Na2EDTA Solution Research Articles

An Isoniazid-Based reversible Schiff base chemosensor for Multi-Analyte (Cu2+, Ni2+, Hg2+) detection

Isoniazid-based Schiff base N’-(furan-2-ylmethylene)isonicotinohydrazide (FINH) has been synthesized. FINH has proven its ability to selectively sense and respond to Cu2+, Ni2+, and Hg2+, which shows its potential as a chemosensor. UV–visible experiments, the absorption band (at 360 nm) of FINH shifted with the gradual addition of Cu2+, Ni2+, and Hg2+. A significant quenching in the emission band of FINH in fluorescence spectra has been observed with the addition of analytes at the physiological pH range. Cyclic voltammetric experiments have been conducted to determine the electron transfer process that occurs during the complexation of FINH with analytes. Moreover, the interactions of FINH-metal ions are reversible, and their reversible behavior has been demonstrated with the Na2EDTA solution. The binding insights among FINH and Cu2+, Ni2+, and Hg2+ are explained by IR spectral study. Additionally, the FINH works within the appreciable detection limit of 9.472 x 10−7 M (for Cu2+), 7.685 x 10−7 M (for Ni2+) and 2.411 x 10−7 M (for Hg2+), limit of quantitation of 3.15 x 10−6 M (for Cu2+), 2.561 x 10−6 M (for Ni2+) and 8.036 x 10−7 M (for Hg2+). Applying this isoniazid-based reversible chemosensor in analyzing real samples demonstrates its practicality and effectiveness for multi-analyte detection. This sensor could consistently measure metal ion concentrations in various environmental and biological samples, providing a valuable tool for monitoring pollutants and evaluating exposure risks.

Ultra-sensitive fluorescent biosensor for multiple bacteria detection based on CDs/QDs@ZIF-8 and microfluidic fluidized bed.

An ultra-sensitive fluorescent biosensor based on CDs/QDs@ZIF-8 and microfluidic fluidized bed was developed for rapid and ultra-sensitive detection of multiple target bacteria. The zeolitic imidazolate frameworks (ZIF-8) act as the carrier to encapsulate three kinds of fluorescence signal molecules from the CDs/QDs@ZIF-8 signal amplification system. Besides, three kinds of target pathogenic bacteria were automatically, continuously, and circularly captured by the magnetic nanoparticles (MNPs) in the microfluidic fluidized bed. The neutral Na2EDTA solution was the first time reported to not only dissolve the ZIF-8 frameworks from the MNPs-bacteria-CDs/QDs@ZIF-8 sandwich complexes, but also release the CDs/QDs from sandwich complexes with no loss of fluorescence signal. Due to the advantages of signal amplification and automated sample pretreatment, the proposed fluorescent biosensor can simultaneously detect Escherichia coli O157:H7, Salmonella paratyphi A, and Salmonella paratyphi B as low as 101CFU/mL within 1.5h, respectively. The mean recovery in spiked milk samples can reach 99.18%, verifying the applicability of this biosensor in detecting multiple bacteria in real samples.

Preparation of Silver-Based Mercury Film Electrodes for Anodic Stripping Voltammetry

