studied
using other advanced oxidation techniques and their hybrid combinations".
One of these techniques is heterogeneous photocatalysis (a reaction in
which a semiconductor such as titanium dioxide absorbs UV light to break
down the organic pollutants into CO2, water and mineral acids, which are
harmless to the environment). Another technique is the photo-Fenton
reaction in which iron salts, oxygenated water and light are used to break
down the compounds).
Méndez-Arriaga points out that the final objective of these techniques
is to eliminate pharmaceutical compounds from the environment, where they
end up after consumption, thanks precisely to the chemical properties they
were created with, namely their biological resistance and high solubility.
Pharmaceutical products or their metabolised forms are released into
the environment through excretion (domestic, veterinary or hospital),
disposal of unused surplus or expired products and also with the waste
from drug manufacturing plants.
Consequences for the fauna
In nature it is the fauna which is mainly affected by these compounds.
Scientists from North American universities have shown, for example, that
exposure to anti-depressants delays the development of the legs in
tadpoles and that pharmaceutical products and toiletries, such as
perfumes, cause toxic effects in the swordfish and other marine species.
Méndez-Arriaga''s study highlights that it is very difficult to know
the quantity of pharmaceutical pollutants found in water; however it can
be asserted that it is a world-wide health problem, for which there is
still no defined legal framework.
SOURCE: University of Barcelona