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The chelating agent EDTA (ethylenediaminetetraacetic acid) is a compound of massive use world wide with household and industrial applications, being one of the anthropogenic compounds with highest concentrations in inland European waters. In this review, the applications of EDTA and its behavior once it has been released into the environment are described. At a laboratory scale, degradation of EDTA has been achieved; however, in natural environments studies detect poor biodegradability. It is concluded that EDTA behaves as a persistent substance in the environment and that its contribution to heavy metals bioavailability and remobilization processes in the environment is a major concern.
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Quim. Nova, Vol. 26, No. 6, 901-905, 2003
Claudia Oviedo and Jaime Rodríguez*
Renewable Resources Laboratory, Universidad de Concepción Casilla 160-C, Concepción, Chile
Recebido em 6/3/03; aceito em 28/4/03
(ethylenediaminetetraacetic acid) is a compound of massive use world wide with household and industrial applications, being
one of the anthropogenic compounds with highest concentrations in inland European waters. In this review, the applications of
EDTA and its behavior once it has been released into the environment are described. At a laboratory scale, degradation of EDTA
has been achieved; however, in natural environments studies detect poor biodegradability. It is concluded that EDTA behaves as
a persistent substance in the environment and that its contribution to heavy metals bioavailability and remobilization processes
in the environment is a major concern.
Keywords: EDTA; environment; degradation.
Metal ions cause detrimental effects in several industrial proces-
ses and in the formulation of many products. Earth alkaline divalent
cations such Ca(II), Mg(II) and Ba(II) form insoluble precipitates
with carbonates, sulfates and phosphates. In addition, the presence
of transition metal ions such as those of copper, iron, zinc and
manganese may trigger chemical processes of corrosion, catalytic
degradation, polymerization inhibition, redox reactivity and changes
in the coloring of products1. In industrial processes these metal cations
may come from the process waters, raw materials, equipment erosion
and corrosion. They may also be added as a specific metal species,
but they may later suffer undesired alterations due to changes in
concentration, pH, oxidation, or reactions with other ingredients
during the process. EDTA is a chelate ligand with a high affinity
constant to form metal-EDTA complexes, being deliberately added
to sequester metal ions .
EDTA was patented in Germany in 1935 by F. Munz. The
molecule is a substituted diamine (Figure 1) usually marketed as its
sodium salts. It is a powerful complexing agent of metals and a highly
stable molecule, offering a considerable versatility in industrial and
household uses2 (Table 1). Since it is applied predominantly in
aqueous medium, it is released into the environment through
wastewaters. Its presence in soils may be due to agrochemical
application or to the disposal of products containing EDTA in garbage
reservoirs. It is highly unlikely to find the compound in the air because
of the impossibility of volatilization from waters or soils. Although
this could occur for example, in the event of aerial application of the
compound (e.g.: agrochemical application).
The product is marketed worldwide under 30 different trademarks
and its use in the world is massive and increasing3. In 1992, the
annual consumption in Europe was in the order of 26,000 tons4 and
in 1997 this value had increased to 32,550 tons5. Given the magnitu-
de of this use, EDTA is one of the organic pollutants found in highest
proportions in surface waters in central Europe6,7.
As it can be seen in Table 1, the main application of EDTA is in
cleaning products and detergents based on perborates as stabilizers
and, in some countries, as an alternative to phosphates in detergent
formulation. In 1990, a consumption of 25,000 tons was estimated
in Germany in laundry detergents8.
The use of the chelate in the pulp and paper industries is of
considerable magnitude (13% of the world market). This proportion
could increase progressively if the pulp and paper industry favors
pulp producing processes in which bleaching is free from chlorine
containing compounds or TCF pulp (totally chlorine free). EDTA or
DTPA (diethylenetriaminepentaacetic acid) are used to avoid the
undesirable effects of ferric, cupric and manganic ions in bleaching.
In the bleaching stage with hydrogen peroxide or ozone, those metals
promote the formation of hydroxyl radical (OH·) which destroys the
cellulose fiber and decompose the bleaching agents. In some cases,
Table 1. Industrial and household uses of EDTA and its ligands (as
percentages of the world market)a
Use % of world market
Detergents 33
Water treatment 18
Pulp and Paper Industry 13
Photography 5
Metal Cleaning 5
Cosmetics, foodstuffs, pharmaceuticals 5
Agrochemicals 4
Textile Industry 4
Printing inks 3
Concrete admixtures 2
Miscellaneous 12
a Modified from ref. 2
Figure 1. Molecular structure of EDTA
902 Quim. NovaOviedo and Rodríguez
chelators are also used during the oxygen delignification stage. It is
illustrative to point out the Scandinavian situation, where a rapid
increase in the consumption of EDTA and DTPA has been observed,
associated with the production of TCF pulp. It should be born in
mind that the Scandinavian pulp and paper industry alone used 23,000
tons of chelating agents during 19983 which is close to the 26,000
tons of the total consumption of EDTA in Western Europe in 19924.
There is increasing concern about the direct or indirect potential
effects of the presence of EDTA in the environment. Numerous field
studies have shown that complexation with EDTA may mobilize
contaminant metal ions. EDTA may avoid the precipitation of heavy
metals in solution or, on the contrary, cause a dissolution effect of
heavy metals adsorbed in sediments7,9,10. Hence, the result is an
enhanced mobilization of heavy metals. Attention has also been paid
to the fact that EDTA can solubilize radioactive metals and increase
their environmental mobility12-14.
Another aspect to be considered, is the possible contribution of
EDTA in eutrophication water processes. Sillanpää7 warns that this
phenomenon is relevant, since the molecule contains approximately
10% of nitrogen that could eventually be available to the aquatic
microbiota. EDTA would also have an indirect effect, when it
redissolves the calcic and ferric phosphates, releasing phosphorous
and thus contributing to an increase in the productivity of the waters.
There could also be a larger bioavailability of Fe+3 (essential
micronutrient for microalgae) thus stimulating their growth.
