Presence Of Ethylenediaminetetraacetic Acid Research Articles

Agricultural waste materials enhance protease production by Bacillus subtilis B22 in submerged fermentation under blue light-emitting diodes

Bacillus bacteria have major utility in large-scale production of industrial enzymes, among which proteases have particular importance. B. subtilis B22, an aerobic and chemotrophic strain, was isolated from kimchi and identified by 16S rRNA gene sequencing. Extracellular protease production was determined in basic medium, with 1% (w/v) casein as substrate, by submerged fermentation at 37°C under blue, green, red and white light-emitting diodes (LEDs), white fluorescent light and darkness. Fermentation under blue LEDs maximized protease production (110.79 ± 1.8U/mL at 24h). Various agricultural waste products enhanced production and groundnut oil cake yielded the most protease (334 ± 1.8U/mL at 72h). Activity and stability of the purified protease were optimum at pH 7-10 and 20-60°C. Activity increased in the presence of Ca2+, Mg2+ and Mn2+, while Fe2+, Zn2+, Co2+ and Cu2+ moderated activity, and Ni2+ and Hg2+ inhibited activity. Activity was high (98%) in the presence of ethylenediaminetetraacetic acid (EDTA) but inhibited by phenylmethanesulfonyl fluoride (PMSF). The protease was unaffected by nonionic surfactants, tolerated an anionic surfactant and oxidizing agents, and was compatible with multiple organic solvents. These properties suggest utility of protease produced by B. subtilis B22 under blue LEDs for industrial applications.

Enhancement of the reactivity of sulfidized nanoscale zero-valent iron-persulfate by ligand addition for the oxidative degradation of water pollutants

The main objective of the study was to derive an appropriate ligand in sulfidized nanoscale zero-valent iron-persulfate (S-nZVI-PS) system for the efficient and rapid degradation of recalcitrant organic pollutants. In this aspect, we have compared the efficiency of three ligands (L) such as ethylenediaminetetraacetic acid (EDTA), oxalic acid (OA) and citric acid (CA) for the degradation of benzoic acid (BA). Complete degradation of BA was achieved within 10 min in S-nZVI-L-PS system. In order to investigate the controlling factors in ligand assisted degradation, Fe dissolution, the thermodynamic feasibility of Fenton reactions and adsorption of ligands on the material surface has been studied. It is found that CA and OA caused more Fe dissolution and there by a more feasible Fenton condition compared to other ligands. Whereas EDTA has high affinity for the Fe surface and it attracts the PS after adsorption. Thus, we confirmed that heterogeneous Fenton like reactions are more favorable in the presence of EDTA and homogeneous Fenton like reaction is more favorable in presence of CA and OA. All these reactions produce OH and SO4− (confirmed by electron spin resonance (EPR) measurements). However, for used S-nZVI the adsorption possibility is less and only CA is the choice in this case. Thus our study concluded that S-nZVI-CA-PS system would be the conclusive solution for field remediation.

Impact of metal ions on structural EPS hydrogels from aerobic granular sludge

Structural extracellular polymeric substances (structural EPS) can form stable hydrogels and are considered to be responsible for the stability of biofilms and aerobic granular sludge. Structural EPS were extracted from aerobic granular sludge and characterized for their gel-forming capacity with different alkaline earth and transition metal ions. The structural EPS hydrogels were compared to alginate hydrogels. Alginate is a well characterized polymer which is able to form stiff hydrogels with multivalent ions. The stiffness of the obtained hydrogels was measured with dynamic mechanical analysis and quantified by the Young’s modulus. Furthermore the stability of structural EPS hydrogels towards disintegration in the presence of ethylenediaminetetraacetic acid (EDTA) was evaluated at pH 4.5–10.5 and compared to that of alginate, polygalacturonic acid and κ-carrageenan. The stiffness of alginate hydrogels was multiple times higher than that of structural EPS. Alkaline earth metals resulted in stiffer alginate hydrogels than transition metals. For structural EPS this trend was opposite to alginate. Independent of the pH, polysaccharide hydrogels were quickly disintegrated when being exposed to EDTA. Structural EPS hydrogels demonstrated greater stability towards EDTA and were still intact after one month at pH 4.5–8.5. It is suggested that the gelling mechanism of structural EPS is not only related to metal ion complexation of the polymers, but to a combination of interactions of multiple functional groups present in structural EPS. This study helps to further understand and characterize structural EPS from aerobic granular sludge, and therewith understand its stability and that of biofilms in general.

