Chelating Agents Citric Acid Research Articles

Mesoporous Biodegradable Magnesium Phosphate-Citrate Nanocarriers Amplify Methotrexate Anticancer Activity in HeLa Cells.

We present the synthesis of amorphous, mesoporous, colloidal magnesium phosphate-citrate nanoparticles (MPCs) from biogenic precursors, resulting in a biocompatible and biodegradable nanocarrier that amplifies the action of the anticancer drug methotrexate (MTX). Synthesis conditions were gradually tuned to investigate the influence of the chelating agent citric acid on the colloidal stability and the mesoporosity of the obtained nanoparticles. With optimized synthesis conditions, a large BET surface area of 560 m2/g was achieved. We demonstrate the potential of these biocompatible and biodegradable mesoporous MPCs as a drug delivery system. Lipid-coated MPCs were used to load the fluorescent dye calcein and the chemotherapeutic agent MTX into the mesopores. In vitro experiments show very low premature release of the cargo but efficient stimuli-responsive release in an environment of pH 5.5, in which MPCs degrade. Lipid-coated MPCs are taken up by cancer cells and are nontoxic up to concentrations of 100 μg/mL. When loaded with MTX serving as a representative model drug for in vitro studies, MPCs induced efficient cell death with an IC50 value of 1.1 μg/mL. Compared to free MTX, its delivery with MPCs enhances its efficiency by an order of magnitude. In summary, we have developed a biodegradable nanomaterial synthesized from biocompatible precursors that are neither toxic by themselves nor in the form of nanoparticles. With these features, MPCs may be applied as drug delivery systems and have the potential to reduce the side effects of current chemotherapies.

Remediation of polycyclic aromatic hydrocarbons by sulfate radical advanced oxidation: Evaluation of efficiency and ecological impact

Remediation of polycyclic aromatic hydrocarbon (PAH) contamination in soil remains expensive and difficult. Sulfate radical advanced oxidation processes (SR-AOPs) can be used for in situ PAH oxidation but their efficiency and ecological impacts require evaluation. Here, we tested the remediation efficiency and ecological impacts of an SR-AOP combining sodium persulfate and ferrous sulfate (FS), the FS SR-AOP with the chelating agent citric acid (FS+CA), and the FS SR-AOP with chelating agent and the surfactant IGEPALCA-720 (FS+CA+IG) compared with natural attenuation (control, CK). We measured PAH, soil physicochemical properties (pH, soil organic matter [SOM]), and soil biological properties (polyphenol oxidase [PPO] activity, peroxidase [POD] activity, soil microbes) in contaminated soil samples after incubation with FS, FS+CA, FA+CA+IG, or CK for 1, 15, and 30 d. Compared with CK, all SR-AOPs significantly decreased PAH after 1 d, with FS+CA+IG showing the highest efficiency (80.8%) and PAH removal peaking at 15 d. FS+CA+IG treatment reduced SOM the least and soil pH the most; after 30 d, SOM recovered to ~80% of the level observed in CK, but soil pH decreased further. PPO and POD activities were highest after 15 and 30 d of FS+CA+IG treatment. Real-time quantitative PCR demonstrated that SR-AOPs significantly decreased quantities of PAH-degrading bacteria, soil bacteria, fungi, and actinobacteria at 1 d, but after 30 d, the microbes recovered to levels similar to those observed in CK, with no significant differences among SR-AOPs. SR-AOPs reduced bacterial diversity and changed the dominant phylum from Acidobacteria to Firmicutes. In summary, SR-AOP treatment with both the chelating agent and the surfactant produced the best PAH removal and least SOM destruction but the largest pH decrease, although some factors recovered with longer incubation. This study provides key information for improving PAH remediation and evaluating its ecological impact

Characteristics and mechanism of uranium photocatalytic removal enhanced by chelating hole scavenger citric acid in a TiO2 suspension system

Polycarboxylic acid acts as hole scavenger and chelating agent, which is essential for the photocatalytic removal of multivalent metal ions. The photocatalytic uranium removal, role of chelating hole scavenger citric acid (CA), and removal mechanism were investigated in a TiO2 suspension system. The results show that chelating agent CA is an efficient hole scavenger. The maximum removal efficiency of U(VI) reaches up to 98.6%. The uranium-bearing precipitates contains Na[(UO2)(Cit)], UO2, or UO4·2H2O. The mechanisms for the photocatalytic removal of U(VI) and the role of CA are discussed. These results suggest that proper chelating hole scavengers can promote and regulate the photocatalytic removal of multivalent metal ions.