Although the isolated molecule does not present a risk of
bioaccumulation, the ligand-metal complexes may significantly
increase the bioavailability of extremely dangerous heavy metals. In
fact, the dissolution and bioavailability of heavy metals are
phenomena worth of greater attention. Vassil et al.15 studying the
role of EDTA in the consumption of lead in a variety of the mustard
plant, discovered a concentrating effect of 75 times, which is highly
significant if account is taken that it is a potentially dangerous
phenomenon in terms of metal biomagnification processes. Enhanced
uptake of heavy metals by plants has been extensively studied16-18
due to its potential use in heavy metal phytoextraction technologies,
but special attention has been paid to their concomitant lixiviation
and migration phenomena17.
Dufková19 studied the interaction of EDTA with photosynthetic
organisms and found that EDTA is toxic, since it inhibits cellular
division, chlorophyll synthesis and algal biomass production. It is
interesting to note that the same concentration of EDTA chelated
with micronutrients did not present these toxic effects.
Greman et al.17 found strong inhibitory effects of EDTA over
plants such as: necrotic lesions on leaves of Chinese cabbage, absence
of development of arbuscular mycorrhizae in Red clover plants, and
stress on soil microfauna, being soil fungi the most affected
Research of the cellular toxicity of chelates indicates, in general,
noxious effects normally attributed to the lack of metals essential to
various cellular functions. The findings of Hugenschmidt et al.20 are
particularly interesting. They trace the effects of chronic exposure to
low levels of EDTA (< 100 µM) in cultured cells of rat kidney,
resulting in high rates of cellular death. In addition, Gabard21 reported
inhibition of DNA, RNA and protein synthesis due to the chelation
of zinc and manganese in rat liver cells after EDTA-Ca(II)
Regarding to oral human exposure, Fe(III)-EDTA salts are
considered safe and used as an iron supplement22 source. However, a
recent study proposes carbonyl iron as a better fortificant than
NaFeEDTA salts, because it resulted to be less toxic when tested in
acute toxicity in young rats23. Free EDTA has been shown to produce
adverse reproductive and developmental effects in mammals.
However, it is considered as a safe substance if used externally; which
is relevant considering that EDTA is a common ingredient in cosmetic
EDTA has antibacterial activity and metal chelation of the ligand
reduces this activity25. The effect of chelating agents upon gram
negative bacteria has been reported. EDTA causes disruption of the
outer membrane, since it is capable of removing its calcic and
magnesic divalent cations, with the consequent loss of substantial
amounts of lipopolysacharide, which in turn, make cells susceptible
to the action of many substances such as detergents, proteases, lipases
and lysozymes26-28. Hennecken et al.4 clearly show a total inhibition
of a bacterial consortium by free EDTA, these bacteria only manage
to degrade EDTA if it is complexed with equimolar quantities of
calcium or magnesium ions.
Paradoxically, even though literature provides evidence of the
persistence and low natural degradability of the chelate, the study of
its toxicity is basically documented for acute toxicity bioassays and
there is not sufficient information for the evaluation of chronic
Until recently, it used to be postulated that the concentration of
free metals in solution was the main factor in the bioavailability and
toxicity of metals. It has also been proved that heavy metals
complexed with EDTA (and also with humic acids) are biologically
available and toxic. This has been demonstrated in the study of
Tubbing et al.28 with river microalgae in which photosynthesis is
inhibited at low concentrations of EDTA chelated with copper (II)
(5-10 µM) and unchelated EDTA. As stated previously, this is also
evident in the work of Vassil et al.15.
Acute toxicity bioassays have been used to compare the toxicity
of free heavy metals (Hg+2, Cd+2, Pb+2, Zn+2, Cu+2, Fe+3, Mn+2 ) with
the EDTA-complexes, in Photobacterium phosphoreum bacteria29
and for the fresh water cladoceran Daphnia magna30. These studies
show that the formation of the chelate-metal coordination compound,
achieves a decrease in the toxicity of free heavy metals. On the
contrary Guilhermino et al.31 found that Cd(II)-EDTA and Cu(II)-
EDTA complexes were more toxic than their respective free metals
in acute toxicity test in Daphnia magna.
Although there is not enough research describing the behavior
of the chelate in surface waters, it can be seen that this is a complex,
multivariable and dynamic phenomenon, which makes it difficult to
predict fate and to quantify the speed of the processes involved. Some
authors warn that the theoretical calculations based on chemical ba-
lance are not a useful tool for predicting EDTA speciation in effluents,
since the kinetic dimension of the processes of metal interchange
cannot be overlooked32,33. The influence of the suspended material
and the consequent occurrence of adsorption and desorption
phenomena on their surface, must be also considered.
The validity of the theoretical approximation is further diminished
if account is taken of the fact that EDTA is one of many natural and
anthropogenic ligands which can be found in the aquatic medium.
Moreover, the geochemical nature of rocks underlying the type of
fresh water studied must be taken into consideration, since this will
influence the pH and the provision of metals to the waters.
In natural environments EDTA occurs as metal–EDTA
complexes. At present, there is not enough information on the aquatic
speciation and on the natural ligands competition phenomena which
are crucial for predicting the metal-EDTA complexes environmental
903EDTA: the Chelating Agent Under Environmental ScrutinyVol. 26, No. 6
fate33. Table 2, shows some of the ranges of concentration of EDTA
found in natural waters. The highest value has been found in England
(1120 µgL-1).
In surface waters, the only significant process of removal of EDTA
is the possibility of photolysis by means of the action of sunlight
upon the Fe (III)-EDTA complex32,34. It could be possible, in theory,
to speculate on a continuous photolysis of the complex EDTA-Fe(III)
which would entail the massive degradation of the chelate. However,
Kari and Giger32 point out the factual impossibility of such
phenomenon on the basis of the intensity of light and the adsorption
phenomena of photostable complexes of EDTA. This is in agreement
with its relatively high concentrations that have been found in
European continental waters6,7.
According to the literature, there may be photolysis under high
transparency conditions and in shallow watercourses. In the study of
Kari and Giger32, performed in natural waters, photodecomposition
of the EDTA-Fe(III) complex is reported as the main degradation
The studies on the photodegradability of EDTA in the
environment should also take into account the cloud cover in the sky
and suspended material in the waters, since these are factors that
condition the intensity of light received by water32,34.