Further studies on the signal enhancement effect in laser diode thermal desorption-triple quadrupole mass spectrometry using microwell surface coatings.

The laser diode thermal desorption (LDTD) ionization source allows ultrafast and sensitive analysis of small molecules by mass spectrometry. Signal enhancement in LDTD has been observed when coating the surface of sample microwells with a solution of ethylenediaminetetraacetic acid (EDTA) or nitrilotriacetic acid. Here we present a quantitative analysis of signal enhancement using solutions of diverse commercial proteins (lysozyme, immunoglobulin G, albumin, and fibrinogen) as coatings. Results showed that compounds with polar chemical functions such as carboxylic acid, sulfonyl, and nitro had signal enhancement factors, in most cases higher than 10, when using any of the tested proteins as coating agent. Analysis of variance revealed that immunoglobulin G and fibrinogen gave the best results. However, the signal enhancement factors obtained with these proteins were not superior to those observed with EDTA. To explain the signal enhancement effect of proteins, analysis by scanning electron microscopy of dried samples on the microwell sample plates was carried out. Images showed that salicylic acid, one of the compounds with the highest observed signal enhancement, formed a thick layer when applied directly on the uncoated surface, but it formed small crystals (<1μm) in the presence of protein or EDTA coatings. Further crystallographic studies using powder X-ray diffraction showed that the crystalline form of salicylic acid is modified in the presence of EDTA. Salicylic acid when mixed with EDTA had a higher percentage of amorphous phase (38.1%) than without EDTA (23.1%). These results appear to confirm that the diminution of crystal size of analytes and the increase of amorphous phase are implicated in signal enhancement effect observed in LDTD using microwell surface coatings. To design better coatings and completely elucidate the signal enhancement effect in LDTD, more studies are necessary to understand the effects of coatings on the ionization of analytes.

Enhanced dielectric performance of BaxSr(1-x)TiO3 films prepared by the direct current micro-arc oxidation in the presence of ethylenediamine tetraacetic acid

BaxSr(1-x)TiO3 (BST) thin-films are fabricated on a Ti-substrate by micro-arc oxidation method in the presence of an aqueous solution of ethylenediamine tetraacetic acid (EDTA) and effects of EDTA, as additive, are investigated on the micro-structure and dielectric properties of BST thin-films. The obtained results show that EDTA delays the micro-arc oxidation reaction and results in a controllable slow-growth of the thin-film. Although, a remarkable thin film is obtained, however, capacitance of the prepared film is prominently increased. When concentration of EDTA is 0.05 M, the best compactness and smoothness for the film are observed. Moreover, the largest dielectric constant and smallest dielectric-loss are attained. In addition, the largest residual polarization strength (2Pr) of 3.4 μC/cm2 is also attained under this condition.