The aim of this study was to develop an electrochemical method for reproducible preparation and evaluation of silver-based mercury film electrodes (SBMFE) for applications such as anodic stripping voltammetry of transition metals and lanthanides. The mercury film was electrochemically deposited on a silver disk electrode and the thickness and reproducibility of the deposited mercury film was determined by using a controlled electrochemical dissolution in a Na2EDTA and acetate buffer solution. Though this electrochemical dissolution method was previously used by other authors in the past, it was specifically optimized for this application. Upon optimization we have shown a correlation between the dissolution charges and mercury film thickness.Additionally, this study also aimed to expand the current understanding of the role of the silver amalgam formation process of the stability and aging of the mercury film. Previous work has confirmed that the mercury film has a finite lifetime that is related to the thickness of both the mercury film and the amalgam. However, while it is known that the film degrades with time, the impact that film thickness and rate of amalgamation have on the lifetime and performance stability of the mercury film is not understood. Moreover, though increased stability of the mercury film when deposited on an amalgam has been noted in previous studies, no work has been done to provide quantitative results for the effect of the amalgam on the film’s longevity.The controlled removal of the mercury film allows for accurate quantitative analysis to determine the amount of mercury in the film and stability when used with electroanalytical techniques such as anodic stripping voltammetry. Moreover, without completely removing the mercury film before a new deposition the mercury film thickness can increase at an unpredictable rate and thus hindering the performance and reproducibility of results. Therefore, electrochemically removing the mercury film without harming the amalgam is ideal for the performance stability of the electrode.This work provides quantitative results for the effect of the amalgam on the films longevity and performance. The continuous monitoring of the performance and stability of the SBMFE in anodic stripping voltammetry applications confirmed a definitive impact of the formation and growth of the solid silver amalgam at the Ag/Hg interface. More specifically, we demonstrated the performance and stability of SBMFE clearly increases with a thicker silver amalgam. Moreover, the impact of the mercury film thickness was also evaluated to achieve the required thin layer behavior during the anodic stripping voltammetry experiments.In conclusion, we have established an extensive protocol for the preparation of reliable and reproducible SBMFE as well as demonstrated an electrochemical method to quantitatively remove the mercury film without harming the amalgam. Moreover, we found that the expected dissolution charge is twice the deposition charge, which can be accurately predicted based on the deposition charge. Additionally, we have determined the performance stability of the SBMFE over several days of use in anodic stripping voltammetry of metals and have correlated the results with the time dependence of the amalgamation rate.

Comparative Analysis of Alternative Calcium Chelators for the Treatment of Calcific Band Keratopathy.

In this study, we compared clinically relevant biochemical properties of each chelator for pH, osmolarity, and calcium chelation potential. In total, 0.2 M K 2 EDTA and K 3 EDTA (BD vacutainer tubes by Becton, Dickinson and Company) and Na 2 EDTA (Sigma Aldrich) solutions were made. The pH of each solution was measured (Mettler Toledo pH meter), and the theoretical osmolarity was calculated. Next, we determined the calcium chelation potential of each EDTA salt by titrating it with 10 μmol of calcium hydroxyapatite or CaCl 2 containing Patton-Reeder colorimetric indicator. Statistical significance was analyzed using analysis of variance. The 0.2 M solutions of Na 2 EDTA, K 2 EDTA, and K 3 EDTA have pH values of 4.43, 5.71, and 9.191 and theoretical osmolarities of 600, 600, and 800 mOsm/L, respectively. Calcium chelation ability was similar among all 3 solutions: 0.94 to 0.98 mol of EDTA was needed to fully chelate 1 mol calcium ions of CaCl 2 ( P = 0.296), 0.100 to 0.108 mol of EDTA for 1 mol calcium ions of the hydroxyapatite aqueous suspension ( P = 0.296), and 0.992 to 0.996 mol for 1 mol calcium ions of hydroxyapatite in acidic solution ( P = 0.178). Compared with the clinical standard of 3% (30 mg/mL) Na 2 EDTA, approximately 3.3% (33 mg/mL) K 2 EDTA and 3.6% (36 mg/mL) K 3 EDTA are needed to chelate an equivalent amount of calcium. In this article, we provide clinically relevant biochemical properties of 2 alternatives to Na 2 EDTA and demonstrate comparable calcium chelation ability among all 3 solutions. In situations where sterile sources of Na 2 EDTA are unavailable, potassium EDTA may provide a convenient and equally effective method of treatment for band keratopathy.

Ratiometric detection of Zn(II) and Cd(II) ions by a benzobisimidazole based probe in aqueous systems and theoretical calculations

The probe 2,6-di(2-pyridyl)-1,5-dihydroimidazo[4,5-f]benzimidazole (LH2) was investigated for its sensing application towards metal ions. This probe can detect Zn2+ and Cd2+ ions in three different aqueous systems viz., water, DMSO/HEPES buffer (1:1, pH = 7.34, rt), and DMSO/water (1:1, rt). In water a “turn-on” response was observed for both metal ions, whereas in the later two solvent systems, a ratiometric change in fluorescence maximum was observed. The detection limit of this probe is as low as 0.3 μM and 0.62 μM (in water) for Zn2+ and Cd2+ ions, respectively. In both DMSO/HEPES buffer and DMSO/water (1:1), LOD values were identically 1.67 μM (for Zn2+) and 1.93 μM (for Cd2+). This probe has a good pH tolerance range which is 4–8 (for Zn2+) and 4–11 (for Cd2+). Lehrer and Chipman plot and Job’s plot suggested a 2:1 binding ratio between metal ion and LH2. The high binding constants obtained from the Lehrer and Chipman method are suggestive of the formation of a very stable complex in the solution. The binding of Zn2+ and Cd2+ ions to the probe was further confirmed by the NMR titration method which indicated the intensity of N–H protons is halved upon addition of the respective metal ion solution in DMSO‑d6. Reversibility of the detection was also established using Na2EDTA solution. DFT/TD-DFT calculation supported the experimentally observed red-shift of the absorption band.