Essentially, the studies of EDTA behavior in soil and ground
water attempt to verify metal lixiviation phenomena. The possibility
that organic anthropogenic ligands increase the concentration of
metals dissolved in subsoil water has been formulated. Nowack et
al.35 established that EDTA behaves as a persistent substance in its
passage towards ground water and that its speciation varies.
Remobilization of metals through the infiltration course of water
from a calcarean lithic riverbed towards subsoil water was
The removal of heavy metals in soil by EDTA is known and in
fact, it is a proposed technique for washing soil contaminated with
heavy metals36-38. With respect to the passage of EDTA to ground
water, through the soil, it is necessary to mention a mobility study of
heavy metals in a landfill by Lo et al.9 They establish that the presence
of EDTA inhibits the adsorption of heavy metals to the soil, thus
inducing their lixiviation.
The mobility of heavy metals in soils is conditioned by numerous
factors, among which, CO2 partial pressure, temperature, dissolved
organic matter, micro-organisms, identity of the metal(s) and its (their)
respective concentration(s), etc. Thus, the way, in which EDTA
influences the mobility of metals, is also multivariable and complex39.
The possibility of finding EDTA biodegrading activity in ground
water and soil would be of interest, since in this substrate photolysis
could not constitute a degradation option. However, significant
biodegrading activities have not been found. There are only registers
of poor and slow performances of microbial consortia in soil and
subsoil 40-42.
EDTA resistance to bacterial biodegradation is widely
documented41-44. The compound is harmful to gram negative bacteria,
causing the destruction of their outer membrane26-28.
At laboratory scale, biodegradation by enriched bacterial cultures
has been achieved. Nörtemann5, suggested catabolic pathways of
EDTA in bacteria, this approach considers uncomplexed EDTA
entrance to the cell, and shows the loss of an acetyl group as the first
step in this intracellular oxidation. However, it has been recently
demonstrated that the bacterial strain DSM 9103 (located in the
Rhizobium-Agrobacterium branch), degrades EDTA as a sole carbon
source and it is able to perform the cellular uptake of the metallic
complex EDTA-Ca (II), with intracellular calcium polyphosphates
accumulation45. The identified bacterial strains with EDTA degrading
abilities are all aerobic, gram negative bacteria46.
In cases in which degradation of the chelate has been proved, it
is necessary to point out that both the metal-chelate speciation and
the bacterial species in question, are determining factors in the ability
to degrade the compound. Thus, in certain cases there is only the
ability to degrade metal-chelate complexes of low stability constant,
as for example EDTA-Ca (II) and EDTA-Mg (II) complexes4,45,47 and
that in other cases, the exact opposite occurs: the EDTA-Fe(III)
complex with a high stability constant is degraded13,48,49. Furthermore,
from the data available for the intracellular catabolism of EDTA, no
generalizing pattern with respect to the influence of metal speciation
on degradation can be deduced50.
Table 3 presents the data of bacterial activities with complete
EDTA mineralization and their respective references. Palumbo et al.13
found that the bacterial ability to degrade EDTA is rare, since they
could not obtain degrading consortia from places polluted with the
chelate. The only degradation achieved was with a strain of
Agrobacterium sp. previously isolated from a nuclear waste disposal
facility and of known EDTA degrading activity, and not with other
related Agrobacterium strains.
In drinking water plants
In drinking water plants, filtering trough activated carbon is
useless to remove the chelate (given its hydrophilic character).
According to Gilbert and Hoffmann-Glewe51, in drinking water
producing plants with ozone treatment it is possible to degrade EDTA,
the degree of degradation depending on the ozone level.
Attempts have been made to degrade EDTA, in order to produce
drinking water, by means of technologies contemplating the use of
photochemical oxidation systems like UV/H2O2 treatment52,53.
However, the same authors warn that the required concentration of
Table 2. EDTA in natural waters b
Range of concentration Type of fresh Location
(µgL-1) water
158 River France
14 -1120 River England
3.4 - 22.2 River Germany
2.9 Lake Germany
9.1 - 28.0 River Germany
900 River Jordan
5.0 - 60 River Germany
2.0 - 45 River Switzerland
10 - 80 River Germany
7 - 104 River Germany
0.52 Lake Greece
5.85 Sea Greece
1.6 - 13.5 River Germany
2.6 - 29.2 Surface Netherlands
2.0 – 25 River Germany
1.7 - 44.0 Lake Finland
b Data extracted from refs. 7 and 75
904 Quim. NovaOviedo and Rodríguez
peroxide is such that the residual peroxide exceeds the peroxide
concentration allowed by the German standards they also point out
that by-products of EDTA degradation can be promoters of microbial
re-growth. In order to avoid the potential microbial enrichment, they
suggest a later chlorinating phase, but they do foresee the potential
danger of the production of highly toxic substances resulting from
this step, as well as pointing out that chlorinating might be inefficient,
since both glycinate and iminodiacetate (products of EDTA
degradation through UV/H2O2 treatment) may reduce the disinfecting
ability of the chlorinating step since they can be substrates of
microbial growth.
In waste water treatment plants
Most of the reports indicate that biological treatments are not
efficient in the degradation of the chelate. Hinck et al.44 evaluate EDTA
biodegradation in a complete study using four types of different
sludge, finding a total absence of EDTA degradation.
The chelate passes unmodified through wastewater treatment
plants because of its resistance to biodegradation and scarce
adsorbability. Thus, in Swiss sewage treatment plants equipped with
both chemical and biological treatment systems, it is found that no
significant EDTA elimination is achieved54,55. Nirel et al.55 found that
10 of 12 domestic sewage treatment plants had EDTA in their
effluents. In industrial waste water treatment plants, the chelate
generally shows poor biological degradability44,56 and presents two
additional problems: it affects their efficiency to remove heavy metals
and increases the charge of dissolved nitrogen in effluents.
Saunamäki56, shows EDTA increases the level of nitrogen released
by activated sludge of a pulp plant run under TCF processes , which
is highly undesirable since this input could increase the receiving
water’s productivity. The study also reported that activated sludge
treatment does not remove the chelate but that, with the addition of
aluminum sulfate, a 65% removal of EDTA was achieved.