Enhancing the antimicrobial properties of borates in coolant fluids

Studied the effects of C10H16O8N2 ethylenediaminetetraacetic acid (EDTA) and its C10H14O8N2Na2 disodium salt (trilon B) on the antimicrobial properties of lithium monoborate (LiBO2), sodium (NaBO2) and potassium (KBO2) in 3% emulsion coolant «Ukrinol-1». Established that the listed monoborates have antimicrobial properties in 3% emulsion coolant «Ukrinol-1». The addition of EDTA and trilon B separately at concentration of 1 g/l, enhances almost 2 times the antimicrobial activity of monoborates in the coolant emulsion. Thus, the addition of 30 g/l of sodium monoborate in combination with 1 g/l of EDTA increases the service life of 3% emulsion of «Ukrinol-1» coolant fluid up to 87 days. In combination with trilon B the term of the antimicrobial action of borates in 3% emulsion of the coolant «Ukrinol-1» increases to greater extent than in the presence of EDTA and its service life increases up to 110 days. All this allows us to recommend the studied composition as the antimicrobial additive to improve the sanitary and hygienic working conditions of machine workers and increasing the service life of the 3% emulsion coolant «Ukrinol-1» used for machining of metals.

Kinetic study of the degradation of rhodamine B using a flow-through UV/electro-Fenton process with the presence of ethylenediaminetetraacetic acid

An UV enhanced electro-Fenton (EF) process was conducted in a flow-through system to remove rhodamine B (RhB) in the presence of ethylenediamine tetraacetate (EDTA). The process was denoted as UV/EDTA/EF where EDTA formed complexes with iron ions, thus keeping them soluble at high pH values. The process was very efficient as it could initiate the fast reduction of FeIII to FeII and thus the decomposition of H2O2. The influence of Fe dose, the ratio of EDTA:Fe, aeration rate, flow rate, current, initial RhB concentration and pH on the RhB removal in the UV/EDTA/EF process was investigated. The best RhB removal was obtained as 89.9% at [Fe]0 = [EDTA]0 = 0.2 mM, current = 50 mA, aeration rate = 20 mL min−1, flow rate = 7 mL min−1, pH = 7 and [Na2SO4]0 = 0.05 M. The degradation of EDTA during the process was also studied. Radical scavenging experiments indicated that OH was the dominant radical for RhB removal. While, the photolysis of FeIIIEDTA was mainly responsible for EDTA degradation. RhB and EDTA removal in different systems was compared. The stability test proved that in the presence of EDTA, the UV/EF process could remove RhB with high efficiency in the first two runs. While, the efficiency dropped remarkably after EDTA’s complete depletion. The mechanisms of the UV/EDTA/EF process were proposed. UV/EDTA/EF conducted in the flow-through system was able to efficiently remove RhB as well as EDTA in a wide pH range and proposed as a promising approach for wastewater treatment.

Enhanced photocatalytic reduction of toxic Cr(VI) with Cu modified ZnO nanoparticles in presence of EDTA under UV illumination

In this study, the photocatalytic reduction of Cr(VI) to Cr(III) in aqueous solution using 1 wt% Cu/ZnO photocatalyst in presence of ethylenediaminetetraacetic acid (EDTA) under UV irradiation was investigated. The photocatalytic Cr(VI) reduction with ZnO under UV irradiation was significantly low. A fast Cr(VI) reduction with ZnO was recorded in presence of EDTA. Results demonstrated that the rate constant raised from 1.6 × 10−2 to 7.5 × 10−2 min−1 with 20 ppm EDTA addition. The optimum reduction (90%) was observed within 30 min at pH 3. The reduction efficiency of Cr(VI) was evidently increased from 6% to 99%, with increasing ZnO dosages up to 40 mg. The role of co-catalysts such as Au, Ag, Cu and NiO was also studied. The addition of Cu ion remarkably accelerated the reduction of Cr(VI), compared with ZnO/EDTA system alone. The Cu motivated ZnO/EDTA system completed the 99% reduction within only 30 min. The Cu ions were reduced to metallic copper and Cu2O by conduction band electrons of ZnO. The electron–hole recombination was gently declined by the shallow electron trapping of Cu. On the other hand, EDTA could be performed in two ways by forming Cr(III)-complex and separating Cr(III) from ZnO surface and by consuming valence band holes. The Cu modified ZnO photocatalyst was characterized by N2 adsorption- desorption isotherm, TEM, EDX, XPS, DRS and PL spectra. We evaluated the influence of pH, photocatalyst dosage, initial concentration of EDTA and initial concentration of Cu2+ ion (Cu doping amount) on photocatalytic reduction of Cr(VI). The pseudo first order kinetic reaction was confirmed for this reduction process. Herein, a probable mechanism of this photocatalytic reduction process was also presented.

