Degradation Of EDTA Research Articles

Cu(Ⅱ)-EDTA degradation and copper recovery from wastewater in wide pH ranges by an electrooxidation-capacitive deionization system

The treatment and recovery of metal resources from complex industrial wastewater has posed significant challenges due to the presence of multiple heavy metal ions, heavy metal complexes, and acidic conditions. In this study, a novel electrooxidation-capacitive deionization (EO-CDI) system was proposed, which ingeniously harnessed the unheeded Faraday side reaction in capacitive deionization for simultaneous degradation and recovery of copper complexes from wastewater through two electrode integration. Specially, the cathode CuS0.78Se0.22 synthesized through the anionic Se-substitution strategy exhibited a remarkable adsorption capacity up to 672.02 mg/g for Cu ions, outstanding selectivity and stability, particularly in acidic environments. The water oxidation process occurring at the activated carbon anode played a crucial role by generating active species that contribute to the degradation of Cu(Ⅱ)-EDTA, which leaded to the release of copper ions, facilitating their subsequent recovery. Cyclic experiments further confirmed the excellent cyclic stability of the hybrid EO-CDI system, along with its impressive performance in copper extraction when applied to real industrial wastewater. This innovative approach offered promising prospects for addressing the challenges associated with the treatment of complex industrial wastewater and the recovery of valuable metal resources.

Preparation of formic acid modified industrial zero-valent iron (FA-ZVIbm) for CdII-EDTA removal: CdII capturing and self-enhanced oxidative degradation of EDTA

Cadmium (Cd) contamination is highly toxic to human health, and the complexed Cd in wastewater is tricky to remove owing to its stable chelating structure. In this study, industrial zero-valent iron (ZVI) was modified by ball-milling with tiny formic acid (FA), and the as-prepared sample (FA-ZVIbm) was attempted in the treatment of CdII-ethylenediaminetetraacetic acid (CdII-EDTA). Little FA addition to ball-milling could dramatically improve the performance of FA-ZVIbm towards CdII-EDTA elimination and raise the elimination rate constant by more than 200 times. Results ascertained that the (HCOO)2FeII shell formed on FA-ZVIbm promoted CdII-EDTA decomplexation and activation of dissolved O2 to reactive oxygen species (ROS) for oxidative degradation of EDTA ligands. CdII-EDTA was instantly decomplexation by Fe3+ replacement, and the decomplexed Cd2+ was rapidly captured by FA-ZVIbm. At the same time, the EDTA ligands underwent oxidative degradation, avoiding the re-chelation ecological hazard. Interestingly, we found that replacement decomplexation has a synergistic mechanism for activating dissolved O2 to ROS, facilitating oxidative destruction of EDTA ligands. Furthermore, the FA-ZVIbm fixed-bed reactor could remediate CdII-EDTA contaminated environmental water one-stop, and the effluent stably meets the emission standards. This study demonstrated that FA-ZVIbm could be a viable approach for CdII-EDTA decontamination and clarified the remediation mechanism.

Boosting the Ni(II)-EDTA decomplexation and Ni(II) immobilization in a heterogeneous Fenton-like system with L-cysteine functionalized zero-valent iron

The remarkable stability and detrimental environmental impacts of nickel(II)-ethylenediaminetetraacetic acid (Ni(II)-EDTA) complexes originated from electroplating effluents have sparked a growing curiosity about their efficient remediation. In this study, L-cysteine functionalized zero-valent iron (C-ZVIbm) was synthesized via a ball-milling method and employed as a heterogeneous Fenton-like catalyst to decomplex Ni(II)-EDTA and immobilize Ni(II) from wastewater. The results demonstrated that the pseudo-second-order kinetic rate constant (2.096 L·mol−1·min−1) for EDTA degradation in the C-ZVIbm/H2O2 system was 123.3 times that in the ZVIbm/H2O2 system (0.017 L·mol−1·min−1). The incorporation of L-cysteine onto the surface of ZVI significantly enhanced the H2O2 activation, reactive oxygen species (OH, O2−, and 1O2) generation, and the sequential Ni(II)-EDTA decomplexation and EDTA degradation. The results of capture experiments revealed that 1O2 played a crucial role in the degradation of EDTA in the C-ZVIbm/H2O2 system. The optimization of the experimental variables indicated that the degradation of EDTA and the reduction/adsorption of Ni(II) were antagonistic in the C-ZVIbm/H2O2 system, resulting in an efficient reduction/immobilization of Ni(II) and an inhibition of EDTA degradation at a higher dosage of C-ZVIbm. Our findings provide new insights into the promising heterogeneous Fenton-like process that enables the decomplexation of Ni(II)-EDTA, the degradation of EDTA, and the synchronous immobilization of Ni(II).