Sillanpää57, reports a 17% to 30% of EDTA reduction, in three
plants of activated sludge of finish pulp and paper mills. Using a
synthetic TCF cellulose bleaching effluent Mutis et al.58 report a
maximum of 33% EDTA removal and 19% DTPA removal in
activated sludge acclimatized to a mixture of EDTA and DTPA.
Virtapohja and Alén59, reported an increase in the degrading efficiency
in activated sludge from pulp and paper effluents, when operating
with alkaline pH, in which an average EDTA reduction of 10% at
neutral pH, increases to 50% at pH 8 to 9. The greatest degrading
efficiencies are reported by Van Ginkel et al.60 with an 80% EDTA
degradation at pH 8 and by Kaluza et al.61 which reached an 80%
removal in a pulp and paper mill TCF effluent.
The presence of EDTA and DTPA cause serious effects in the
biological treatment system, being more notorious with EDTA58.
EDTA is undesirable in biological treatment systems specially of
those used to achieve metal removal, because the ligand prevents
bacterial metal adsorption phenomenon62. These results have lead to
the study of chemical treatment previous to the biological systems to
increase the efficiency of this last one.
At laboratory scale, combined UV/H2O2 treatment achieves rapid
degradation in a synthetic TCF effluent63; just like the combined UV/
ozone treatment proved to be very efficient in the degradation of
EDTA and DTPA chelates (98%) degradation on synthetic TCF
effluent64. The use of catalytic photooxidation processes to degrade
EDTA is also currently being studied65-66, in which a semiconductor
like TiO2 or iron doped TiO2 is used and activated by means of
ultraviolet light. It has also been suggested that in order to treat large
quantities of waste water, it would be economically more convenient
to perform a pre-treatment combining ozone or TiO2 with the use of
ionizing radiation (gamma rays) followed by a classic phase of
biodegradation68. The authors foresee that the main problems of the
former techniques are energetic and economic, apart of achieving a
complete toxicity assessment of the resulting by-products.
EDTA degradation has been attempted by diverse AOTs which
has been extensively reviewed by Sillanpää and Pirkanniemi69. These
technologies include: γ-radiolysis68, TiO2 photocatalysis66, UV/O3
53,64, solar ferrioxalate/H2O2
70, UV/electrochemical
treatment71, Fenton treatment H2O2/Fe(II)72, CAT-driven Fenton
reaction73, H2O2 microwave-activated photochemical reactor
treatment74 among others.
In general, it can be seen that EDTA behaves as a persistent
pollutant in the environment, enhancing the mobility and
bioavailability of heavy metals. In natural environments studies detect
poor bio-degradability of the ligand.
The interaction mechanisms of EDTA with living organisms are
not sufficiently clarified and the range of their potential risks is not
known. The studies that evaluate the toxicity of free heavy metals
and complexed with EDTA do not enable the prediction of what the
effect of the chelate presence will be. The effects of EDTA vary
according to the type of organism studied, the concentration of EDTA
and the metal analyzed.
There is an urgent need to investigate more on the bioaccumulation
of heavy metals in the trophic chain promoted by EDTA and on the
remobilization effect of metals in waters and soils. Studies on the
potential risk of increased bioavailability of heavy metals by edible
plant species exposed to metal-EDTA complexes are also missing.
The studies made so far, have focused, predominantly, on the
evaluation of the bacterial ability to biodegrade EDTA at a laboratory
scale, and it is to be noted that this property is extremely scarce in
We thank FONDECYT Grant No 1010840 and to Dr. S.
Valenzuela for the critical lecture of the manuscript.
Table 3. Microbial mineralization of EDTA
Degrading Microorganism Tested concentration Time (days) Reference
Agrobacterium sp. 35 mM 3 48
Agrobacterium sp. 35 mM 2.8 13
Activated sludge 3 mM 5 76
Bacterial strain DSM 9103 1 mM < 0.5 45
Bacterial consortia rich in strain BNC11.53 mM 3.3 77
Soil consortia and agricultural sediment 4 ug 14C-EDTA/g of soil 28 – 49 40
Surface and subsurface soil consortia 0.01mM 115 41
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... Ethylenediaminetetraacetic acid (EDTA), a substituted diamine compound, is a well-known and highly effective polydentate ligand, prone to share six electron pairs to form metal-complexes entropicallystabilized by the chelate effect. Widely commercialized as a metal sequestering agent, it has shown high versatility in many industrial processes and formulations of countless products [1]. Its presence is markedly found in detergents, cosmetics, food additives, pharmaceuticals, agrochemicals and printing inks, while it participates in water treatment, pulp and paper bleaching, galvanic electrodeposition baths, general metal cleaning and textile industry processes [1]. ...
... Widely commercialized as a metal sequestering agent, it has shown high versatility in many industrial processes and formulations of countless products [1]. Its presence is markedly found in detergents, cosmetics, food additives, pharmaceuticals, agrochemicals and printing inks, while it participates in water treatment, pulp and paper bleaching, galvanic electrodeposition baths, general metal cleaning and textile industry processes [1]. In analytical chemistry, EDTA is classically applied in complexometric titrations to determine the concentration of various metals [2], and is the standard reagent in the hardness test protocols published, e.g., by American Petroleum Institute (API) [3]. ...
... It is released to the environment mostly via wastewaters [1] and causes increased mobility and bioavailability of toxic metals [4][5][6][7] (including radioisotopes [8][9][10]) in water bodies. Some metal-EDTA complexes have shown higher acute toxicities than the free-metal itself [11], that's why, EDTA has been listed as an emerging contaminant in waters of the class of industrial additives and agents [12][13][14][15]. ...