Microstructural evaluation of CoAl2O4 nanoparticles by Williamson–Hall and size–strain plot methods

ABSTRACTCoAl2O4 nanoparticles were prepared by a Pechini method using chelating agent citric acid. CoAl2O4 nanoparticles were synthesized at different calcination temperatures of 600–900°C. The crystalline spinel cubic phase was confirmed by X-ray diffraction results. High-resolution scanning electron microscopy (HRSEM) revealed that nanoparticles of CoAl2O4 morphology showed spherical forms with a certain degree of agglomeration. The Williamson–Hall (W–H) method and size–strain method to evaluate the size of crystallites and strain in the CoAl2O4 nanoparticles’ peak broadening were applied. Physical parameters such as strain and stress values were calculated for all XRD reflection peaks corresponding to the cubic spinel phase of CoAl2O4 in the range of 20–70° from the modified plot shape by the W–H plot assuming a uniform deformation model (UDM), uniform stress deformation model (USDM), uniform deformation energy density model (UDEDM), and by the size–strain plot (SSP) method. The crystal size of the CoAl2O4 NPs calculated on the W–H plots and the SSP method are in good agreement with the HRSEM and Scherrer method.

The Role of Metal Ions in Protein and Fatty Acids Biosynthesis in Soybean under Micronutrients Application to Soil

The present study is part of our ongoing investigation to study the role of trace elements on soybean seed composition (protein, oil, and fatty acids). This study was conducted to study the effects of five trace elements (Mn, Cu, Zn, Mo, B). The treatments of Mn, Cu, Zn, Mo, and B were chlorides, except Mo as oxide, and B as boric acid. The treatments were Mn, Cu, Zn, Mo, and B alone and in combination with the chelating agent citric acid (CA), for example Mn + CA, Cu + CA, and Zn + CA. Soybean cultivar (Bolivar with maturity group V) was grown in a repeated greenhouse experiment in a randomized complete block design. The compounds were applied to three-week-old soybean plants at V3 (vegetative) and at R3 (beginning of seed-pod initiation) stages. The plants were allowed to grow until maturity under greenhouse conditions. The harvested seeds were analyzed for mineral, protein, and fatty acid contents. Results showed that Mn, Cu, and B treatments increased seed protein, while Zn, Mo, Cu + CA, and B + CA decreased the protein. Treatments of Zn, Mo, CA, Cu + CA, Zn + CA, Mo + CA, and B + CA increased the oil. Treatments of Mn and Cu decreased the oil. The Cu and B treatments increased oleic acid by 8.0% and 7.4%, respectively for Cu and B. Treatments of Mn, Mo, CA, and Mn + CA, Cu + CA, Zn + CA, Mo + CA, and B + CA decreased oleic acid by 0.6% to 14.4%. Treatments of Cu, Zn, Mo, B, CA, Mn and their combination with CA increased linoleic acid by 1.3% to 6.5%. Our goal was to identify the trace elements that would make desirable alteration in the seed composition qualities.

Potential of Vetiveria zizanoides L. Nash for phytoremediation of plutonium (239Pu): Chelate assisted uptake and translocation

Plants have demonstrated a great potential to remove toxic elements from soils and solutions and been successfully used for phytoremediation of important radionuclides. Uptake potential of vetiver plants (V. zizanoides) for the remediation of 239Pu in hydroponic and soil conditions was studied in the present work. High efficiency of V. zizanoides for the removal of 239Pu was recorded with 66.2% being removed from the hydroponic solution after 30 days. However, remediation of 239Pu from soil was limited. Remediation of 239Pu from soil was increased with the addition of chelating agents citric acid (CA) and diethylenetriaminepentaacetic acid (DTPA). Accumulation of 239Pu was recorded higher in roots than shoots, however its translocation from roots to shoots increased in the presence of chelators in hydroponic as well as soil conditions. DTPA was found more effective than CA showing higher translocation index (TI). Increase in TI was observed 8 and 6 times in the solution and soil respectively when plants were exposed to 239Pu-DTPA in comparison to only 239Pu. The present study demonstrates that V. zizanoides plant is a potential plant for phytoremediation of 239Pu.

