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1.
Chem Commun (Camb) ; 56(18): 2775-2778, 2020 Mar 03.
Artigo em Inglês | MEDLINE | ID: mdl-32022095

RESUMO

The expeditious construction of phenanthridine scaffolds via a Pd/MnO2-mediated C-H arylation/oxidative annulation cascade involving aldehydes, aryl iodides and amino acids is disclosed. This reaction proceeds smoothly involving the formation of multiple chemical bonds with the tolerance of a wide range of functional groups. The control experiments suggest a radical mechanism for C-N bond formation via MnO2-promoted oxidative annulation of imine compounds. The synthetic utility of this transformation has been demonstrated via the straightforward access to bioactive natural alkaloid trisphaeridine and its analogue.


Assuntos
Aldeídos/química , Aminoácidos/química , Hidrocarbonetos Iodados/química , Ácido Oxálico/química , Paládio/química , Fenantridinas/síntese química , Estrutura Molecular , Oxirredução , Fenantridinas/química
2.
Chemosphere ; 241: 125025, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31604190

RESUMO

Metals in atmospheric aerosols play potentially an important role in human health and ocean primary productivity. However, the lack of knowledge about solubility and speciation of metal ions in the particles or after solubilisation in aqueous media (sea or surface waters, cloud or rain droplets, biological fluids) limits our understanding of the underlying physico-chemical processes. In this work, a wide range of metals, their soluble fractions, and inorganic/organic compounds contained in urban particulate matter (PM) from Padua (Italy) were determined. Metal solubility tests have been performed by dissolving the PM in water and in solutions simulating rain droplet composition. The water-soluble fractions of the metal ions and of the organic compounds having ligand properties have been subjected to a multivariate statistical procedure, in order to elucidate associations among the aqueous concentrations of these PM components in simulated rain droplets. In parallel, a multi-dimensional speciation calculation has been performed to identify the stoichiometry and the amount of metal-ligand complexes theoretically expected in aqueous solutions. Both approaches showed that the solubility and the aqueous speciation of metal ions were differently affected by the presence of inorganic and organic ligands in the PM. The solubility of Al, Cr, and Fe was strongly correlated to the concentrations of oxalic acid, as their oxalate complexes represented the expected dominant species in aqueous solutions. Oxalates of Al represented ∼98% of soluble Al, while oxalates of Cu represented 34-75% of the soluble Cu, and oxalates of Fe represented 76% of soluble Fe. The oxidation state of Fe can strongly impact the speciation picture. If Fe is present as Fe(II) rather than Fe(III), the amount of Cr and Cu complexed with diacids can increase from 75% to 94%, and from 32% to 53%, respectively. For other metals, the solubility depended on the formation of soluble aquo-complexes, hence with a scarce effect of the organic ligands. An iron-oxalate complex was also directly detected in aerosol sample extracts.


Assuntos
Complexos de Coordenação/química , Metais/química , Ácido Oxálico/química , Material Particulado/análise , Aerossóis/análise , Humanos , Itália , Ligantes , Oxirredução , Solubilidade , Reforma Urbana , Água
3.
Chemosphere ; 238: 124598, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31446276

RESUMO

Sewage sludge dewatering is an efficient approach to reduce the volume of sludge for the subsequent disposal. In this study, a novel one-step acidification sludge dewatering method was developed with using oxalic acid as a conditioner. In laboratory-scale experiments with the dosage of 200 mg/g dry solid (DS), the normalized capillary suction time and the specific resistance to filtration were respectively decreased by 78.7% and 60.0% after 30 min of oxalic acid conditioning, much more efficient than those conditioned with sulfuric acid and hydrochloric acid at the same pH value. This superior dewatering performance was attributed to two factors. One was that oxalic acid could more efficiently promote the hydrolysis of polysaccharide, especially pectins, to release bound water. The other was that OA could dissolve more Fe3+ and Al3+, as well as form precipitate with Ca2+ in sludge, which may act as flocculants or co-precipitator for the subsequent sludge particles coagulation. In pilot-scale experiments, the water content of oxalic acid conditioned sludge cake was reduced to 60% under the optimum conditions, while the reagent cost was as low as 110.0 USD/t DS. This work provides a cost-effective and easy-operated sewage sludge disposal technique, and also sheds light on the potential of oxalic acid in environmental waste treatment.