UV irradiation induced simultaneous reduction of Cu(II) and degradation of EDTA in Cu(II)-EDTA in wastewater containing Cu(II)-EDTA

Decomplexation of Cu(II)-EDTA followed by chemical precipitation of free Cu(II) ions can effectively degrade EDTA in Cu(II)-EDTA and remove Cu(II), but requires large precipitant dosage and inevitably produces a large amount of copper-containing sludge that is difficult to deal with. Herein, we demonstrated that simultaneous reduction of Cu(II) and degradation of EDTA in Cu(II)-EDTA can be achieved by UV irradiation of wastewater containing Cu(II)-EDTA without adding reagent. 93.65% of Cu(II) was reduced to Cu(0) with a high purity of 99.93 wt%, which can be recycled, thus avoiding the generation of copper-containing sludge. 96.67% of EDTA in Cu(II)-EDTA was degraded, and the final products were HCHO, NH4+, NO3- and low-molecular acids. In depth, the dominant degradation mechanism of EDTA in Cu(II)-EDTA was photo-induced successive decarboxylation through homolysis of C-O and C-C bond of -CH2-COOH group, followed by ligand to metal charge transfer (LMCT) and hydrolysis reactions. The minor degradation mechanism of EDTA in Cu(II)-EDTA was successive decarboxylation by •OH radicals. Simultaneously, Cu(II) was reduced to Cu(0) by H• and eaq- produced by UV irradiation of Cu(II)-EDTA. This study provided an approach of simultaneous removal of heavy metals and degradation of EDTA in Cu(II)-EDTA in wastewater containing heavy metal-EDTA complex.

Synergistic effect and mechanism of zero-valent iron activated persulfate on Cu(II)–EDTA decomplexation enhanced with weak magnetic field

Herein, a weak magnetic field (WMF) was applied to improve the catalytic degradation of the copper-ethylene diamine tetraacetic acid complex (Cu(II)–EDTA) and recovery of Cu using zero-valent iron/peroxomonsulfate (ZVI/PS). The removal rates of Cu(II)–EDTA in the WMF/ZVI/PS system were 7.92 and 1.33 times those in the ZVI and ZVI/PS systems, respectively. The recovery rates of Cu in the WMF/ZVI/PS system were 4.78 and 1.25 times more than those in ZVI and ZVI/PS systems, respectively. Scavenger quenching experiments and electron spin resonance (ESR) results showed that more active radicals (SO4•− and •OH) were produced and both SO4•− and •OH played the important role in Cu(II)–EDTA degradation in the WMF/ZVI/PS system. The ZVI and PS dosages and initial solution pH considerably affected the removal efficiency of Cu(II)–EDTA. X-ray energy-dispersive spectroscopy (EDS) results showed that WMFs could accelerate the enrichment of paramagnetic Cu2+ on the ZVI surface. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) results showed that Cu2+ ions were first adsorbed on the corroded ZVI and then reduced to Cu0 with time. A possible Cu(II)–EDTA decomposition and Cu reduction mechanism was also proposed. This study provides a promising and ecofriendly technique for treating industrial wastewater containing organic complexed metals.