Development and Evaluation of EDTA-Treated Rabbits for Bioavailability Study of Chelating Drugs Using Levofloxacin, Ciprofloxacin, Hemiacetal Ester Prodrugs, and Tetracycline.

Laboratory rabbits are fed foods rich with cationic metals, and while fasting cannot empty gastric contents because of their coprophagic habits. This implies that, in rabbits, the oral bioavailability of chelating drugs could be modulated by the slow gastric emptying rates and the interaction (chelation, adsorption) with gastric metals. In the present study, we tried to develop a rabbit model with low amounts of cationic metals in the stomach for preclinical oral bioavailability studies of chelating drugs. The elimination of gastric metals was achieved by preventing food intake and coprophagy and administering a low concentration of EDTA 2Na solution one day before experiments. Control rabbits were fasted but coprophagy was not prevented. The efficacy of rabbits treated with EDTA 2Na was evaluated by comparing the gastric contents, gastric metal contents and gastric pH between EDTA-treated and control rabbits. The treatment with more than 10 mL of 1 mg/mL EDTA 2Na solution decreased the amounts of gastric contents, cationic metals and gastric pH, without causing mucosal damage. The absolute oral bioavailabilities (mean values) of levofloxacin (LFX), ciprofloxacin (CFX) and tetracycline hydrochloride (TC), chelating antibiotics, were significantly higher in EDTA-treated rabbits than those in control rabbits as follows: 119.0 vs. 87.2%, 9.37 vs. 13.7%, and 4.90 vs. 2.59%, respectively. The oral bioavailabilities of these drugs were significantly decreased when Al(OH)3 was administered concomitantly in both control and EDTA-treated rabbits. In contrast, the absolute oral bioavailabilities of ethoxycarbonyl 1-ethyl hemiacetal ester (EHE) prodrugs of LFX and CFX (LFX-EHE, CFX-EHE), which are non-chelating prodrugs at least in in vitro condition, were comparable between control and EDTA-treated rabbits irrespective of the presence of Al(OH)3, although some variation was observed among rabbits. The oral bioavailabilities of LFX and CFX from their EHE prodrugs were comparable with LFX and CFX alone, respectively, even in the presence of Al(OH)3. In conclusion, LFX, CFX and TC exhibited higher oral bioavailabilities in EDTA-treated rabbits than in control rabbits, indicating that the oral bioavailabilities of these chelating drugs are reduced in untreated rabbits. In conclusion, EDTA-treated rabbits were found to exhibit low gastric contents including metals and low gastric pH, without causing mucosal damage. Ester prodrug of CFX was effective in preventing chelate formation with Al(OH)3 in vitro and in vivo, as well as in the case of ester prodrugs of LFX. EDTA-treated rabbits are expected to provide great advantages in preclinical oral bioavailability studies of various drugs and dosage formulations. However, a marked interspecies difference was still observed in the oral bioavailability of CFX and TC between EDTA-treated rabbits and humans, possibly due to the contribution of adsorptive interaction in rabbits. Further study is necessary to seek out the usefulness of the EDTA-treated rabbit with less gastric contents and metals as an experimental animal.

"On-Off" Control for On-Demand H2 Release upon Dimethylamineborane Hydrolysis over Ru0.8Ni0.2/MoS2 Nanohybrids.