Characterization and functional properties of mango peel pectin extracted by ultrasound assisted citric acid

Pectin was extracted from ‘Tainong No. 1’ mango peels, using a chelating agent-citric acid as extraction medium by ultrasound-assisted extraction (UAE) and conventional extraction (CE) at temperatures of 20 and 80°C. Chemical structures, rheological and emulsifying properties of mango peel pectins (MPPs) were comparatively studied with laboratory grade citrus pectin (CP). All MPPs exhibited higher protein content (4.74%–5.94%), degree of methoxylation (85.43–88.38%), average molecular weight (Mw, 378.4–2858kDa) than the CP, but lower galacuronic acid content (GalA, 52.21–53.35%). CE or UAE at 80°C resulted in significantly higher pectin yield than those at 20°C, while the extraction time for UAE–80°C (15min) was significantly shorter compared to CE–80°C (2h) with comparable pectin yield. Moreover, MPPs extracted at 80°C were observed with higher GalA and protein content, higher Mw, resulting in higher viscosity, better emulsifying capacity and stability, as compared to those extracted at 20°C and the CP. Therefore, these results suggested that MPPs from ‘Tainong No. 1’ may become a highly promising pectin with good thickening and emulsifying properties, using ultrasound-assisted citric acid as an efficient and eco-friendly extraction method.

Electro-remediation of lead contaminated kaolinite: An electro-kinetic treatment

Electroextraction is an innovating separation process which removes in situ heavy metal contained in soil, under the application of an electric field. The paper reports the remediation of kaolinite contaminated with lead by electro-kinetic treatment using a three compartment cell. As a consequence of intensive water dissociation, the high concentration of hydroxyl ions led to precipitation of lead from the soil and formed non-conducting species such as Pb(OH)2. The two chelating agents Citric acid and EDTA are used as anode reservoir to produce protons which exchanged lead cation. Meanwhile, they were also used as cathode reservoir to neutralize hydroxyl anions generated at the electrode, to avoid the formation of the solid species. After seven days, EDTA allowed complete lead removal twice than citric acid, with low energy consumption. The ion migration and the concentration gradient were described by Nernst–Planck equations. In contrast to long period experiments, the ion migration inside the soil progressed from cathode toward anode for short periods. This finding was well supported by pH values.

Precursor solution additives improve desiccated La0.6Sr0.4Co0.8Fe0.2O3–x infiltrated solid oxide fuel cell cathode performance

Here, the addition of the surfactant Triton X-100 or the chelating agent citric acid to Solid Oxide Fuel Cell (SOFC) La0.6Sr0.4Co0.8Fe0.2O3–x (LSCF) precursor nitrate solutions is shown via scanning electron microscopy (SEM) and X-ray diffraction (XRD) to reduce average infiltrate nano-particle size and improve infiltrate phase purity. In addition, the desiccation of LSCF precursor solutions containing the aforementioned organic solution additives further reduces the average LSCF infiltrate nano-particle size and improves the low-temperature infiltrate phase purity. In particular, CaCl2-desiccation reduces the average size of Triton X-100 derived (TXD) LSCF particles fired at 700 °C from 48 to 22 nm, and reduces the average size of citric acid derived LSCF particles fired at 700 °C from 50 to 41 nm. Modeling and electrochemical impedance spectroscopy (EIS) tests indicate that particle size reductions alone are responsible for desiccation-induced cathode performance improvements such as CaCl2-desiccated TXD La0.6Sr0.4Co0.8Fe0.2O3-x – Ce0.9Gd0.1O1.95 (LSCF-GDC) cathodes reaching a polarization resistance of 0.17 Ωcm2 at 540 °C, compared to 600 °C for undesiccated TXD LSCF-GDC cathodes. This excellent low-temperature performance, combined with a low open-circuit 540 °C degradation rate, suggests that the desiccation of organic-additive-containing infiltrate precursor solutions may be useful for the development of durable, high-power, low-temperature SOFCs.