EDTA Degradation by UV/Chlorine Treatment: Efficiency, Formation of Oxidation Byproducts and Toxicity Evaluation

UV and chlorination are worldwide employed tertiary treatment for disinfection/oxidation of secondary effluents in sewage treatment plants. However, However, the combined UV and chlorination process (UV/chlorine) for removing non-biodegradable EDTA in secondary effluents is still unknown. In this study, we evaluated UV/chlorine for EDTA degradation and compared its formation of typical oxidation byproducts and toxicity change with chlorination. UV/chlorine showed synergistic effect on EDTA degradation, with removal efficiency of higher than 90% within 60 s at chlorine dosage of 0.30 mM, compared to UV irradiation of less than 2% and chlorination of about 65%. Increasing chlorine dosage from 0.050 to 0.30 mM and solution pH from 5.0 to 7.0 accelerated EDTA degradation. The coexisting bicarbonate and nitrate showed slight effects on EDTA degradation, but natural organic matter exhibited remarkable inhibition. As well, about 50%-80% of EDTA in realistic secondary effluent was removed by UV/chlorine. Three chlorinated byproducts including trichloromethane (TCM), dichloroacetic acid and trichloroacetic acid were formed in both chlorination and UV/chlorine, and UV/ chlorine treatment slightly enhanced the production of TCM. The acute toxicities of treated wastewater by UV/chlorine to luminescent bacterium and rice seeds were greater than that by chlorination, which deserves extensive concerns in advanced treatment processes for secondary effluents.

Effect of green synthesized ZnO nanoparticles using Paspalum scrobiculatum grains extract in biological applications.

In this report, ZnO nanoparticles were biosynthesized using Paspalum scrobiculatum grains extract for the first time. GC-MS analysis explicated that diethyl phthalate was the major phytocompound with 94.09% in aqueous extract. ZnO nanoparticles formation was confirmed by various physicochemical analyses. HR-TEM images showed the hexagonal, rectangular shaped nanoparticles in 15-30 nm size. The antioxidant, anti-inflammatory, and anti-diabetic analyses showed the effective bioactivity of ZnO nanoparticles in 80 μg/ml concentration with 95.36%, 94.08%, and 91.96%, respectively. The morphological and tissue changes witnessed in larvicidal and insecticidal activities against Culex tritaeniorhynchus and Tribolium castaneum revealed the efficient nature of ZnO nanoparticles in 100 ppm at 48 h and 100 μg/kg at 72 h, respectively. The morphological changes in antibacterial activity demonstrated the bactericidal nature of ZnO nanoparticles against Salmonella typhi and Staphylococcus aureus in 150 μg/ml concentration. The morphological observations in anticancer activity against HepG2 liver cancer cells showed the potent drug features of ZnO nanoparticles in 100 μg/ml concentration with 97.18% of cytotoxicity. The ZnO nanoparticles showed no toxicity against HDF normal cells in lower concentrations and it explicated the biocompatible features of nanoparticles. The Vigna radiata plant growth was efficiently promoted by low (60 ppm) concentration of nanoparticles. The ZnO nanoparticles divulged effective degradation of IPA, EDTA, BQ, and DPBF in 75%, 45%, 55%, and 80% through ROS formation, respectively. Thus, the synthesized ZnO nanoparticles are biocompatible and inexpensive material compared to the traditional one and can be utilized as an efficient material in biological fields. RESEARCH HIGHLIGHTS: Efficient larvicidal and insecticidal activities were evinced at low IC50 value. The ZnO nanoparticles were non-toxic to HDP (fibroblast) normal cells. Efficient plant growth was attained at 60 ppm concentration.

Enhanced removal of Cu-EDTA in a three-dimensional electrolysis system with highly graphitic activated biochar produced via acidic and K2FeO4 treatment

Herein, we report a novel strategy for the fabrication of almond shell biochar-based materials containing highly dispersed graphene nanosheet structures by sequential treatment with hydrochloric acid and potassium ferrate. The resulting material serving as particle electrodes endowed the three-dimensional electrolysis system with excellent and stable Cu-ethylene diamine tetraacetic acid (Cu-EDTA) decomplexation and mineralization ability, along with Cu(Ⅱ), chemical oxygen demand, and dissolved total organic carbon removal efficiencies of 96.8%, 92.5%, and 86.2%, respectively. In contrast to excess Cu(Ⅱ) or EDTA, the complete complexation between Cu(Ⅱ) and EDTA facilitated EDTA degradation. During the reaction, the adsorption toward Cu(Ⅱ), rather than EDTA, in the complexing system, alleviated the burden of electrochemical oxidation for Cu-EDTA decomplexation. This, together with direct and indirect electrocatalytic oxidation mediated by adsorbed hydroxyl radicals on the particle electrode surface, contributed to the enhanced removal of Cu-EDTA. Density functional theory calculations further demonstrated the main types of active sites and the importance of the graphene nanosheet structure of the particle electrodes. This work provides different perspectives on the electrocatalytic removal of heavy metal complexes.