Synthesis of tetragonal prismatic γ-In2Se3 nanostructures with predominantly {110} facets and photocatalytic degradation of tetracycline

Crystals grown in the direction of high-energy facets have reduced surface energy, a small portion of high-energy crystal facets, and high photocatalytic activity. In this work, γ-In2Se3 nanoparticles with predominantly exposed {110} facets are synthesized hydrothermally in the presence of ethylenediaminetetraacetic acid (EDTA). EDTA plays a key role in regulating the exposed {110} facets and by adding 0.04 M of EDTA, tetragonal prismatic γ-In2Se3 nanoparticles with the {110} facets are produced. Studies of the photocatalytic activity of tetracycline (TC) reveal that the tetragonal prismatic γ-In2Se3 prepared with 0.04 M EDTA has the optimal activity that is about 1.9 times higher than that of conical γ-In2Se3 prepared without EDTA. The capture experiments show that h+ and O2− affect degradation of TC and our results reveal a novel strategy to synthesize γ-In2Se3 with the optimal morphology and photocatalytic activity.

Adsorption of U(VI) on montmorillonite in the presence of ethylenediaminetetraacetic acid

The adsorption, diffusion and migration behaviors of uranium may be highly influenced by organics in natural environments. Ethylenediaminetetraacetic acid (EDTA) is one of the most important small organics in groundwaters, especially at the radioactive contaminated sites. In this work, we studied U(VI) adsorption on montmorillonite in the presence of EDTA with batch method. Our results indicated that U(VI) adsorption was significantly different in the presence and absence of EDTA. The equimolar EDTA inhibited the U(VI) adsorption at a wide pH range while only enhanced the adsorption at pH ˜7.0. The pseudo-second-order model showed the best fit for describing the adsorption kinetics in comparison with three other popular models. The influence of different addition sequences on adsorption of EDTA and U(VI) on montmorillonite was also investigated, and the results indicated that EDTA played the role as a bridge between montmorillonite surface sites and U(VI). The X-ray photoelectron spectroscopy and attenuated total reflectance Fournier-transform infrared spectroscopy also suggested the formation of EDTA-bridge inner-sphere surface complexes on montmorillonite. This work provides the valuable information of U(VI) adsorption on montmorillonite in the presence of EDTA, and helps us understand the diffusion and migration behaviors of uranium in natural environments.

Enhanced photoreductive degradation of perfluorooctanesulfonate by UV irradiation in the presence of ethylenediaminetetraacetic acid

Perfluorooctanesulfonate (PFOS) is a persistent organic pollutant (POP) that is globally distributed. Hydrated electrons (eaq−) are known to effectively initiate the decomposition of PFOS. In this study, we explore an alternative photolytic approach employing aquated electrons, eaq− in the presence of ethylenediaminetetraacetic acid (EDTA) in order to enhance the photo-induced degradation of PFOS. EDTA, in this case, serves primarily as a hydroxyl radical scavenger, which inhibits the recombination of eaq− with ·OH resulting in an increased average photolytic lifetime for eaq−. The net effect is to enhance the degradation of PFOS. UV/EDTA irradiation is shown to increase the overall decomposition percentages of PFOS. The empirical pseudo first-order rate constant for the loss of PFOS is 0.113 h−1. In addition, we used laser flash photolysis kinetics to show that the eaq− is the dominant species responsible for the decomposition of PFOS. EDTA also allows for the photolytically-produced hydrated electrons to be used in the presence of air over a wide range of pH. Furthermore, perfluoroalkyl sulfonates with longer chain lengths have higher overall decomposition percentages and increased defluorination percentages. The observed kinetic enhancements appear to be due primarily to the impact of the amine and methylene groups of EDTA with respect of hydroxyl radical scavenging.