Assuntos
Dessecação/métodos , Ácido Oxálico/química , Esgotos/química , Eliminação de Resíduos Líquidos/métodos , Filtração , Floculação , Ácido Clorídrico/química , Concentração de Íons de Hidrogênio , Hidrólise , Polissacarídeos/metabolismo , Ácidos Sulfúricos/química , Água/química
4.
Chemosphere ; 239: 124706, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31493754

RESUMO

The remediation effect of organic acids in heavy metal contaminated soil was widely studied. However, the comprehensive evaluation of organic acids on micro-ecological environment in heavy metal contaminated soil was less known. Herein, this experiment was conducted to investigate the impact of malic acid, citric acid and oxalic acid on soil fertility, cadmium (Cd) speciation and ecotoxicity in contaminated soil. Especially, to evaluate the ecotoxicity of Cd, high-throughput sequencing was used to investigate the soil bacterial community structure and diversity after incubation with organic acids. The results showed that obvious changes in soil pH were not observed. Whereas, the contents of available phosphorus (Olsen-P) and alkali hydrolysable nitrogen (Alkeline-N) evidently increased with a significant difference. Furthermore, compared to control, the proportion of acetic acid-extractable Cd increased by 3.06-6.63%, 6.11-9.43% and 1.91-6.22% respectively in the groups amended with malic acid, citric acid and oxalic acid, which indicated that citric acid did better in improving the availability of Cd than malic acid and oxalic acid. In terms of biological properties, citric acid did best in bacteria count increase, enzyme activities and bacterial community structure improvement. Accordingly, these results provided a better understanding for the influence of organic acids on the micro-ecological environment in Cd contaminated soil, based on physicochemical and biological analysis.


Assuntos
Cádmio/toxicidade , Ácidos Carboxílicos/farmacologia , Recuperação e Remediação Ambiental/métodos , Microbiologia do Solo , Poluentes do Solo/química , Bactérias/efeitos dos fármacos , Cádmio/análise , Cádmio/química , Ácidos Carboxílicos/química , Ácido Cítrico/química , Ácido Cítrico/farmacologia , Ecotoxicologia , Poluição Ambiental/análise , Malatos/química , Malatos/farmacologia , Ácido Oxálico/química , Ácido Oxálico/farmacologia , Solo/química , Poluentes do Solo/análise
5.
Environ Sci Pollut Res Int ; 26(36): 36287-36295, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31713827

RESUMO

Preparation of the value-added products from e-waste resources is an important step in the recycling process. The present paper aims to propose a methodology for the recovery of In from scrap LCD panel via preparation of InBO3 nanostructure. Discarded LCD panel was subjected to a recycling process through crushing, milling, and oxalic acid leaching to prepare In2(C2O4)3·6H2O. Through the leaching process, B(OH)3 from glass part (alumina borosilicate) has been leached out along with indium oxalate hydrated. Further thermal treatment on these extracted materials at 600 °C could result in the formation of InBO3 nanostructures with an average particle size of 20 nm. A multistep mechanism based on thermodynamic calculations for the recycling of the InBO3 form extracted precursors was proposed. Graphical abstract.


Assuntos
Resíduo Eletrônico , Cristais Líquidos/química , Nanoestruturas/química , Reciclagem/métodos , Compostos de Boro/química , Vidro/química , Temperatura Alta , Índio/química , Ácido Oxálico/química , Tamanho da Partícula
6.
Artigo em Inglês | MEDLINE | ID: mdl-31382525

RESUMO

Soil leaching is an effective remediation technique using agents to leach the target pollutants from the soil. However, the dynamics and mechanisms for leaching of Cr and other non-pollutant metals from Cr-contaminated soils are not yet well understood. Here, column leaching experiments were conducted to determine the effect of hydrochloric acid (HCl), citric acid (CA), and oxalic acid (OX) on the leaching of Cr, as well as of Ca, Mg, Fe, and Mn, from a soil contaminated by a Cr slag heap. Acid leaching decreased soil pH and enhanced the mobility of all the surveyed metals. Leaching dynamics varied with both metals and acids. OX had the highest removal rates for Cr, Fe, Mn, and Mg, but had the poorest ability to leach Ca. HCl leached the largest amount of Ca, while CA leached similar amounts of Mg and Mn to OX, and similar amounts of Fe and Cr to HCl. Cr in the leachates was correlated with Ca, Mg, Fe, and Mn. Cr mainly interacted with soil mineral components and showed a punctate distribution in soil particles. The X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS), and X-ray photoelectron spectroscopy (XPS) analyses showed soil mineralogical and morphological properties were differently altered after leaching by different acids. Complexation of Cr(III), competitive desorption, and reduction of Cr(VI) make significant contribution to Cr leaching by organic acids. In conclusion, OX can be applied in leaching remediation of Cr-contaminated soil, but the concomitant removal of other non-targeted metals should be taken into account because of the loss of soil minerals and fertility.