Sonocatalytic degradation of EDTA in the presence of Ti and Ti@TiO2 nanoparticles

The sonocatalytic degradation of EDTA (C0 = 5 10−3 M) in aqueous solutions was studied under 345 kHz (Pac = 0.25 W mL−1) ultrasound at 22–51 °C, Ar/20%O2, Ar or air, and in the presence of metallic titanium (Ti0) or core-shell Ti@TiO2 nanoparticles (NPs). Ti@TiO2 NPs have been obtained using simultaneous action of hydrothermal conditions (100–214 °C, autogenic pressure P = 1.0–19.0 bar) and 20 kHz ultrasound, called sonohydrothermal (SHT) treatment, on Ti0 NPs in pure water. Ti0 is composed of quasi-spherical particles (30–150 nm) of metallic titanium coated with a metastable titanium suboxide Ti3O. SHT treatment at 150–214 °C leads to the oxidation of Ti3O and partial oxidation of Ti0 and formation of nanocrystalline shell (10–20 nm) composed of TiO2 anatase. It was found that Ti0 NPs do not exhibit catalytic activity in the absence of ultrasound. Moreover, Ti0 NPs remain inactive under ultrasound in the absence of oxygen. However, significant acceleration of EDTA degradation was achieved during sonication in the presence of Ti0 NPs and Ar/20%O2 gas mixture. Coating of Ti0 with TiO2 nanocrystalline shell reduces sonocatalytic activity. Pristine TiO2 anatase nanoparticles do not show a sonocatalytic activity in studied system. Suggested mechanism of EDTA sonocatalytic degradation involves two reaction pathways: (i) sonochemical oxidation of EDTA by OH/HO2 radicals in solution and (ii) EDTA oxidation at the surface of Ti0 NPs in the presence of oxygen activated by cavitation event. Ultrasonic activation most probably occurs due to the local heating of Ti0/O2 species at cavitation bubble/solution interface.

Formic acid recovery from EDTA wastewater using coupled ozonation and flow-electrode capacitive deionization (Ozo/FCDI): Performance assessment at high cell voltage

Carbon resource recovery from toxic organic wastewater to reduce unnecessary energy loss and greenhouse gas emissions is rarely pursued. In the present study, a promising approach for formic acid (FA) recovery from EDTA wastewater was proposed by coupling ozonation and flow-electrode capacitive deionization (Ozo/FCDI). In the ozonation process, a FA productivity of 25% was obtained with the complete degradation of EDTA. The FA recovery from wastewater was compared under electrodialysis (i.e., without the use of flowable carbon electrodes, 0 wt%) and FCDI (i.e. using 5 wt% flowable carbon electrodes) processes and the results demonstrated the superiority of the FCDI process. After 390 min of operation, the accumulated FA concentration in the anode chamber of the FCDI system had increased to 633.6 mg/L with a low energy consumption of 8.0 kWh/kg FA, which was 1.8 times of the FA concentration in the electrodialysis (ED) process and nearly 6.4 times in the feed stream. These findings suggest the effective acquisition of high value-added FA in the Ozo/FCDI system; may provide new opportunities and challenges for the recovery of organic compounds.

Removal of Edta from Photovoltaic Industry Wastewater by Ag-tio2 Photocatalyst

The presence of EDTA in wastewaters originating from photovoltaic (PV) process may cause significant environmental impacts. The aim of this work was the treatment of the effluents, resulting from the baths of the PV process, by a photocatalytic process based on TiO2 silver doped (Ag-TiO2) and using synthetic solutions containing EDTA.The influence of the various parameters such as the quality and quantity of the photocatalyst, initial concentration of the pollutant, the initial pH was studied. XRD characterizations were also done. Results mainly showed that with doping TiO2 with Ag, it possible to obtain higher yields in the photocatalytic degradation of EDTA than in absence of dopant. The optimal Ag-TiO2 catalyst dose was found to be 1.5 g/L, whereas, the optimal initial pH value was found to be 2.5.Keywords : Photovoltaic wastewater, EDTA, Doped Ag-TiO2 photocat