In spite of the fact that remarkable developments are achieved in the design and development of novel nanocatalysts for H2 release upon dimethylamineborane hydrolysis, the development of an "on-off" switch for demand-based H2 evolution upon dimethylamineborane hydrolysis is still a matter of supreme importance, however. Herein, we synthesized a string of MoS2 nanosheet-supported RuNi bimetallic nanohybrids (RuxNi1-x/MoS2), by fixation of RuNi nanoparticles at the MoS2 surface, for the H2 evolution upon the hydrolysis of dimethylamineborane at 30 °C. For safely and effectively generating, transporting, and storing H2 gas, the selective "on-off" switch for on-demand H2 evolution upon dimethylamineborane hydrolysis over the Ru0.8Ni0.2/MoS2 nanohybrid has been successfully realized by the Zn2+/EDTA-2Na system. In particular, the H2 evolution is totally switched off by adding Zn(NO3)2. It seems that Zn2+ ions are attached and anchored at the Ru0.8Ni0.2/MoS2 surface, inhibiting their surface-active sites, leading to the termination of H2 evolution. Then, the H2 generation is subsequently reactivated by adding the EDTA-2Na solution because of its excellent coordination ability with Zn2+ ions. This study not only offers a new and efficient RuNi nanocatalyst for dimethylamineborane hydrolysis but also proposes a new method for the demand-based H2 production.

The SEM and TEM study on the structure of organic scaffold (conchix) isolated from Mytilus edulis L. mussel shells

Demineralised shell of marine molluscs represents an scaffold matrix or conchix and a promising mineral-free biomaterial. The purpose of this work was to study the microstructure of the demineralized shell of the mussel Mytilus edulis L. – an organic matrix isolated with various decalcified reagents – a solution hydrochloric acid HCl and a solution of ethylenediaminetetraacetic acid disodium salt Na2-EDTA. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used as experimental methods in this study. It is shown that the chemical nature of the demineralising reagent determines the structural features of the studied conchix samples, their three layers – periostracum, prismatic layer and nacreous layer in particular. Treatment of mussel shells with HCl solution to remove calcium carbonate leads to partial destruction of the biopolymer structure of the binding organic matrix of mussel shells. Gentle treatment of mussel shells with EDTA solution ensures the preservation of the native structure of the organic matrix. This mineral-free biopolymer has high potential for using in food industry and biomedical applications.

Azophenyl appended Schiff base probe for colorimetric detection of Cu2+ in semi‐aqueous medium and live cell imaging

AbstractA phenylazo appended ortho‐vanillin Schiff base scaffold (HAZ) has been used for selective colorimetric sensing of Cu2+ in semi‐aqueous medium (methanol–water, 1:1, v/v) in the presence of 16 cations and 20 anions, and the limit of detection is 1.8 × 10−7 M. The structures of HAZ and Cu (II) complex, [Cu(AZ)2], have been characterised by spectroscopic data (UV–Vis, Fourier transform infrared and electron paramagnetic resonance) and established by the single crystal X‐ray diffraction measurement. The Job's plot from the absorption studies has also confirmed the 1:2 stoichiometry of Cu2+:HAZ. The absorption spectrum of [Cu (AZ)2] has returned to the spectrum of HAZ on the addition of Na2EDTA solution which is again recovered upon the addition of Cu2+ solution. Discrete Fourier transform computations were carried out using the coordinates of the X‐ray structures of the compounds, and the molecular functions were used to correlate the solution spectroscopic properties. In addition to this, the probe is treated on MDA‐MB 231 breast cancer cells to check the cytotoxicity. The probe is used for the detection of trace quantity of Cu2+ in the cancer cell.

Efficient and selective lanthanide recovery from highly acidic solutions by using a porous pillar[5]arene-based diglycolamide impregnated resin

The recovery of lanthanides from high level liquid waste (HLLW) is of great significance for both environmental protection and sustainable development of resources. Traditional methods for this purpose are often plagued by poor selectivity, low capacity, and limited acid tolerance. Here we report a new material prepared by impregnating P[5]A-DGA onto porous Amberlite XAD-7 resin for efficient and selective lanthanide adsorption from highly acidic solutions. The as-prepared composite material (PDA resin) shows outstanding sorption efficiency for lanthanides in a wide range of acidities (0.01–3 M HNO3) and exhibits good selectivity towards lanthanides over different kinds of competing metal ions in simulated nuclear wastewater. Adsorption equilibrium can be achieved within 60 min and the pseudo-second-order model shows better correlation with the kinetic data, indicating that chemical adsorption is the rate determining step. Adsorption isotherm data can be well fitted by Langmuir model, giving a Eu(III) sorption capacity of 33.3 mg/g at 1 M HNO3, which is superior to other materials employed for the similar purpose. Importantly, the adsorption capacity can be regenerated by using a mixture of 1 M guanidine carbonate and 0.05 M EDTA-2Na solution as the eluent, and the lanthanide adsorption efficiency from simulated nuclear wastewater remains at the initial level after three desorption-adsorption cycles. Finally, the possible configurations of the ligand-Ln(III) complexes were optimized by DFT calculations, which suggest that each Ln(III) tends to bind to three DGA arms via a nine coordination mode. This research advances the development of pillar[5]arenes for lanthanide recovery by demonstrating a simple and generally applicable method to convert P[5]A-DGA extractant into an efficient adsorbent.