Assuntos
Cromo/isolamento & purificação , Ácido Cítrico/química , Ácido Clorídrico/química , Ácido Oxálico/química , Poluentes do Solo/isolamento & purificação , Concentração de Íons de Hidrogênio , Metais/isolamento & purificação , Minerais/isolamento & purificação , Espectroscopia Fotoeletrônica , Solo/química , Espectrometria por Raios X , Difração de Raios X
7.
Sci Total Environ ; 695: 133879, 2019 Dec 10.
Artigo em Inglês | MEDLINE | ID: mdl-31425980

RESUMO

It remains unclear whether biochar amendment can mediate changes in soil microbial communities caused by organic contaminants in the rhizosphere. In this study, phenanthrene-contaminated soil was amended with biochar and oxalic acid (OA) alone or in combination and incubated for 21 days. Phospholipid fatty acids (PLFAs) and high-throughput sequencing were used to evaluate shifts in bacterial and fungal community structure. Phenanthrene stress led to significant shifts in both soil bacterial and fungal community structure, in particularly, 82% of microbial phyla decreased in abundance. Biochar and/or OA improved the phenanthrene-polluted soil by positively mediating shifts in soil microbial communities stressed by phenanthrene. Specifically, biochar and/or OA led to the survival of certain microbial taxa that were inhibited by phenanthrene stress. In addition, many functional microbial individuals and genes participating in polycyclic aromatic hydrocarbon (PAH) degradation were positively stimulated by high phenanthrene stress and further stimulated by the simultaneous application of biochar and OA. Based on these findings, tandem biochar and rhizoremediation may be a feasible strategy for relieving PAH toxicity to soil microbial communities.


Assuntos
Carvão Vegetal/química , Recuperação e Remediação Ambiental/métodos , Ácido Oxálico/química , Hidrocarbonetos Policíclicos Aromáticos/toxicidade , Microbiologia do Solo , Poluentes do Solo/toxicidade , Biodegradação Ambiental , Microbiota
8.
Environ Sci Pollut Res Int ; 26(29): 30268-30278, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31428966

RESUMO

The excellent hierarchical porous carbon was fabricated from corn straw-derived hydrochar by chemical activation using potassium oxalate (K2C2O4). SEM, BET, XPS, XRD, and Raman analysis were carried out for the characterization of the as-obtained samples. The morphology of the as-obtained porous carbon with hierarchical porous structures is made up of a large number of nano-particle aggregates and some nanosheet-like structures, possessing a super-large specific surface area (SSA, up to 2523 m2 g-1) with a large total pore volume of 1.464 cm3 g-1. The as-fabricated carbon material rapidly removes atrazine in the first 3 h at the initial concentration of 20 mg L-1 with an adsorption efficiency of 93.6%, which is faster and better than other representative materials reported previously. The acidic conditions are favorable for the atrazine adsorption onto the porous carbon. An efficient adsorbent was fabricated for environmental remediation, and in-depth insights into the interface mechanism between hierarchical porous carbon and atrazine are proposed. In addition, 95% of the adsorption capacity of MPC-1:3 can be recovered by simple annealing treatment.


Assuntos
Atrazina/análise , Carbono/química , Poluentes Ambientais/análise , Recuperação e Remediação Ambiental/métodos , Caules de Planta/química , Zea mays/química , Adsorção , Ácido Oxálico/química , Porosidade , Propriedades de Superfície
9.
Environ Sci Pollut Res Int ; 26(29): 29780-29788, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31402437