The agricultural use potential of the detoxified textile dyeing sludge by integrated Ultrasound/Fenton-like process: A comparative study

Enhancing industrial sludge detoxification is of scientific and practical significance in confronting urban development and stringent environmental regulations. A strategy combining ultrasound (US) with the zero-valent iron/EDTA/Air (ZEA) process was proven to be eco-friendly, being efficient in the removal of toxic compounds from textile dyeing sludge in our previous studies. In this paper, therefore, the detoxification effects of three advanced oxidation processes (US, ZEA, US/ZEA) on textile dyeing sludge were comparatively evaluated for the first time through alteration of the sludge's physico-chemical parameters (e.g., macronutrients, heavy metals, and persistent organic pollutants) and toxicity (plants and aquatic biota), by which the appropriateness of industrial sludge's agricultural use was assessed. The results showed that US led to the least alteration of the physico-chemical properties, and the treated sludge became less biodegradable, as demonstrated by XPS. With ZEA treatment, persistent organic pollutants (POPs) were degraded by oxidation, and heavy metals were more leachable, leading to effective detoxification with a relatively low sludge dose, but an excessive amount of EDTA would negatively change the fertilizing properties of the sludge. However, the integration of US and ZEA could avoid this situation, as US promoted the degradation of EDTA and POPs, thus causing the least inhibition or even a noticeable stimulation of plant growth when the sludge dosage was 7.5 tdw/ha (recommended dosage by the latest legislation in China). Aquatic organism toxicity tests further confirmed that US/ZEA treatment realized the most significant toxicity reduction, leading to the slightest environmental disruption. This study could be instructive in providing guidance for industrial sludge management considering agricultural use.

Autocatalytic Decomplexation of Cu(II)-EDTA and Simultaneous Removal of Aqueous Cu(II) by UV/Chlorine.

Traditional processes usually cannot enable efficient water decontamination from toxic heavy metals complexed with organic ligands. Herein, we first reported the removal of Cu(II)-EDTA by a UV/chlorine process, where the Cu(II)-EDTA degradation obeyed autocatalytic two-stage kinetics, and Cu(II) was simultaneously removed as CuO precipitate. The scavenging experiments and EPR analysis indicated that Cl• accounted for the Cu(II)-EDTA degradation at diffusion-controlled rate (∼1010 M-1 s-1). Mechanism study with mass spectrometry evidence of 11 key intermediates revealed that the Cu(II)-EDTA degradation by UV/chlorine was an autocatalytic successive decarboxylation process mediated by the Cu(II)/Cu(I) redox cycle. Under UV irradiation, Cu(I) was generated during the photolysis of the Cl•-attacked complexed Cu(II) via ligand-to-metal charge transfer (LMCT). Both free and organic ligand-complexed Cu(I) could form binary/ternary complexes with ClO-, which were oxidized back to Cu(II) via metal-to-ligand charge transfer (MLCT) with simultaneous production of Cl•, resulting in the autocatalytic effect on Cu(II)-EDTA removal. Effects of chlorine dosage and pH were examined, and the technological practicability was validated with authentic electroplating wastewater and other Cu(II)-organic complexes. This study shed light on a new mechanism of decomplexation by Cl• and broadened the applicability of the promising UV/chlorine process in water treatment.

Estudio comparativo del uso de diferentes agentes de sacrificio para la producción de hidrógeno mediante fotocatálisis heterogénea utilizando el mineral arena negra como semiconductor