Polyethyleneimine/hydrated titanium oxide-functionalized fibrous adsorbent for removing cobalt: Adsorption performance and irradiation stability

Radionuclides of 60Co often encountered in the fields of radiation therapy, medical preparation, and equipment sterilization, which have been considered fatal. Therefore, developing efficient and irradiation-stable adsorbents for the removal of 60Co in wastewater is urgently needed. An irradiation-stable fibrous adsorbent was fabricated through the surface functionalization of collagen fibers (CFs) by polyethyleneimine (PEI) and hydrated titanium oxide (TiO) (PEI-TiO-CFs). PEI-TiO-CFs, including their adsorption performance and irradiation stability, were systematically investigated. Results showed that PEI-TiO-CFs exhibit a maximum adsorption capacity of 0.5575 mmol g−1. In addition, the adsorption capacity of PEI-TiO-CFs only demonstrated a slight decrease in the selectivity investigation of Co2+ mixed with another coexisting ion, such as Na+, K+, and NO3−, Cl−. Furthermore, breakthrough point of PEI-TiO-CFs in column is high at 80 BV (bed volume) and the PEI-TiO-CF column can be mostly regenerated using 12 BV of Na2EDTA solution. Excellent irradiation stability of PEI-TiO-CFs was confirmed by the maintained morphology and adsorption capacity after irradiation at 350 kGy of 60Co γ-ray. Results indicated that PEI-TiO-CFs are an effective adsorbent for radioactive cobalt removal from aqueous solutions.

Aza-Crown-Based Macrocyclic Probe Design for "PET-off" Multi-Cu2+ Responsive and "CHEF-on" Multi-Zn2+ Sensor: Application in Biological Cell Imaging and Theoretical Studies.

The work represents a rare example of an aza-crown-based macrocyclic chemosensor, H2DTC (H2DTC = 1,16-dihydroxy-tetraaza-30-crown-8) for the selective detection of both Zn2+ and Cu2+ in HEPES buffer medium (pH 7.4). H2DTC exhibits a fluorescence response for both Zn2+ and Cu2+ ions. The reversibility of the chemosensor in its binding with Zn2+ and Cu2+ ions is also examined using a Na2EDTA solution. H2DTC exhibits a chelation-enhanced fluorescence (CHEF) effect in the presence of Zn2+ ions and a quenching effect (CHEQ) in the presence of paramagnetic Cu2+ ions. Furthermore, the geometry and spectral properties of H2DTC and the chemosensor bound to Zn2+ have been studied by DFT and TDDFT calculations. The limit of detection (LOD) values are 0.11 × 10-9 and 0.27 × 10-9 M for Cu2+ and Zn2+, respectively. The formation constants for the Zn2+ and Cu2+ complexes have been measured by pH-potentiometry in 0.15 M NaCl in 70:30 (v:v) water:ethanol at 298.1 K. UV-vis absorption and fluorometric spectral data and pH-potentiometric titrations indicate 1:1 and 2:1 metal:chemosensor species. In the solid state H2DTC is able to accommodate up to four metal ions, as proved by the crystal structures of the complexes [Zn4(DTC)(OH)2(NO3)4] (1) and {[Cu4(DTC)(OCH3)2(NO3)4]·H2O}n (2). H2DTC can be used as a potential chemosensor for monitoring Zn2+ and Cu2+ ions in biological and environmental media with outstanding accuracy and precision. The propensity of H2DTC to detect intracellular Cu2+ and Zn2+ ions in the triple negative human breast cancer cell line MDA-MB-468 and in HeLa cells has been determined by fluorescence cell imaging.