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EDTA is an important metal sequestering agent in industrial processes and household products, but also an emerging pollutant and a challenge for wastewater treatment due to its high resistance to biodegradation. Conventional strategies for recovering metals from the metal chelates require a previous oxidation step. Herein, P25 TiO2 photocatalyst was applied to assemble nanoparticulate films on gold (model conducting substrate) with highly reproducible photocatalytic activity toward EDTA and Cu(II)-EDTA (model chelate) UVA-photooxidation. Films were obtained from P25 suspensions in acidic medium by a quick cold drop-casting method without thermal annealing. The involved TiO2 agglomerates were characterized by Dynamic Light Scattering (DLS), Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), voltammetric DC techniques and zero-current chronopotentiometry. Photocatalytic treatment of Cu(II)-EDTA solutions and electrochemical essays were accomplished in a thin layer-type cell coupled with a 365 nm UV-LED. Synthetic samples of the chelate at stoichiometric ratio or with EDTA in excess were exposed to the irradiated TiO2 film to promote the photooxidation of the ligand, and recovery of copper mainly by direct (photo)electrodeposition on gold. Three potential programs were tested during UV-irradiation: open circuit potential (OCP), +0.5 V and –0.3 V vs Ag/AgCl. Overall best results were obtained at –0.3 V, showing that it is more effective to favor in-situ metal reduction rather than collecting photogenerated electrons via +0.5 V biasing to diminish electron/hole (exciton) recombination. Nevertheless, operation without external biasing, i.e., at OCP, is nearly as effective since the substrate is spontaneously driven to circa –0.7 V by photogenerated electrons plus electrons injected into photoholes by EDTA, as it oxidizes. The Cu(II)-EDTA treatment can be abbreviated by coupling both redox processes at the same photoelectrode, thus, avoiding the transport of Cu(II) from the photoanode to the cathode, conceivably with risk of rechelation, like in conventional photoelectrochemical cells. Similar results were obtained with the TiO2 drop-casted on other conducting substrates including carbon, a relevant finding for a forthcoming scale-up of the treatment process.
... The literature shows a range of organic ligands of this type, some of which have been approved for use in medicine and agriculture. These include ethylenediaminetetraacetic acid (EDTA) [36], N-(hydroxyethyl)ethylenediaminetriacetic acid (HEEDTA) [37], ethylenediamine-N,N -bis(o-hydroxy-p-methylphenyl)acetic acid (EDDHMA) [38], diethylenetriaminepentaacetic acid (DTPA) [39], nitrilotriacetic acid (NTA) [40], glucoheptanoic acid [41], and citric acid [42,43]. Unfortunately, despite the excellent chelating properties, not all fertilizing chelates show the adequate biodegradation. ...
... The literature shows a range of organic ligands of this type, some of which have been approved for use in medicine and agriculture. These include ethylenediaminetetraacetic acid (EDTA) [36], N-(hydroxyethyl)ethylenediaminetriacetic acid (HEEDTA) [37], ethylenediamine-N,N′-bis(o-hydroxy-pmethylphenyl)acetic acid (EDDHMA) [38], diethylenetriaminepentaacetic acid (DTPA) [39], nitrilotriacetic acid (NTA) [40], glucoheptanoic acid [41], and citric acid [42,43]. Unfortunately, despite the excellent chelating properties, not all fertilizing chelates show the adequate biodegradation. ...
Full-text available
A series of new symmetrical 2,5-dialkyl-1,3,4-oxadiazoles containing substituted alkyl groups at the terminal positions with substituents, such as bromine, isopropyloxycarbonylmethylamino, and carboxymethylamino, were successfully synthesized. The developed multistep method employed commercially available acid chlorides differing in alkyl chain length and terminal substituent, hydrazine hydrate, and phosphorus oxychloride. The intermediate bromine-containing 2,5-dialkyl-1,3,4-oxadiazoles were easily substituted with diisopropyl iminodiacetate, followed by hydrolysis in aqueous methanol solution giving the corresponding 1,3,4-oxadiazoles bearing carboxymethylamino substituents. The structure of all products was confirmed by conventional spectroscopic methods including 1H NMR, 13C NMR, and HRMS.
... This is confirmed using chelators such as EDTA in the detoxification of heavy metals from the environment. According to Oviedo and Rodríguez (2003), EDTA has poor biodegradability, hence the study should use another chelator with greater biodegradability than EDTA. Mung bean plants grow well and much faster than other plants, and also show a reduction in root growth and cell death after Cd exposure. ...
Full-text available
This research studied the effect of cadmium (Cd) on the growth of mung bean (Vigna radiata (L.) R. Wilczek). The mung bean was cultured in a Hoagland solution containing different concentrations of Cd (0, 0.1, 0.3 and 0.5 mg/L) for 5 days. The result showed a significant decrease in the lengths of the roots and shoots of mung bean that was grown in cadmium solution. This effect was proportional to the concentrations of Cd. To assess cell death in the root of mung bean, Evan’ s blue staining technique was used in this study. The results showed that the concentrations of Evan's blue dye taken up by Cd-exposed mung beans at 0.1, 0.3, and 0.5 mg/L were 1.5612 ± 0.5417, 6.8641 ± 1.7447, and 8.0850 ± 2.6336 mg/L, respectively. A concentration-dependent increase of dead cellswas found in the Cd-treated group, mostly at the root cap zone. With respect to this result, the level of dead cells that was stained with Evan’s blue dye could be used as a biomarker to indicate cadmium contamination in water. Furthermore, the effects of chelating agents (EDTA) on cadmium removal were also studied. The results showed the possibility of using EDTA as a cadmium treatment agent and promoted plant growth in cadmium contamination areas.
... Likewise, fluorinated chemicals such as perfluorooctane sulfonates (PFOS) must be avoided because they are highly persistent in nature and can survive in ecological systems for decades, if not centuries. There is no place in circular hydrometallurgy for these ''forever chemicals'' [113,114]. Furthermore, we must realize that many ionic liquids that are considered as green solvents for ionometallurgy often contain fluorinated anions such as bis(trifluoromethylsulfonyl)imide (vide infra). A good example is betainium bis(trifluoromethylsulfonyl)imide, [HBet] [Tf 2 N], which is a powerful lixiviant for oxide minerals, but which combines persistency with a relatively high solubility in water [115,116]. ...