In vitro Antimicrobial Activity of Robenidine, Ethylenediaminetetraacetic Acid and Polymyxin B Nonapeptide Against Important Human and Veterinary Pathogens.

The emergence and global spread of antimicrobial resistance among bacterial pathogens demand alternative strategies to treat life-threatening infections. Combination drugs and repurposing of old compounds with known safety profiles that are not currently used in human medicine can address the problem of multidrug-resistant infections and promote antimicrobial stewardship in veterinary medicine. In this study, the antimicrobial activity of robenidine alone or in combination with ethylenediaminetetraacetic acid (EDTA) or polymyxin B nonapeptide (PMBN) against Gram-negative bacterial pathogens, including those associated with canine otitis externa and human skin and soft tissue infection, was evaluated in vitro using microdilution susceptibility testing and the checkerboard method. Fractional inhibitory concentration indices (FICIs) and dose reduction indices (DRI) of the combinations against tested isolates were determined. Robenidine alone was bactericidal against Acinetobacter baumannii [minimum inhibitory concentrations (MIC) mode = 8 μg/ml] and Acinetobacter calcoaceticus (MIC mode = 2 μg/ml). Against Acinetobacter spp., an additivity/indifference of the combination of robenidine/EDTA (0.53 > FICIs > 1.06) and a synergistic effect of the combination of robenidine/PMBN (0.5 < FICI) were obtained. DRIs of robenidine were significantly increased in the presence of both EDTA and PMBN from 2- to 2048-fold. Robenidine exhibited antimicrobial activity against Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa, in the presence of sub-inhibitory concentrations of either EDTA or PMBN. Robenidine also demonstrated potent antibacterial activity against multidrug-resistant Gram-positive pathogens and all Gram-negative pathogens isolated from cases of canine otitis externa in the presence of EDTA. Robenidine did not demonstrate antibiofilm activity against Gram-positive and Gram-negative bacteria. EDTA facilitated biofilm biomass degradation for both Gram-positives and Gram-negatives. The addition of robenidine to EDTA was not associated with any change in the effect on biofilm biomass degradation. The combination of robenidine with EDTA or PMBN has potential for further exploration and pharmaceutical development, such as incorporation into topical and otic formulations for animal and human use.

Evaluation of synthetic gene encoding α-galactosidase through metagenomic sequencing of paddy soil

Many genes of industrial relevance can be found in soil. In this study, metagenome sequencing of paddy soil was performed with 55.68Gb sequences and 1,787,113 putative open reading frames (ORFs). The functional profiles and metabolic pathway of soil metagenomes were examined using Gene Ontology, Metagenomics RAST, and Kyoto Encyclopedia of Genes and Genomes. To verify the protein function and assembly of ORFs, a putative gene encoding α-galactosidase, namely GalR, which shares 65% identity with an unpublished glycoside hydrolase (GH) 27 family protein, was synthesized using its optimal codon for overexpression in Escherichia coli. GalR was successfully obtained and characterized. The optimal temperature and pH for GalR activity were 30°C and pH 9, respectively. Enzymatic activity indicated that GalR was alkaliphilic and different from acidophilic α-galactosidase in the GH 27 family. Furthermore, 50% of the relative activity of GalR can be attained for 1.7 and 0.7h preincubation at 40°C and 50°C, respectively. Significant inhibition of GalR was observed in the presence of ethylenediaminetetraacetic acid (EDTA), MgCl2, sodium dodecyl sulfate (SDS), and H2O2; however, it was resistant to 0.1% methanol and ethanol and was slightly activated with NaCl and KCl. The specific activity of GalR was achieved at 11.6 and 0.59μmol/min/mg of protein using p-nitrophenyl-α-d-galactopyranoside and raffinose as substrates, respectively. Consequently, the metagenomic sequencing-based strategy can provide information for mining novel genes.