El mineral arena negra es una mezcla de óxidos de hierro (FeO, Fe2O3, Fe3O4), TiO2 y SiO2 dispuestos en una estructura natural, que podría ser utilizado como semiconductor. En este trabajo se evaluó el efecto del agente de sacrificio para la generación fotocatalítica de hidrógeno utilizando este material como catalizador. Para tal fin se evaluó el efecto de variables del proceso tales como tipo de agente de sacrificio (EDTA, Na2SO3 y metanol) normalmente utilizados como donadores de electrones en la reacción fotocatalítica de producción de hidrógeno, pH inicial de la suspensión (3.0, 7.0 y 9.0) y la concentración del sustrato. Estas variaron entre 1.0, 25.0 y 50.0 mM (EDTA, Na2SO3) y 10.0, 30.0 y 50.0% (v/v) para metanol. Bajo las condiciones de reacción evaluadas, los niveles de máxima producción de hidrógeno fueron Na2SO3>EDTA>CH3OH, respectivamente y la máxima producción de hidrógeno se obtuvo con 25.0 mM Na2SO3 en medio ácido (pH 7.0). La degradación de EDTA y simultánea producción de hidrogeno mediante reacción fotocatalítica, se vieron favorecidos a pH 3.0 y una concentración 1.0 mM

Sonocatalytic oxidation of EDTA in aqueous solutions over noble metal-free Co3O4/TiO2 catalyst

The sonocatalytic degradation of EDTA in aqueous solution was studied under ultrasound irradiation (345 kHz, 73 W, acoustic power 0.20 W·mL−1, Ar and Ar/O2 saturating gases, T = 20–50 °C) in the presence of Co3O4/TiO2 and Pt/TiO2 nanocatalysts. About 90% of EDTA (C0 = 5 10-3 M) was oxidized during ultrasonic treatment at 40 °C in the presence of the Co3O4/TiO2 catalyst and Ar/O2 gas mixture. By contrast, Pt/TiO2 catalyst exhibited much lower sonocatalytic activity in this system. Suggested mechanism of EDTA oxidation in the presence of Co3O4/TiO2 catalyst involved the generation of oxidizing radicals by acoustic cavitation and Co(II)-Co(III) redox process. Quite low apparent activation energy of the sonocatalytic process (Ea = 19 kJ mol−1) was attributed to diffusion of reagents in the vicinity of the active sites of catalyst. Sonocatalytic degradation of EDTA is accompanied by formation of iminodiacetic acid, formic acid, oxalic acid, glycolic acid and acetic acid as intermediate products in an agreement with radical-driven mechanism.

Degradation of EDTA in H2O2 -containing wastewater by photo-electrochemical peroxidation

Semiconductor wastewater currently contains H2O2 which is an important reagent in wafers cleaning. Recalcitrant organic pollutant such as EDTA are always present in this type of wastewater and may represent a threat for the environment. In this work, a new photoelectrochemical reactor is proposed to remove EDTA from H2O2 contaning wastewater. First, photolysis, electrochemical peroxidation and photo-electrochemical peroxidation were compared. The results showed that the removal efficiency decreases in the sequence: UV/H2O2 «EC/H2O2 <UV/EC/H2O2. The main parameters affecting the photo-electrochemical peroxidation process were studied. The study revealed that the optimal current was 50 mA, while the optimum initial pH was found in the acidic range from 2.25 to 3.0, with a peak at 2.25. Increasing H2O2 concentration results in increasing in EDTA removal up to 92.1%, while decreasing initial EDTA concentration up to 22.5 mg L−1 gives a complete removal in only 90 min. It was also found that the degradation of EDTA greatly depends on the nature of the present cation.

Effect of chelating agents on Reactive Green 19 decolorization through Fe0-activated persulfate oxidation process

The effect of chelating agents on the decolorization of Reactive Green 19 (RG19) through Fe0 activated persulfate (PS/Fe0) process was investigated. Though other previous studies reported that chelating agent can enhance the degradation of organic contaminant in Fenton-like system, our finding showed that the presence of chelating agents would chelate free Fe2+ and minimize free Fe2+ concentration, which resulted in the retardation of RG19 decolorization. RG19 decolorization decreased to 7%, 21%, and 15% in the presence of sodium citrate, sodium EDTA, and sodium oxalate, compared with control test (without chelating agent, 99%) within 10 min. The degradation efficiencies decreased with increasing chelating agent concentrations because of complex formation with Fe2+. Higher PS concentration, Fe0 dosage, and temperature had an obvious enhancement for RG19 decolorization efficiency. Elucidation of RG19 containing sodium EDTA degradation pathways indicated that PS/Fe0 process could degrade RG19 to carboxylic acids and inorganic salts efficiently. The presence of sodium EDTA had no influence on by-products, and EDTA just played a chelating agent function for chelating Fe ions.