3-(2-Hydroxyphenyl)imidazo[5, 1-a]isoquinoline as Cu(II) sensor, its Cu(II) complex for selective detection of CN− ion and biological compatibility

The heterocyclic probe 3-(2-hydroxyphenyl)imidazo[5, 1-a]isoquinoline (LH) has exhibited specific recognition of Cu2+ ion by forming a complex of formula [Cu(L)2], which in turn showed recognition for CN− ions in CH3CN/aqueous HEPES-buffer solution (5 mM, pH = 7.4, 6:4, v/v). The selective colorimetric and fluorescence response of LH towards Cu2+ was achieved over other competing metal ions. Change of color from colorless to yellowish green upon incremental addition of Cu2+ into LH solution can be easily observed with naked-eye. Emission intensity of LH was quenched in presence of Cu2+ ion due to chelation enhanced quenching (CHEQ) process. From Job’s plot and mass spectral analysis the binding stoichiometry was found to 2:1 between LH and Cu2+. Binding of the probe LH with Cu2+ ion can be reversed by sequestering Cu2+ ion using Na2EDTA solutions. Red shift in UV–visible spectrum upon addition of Cu2+ ion into LH solution was a consequence of decrease in HOMO-LUMO energy gap. From life time decay curve the average fluorescence life time (τ) was found to be 3.8 ns for free LH whereas in presence of Cu2+ τ decreased to 2.4 ns. In addition, so formed [Cu(L)2] complex was able to detect cyanide ion over other anions through removal of copper from the complex, as insoluble [CuCN]x. Limit of detection of LH for Cu2+ and [Cu(L)2] for CN− were found to be 0.45 μM and 0.30 μM respectively. Detection of Cu2+ and CN− were also performed in environmental real water samples. Based on the cytotoxic analysis, 5 μM of LH was selected for determining its fluorescence attributes in cellular imaging in MDA-MB-231 and HDF cells. The cell images showed that intracellular Cu2+ and CN− can be detected using LH and [Cu(L)2] complex respectively.

Induction of hypocalcaemia and evaluation of reticuloruminal motility using a three-axis accelerometer

Context Reticuloruminal motility, which is continuous and regular, is essential for digestive activity, but some functional abnormalities can appear in cattle with several metabolic disorders. Particularly in periparturient dairy cows, decreased blood calcium concentrations induce deterioration of rumen motility as well as the risk of reproductive disorders. Aims This study aimed to evaluate reticuloruminal motility using a bolus-type biosensor incorporated with a three-axis accelerometer (3XA) following induction of hypocalcaemia by infusion of ethylenediamine–tetraacetic acid disodium salt dihydrate (Na2EDTA) solution. Methods In the 2 × 2 crossover experiment, six non-pregnant and non-lactating cows were assigned to each of the treatment (TRE) and control (CON) groups and infused for 1 h with 13% Na2EDTA solution and physiological saline respectively. The cylindrical biosensor was fed and placed in the reticulum before the experiment, and the three acceleration values of each cow were recorded and transmitted wirelessly. Considering the device shape, the reticuloruminal motility was represented as the vector value (V2) calculated with each change in X- and Z-axis acceleration over time. Key results Plasma calcium concentrations were measured to confirm hypocalcaemia, and the average was significantly decreased to 1.23 mmol/L at 1 h in TRE. The mean V2 value was significantly decreased in TRE compared with CON, from 1 to 2 h after Na2EDTA infusion. Conclusion 3XA was able to detect a change in reticuloruminal motility caused by hypocalcaemia. The use of 3XA in cattle will allow for rapid treatment of hypocalcaemia or other metabolic disorders that reduce productivity. Implications The 3XA inserted into the reticulum of a dairy cow detected a decrease in reticuloruminal motility wirelessly caused by induced hypocalcaemia.

Removal of copper ions from the Contaminated soil by soil washing technique

The experimental work examined the efficiency of Na2-EDTA solution to remove copper from the polluted soil. The results showed Maximum extraction efficiency when used Na2-EDTA- as extracting solution was at pH 5.5, as compared with the pH 8 for the polluted soil. The extraction efficiency for copper ions from the polluted soil were approximately the same values with increase liquid/solid (L/S) ratio (ranged from L/S = 10 to L/S = 40).