Full-text available
In this academic position paper, we propose the 12 Principles of a novel and more sustainable approach to hydrometallurgy that we call “circular hydrometallurgy.” The paper intends to set a basis for identifying future areas of research in the field of hydrometallurgy, while providing a “sustainability” benchmark for assessing existing processes and technological developments. Circular hydrometallurgy refers to the designing of energy-efficient and resource-efficient flowsheets or unit processes that consume the minimum quantities of reagents and result in minimum waste. The application of a circular approach involves new ways of thinking about how hydrometallurgy is applied for both primary and secondary resources. In either case, the emphasis must be on the regeneration and reuse of every reagent in the process. This refers not only to the acids and bases employed for leaching or pH control, but also any reducing agents, oxidizing agents, and other auxiliary reagents. Likewise, the consumption of water and energy must be reduced to an absolute minimum. To consolidate the concept of circular hydrometallurgical flowsheets, we present the 12 Principles that will boost sustainability: (1) regenerate reagents, (2) close water loops, (3) prevent waste, (4) maximize mass, energy, space, and time efficiency, (5) integrate materials and energy flows, (6) safely dispose of potentially harmful elements, (7) decrease activation energy, (8) electrify processes wherever possible, (9) use benign chemicals, (10) reduce chemical diversity, (11) implement real-time analysis and digital process control, and (12) combine circular hydrometallurgy with zero-waste mining. Although we realize that the choice of these principles is somewhat arbitrary and that other principles could be imagined or some principles could be merged, we are nevertheless convinced that the present framework of these 12 Principles, as put forward in this position paper, provides a powerful tool to show the direction of future research and innovation in hydrometallurgy, both in industry and in academia. Graphical Abstract
... From previous studies, the ammonium acetate buffer, was shown to have a significant effect on peak resolution and intensity of target compounds [46,47,49]. Hence, a buffer test was done on the MCX cartridge, a bar chart of the results is presented in Fig. 1. ...
... Soil chelation may be improved based on the activation efficiency of the chelating agent used, but that is widely dependent on specific heavy metal interactions within soil (Evangelou et al., 2007;Liu et al., 2020). Ethylenediaminetetraacetic acid (EDTA) was previously identified as a successful chelator in several phytoremediation studies but has raised environmental concerns related to its limited biodegradability (Elliott and Brown 1986;Oviedo and Rodríguez 2003;Greipsson 2011;Johnson et al., 2015;Aderholt et al., 2017). To limit potential environmental impacts, biodegradable chemicals other than EDTA including nitrilotriacetic acid (NTA) and natural chelates like citric acid have been tested in phytoremediation studies as well (Freitas et al., 2013;Aderholt et al., 2017;Hart et al., 2022). ...
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The accumulation of Pb deposits in soil is a growing global concern. Soil remediation options include phytoextraction that involves the use of plants and associated soil microorganism. Switchgrass (Panicum virgatum L.), a second-generation bioenergy crop was used in this study due to its ability to produce high biomass and grow in metal polluted soils. Plants were grown in Pb-contaminated soil (5,802.5 mg kg −1) in an environmentally controlled greenhouse. Plants were treated with exogenous application of the plant growth regulator (PGR) benzylaminopurine (BAP) or complete foliar nutrient solution (Triple-12 ®) twice a week until harvested. Plants also received the soil fungicide propiconazole (Infuse ™) that was followed by the soil chelate nitrilotriacetic acid (NTA). Two concentrations of NTA were compared (5 mM and 10 mM) and combined application of NTA (10 mM) + APG (alkyl polyglucoside). Soil fungicide (propiconazole) was used to arrest arbuscular mycorrhizal fungi (AMF) activities in the roots of switchgrass in order to enhance Pb-phytoextraction. Lead (Pb) was measured in dry plant materials using an ICP-OES. Phytoextraction by switchgrass was significantly improved by dual soil applications of 10 mM NTA, APG and foliar applications of BAP which resulted in the greatestaverage Pb concentration of 5,942 mg kg −1. The average dry mass of plants and the average value for total phytoextracted Pb (mg) per pot were significantly greatestfor plants treated with 10 mM NTA, APG and BAP. Also, plants treated with NTA and BAP showed average bioconcentration factor of 1.02. The results suggested that chemically enhanced phytoextraction significantly improved biomass production of switchgrass and at the same time increased phytoextracted Pb which is important for phytoremediation and bioenergy industry.
... EDTA was in fact already cited as a dissolving agent for calcite since it affects the crystalline lace removing calcium cation [46]. Moreover, EDTA is a persistent compound in soil and water, harmful if inhaled and noxious for internal organs, which is why it does not comply with green chemistry principles [47,48]. Solvents (Polar Varnish Rescue and water) and surfactants (alkoxylated) could not remove the discoloration. ...
Full-text available
In spite of the application of different cleaning procedures, the marble used for the portrait bust of Queen Margherita di Savoia continued to show permanent discoloration, consisting of an unevenly distributed grayish alteration, mainly on the front part. In this work, a multi-analytical, non-invasive approach was proposed using spectrocolorimetry, reflectance spectroscopy and multispectral imaging. The initial assumption, suggesting the presence of altered protective materials based on organic products (such as waxes or oils,) applied in the past according to traditional practices, was excluded, revealing instead the presence of deposits of particulate matter, which penetrated inside the crystalline structure of the marble, leading to a variation in its shade. Cleaning tests were also carried out to define the best product, using sustainable chemicals such as Polar Varnish Rescue®, alkoxyde surfactant, disodium EDTA, GLDA and Politect® Base in order to identify the best methodology and materials for sustainable cleaning, respecting the integrity of the original matter. Politect® Base demonstrated better action in comparison to the other products tested, and similar results were obtained with GLDA, which could be applied in areas where the Politect® is less efficient (e.g., lace).
... However, it is possible that mobile EDTA-metal complexes were already washed out from the root zone before becoming accessible by plant roots. EDTA is very persistent in soil and its resistance to chemical and biological degradation processes is well documented [130]. The high leachability of EDTA and metal-EDTA complexes into the subsurface or groundwater would occur without stabilizing these compounds though the ZVI amendment [15,38,131]. ...
