Removal Of Ethylenediaminetetraacetic Acid Research Articles

Vermifiltration for removal of emerging contaminant EDTA (ethylenediaminetetraacetic acid). Kinetics models for adsorption, bio- and vermidegradation

Vermifiltration is a sustainable technology that combines the action of microorganisms and earthworms to remove contaminants in wastewater. In this work, vermifiltration was used to remove the emerging contaminant, EDTA, from simulated greywater. Three types of filters were designed: Azide Filter (AF) to evaluate the adsorption process, Bio filter (BF), to evaluate adsorption plus the action of the microorganisms, and Vermi Filter (VF), to assess the previously described processes and the action of the earthworms. Each filter was filled with gravel, sand and an active layer, and VF was inoculated with 60 Eisenia fetida. The filters were operated on a batch system with recycling. Different regimes were observed: an initial rapid decrease of EDTA concentration by adsorption; a lag phase, which lasted from 7 to 18 days, and a final EDTA decrease due to biological or vermi degradation. A mathematical model was developed performing the EDTA mass balance in the system and considering a first order kinetic rate for EDTA removal. Experimental data was fitted by the model, determining kinetic constants for adsorption or degradation process, kads and kd respectively. The kads values were similar for all filters, whereas VF showed a kd 53 % higher than that of BF and AF. Earthworms survival was 85 % and, although the biomass was significantly reduced (64.8 %), there was cocoons and juveniles. Bioassays with Lactuca sativa showed no phytotoxicity of the treated wastewaters. All the systems were efficient but the VF was faster, supporting that vermifiltration is a suitable technology for treating EDTA greywater.

Electrochemical treatment of wastewaters containing metal-organic complexes: A one-step approach for efficient metal complex decomposition and selective metal recovery

Metal-organic complexes, especially those of ethylenediaminetetraacetic acid (EDTA) with metals such as copper (Cu) and nickel (Ni) (denoted here as Cu-EDTA and Ni-EDTA), are common contaminants in wastewaters from chemical and plating industries. In this study, a multi-electrode (ME) system using a two-chamber reactor and two pairs of electrodes is proposed for simultaneous electrochemical oxidation of a wastewater containing both Cu-EDTA and Ni-EDTA complexes as well as separation and selective recovery of Cu and Ni onto two different cathodes via electrodeposition. Our results demonstrate that the ME system successfully achieved 90% EDTA removal, 99% solid Cu recovery at the Cu recovery cathode and 56% Ni recovery (33.3% on the Ni recovery cathode and 22.6% in the solution) after a four-hour operation. The system further achieved 85.5% Ni recovery after consecutive five cycles of operation for 20 h. While Cu removal was mainly driven by the direct reduction of EDTA-complexed Cu(II) at the cathode, oxidation of EDTA within the Ni-EDTA complex at the anode was a prerequisite for Ni removal. The oxidation of metal-bound EDTA and free EDTA was driven by •OH and direct electron transfer on the PbO2 anode surface and graphite anode, respectively. We further show that ME system performs well for all pH conditions, treatment of real wastewaters as well as wastewaters containing other metals ions (Cr and Zn) along with Cu/Ni. The separation efficiency of Cu and Ni is dependent on applied electrode potential as well as nature and concentration of binding ligand present with comparatively lower separation efficiency achieved in the presence of weaker binding capacity and/or at lower ligand concentration and lower applied electrode potential. As such, some optimization of electrode potential is required depending on the nature/concentration of ligands in the wastewaters. Overall, this study provides new insights into the design and operation of EAOP technology for effective organic abatement and metal recovery from wastewaters containing mixtures of various metal-organic complexes.

Heterogeneous Fenton-like degradation of EDTA in an aqueous solution with enhanced COD removal under neutral pH.