Identifying Controlling Factors of Bioaccumulation of Selected Metal(loid)s in Various Soil–Cereal Crop Systems within Cultivated Fluvisols

The paired Fluvisol and cereal samples in both the field screening and controlled experiments are reported to elucidate the soil–crop relationship for As, Cd, and Pb in relation to changing contamination levels. Significant varietal differences in plant uptake were observed for crop type (barley, triticale) and the harvested part of the crop (oat shoots and grain). When parametrizing the stepwise regression models, the inclusion of soil properties often improved the performance of soil–crop models but diverse critical soil parameters were retained in the model for individual metal(loid)s. The pH value was often a statistically significant variable for Cd uptake. For As and Pb, the more successful model fit was achieved using the indicators of quantity or quality of soil organic matter, but always with lower inherent model reliability compared to Cd. Further, a single correlation analysis was used to investigate the relationship between extractable metal concentrations in soil solution and their crop accumulation. For Cd, there were strong intercorrelations among single extractions, the NH4NO3 extraction stood out with perfect correlation with plant uptake in both experiments. For As and Pb, the CaCl2 and Na2EDTA solutions outperformed other single extractions and were the better choice for the assessment of depositional fluvial substrates.

Evaluation of Polyurea-Crosslinked Alginate Aerogels for Seawater Decontamination.

Polyurea-crosslinked Ca-alginate (X-Ca-alginate) aerogel beads (diameter: 3.3 mm) were evaluated as adsorbents of metal ions, organic solvents, and oils. They were prepared via reaction of an aromatic triisocyanate (Desmodur RE) with pre-formed Ca-alginate wet gels and consisted of 54% polyurea and 2% calcium. X-Ca-alginate aerogels are hydrophobic nanoporous materials (90% v/v porosity), with a high BET surface area (459 m2/g−1), and adsorb PbII not only from ultrapure water (29 mg/g−1) but also from seawater (13 mg/g−1) with high selectivity. The adsorption mechanism involves replacement of CaII by PbII ions coordinated to the carboxylate groups of the alginate backbone. After treatment with a Na2EDTA solution, the beads can be reused, without significant loss of activity for at least two times. X-Ca-alginate aerogels can also uptake organic solvents and oil from seawater; the volume of the adsorbate can be as high as the total pore volume of the aerogel (6.0 mL/g−1), and the absorption is complete within seconds. X-Ca alginate aerogels are suitable for the decontamination of aquatic environments from a broader range of inorganic and organic pollutants.

Removal of heavy metals in medical waste incineration fly ash by Na2EDTA combined with zero-valent iron and recycle of Na2EDTA: Acolumnar experiment study

ABSTRACT In this study, an effective circulating system was developed to remove heavy metals in medical waste incineration (MWI) fly ash. MWI fly ash (MWIFA)-column experiments were performed to remove Cu, Pb, Zn, Cd, and Ni from MWIFA using EDTA disodium (Na2EDTA). Iron-column experiments were conducted to study the removal effect of zero-valent iron on the five heavy metals from washing wastewater. Toxicity Characteristic Leaching Procedure (TCLP) test method was employed to evaluate heavy metals toxicity of MWIFA residues generated after 0–0.2 mol/L Na2EDTA solution treated. After being washed by 0.2 mol/L Na2EDTA solution, TCLP leaching values of Cu, Pb, Zn, Cd, and Ni were the lowest and satisfied the standard (GB 5085.3–2007), and the leaching values were 58.4 ± 2.0 mg/L, 2.81 ± 0.14 mg/L, 64.3 ± 4.0 mg/L, 0.156 ± 0.005 mg/L, 0.381 ± 0.006 mg/L. Concentrations of Cu, Pb, Zn, Cd, and Ni in iron-column effluent were reduced by 99.7%, 91.6%, 91.6%, 75.4%, and 75.7%, respectively. Na2EDTA was recovered and recycled to the removal of heavy metals from MWIFA. Comparing new Na2EDTA solution with recycled Na2EDTA solution, recycled Na2EDTA and water could be reutilized to dispose MWIFA. The removal efficiencies of Cu, Pb, Zn, Cd, and Ni by recycled 0.2 mol/L Na2EDTA solution were 67.1%, 68.8%, 63.2%, 73.9%, 50.7%, respectively, the removal efficiencies using recovered Na2EDTA decreased by 2.6%, 3.9%, 3.3%, 4.2%, and 1.6%, respectively. Successive batch experiments were also conducted to evaluate industrialization potential and reusable times for recycled Na2EDTA. After four recirculation cycles, extraction efficiencies of Pb and Cd (removal efficiency at different cycles divided by removal efficiency of new Na2EDTA) declined toward 80%. Results from this research indicated that this circulating system possessed industrialization potential. Implications: An effective circulating system was developed to remove heavy metals in MWI fly ash (MWIFA). Integration of Na2EDTA with Fe0 promoted the removal of heavy metals from MWIFA. Na2EDTA, NaCl and water were stepwise extracted from iron-column effluent, respectively. Recovered Na2EDTA can still effectively remove heavy metals from MWIFA. Results from this research indicated that this circulating system possessed industrialization potential.