Nano-ceria pre-infiltration improves La0.6Sr0.4Co0.8Fe0.2O3−x infiltrated Solid Oxide Fuel Cell cathode performance

Here, scanning electron microscopy, X-ray diffraction, and thermo-gravimetric analysis experiments show that the pre-infiltration of Ce0.9Gd0.1O1.95 (GDC) nano-particles reduces the average size of La0.6Sr0.4Co0.8Fe0.2O3−x (LSCF) produced from the subsequent infiltration of precursor nitrate solutions containing the surfactant Triton X-100 or the chelating agent citric acid. In contrast, GDC pre-infiltration has no effect on the average size of LSCF particles produced from precursor solutions containing only lanthanum, strontium, cobalt, and iron nitrate. Consistent with the observed particle size trends, electrochemical impedance spectroscopy measurements show that GDC pre-infiltration improves the performance of Triton X-100 Derived (TXD) LSCF–GDC cathodes and Citric Acid Derived (CAD) LSCF–GDC cathodes, but has no effect on the performance of Pure Nitrate Derived (PND) LSCF–GDC cathodes. In particular, TXD LSCF–GDC cathodes with more than ∼5 vol% of GDC pre-infiltration display average LSCF particle sizes of 21 nm and open-circuit polarization resistance values of 0.10 Ωcm2 at 540 °C, compared to 48 nm and 640 °C without GDC pre-infiltration. Results suggest that this 100 °C reduction in cathode operating temperature is caused solely by LSCF particle size reductions. 7.4 vol% GDC pre-infiltrated TXD LSCF–GDC cathodes also display lower 540 °C degradation rates than conventionally infiltrated PND LSCF–GDC cathodes.

Enhancement effects of chelating agents on the degradation of tetrachloroethene in Fe(III) catalyzed percarbonate system

The performance of Fe(III)-based catalyzed sodium percarbonate (SPC) for stimulating the oxidation of tetrachloroethene (PCE) for groundwater remediation applications was investigated. The chelating agents citric acid monohydrate (CIT), oxalic acid (OA), and glutamic acid (Glu) significantly enhanced the degradation of PCE. Conversely, ethylenediaminetetraacetic acid (EDTA) had a negative impact on PCE degradation, which may due to its strong Fe chelation and HO scavenging abilities. However, excessive SPC or chelating agent will retard PCE degradation. In addition, investigations using free radical probe compounds and radical scavengers revealed that PCE was primarily degraded by HO radical oxidation in both the chelated and non-chelated systems, while O2− also participated in the non-chelated system and the OA and Glu modified systems. According to the electron paramagnetic resonance (EPR) studies, the presence of HO in the Fe(III)/SPC system was maintained much longer than that in the Fe(II)/SPC system. The results indicated that the addition of CIT, OA or Glu indeed enhanced the generation of HO in the first 10min and promoted degradation efficiency by increasing the amount of Fe(III) and maintaining the concentration of HO radicals in solution. In conclusion, chelated Fe(III)-based catalyzed SPC oxidation is a promising method for the remediation of PCE-contaminated groundwater.

Effects of Soil Applications of Micro-Nutrients and Chelating Agent Citric Acid on Mineral Nutrients in Soybean Seeds

Micro-nutrient deficiency in soil results in crop yield loss and poor seed quality. Correcting this deficiency is normally done by foliar or soil application. The objective of this research was to determine the effects of soil applications of five micro-nutrients (Mn, Cu, Zn, Mo, and B) alone and in combination with a chelating agent citric acid (CA) on soybean leaf and seed nutrients. Source of micro-nutrient compounds were MnCl2, CuCl2, ZnCl2, MoO3, and H3BO3. Our hypothesis was that micro-and macro-nutrients may be transported to leaves and then to seeds at different rates. They may interact synergistically or competitively during the uptake process. A greenhouse experiment was conducted at Mississippi Valley State University, Itta Bena, Mississippi, USA. Soybean cultivar, Bolivar (maturity group V), was applied with micro-nutrients-chelating agent citric acid at V3 and R3 (pod initiation) stage. The results showed that applications of Cu, Zn, B and Mo increased three unrolled trifoliate leaves Cu, Zn, B by 26.5%, 13.8%, 113% and Mo increased to 179 mg/kg, respectively in the leaves. Also, the application of “Cu, Zn, B and Mo increased Cu, Zn, B by 55.5%, 8.2%, 28.6% and Mo increased to 202 mg/kg” respectively in soybean seeds. Application of Mn had no direct effect on increasing Mn either in leaves or in seeds, however, Mn and Mn + CA treatment affected other mineral contents. Application of Cu, Zn, Mo, B and CA increased macro-nutrients K, N, P, Mg, and S. Irrespective of the applications, the nutrient increase trend in seed was Na > Fe > Zn > Mn > B > Cu > Mo. However, Mo application resulted in the following seed nutrient accumulation pattern: Na > Mo > Fe > Zn > Mn > B > Cu. This may suggest that Mo had higher mobility to seeds than other micro-nutrients. Combination of soil application of Mo + CA increased Mo in leaves at V3 stage; however, Mo + CA soil application during pod-filling stage had no significant effects on Mo accumulation in seeds. The current research showed that some micro-nutrient application with the chelating agent CA could increase seed nutrients. Since these results are conducted under greenhouse experiments, further research under field conditions is needed before conclusive recommendations are made.