By providing the key carbon and nitrogen elements needed for eutrophication, the potential toxicity of ethylenediaminetetraacetic acid (EDTA) prompts the exploration of effective treatment methods to minimize the amount of EDTA released into the environment. In this study, Fe3O4 magnetic nanoparticles (MNPs) were prepared and used as catalysts to study the mineralization of EDTA in Fenton-like reactions under neutral pH. Fe3O4 MNPs were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and Brunauer-Emmett-Teller (BET). The effects of pH, ferric ion leaching, and H2O2 concentration on chemical oxygen demand (COD) removal of EDTA were investigated. The morphological characterization of the nanoparticles suggests a quasi-spherical structure with small particle size and a surface area of 49.9 m2/g. The results show that Fe3O4 MNPs had good catalytic activity for the mineralization of EDTA under pH 5.0-9.0. The optimum conditions for the COD removal of 45% at pH 7.0 were: 40 mM H2O2, 10 mM Fe3O4, and 1 g/L EDTANa2·2H2O at 303 K. Fe3O4 MNPs maintained high catalytic activity after five cycles of continuous degradation of EDTA. According to reactive oxidizing species measurements obtained by electron spin resonance (ESR), it was confirmed that HO· free radicals, presented in the H2O2/Fe3O4 MNPs heterogeneous Fenton-like reaction, were the primary active group in the removal of EDTA. These features can be considered beneficial to the application of Fe3O4 MNPs towards industrial wastewater treatment.

Cu(II)-EDTA removal by a two-step Fe(0) electrocoagulation in near natural water: Sequent transformation and oxidation of EDTA complexes

The widely usage of ethylenediaminetetraacetic acid (EDTA) arises environmental concerns on toxic metal mobilization, and challenges the conventional processes in water treatment. In the study Cu(II)-EDTA in near natural water was efficiently removed during a two-step electrocoagulation using Fe(0) anode (Fe-EC), including a transformation to Fe(III)-EDTA induced mainly by structural Fe(II) in anoxic Fe-EC and further degradation in oxic Fe-EC. The degradation of Fe(III)-EDTA was mostly attributed to an oxygen activation mechanism that involving O2− and hydroxyl radical (OH) generation, as validated by the quenching experiments and electron spin resonance. Furthermore, O2− generated during Fe(II) oxidation took a dominant role on Fe(III)/Fe(II)-EDTA transformation instead of electrochemical reduction. Six intermediates during the Fe(III)-EDTA degradation were identified by LC-Q-TOF, indicating a pathway of stepwise breakage of NC bonds. The results revealed in this work is helpful to understand the contribution and fate of EDTA during Fe-EC treatment of metal-EDTA polluted water.

Adsorption of Ethylenediaminetetraacetic Acid on a Gel-Type Ion-Exchange Resin for Purification of Liquid Waste Containing Cs Ions.

Because of its excellent chelating property, ethylenediaminetetraacetic acid (EDTA) is used as a complex agent, not only for heavy metals, but also for radioactive isotopes during the decontamination of nuclear facilities. The removal of EDTA was investigated by adsorption with commercially available, gel-type, anion-exchange resins (AERs), which are based on cross-linked polystyrene with positive tertiary amine groups. Because of the positive charge on AERs, they could adsorb EDTA effectively even in a solution mixed with ions of cesium (Cs) via electrostatic attraction. Because EDTA adsorption by cation-exchange resins (CERs) was not possible, it was concluded that the negative charges on CERs do not contribute to the interaction with EDTA. The maximum adsorption capacity (qmax) of AER (2 g/L) for EDTA removal, calculated by the Langmuir isotherm model was 0.47 mmol/g for initial EDTA concentrations in the range of 0.01–1 mM in the EDTA/Cs mixed solution. The Langmuir isotherm model was found to be suitable for EDTA adsorption on AERs, indicative of monolayer adsorption. The results clearly suggested that the AERs could efficiently remove EDTA, regardless of the presence of nuclides, such as Cs ions in the aqueous solution.

Electrochemical Oxidation of EDTA in Nuclear Wastewater Using Platinum Supported on Activated Carbon Fibers.

A novel Pt/ACF (Pt supported on activated carbon fibers) electrode was successfully prepared with impregnation and electrodeposition method. Characterization of the electrodes indicated that the Pt/ACF electrode had a larger effective area and more active sites. Electrochemical degradation of ethylenediaminetetra-acetic acid (EDTA) in aqueous solution with Pt/ACF electrodes was investigated. The results showed that the 3% Pt/ACF electrode had a better effect on EDTA removal. The operational parameters influencing the electrochemical degradation of EDTA with 3% Pt/ACF electrode were optimized and the optimal removal of EDTA and chemical oxygen demand (COD) were 94% and 60% after 100 min on condition of the electrolyte concentration, initial concentration of EDTA, current density and initial value of pH were 0.1 mol/L, 300 mg/L, 40 mA/cm2 and 5.0, respectively. The degradation intermediates of EDTA in electrochemical oxidation with 3% Pt/ACF electrode were identified by gas chromatography-mass spectrum (GC-MS).