Full-text available
Soil remediation is an important practice in the restoration of heavy metal-contaminated soils and reduce the heavy metal exposure of the local population. Here, we investigated the effect of an ex-situ soil washing technique, based on ethylenediaminetetraacetic acid (EDTA) as a chelat-ing agent, on a contaminated Cambisol. Lead, Cd and Zn were investigated in different soil fractions , drainage water and four vegetables from August 2019 to March 2021. Three treatments consisting of (C) contaminated soil, (W) washed soil and (WA) washed soil amended with vermicom-post and biochar were investigated in an outdoor raised bed set up. Our results showed that the total and bioavailable metal fractions were significantly reduced but failed to meet Austrian national guideline values. Initial concentrations in the soil leachate increased significantly, especially for Cd. Vegetables grown on the remediated soil took up significantly lower amounts of all heavy metals and were further reduced by the organic amendment, attaining acceptable values within EU guideline values for food safety. Only spinach exceeded the thresholds in all soil treatments. The increase in soil pH and nutrient availability led to significantly higher vegetable yields.
... Ethylene diamine tetra acetic acid (EDTA) is a chelating agent can bind to metals via four carboxylate and two amine groups. It is frequently employed in detergents [9], food industries [10], and as an anticoagulant, among other applications in molecular biology, due to its great complexing ability for most metal ions [11]. When DNA was dissolved in large quantities of EDTA, it remained intact and did not degrade for long periods of time [12]. ...
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ackground: Blood preservation method plays an important role in DNA extraction. The current study was conducted at the laboratories of the applied medical sciences college/ University of Karbala during the period from March to May 2021. Materials: Ten Fresh venous blood samples were collected from healthy males (20-45 years old) by venepuncture and stored at 2-8 o C until used. Each particular sample was subjected to five blood collection options as follows: the blood was freshly aliquoted without any treatments, the blood was collected in EDTA (ethylene diamine tetra acetic acid) tubes, the blood was collected with the addition of phosphate buffered saline (PBS) in a ratio of 1:2, the blood was added to PBS 1:2 and Triton X 100, and the blood was centrifuged and then PBS 1:2 and Triton X 100 were added. The quantity and integrity of the extracted DNA were evaluated by agarose gel electrophoresis. The quantity and purity of the DNA were measured using a NanoDrop Spectrophotometer. Results: The current study indicated statistically significant difference (p ≤0.05) among the treated groups when the concentration of the extracted DNA was taken into consideration. There was a statistically significant difference among the five groups when their absorbance ratio was measured at 260 nm/ 230 nm (p ≤0.05). However, no statistically significant difference (p ≤0.05) was obtained among the groups when the absorbance ratio of 260 nm/280 nm was considered. Conclusion: The pretreatment of blood samples with buffers (PBS containing 5% Triton X100) prior to DNA extraction can lead to an altered DNA yield and purity. B Abstract ISSN 2310-5380/ May 2022
Recently, biodegradable aminopolycarboxylic acid chelating agents have attracted attention as an alternative to environmentally persistent chelating agents such as ethylenediamine-N,N,N′,N′-tetraacetic acid. However, the detection of chelating agents requires complexation with metals or derivatization by esterification reagents, and their direct detection using the currently available analytical methods still represents a challenge. Herein, we describe a direct analytical method for the biodegradable chelating agents ethylenediamine-N,N'-disuccinic acid, 3-hydroxy-2,2′-iminodisuccinic acid, methylglycine-N,N'-diacetic acid, and N,N-bis(carboxymethyl)-l-glutamic acid, via ultra-performance liquid chromatography/electrospray ionization quadrupole/time-of-flight mass spectrometry. Satisfactory retention and separation with a good peak shape were successfully achieved using a metal-free hydrophilic interaction liquid chromatographic column. The calibration curves showed good linearity in the range of 1.0–50 μM with correlation coefficients greater than 0.9988. The detection limits ranged from 0.04 to 0.12 μM. Furthermore, the developed method could be applied to the quantitative analysis of the four chelating agents in biodegradation and photodegradation experiments at the laboratory level. The proposed method, which offers the advantages of quickness, sensitivity, and requiring no complicated pretreatment steps, is expected to contribute significantly to the practical analysis of chelating agents in environmental water samples.Graphical abstract
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EDTA in wastewater from pulp and paper mills was biodegraded by activated sludge maintained under mildly alkaline conditions. Relative to treatment plants operating under acidic or neutral conditions, the alkaline system did not interfere with the biodegradation of other organic compounds. The results of laboratory-scale experiments were confirmed in two full-scale activated sludge plants.
Ethylenediaminetetraacetic acid (EDTA) is used in the pulp and paper industry in bleaching where EDTA forms catalytically inactive complexes with transition metal ions preventing them from catalyzing the decomposition of hydrogen peroxide. EDTA complexes may have harmful effects on the environment and only a minor part of the complexes (about 10%) are eliminated during bioprocessing of the mill wastewaters under normal conditions (at about pH 7). In this study, biodegradation of EDTA in an activated sludge plant of a paper mill was monitored under alkaline conditions (pH 8 to 9). An average EDTA reduction of about 50% was obtained during a seven-week test period.
Widely present in the mixed wastes at the Hanford site, ethylenediametetraacetic acid (EDTA) can solubilize radionuclides such as plutonium and may increase their mobility in the environment. We have evaluated the sorption of Put (IV) onto Hanford soil in the presence and in the absence of EDTA through laboratory-based experiments at ambient temperature and atmosphere. The sorption ratio (R%) was determined as a function of FDTA concentration and solid-liquid ratio. The sorption decreased significantly when EDTA concentration increased. The diffusion of Pu(IV)-EDTA was relatively fast, with an effective diffusion coefficient, D-p = 3.54.10(-6) cm(2)/s at pH 5.25.
Wastewaters from totally chlorine-free (TCF) bleaching were compared with wastewaters from chlorine-gas (CG) bleaching and elemental-chlorine-free (ECF) bleaching. Activated-sludge treatment of TCF wastewaters reduced COD by 55-65%, compared with 35-45% for wastewaters containing chlorine compounds. Chemical flocculation of biologically treated TCF wastewaters with aluminum sulfate resulted in 85% total removal of COD. TCF wastewaters were very light in color, in contrast to wastewaters from CG bleaching. Combined biological and flocculation treatments of TCF wastewaters reduced phosphorus by 97-99%. Nitrogen in TCF wastewaters was high because of the presence of EDTA (ethylenediamine tetraacetic acid). Activated-sludge treatment did not remove EDTA, but addition of aluminum sulfate to treated wastewaters reduced EDTA by 65%. Residual peroxide in TCF wastewaters made them highly toxic, although biological treatment removed this toxicity. Treated TCF wastewaters had higher levels of heavy metals and nonprocess elements than CG and ECF wastewaters. Changing the composition of the wastewaters had little effect on the operation of the activated-sludge treatment system.