Steel Wool for Water Treatment: Intrinsic Reactivity and Defluoridation Efficiency

Studies were undertaken to characterize the intrinsic reactivity of Fe0-bearing steel wool (Fe0 SW) materials using the ethylenediaminetetraacetate method (EDTA test). A 2 mM Na2-EDTA solution was used in batch and column leaching experiments. A total of 15 Fe0 SW specimens and one granular iron (GI) were tested in batch experiments. Column experiments were performed with four Fe0 SW of the same grade but from various suppliers and the GI. The conventional EDTA test (0.100 g Fe0, 50 mL EDTA, 96 h) protocol was modified in two manners: (i) Decreasing the experimental duration (down to 24 h) and (ii) decreasing the Fe0 mass (down to 0.01 g). Column leaching studies involved glass columns filled to 1/4 with sand, on top of which 0.50 g of Fe0 was placed. Columns were daily gravity fed with EDTA and effluent analyzed for Fe concentration. Selected reactive Fe0 SW specimens were additionally investigated for discoloration efficiency of methylene blue (MB) in shaken batch experiments (75 rpm) for two and eight weeks. The last series of experiments tested six selected Fe0 SW for water defluoridation in Fe0/sand columns. Results showed that (i) the modifications of the conventional EDTA test enabled a better characterization of Fe0 SW; (ii) after 53 leaching events the Fe0 SW showing the best kEDTA value released the lowest amount of iron; (iii) all Fe0 specimens were efficient at discoloring cationic MB after eight weeks; (iv) limited water defluoridation by all six Fe0 SW was documented. Fluoride removal in the column systems appears to be a viable tool to characterize the Fe0 long-term corrosion kinetics. Further research should include correlation of the intrinsic reactivity of SW specimens with their efficiency at removing different contaminants in water.

Highly efficient and selective capture of heavy metals by poly(acrylic acid) grafted chitosan and biochar composite for wastewater treatment

A novel poly(acrylic acid) grafted chitosan and biochar composite (PAA/CTS/BC) for highly efficient and selective capture of heavy metals (HMs) was prepared. PAA/CTS/BC showed efficient and rapid adsorption of Cu2+, Zn2+, Ni2+, Pb2+, Cd2+, Mn2+, Co2+, and Cr3+, well fitted by Langmuir and pseudo-second-order kinetic models, respectively, and it could be applied in a wide pH range (2–7) with high adsorption capacity. Attractively, PAA/CTS/BC showed strongly selective adsorption in the order of Cr3+ > Pb2+ > Cu2+ ≫ Cd2+ > Ni2+ > Zn2+ > Co2+ > Mn2+. The distribution coefficients of Cu2+, Pb2+, and Cr3+ (~104, ~106, and ~107 mL/g, respectively) nearly matched or exceeded that of reported adsorbents in literatures. Surface complexation via inner-sphere complexes with carboxyl, hydroxyl, or amine groups is proposed as the major removal mechanism of HMs by PAA/CTS/BC; however, the covalent bond strength between HMs and oxygen/nitrogen atoms significantly differed among HMs based on the principle of hard and soft acids and bases, essentially determining the adsorption affinity and selectivity of HMs on PAA/CTS/BC. Surface precipitation was also an important mechanism for adsorption of Cr3+ by PAA/CTS/BC. Additionally, Cr3+ adsorbed on PAA/CTS/BC was almost completely resistant to desorption by 0.01 mol/L Na2EDTA solution, while other HMs could be mostly recovered (>80%) by the same method, indicating its promising potential of recycling pure Cr3+ and excellent reusability. Finally, the case study on the treatment of metal finishing wastewater confirmed that PAA/CTS/BC could efficiently achieve both wastewater purification and metal recycling for specific industrial wastewater.