Drawbacks of Dialysis Procedures for Removal of EDTA.

Ethylenediaminetetraacetic acid (EDTA) is a chelating agent commonly used in protein purification, both to eliminate contaminating divalent cations and to inhibit protease activity. For a number of subsequent applications EDTA needs to be exhaustively removed. Most purification methods rely in extensive dialysis and/or gel filtration in order to exchange or remove protein buffer components, including metal chelators. We report here that dialysis protocols, even as extensive as those typically employed for protein refolding, may not effectively remove EDTA, which is reduced only by approximately two-fold and it also persists after spin-column gel filtration, as determined by NMR and by colorimetric methods. Remarkably, the most efficient removal was achieved by ultrafiltration, after which EDTA became virtually undetectable. These results highlight a potentially widespread source of experimental variability affecting free divalent cation concentrations in protein applications.

Decomplexation efficiency and mechanism of Cu(II)-EDTA by H2O2 coupled internal micro-electrolysis process.

Internal micro-electrolysis (IE) coupled with Fenton oxidation (IEF) was a very effective technology for copper (Cu)-ethylenediaminetetraacetic acid (EDTA) wastewater treatment. However, the mechanisms of Cu2+ removal and EDTA degradation were scarce and lack persuasion in the IEF process. In this paper, the decomplexation and removal efficiency of Cu-EDTA and the corresponding mechanisms during the IEF process were investigated by batch test. An empirical equation and the oxidation reduction potential (ORP) index were proposed to flexibly control IE and the Fenton process, respectively. The results showed that Cu2+, total organic carbon (TOC), and EDTA removal efficiencies were 99.6, 80.3, and 83.4%, respectively, under the proper operation conditions of iron dosage of 30g/L, Fe/C of 3/1, initial pH of 3.0, Fe2+/H2O2 molar ratio of 1/4, and reaction time of 20min, respectively for IE and the Fenton process. The contributions of IE and Fenton to Cu2+ removal were 91.2 and 8.4%, respectively, and those to TOC and EDTA removal were 23.3, 25.1, and 57, 58.3%, respectively. It was found that Fe2+-based replacement-precipitation and hydroxyl radical (•OH) were the most important effects during the IEF process. •OH played an important role in the degradation of EDTA, whose yield and productive rate were 3.13mg/L and 0.157mg/(Lmin-1), respectively. Based on the intermediates detected by GC-MS, including acetic acid, propionic acid, pentanoic acid, amino acetic acid, 3-(diethylamino)-1,2-propanediol, and nitrilotriacetic acid (NTA), a possible degradation pathway of Cu-EDTA in the IEF process was proposed. Graphical abstract The mechanism diagram of IEF process.

Evaluation of the smear layer removal and decalcification effect of QMix, maleic acid and EDTA on root canal dentine

ObjectivesThe objective of the presentin vitro study was to evaluate the canal wall smear layer removal capacity and mineral content distribution of root canal dentine after irrigation with QMix, 7% maleic acid (MA) and 17% ethylenediaminetetraacetic acid(EDTA). MethodsForty single-rooted teeth were subjected to root canal instrumentation and divided into four groups: [1] 7% MA+2.5% sodium hypochlorite (NaOCl), [2] 17% EDTA+ 2.5% NaOCl, [3] QMix+2.5% NaOCl and [4] 0.9% saline (negative control). After irrigation, the teeth were examined byscanning electron microscopy (SEM) to determine the presence or absence of smear layer. Formineral content assessment, 40 root-halves were divided into four groups and treated with 7% MA, QMix, 17% EDTA and saline. Mineral content was evaluated using SEM-energy dispersive X-ray analysis. ResultsThere was no significant difference between QMix, MA and EDTA in removal of smear layer from coronal and middle third of the canal spaces. In the apical third, MA performed better. Calcium was decreased more with QMix with no difference between MA and EDTA. Phosphorous was reduced more with MA and QMix than EDTA with no difference between MA and QMix. Similar result was observed with magnesium level. Carbon was reduced more with EDTA with no difference between QMix and MA. Oxygen was reduced significantly more with MA with no difference between QMix and EDTA. Conclusion7% MA had superior smear layer removal ability compared with QMix and 17% EDTA. Calcium level was decreased more with QMix while phosphorus level was decreased more with 7% MA and QMix respectively. Clinical significanceThe present study highlights the effect of newer chelating agentson smear layer removal and decalcification of root canal dentine, which is required for disinfection of the root canal space and maintenance of the structural integrity of the teeth.