A Highly Selective Turn-on and Reversible Fluorescent Chemosensor for Al3+ Detection Based on Novel Salicylidene Schiff Base-Terminated PEG in Pure Aqueous Solution.

The development of highly selective and sensitive chemosensors for Al3+ detection in pure aqueous solution is still a significant challenge. In this work, a novel water-soluble polymer PEGBAB based on salicylidene Schiff base has been designed and synthesized as a turn-on fluorescent chemosensor for the detection of Al3+ in 100% aqueous solution. PEGBAB exhibited high sensitivity and selectivity to Al3+ over other competitive metal ions with the detection limit as low as 4.05 × 10−9 M. PEGBAB displayed high selectivity to Al3+ in the pH range of 5–10. The fluorescence response of PEGBAB to Al3+ was reversible in the presence of ethylenediaminetetraacetic acid (EDTA). Based on the fluorescence response, an INHIBIT logic gate was constructed with Al3+ and EDTA as two inputs. Moreover, test strips based on PEGBAB were fabricated facilely for convenient on-site detection of Al3+.

Influence of Divalent Metal Ions on Biofilm Formation by Bacillus subtilis

The wild strain of B. subtilis 168, the protease-deficient strain of B. subtilis BRB14, and the regulatory mutants of B. subtilis 168 degU and B. subtilis 168 ccpA were examined for their ability to form biofilms under stress conditions—with elevated concentrations of divalent metal ions (Ca2+, Mg2+, Mn2+, and Zn2+), as well as in the presence of ethylenediaminetetraacetic acid (EDTA). It was shown that regulatory mutants are more resistant to the addition of divalent metal ions than wild and protease-deficient strains. At the same time, the introduction of EDTA reduces the level of biofilm formation by all strains on average by 50%.

Effects of Thylakoid-Rich Spinach Extract on the Pharmacokinetics of Drugs in Rats.

Thylakoid-rich spinach extract is being used as dietary weight-loss supplements in Japan. A recent rat study has suggested that intake of thylakoid-rich spinach extract with dietary oil inhibits dietary fat absorption via binding to bile acids, which promotes excretion of bile acids in feces. While, we confirmed that a serving size of thylakoid-rich spinach extract contains a large amount of calcium (130 mg/5 g). Therefore, using rats, we evaluated whether one-time ingestion of thylakoid-rich spinach extract affects the gastrointestinal absorption of water-insoluble drugs, such as griseofulvin (GF) and indomethacin (IM), or ciprofloxacin (CPFX) that chelate with polyvalent metal cations. Pretreatment of the rats with thylakoid-rich spinach extract (100 or 300 mg/kg) for 15 min prior to oral administration of GF (50 mg/kg) or IM (10 mg/kg) did not significantly alter the pharmacokinetic properties of either drug. Meanwhile, co-administration of thylakoid-rich spinach extract (500 mg/kg) and CPFX (20 mg/kg) significantly reduced the peak plasma concentration and the area under the plasma concentration-time curve of CPFX to 25 and 40%, respectively in rats. In vitro studies demonstrated that when a mixture of thylakoid-rich spinach extract and CPFX was centrifuged, there was a significant reduction in the supernatant concentration of CPFX relative to the control. When the experiment was repeated in the presence of ethylenediaminetetraacetic acid, the concentration of CPFX was unchanged. These results suggest that the intake of thylakoid-rich spinach extract may reduce the absorption of drugs that form a chelate with polyvalent metal cations, such as CPFX.

Effect of Citric Acid on Prolonging the Half-life of Dissolved Ozone in Water.