Coupled Cu(II)-EDTA degradation and Cu(II) removal from acidic wastewater by ozonation: Performance, products and pathways

Effective removal of toxic metal–organic ligand complexes from contaminated water is still a challenging task. Here, we found that ozonation could achieve efficient degradation of Cu(II)-EDTA and simultaneous removal of Cu(II) from acidic solution (pH 3.1–6.3) as well as from an electroplating effluent (pH 3.6). A complete Cu-EDTA and 75–80% of TOC removal could be achieved from a synthetic solution at the initial Cu(II) of 64mgL−1 and ozone dosage of 30mgmin−1L−1. The acidic pH changed to circumneutral during ozonation, resulting in 90–97% of Cu(II) removal through precipitation finally. HO-mediated oxidation was predominantly responsible for the degradation of Cu-EDTA, as proved by the radical scavenging experiments and electron paramagnetic resonance. Based on the evolution of HPLC spectra and HPLC–MS analysis, a stepwise decarboxylation (i.e., cleavage of N–C bond) was found to responsible for the ozonation of Cu-EDTA, where six intermediates/products were identified. Thus, a plausible mechanism involving decarboxylation followed by Cu(II) precipitation was proposed. Ozonation could also realize efficient removal of Cu(II)-EDTA, Cu(II) and TOC from a realistic electroplating effluent. We believe this study would provide a simple and promising option for water decontamination from toxic metal–organic ligand complexes.

Pathway of FeEDTA transformation and its impact on performance of NOx removal in a chemical absorption-biological reduction integrated process.

A novel chemical absorption-biological reduction (CABR) integrated process, employing ferrous ethylenediaminetetraacetate (Fe(II)EDTA) as a solvent, is deemed as a potential option for NOx removal from the flue gas. Previous work showed that the Fe(II)EDTA concentration was critical for the NOx removal in the CABR process. In this work, the pathway of FeEDTA (Fe(III)/Fe(II)-EDTA) transformation was investigated to assess its impact on the NOx removal in a biofilter. Experimental results revealed that the FeEDTA transformation involved iron precipitation and EDTA degradation. X-ray photoelectron spectroscopy analysis confirmed the iron was precipitated in the form of Fe(OH)3. The iron mass balance analysis showed 44.2% of the added iron was precipitated. The EDTA degradation facilitated the iron precipitation. Besides chemical oxidation, EDTA biodegradation occurred in the biofilter. The addition of extra EDTA helped recover the iron from the precipitation. The transformation of FeEDTA did not retard the NO removal. In addition, EDTA rather than the iron concentration determined the NO removal efficiency.

Green approach for photocatalytic Cu(II)-EDTA degradation over TiO2: toward environmental sustainability.

A green approach was successfully developed to reap three environmental benefits simultaneously: (1) clean water production, (2) hydrogen (H2) generation, and (3) well-dispersed in situ Cu(2+) recovery for direct TiO2-CuO composite reclamation, by exploiting the synergistic integration of photocatalytic reaction of Cu-EDTA and one-dimensional (1D) ultralong and ultrathin TiO2 nanofibers. In this light-initiated system, Cu-EDTA was oxidized by TiO2 thus releasing Cu(2+) which was reduced and recovered through uniform adsorption onto the long and porous TiO2 surface. A win-win platform was thus attained, on which Cu was recovered while providing active sites for H2 generation via photoreduction of H2O and enhancing photo-oxidation of remaining intermediate oxidation byproducts. Experimental results showed a H2 generation rate of 251 μmol/h concomitantly with TOC reduction. The used TiO2 nanofibers deposited with Cu were reclaimed directly as the TiO2-CuO composite after a facile heat treatment without additional chemicals and subsequently reusable for photocatalytic treatment of other wastewater (glycerol) to cogenerate H2 and clean water under both UV-visible and visible light. This study expounds a significant advancement through an ingenious integration which enhances the environmental sustainability of Cu-EDTA treatment via TiO2 photocatalysis. It also represents a promising and adoptable approach to synthesize other functional composite nanomaterials in a green manner thus broadening its environmental application spectrum, as it promotes industrial environmental management via waste segregation and motivates research to recover more resources from wastewater.