H2O2 and/or photocatalysis under UV-C irradiation for the removal of EDTA, a chelating agent present in nuclear waste waters

In this study, we compare the efficiency of photocatalytic processes based on TiO2 (Degussa P-25) and UV/H2O2 as a means of degrading and mineralizing ethylenediaminetetraacetic acid (EDTA) under UV-C irradiation. EDTA was the molecule studied here because it is present in high proportions at nuclear facilities, where it is used for cleaning and decontamination purposes because of its chelating properties. The photonic power of the UV-C lamps used (13 and 15W) was established using actinometric and Keitz's methods. The adsorption of EDTA on TiO2 Degussa P-25 corresponds to a Langmuir isotherm, and the photocatalytic degradation process is consistent with the Langmuir–Hinshelwood model. During the photocatalytic process, an increase in the initial EDTA concentration favors the formation of large quantities of intermediates, which occupy the active sites, thus delaying the production of detectable quantities of oxalic acid. The results obtained here also show that nitrogen originating from EDTA molecules is mainly converted into ammonium and nitrate ions with a conversion rate of 67%. In addition, the amount of oxalic acid formed increases with the pH. The efficiency of the UV/TiO2 and UV/H2O2 processes as a means of EDTA degradation was found to be similar, provided H2O2 was added continuously during the UV/H2O2 process. The quantum efficiency was calculated and found to be equal to 0.9% in the case of photocatalysis and 1.4% in that of UV/H2O2.

Supported iron-based catalysts under influence of static magnetic field for the removal of TBP and EDTA

Zerovalent metals offer decontamination of organic toxins in aqueous medium. In the present study, alumina-based iron and iron–nickel in the presence and the absence of magnetic field for the decontamination of tributyl phosphate (TBP) and ethylene diamine tetraacetic acid (EDTA) has been compared. TBP decontamination was improved in the presence of zerovalent metals. EDTA decontamination was not enhanced in the presence of zerovalent metals. The decontamination of TBP using iron-based alumina was higher than iron–nickel. The surface interaction on alumina surface, as characterized by attentuated total reflectance-Fourier transform infrared spectroscopy, and the surface interaction on metallic elements, as characterized by evaluating the magnetic moment values helped to understand the reason for the difference in role of alumina-based iron and iron–nickel on decontamination of TBP and EDTA.

Removal of EDTA from Aqueous Solutions Using Activated Carbon Prepared from Rubber Wood Sawdust: Kinetic and Equilibrium Modeling

AbstractAdsorptive removal of EDTA (ethylenediaminetetraacetic acid) from aqueous solution was studied using steam pyrolyzed activated carbon. Rubber wood sawdust, obtained from a local timber facility at Kodangavila, Trivandrum, Kerala, India was used as the precursor for the production of the activated carbon. Batch adsorption experiments were employed to monitor and optimize the removal process. The experimental parameters, i. e., solution pH, agitation time, initial EDTA concentration and adsorbent dosage, affecting the adsorption of EDTA onto sawdust activated carbon (SDAC) were optimized. The inner core mechanism for the interaction between EDTA and SDAC, which resulted in the adsorption process, was also discussed. The change in amount of EDTA adsorbed onto SDAC and CAC (commercial activated carbon) was compared over a wide range of pH (2.0–8.0). The maximum removal of EDTA took place in the pH range of 4.0–6.0 for SDAC and 5.0–5.5 for CAC, which demonstrates the effectiveness of the former adsorbent. Kinetic as well as equilibrium studies were performed to determine the rate constant and adsorption capacity, respectively. The adsorption kinetic data was fitted with pseudo‐first‐order kinetics and the equilibrium data was shown to follow the Langmuir isotherm model. These observations explain the formation of a monolayer of EDTA on the surface of SDAC as confirmed by the slow approach to equilibrium after 4 h of contact time. The adsorption capacity of SDAC for the removal of EDTA was 0.526 mmol/g and is seen to be greater than that of CAC and other reported adsorbents (0.193–0.439 mmol/g). Finally, it is clear that the production of steam pyrolyzed activated carbon in the presence of K2CO3 greatly enhanced EDTA removal and resulted in a product with possible commercial value for wastewater treatment strategies.