To elucidate the effect of citric acid on the stability of dissolved ozone, half-lives of ozone in a citric acid solution was investigated. Prolongation of the half-life of ozone was clearly shown in the presence of citric acid in ozonized water. In the presence of ethylenediaminetetraacetic acid (EDTA), the half-life of ozone was decreased. The addition of various concentrations of citric acid to the EDTA solution, however, reversed the half-life in a concentration-dependent manner. These indicate that citric acid suppresses ozone self-decomposition in water. A citric acid-mediated suppression mechanism of ozone self-decomposition involving hydroxy radical (HO•) was proposed as follows: HO• formed by the radical chain reaction process of ozone is scavenged by a way of abstracting the hydrogen atom bound to a carbon atom located α-position of a carbonyl group. The radical chain reaction of ozone is, thus, suppressed. These findings demonstrate that the addition of citric acid to ozonized water is useful for the stabilization of ozone. This ability may contribute to the application of ozone sterilization in food production processes.

Competitive foam separation of rare earth elements from aqueous solutions using a cationic collector

ABSTRACTCompetitive foam separation of two rare earth elements (REEs), Eu(III) and Tb(III), are investigated in this study in presence of ethylenediaminetetraacetic acid (edta) using cetylpyridinium chloride (CPC). The effects of pH, [edta]/Σ[REEs] and [CPC]/[edta] molar ratio, frother concentration, ionic strength and air-flow rate on the foam separation efficiency are also evaluated. At the optimal experimental condition, Eu(III)/Tb(III) separation factor of 141.56 is obtained. The kinetic data obtained at all the studied parameters are analyzed by the flotation first-order and second-order kinetic models. Eventually, a schematic flow-sheet for Eu(III)/Tb(III) separation is proposed.

From monetite plate to hydroxyapatite nanofibers by monoethanolamine assisted hydrothermal approach

Calcium phosphates offer outstanding biological adaptability. Thanks to their specific physico-chemical properties they are one of the most widely used materials in bone tissue engineering applications. The search for an innovative and economic strategy of synthesizing their different forms has been drawing considerable attention in the field. Herein, we report on a facile hydrothermal process in the presence of ethylenediamine tetraacetic acid and monoethanolamine to obtain various forms of calcium phosphates. The monoethanolamine served as an alkaline source and crystal growth modifier, while ethylenediamine tetraacetic acid was used to control the Ca2+ supersaturation level under high temperature and high pressure conditions. The obtained inorganic compounds were examined for their elemental composition, morphology, and structure using scanning electron microscopy, Raman spectroscopy, and powder x-ray diffraction. We were able to selectively synthesize monetite plate-like microcrystals as well as hydroxyapatite plates and nanofibers by simply varying the concentration of monoethanolamine.

Ligand-mediated contaminant degradation by bare and carboxymethyl cellulose-coated bimetallic palladium-zero valent iron nanoparticles in high salinity environments

The application of nanoscale zero-valent iron (nZVI) for the degradation of contaminants has been extensively investigated, however, few studies have focused on degradation in high salinity environments. In this study, the ability of bare and carboxymethyl cellulose (CMC)-coated bimetallic Pd-nZVI particles to degrade 33′44′-tetrachlorobiphenyl in high saline water (SW) is examined with particular attention given to the effects of ethylenediaminetetraacetic acid (EDTA) on the rate of degradation. EDTA enhances the reactivity of Pd-nZVI in SW, with evidence provided to link this to the removal of the passivating layer. Additionally, a conceptual model is proposed which provides a quantitative description of the removal of these iron oxide layers in the presence of EDTA. An optimum EDTA to bare Pd-nZVI molar ratio of 0.1 exists, with insufficient EDTA unable to remove the passivating layer whilst excess EDTA results in Fe loss and enhanced agglomeration due to magnetic attraction of the bare Fe(0) particles. In contrast, CMC-coating of Pd-nZVI assemblages actually impedes degradation, despite the coated particles displaying a smaller average size compared to uncoated particles, with even the presence of EDTA in this case not significantly improving degradation. The reduced reactivity in the presence of CMC is primarily attributed to the effect of CMC on the association of Pd with nZVI particles. In particular, the presence of CMC reduced the total amount of Pd incorporated with the stabilized particles compared to the non-stabilized particles. Additionally, the presence of CMC results in less Pd present in its reactive zero-valent oxidation state.