Efficient Antioxidant Formulations for Use in Biodiesel

Biodiesel has a lipid origin; thus, antioxidants commonly used in oils and fats have been adopted for the improvement of the oxidative stability of biodiesel. However, these antioxidants have not shown the same efficiency when they are applied to biodiesel. This fact points out the need to investigate additives that warrant the oxidative stability of biodiesel, especially during long storage periods. In this paper, antioxidant formulations were developed for application in biodiesel, from blends including the synthetic antioxidants butylated hydroxytoluene (BHT), tert-butylhydroquinone (TBHQ), the chelating agent citric acid, and organic rosemary extracts. The antioxidants were applied at different concentrations and combinations and were evaluated by the Rancimat method, EN 14112, and by the pressurized PetroOXY method. The results showed that for ethanol soybean biodiesel, the antioxidant compositions formed by TBHQ (2000 mg kg–1) and citric acid (500 mg kg–1) and by the chloroform rosemary extract (2000 mg kg–1) and citric acid (500 mg kg–1) were the most effective in delaying the oxidative process, in a manner independent of the evaluation method. For the methanol cottonseed oil biodiesel, the best result was obtained using the combination of 1500 mg of TBHQ with 1500 mg of ethanol rosemary extract. However, the formulations using low concentrations of rosemary ethanol extract and citric acid induction periods of >6 h were obtained, reaching the limit specified by European Standard EN 14214.

Citric acid as corrosion inhibitor for aluminium pigment

Aluminium pigments corrode in aqueous alkaline media (e.g., water-borne paints) with the evolution of hydrogen. The hydrogen corrosion of aluminium pigment can be inhibited by the chelating agent citric acid, which is a renewable raw material and absolutely non-toxic. At pH 8 more hydrogen is evolved as at pH 10 which can be explained with the isoelectric point of aluminium oxide (pH 9) and a chemical reaction of citrate with aluminium. The product of this reaction should be an aluminium(III)–citric acid-chelate which is assumed to be the actual corrosion inhibitor. This assumption can be corroborated by tests with aluminium(III)–citric acid-chelates. With increasing addition of citric acid the hydrogen volumes evolved increase, which could also be explained with a chemical reaction of citrate with aluminium. Agaric acid (α-hexadecyl-citric acid) can be considered as a surfactant with the chelating agent citric acid as hydrophilic group and inhibits the corrosion reaction of aluminium pigment better when compared to citric acid.

Time-dependent leaching of coal fly ash by chelating agents

The rates of leaching of several transition-metal ions from coal fly ash by pH 7.4 solutions of the chelating agents citric acid, EDTA, Listidine and glycine have been measured as part of an investigation of the potential health effects of inhaled fly ash. The results are compared to leaching of the same fly ash by 0.5M HCl, 0.10 M pH 7.4 Tris buffer, 0.5 M NH/sub 4/OH, and canine serum. For the trace elements, Zn, Mn, G, Ni, and Cu, the initial leaching rates with 0.5 M HCl range from 350 to 850 ppm/d. The rates drop by 1-2 orders of magnitude within 24 h and then level off at 1-10 ppm/d. The initial rates with EDTA and citric acid are also high, 100-400 ppm/d, but they fall off even more rapidly than the HCl leaching rates. The leaching of vanadium is exceptionally rapid, with initial rates of 1000-3000 ppm/d.