Membrane Bioreactor Treatment of a Simulated Metalworking Fluid Wastewater Containing Ethylenediaminetetraacetic Acid and Dicyclohexylamine

Membrane bioreactors (MBRs) have been installed at automotive plants to treat metalworking fluid (MWF) wastewaters, which are known to contain toxic and/or recalcitrant organic compounds. A laboratory study was conducted to evaluate treatment of a simulated wastewater prepared from a semisynthetic MWF, which contains two such compounds, dicyclohexylamine (DCHA) and ethylenediaminetetraacetic acid (EDTA). Primary findings were as follows: During stable operating periods, almost all chemical oxygen demand (COD), total Kjeldahl nitrogen (TKN), and EDTA were removed (by > 96%). During somewhat unstable periods, COD removal was still extremely robust, but removal of EDTA and TKN were sensitive to prolonged episodes of low dissolved oxygen. Nitrogen mass balance suggested 30 to 40% TKN removal by assimilation and 60 to 70% by nitrification (including up to 34% TKN removal via subsequent denitrification). Dicyclohexylamine appeared to be readily biodegraded. Maximum DCHA and EDTA degradation rates between pH 7 and 8 were found. An Arthrobacter sp. capable of growth on DCHA as the sole source of carbon and energy was isolated.

Removal of EDTA from low pH printed-circuit board wastewater in a fluidized zero valent iron reactor

Fluidized zero valent iron (ZVI) process was adopted to reduce ethylenediaminetetraacetic acid (EDTA) from low pH printed-circuit board (PCB) wastewater for two reasons: (1) low pH of the wastewater favoring the ZVI reaction; (2) higher ZVI utilization for fluidized process due to abrasive motion of the ZVI. The results showed that the degradation of EDTA was greatly enhanced under acidic pH, longer hydraulic detention time (HRT) and presence of dissolved oxygen (DO). Without addition of oxygen, 65% of EDTA was removed with capacity of 7.33 mg EDTA/g ZVI at pH 2, ZVI dosage of 424 g/L and HRT 10 min. With 6.8 mg/L of DO, 83% of EDTA was reduced with capacity of 19.01 mg EDTA/g ZVI for the same experimental condition. The presence of oxygen/ZVI initiated a Fenton type reaction to reduce EDTA. The end product after EDTA degradation was analyzed by high performance liquid chromoagraphy (HPLC), where propionic acid (C(2)H(5)COOH) was observed, indicating EDTA (oxidation number for carbon is 2) was oxidized to propionic acid (oxidation number for carbon is 3). Nitrogen species was also measured and the nitrogen in EDTA was converted to ammonium instead of nitrate and nitrite.

The use of Magallanic peat as non-conventional sorbent for EDTA removal from wastewater

Kraft mills are responsible for large volumes discharges of highly polluted effluents. Application of new bleaching processes (i.e. total chlorine-free (TCF) process) is already a feasible option to reduce environmental impacts. The current trend in the increase in the production of TCF pulp will proportionally increase the consumption of chelating agents. The most commonly used chelants, ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DPTA) are supposed to be relatively persistent substances, poorly degradable in biological treatment facilities and are subsequently considered as environmentally critical compounds. Adsorption could be used as a treatment technique to remove recalcitrant compounds from wastewaters. However, in most cases, sorbent and regeneration costs can make the whole process not economically feasible. The goal of this study was to evaluate the use of Magallanic peat as non-conventional sorbent for EDTA removal from wastewater. Adsorption studies were carried out considering a 2 3 factorial design. pH, temperature and sorbent/sorbate (S/S) relationship effects were evaluated in EDTA adsorption onto Magallanic peat. In addition, adsorption isotherm constants were determined according to the Langmuir and Freundlich models. The results showed that the optimal conditions for EDTA adsorption onto Magallanic peat were 20 °C, acid pH (4.0) and a low sorbent/sorbate ratio (0.1/100). At these conditions Magallanic peat showed an adsorption capacity for EDTA (Cs sat) of 128.2 mg/g, comparable and even better than activated carbon (Cs sat 56.5 mg/g). EDTA adsorption data at 60 °C obtained are not shown due to Magallanic peat degradation phenomena.