Pure species of Bacillus licheniformis was used to remove ions from aqueous and simulated waste solutions. Metal ion accumulation on B. licheniformis was fast. Maximum uptake occurred at pH 4±0.5 and at 25±3 °C. One gram of dry B. licheniformis was found to accumulate 115 mg cerium, 34 mg copper and 11 mg cobalt from aqueous solutions. The presence of certain foreign ions such as calcium, sodium and potassium decreased the uptake of ions by B. licheniformis, while citrate and EDTA prevent the uptake. Electron microscopic investigations showed that cerium (III), copper (II) and cobalt (II) accumulated extracellulary around the surface wall of B. licheniformis cells. A bio-adsorption mechanism between the metal ions and B. licheniformis cell wall was proposed.
In this work, a synthetic TCF effluent containing vanillin, glyoxal, sodium formate, sodium acetate and the chelanting agents EDTA and DTPA was treated using, O3, O3/H2O2, O3/UV, UV, UV/H2O2 and UV/H2O2/O3 at pH and 11. The best results were obtained in the O3/UV process. Ozone alone did not degrade EDTA neither DTPA. A combined O3/UV (pH 7.0 by 15 min)-biological treatment was very efficient in the removal of the chelants (98 %) and COD (95 %).
The speciation of EDTA in sewage effluents leaving wastewater treatment plants determines its ultimate fate in natural surface waters, since only the Fe(III)-EDTA complex (FeEDTA) is quickly degraded by direct photolysis, whereas other EDTA species are very slowly transformed, if at all, by biological or chemical processes. Field studies were undertaken to quantify the speciation of EDTA in influents and effluents of sewage treatment plants. Chemical equilibrium calculations are of only limited use for this purpose because several weeks are needed to reach thermodynamic equilibrium in wastewater due to slow metal exchange processes. In the effluents from treatment plants that precipitate phosphate, concentrations of dissolved Fe (0.05 μm- and 0.45 μm-filterable) correlated with the concentrations of EDTA. An operational scheme, using sunlight or artificial light sources for specific photoconversion of FeEDTA species, was applied to distinguish between photo-degradable (=FeEDTA) and photo-resistent EDTA species. Field studies conducted at three municipal wastewater treatment facilities showed that EDTA speciation changes from the input to the output because FeEDTA is formed from other metal-EDTA complexes after addition of iron(II)-containing solutions into the aeration tanks. With respect to total amounts of EDTA, fractions of FeEDTA in the influents and effluents varied from 10 to 55% and from 20 to 90%. Mass balances comprising sampling periods of several days showed that no significant elimination of EDTA occured by biological or chemical processes during sewage treatment, whereas the chemically related phosphate substitute nitrilotriacetic acid (NTA) was efficiently degraded (>90%). As long as the speciation of EDTA in wastewaters is dominated by FeEDTA, and aerobic conditions are maintained, the remobilization of common heavy metals out of sewage sludge is unlikely to occur.
Ozonation of ethylenediaminetetraacetic acid (EDTA) (, ozone dose ) in aqueous solution as a function of pH value (pH 3 and 7) was investigated. At pH 3 ethylenediaminediacetic acid, iminodiacetic acid, nitrilotriacetic acid, glyoxylic-, oxalic-, formic acid, glycine, ammonia, nitrate and H2O2 were identified and their quantities, as a function of ozone consumption, were measured. At pH 7 the same oxidation products, except formic acid and H2O2, are formed. The carbon balance shows that, at pH 3, 84% and, at pH 7, 62–81% of the organic carbon was covered by the identified products. After 100% EDTA-elimination the oxidation products are biodegradable. Whereas the presence of Ca2+ and Cd2+ ions has only little impact on EDTA-elimination, the rate of EDTA degradation is notably reduced by the addition of Fe3+ ions.
Administration of toxic doses of Ca-DTPA (diethylenetriaminepentaacetate) after partial hepatectomy inhibits the synthesis of DNA, RNA and proteins in the regenerating rat liver. Zn-DTPA proved to be ineffective. Impairment by Ca-DTPA of DNA synthesis can be completely restored by subsequent joint administration of Zn2+ and Mn2+. The dependence of the inhibitory action of Ca-DTPA on dosage and on the time of its administration is consistent with the assumption that the inhibition of DNA synthesis is not the primary reaction but the consequence of an impaired synthesis of proteins which is tentatively ascribed to a disturbed conformation of RNA due to removal of Zn2+ and Mn2+. Parallel studies on cell-free systems revealed a direct inhibitory action of Ca- and Zn-DTPA on the syntheses. The different activity pattern in vitro and in vivo is explained by the assumption that in the former case the inhibitory action is partly due to the formation of ternary complexes; a mechanism which is not operative in vivo, because the distribution of the chelates is confined to the extracellular space.
This paper deals with the chemical oxidation to enhance the biodegradability of ethylenediaminetetraacetic acid (EDTA), which is regarded as one of the non-biodegradable substances, as a pretreatment for biological activated carbon (BAC) treatment. The use of EDTA is indispensable in many industries. However, when it is contained in wastewater, difficulty arises concerning treatment because of its stable chemical structure. Wastewaters containing EDTA have been thrown into the ocean, but the prohibition of the marine disposal of such wastewaters came into force in 1995. Therefore, efficient treatment processes are required to remove EDTA from wastewater. In this study, chemical oxidation by Fenton's reagent or ozone was adopted to enhance biodegradability of EDTA followed by semi-continuous BAC treatment. As a result, the biodegradability of EDTA was remarkably enhanced by the chemical oxidation treatment. From the semi-continuous ozone plus BAC treatment, the effectiveness of chemical pretreatment on EDTA removal was observed. The overall removal rate of EDTA increased when the preozonation step was introduced, and more than 80% of EDTA was found to be removed by the ozone plus BAC treatment at the maximum.