Anaerobic treatment of low-strength synthetic TCF effluents and biomass adhesion in fixed-bed systems

Toxicity effects produced by kraft mill effluents are due to the productive process. New bleaching processes have been proposed (e.g. total chlorine free, TCF) to reduce the production of toxic chlorine compounds. In the TCF processes large amounts of chelating compounds like the ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DPTA) are used. The aim of this work is to research the feasibility of the degradation of low-strength synthetic TCF effluents in a anaerobic filter reactor (AF) and the biomass adhesion. The effects on the operation of the AF at different EDTA loading rates were tested in the range from 0.07 to 0.51 g EDTA l(-1) days(-1). The maximum EDTA removal percentage achieved was of 27%. Acute toxicity (measured as 24 h-LC(50)) with Daphnia magna was reduced from 14.23 to 54.53% before and after anaerobic treatment, respectively. Observations of biomass samples from the AF under the scanning microscope verified the attached biomass.

Removal of Decontaminating Agent Ethylenediaminetetraacetic Acid from Aqueous Solution by an Effective Mesoporous Al-MCM-41 Molecular Sieves Adsorbent

Ethylenediaminetetraacetic acid (EDTA) can cause complexes with radioactive cations during decontamination operation in the nuclear industry, which results in impeding the treatment of decontamination wastes by conventional treatment processes such as chemical precipitation and ion exchange and may be potentially dangerous to the environment. To achieve efficient removal of EDTA from aqueous solution, mesoporous Al-MCM-41 molecular sieves (Si/Al = 25, 50, 75, and 100) were synthesized hydrothermally, characterized by XRD, N 2 adsorption studies, and TEM, and evaluated through an adsorption process. Adsorption of EDTA over Al-MCM-41 shows the applicability of Freundlich and Langmuir isotherms. Al-MCM-41, at Si/Al = 25, has proved to be a better adsorbent than its other ratios and commercial adsorbents such as activated charcoal and Hβ zeolite. Retainment of crystallinity of Al-MCM-41 after desorption has been achieved in this study.

EDTA Degradation Induced by Oxygen Activation in a Zerovalent Iron/Air/Water System

A method for the removal of ethylenediaminetetraacetic acid (EDTA) at room temperature and 1 atm is demonstrated. EDTA (1 mM, 50 mL) containing 2.5 g of granular zerovalent iron (ZVI) (20-40 mesh) was degraded in 2.5 h. Using a recently developed form of O2 activation, reactive oxygen species are generated in situ, resulting in the degradation of EDTA when complexed with FeII. ESI-MS measurements indicate that degradation of EDTA yields low-molecular carboxylic acids. The presence of oxygen is crucial: the observed pseudo-first-order rate constants for EDTA removal are kobs = 1.02 h(-1) (kSA = 1.85 +/- 0.046 L h(-1) m(-2)) and kobs = 0.04 h(-1) (kSA = 0.00724 +/- 0.002 L h(-1) m(-2)) under air and under N2 purge, respectively. kSA represents surface area normalized rate constants. Large excesses of EDTA in the reaction mixture slowthe rate of degradation. Increasing the concentration of EDTA from 1.0 to 10.0 mM while holding all other parameters constant gave observed rates of kobs = 1.02 +/- 0.26 h(-1) (kSA = 1.85 +/- 0.046 L h(-1) m(-2)) and kobs = 0.044 +/- 0.01 h(-1) (kSA = 0.00796 +/- 0.002 L h(-1) m(-2)), respectively. The rate-limiting step is determined to be homogeneous oxygen activation.

Removal of Ethylenediaminetetraacetic acid (EDTA) from Pulp Mill Effluents by Ozonation

Ozone application was investigated for its effectiveness in the removal of ethylenediaminetetraacetic acid (EDTA) from bleaching effluent. The objectives were to compare the efficiency of ozone reaction on Na-EDTA solution with pure Fe3+-EDTA complex and EDTA complexes in bleaching effluent, and to test if changing pH and addition of hydrogen peroxide (H2O2) increases the removal of EDTA. Small ozone doses destroyed high proportions of Na-EDTA. This effect was diminished when EDTA formed complexes with other metal ions. It was shown that EDTA present in bleaching effluent was more easily oxidizable than in pure Fe3+-EDTA solution. Variation of initial pH value had no significant influence on the removal of Na-EDTA. Addition of hydrogen peroxide did not increase degradation of EDTA in bleaching effluent.

Improvement of biodegradability of ethylenediaminetetraacetic acid in biological activated carbon treatment by chemical preoxidation

Abstract 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.