RESUMO

Since Cr(VI) is highly toxic, the environmental reduction of Cr(VI) to Cr(III) has attracted significant attention. Oxalic acid, a primary component of dissolved organic matter (DOM), is widely distributed throughout the natural environment but the reduction of Cr(VI) by oxalic acid is insignificant at the low concentrations present in the environment; however, the reduction of Cr(VI) is accelerated significantly in ice. In terms of combined pollution, Cr(VI) can coexist with other organic pollutants in the environment but the impact of organic pollutants on the reduction of Cr(VI), changes to the organic pollutants themselves, and the role of oxalic acid in these reactions are unknown. In this study, we investigated redox reactions between Cr(VI) and phenolic compounds in ice (- 15 °C) in the presence of oxalic acid and compared these to room temperature redox reactions in aqueous solutions (20 °C). While these redox reactions were negligible in aqueous solution, they were significantly accelerated in ice under acidic conditions, which was primarily attributed to the freeze concentration effect. Oxalic acid has two functions in these redox reactions; the first is to provide the H+ required for the reaction and the second is to serve as a reducing agent. When oxalic acid and phenolic pollutants coexist, Cr(VI) preferentially reacts with the phenolic compounds. Phenol, 4-chlorophenol (4-CP), and 2,4-dichlorophenol (2,4-DCP) were each demonstrated to reduce Cr(VI) in ice, but the reaction rate and overall reactivity of these three phenolic compounds are different.


Assuntos
Cromo/análise , Poluentes Ambientais/análise , Gelo , Ácido Oxálico/química , Fenóis/química , Água/química , Cromo/química , Poluentes Ambientais/química , Modelos Teóricos , Oxirredução , Soluções , Temperatura
10.
Environ Sci Pollut Res Int ; 26(26): 26706-26720, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31297708

RESUMO

Since decades, surface water bodies have been exposed to pesticides from agriculture. In many places, retention systems are regarded as an important mitigation strategy to lower pesticide pollution. Hence, the processes governing the transport of pesticides in and through a retention system have to be understood to achieve sufficient pesticide attenuation. In this study, the temporal dynamics of metazachlor and its transformation products metazachlor-oxalic acid (OA) and -sulphonic acid (ESA) were observed in an agricultural retention pond and hydrologic tracers helped to understand system-inherent processes. Pesticide measurements were carried out for 80 days after their application during transient flow conditions. During a short-term (3 days) experiment, the tracers bromide, uranine and sulphorhodamine B were used to determine hydraulic conditions, residence times and sorption potential. A long-term experiment with sodium naphthionate (2 months) and isotopes (12 months) provided information about inputs via interflow and surface-groundwater interactions. During transient conditions, high concentration pulses of up to 35 µg L-1 metazachlor, 14.7 µg L-1 OA and 22.5 µg L-1 ESA were quantified that enduringly raised solute concentrations in the pond. Mean residence time in the system accounted for approximately 4 h showing first tracer breakthrough after 5 min and last tracer concentrations 72 h after injection. While input via interflow was confirmed, no evidence for surface-groundwater interaction was found. Different tracers illustrated potentials for sorption and photolytic degradation inside the system. This study shows that high-resolution sampling is essential to obtain robust results about retention efficiency and that hydrological tracers may be used to determine the governing processes.


Assuntos
Acetamidas/análise , Herbicidas/análise , Hidrologia/métodos , Poluentes Químicos da Água/análise , Acetamidas/química , Agricultura , Biodegradação Ambiental , Brometos/análise , Fluoresceína/análise , Alemanha , Água Subterrânea , Herbicidas/química , Ácido Oxálico/química , Tanques , Rodaminas/análise , Ácidos Sulfônicos/química , Poluentes Químicos da Água/química , Poluição Química da Água/prevenção & controle
11.
J Environ Sci (China) ; 84: 1-12, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31284901

RESUMO

A series of functional organic-metal AgCl-decorated graphitic carbon nitride (AgCl-CNx) composites were synthesized and applied for the degradation of oxalic acid (OA) under visible light. The highest photocatalytic activity was achieved with AgCl decoration ratio of 1.0 (denoted as AgCl-CN1.0). The pseudo-first-order constant for OA degradation was 0.0722 min-1 with the mineralization efficiency of 90.80% after 60 min reaction in the photocatalytic process with AgCl-CN1.0. A variety of characterization techniques including Brunauer-Emmett-Teller, X-ray diffraction, scanning electron microscope, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectra, ultraviolet-visible diffuse reflectance spectra, photoluminescence, and Mott-Schottky were utilized to elucidate the physicochemical, microstructure, and optical properties contributing to the improvement of the photocatalytic performance. The results showed that AgCl-CN1.0 had an oblate flaky erythrocyte-like structure with a moderate band gap energy of ~3.00 eV. In addition, the effects of the key parameters (i.e., AgCl-CN1.0 dosage, initial OA concentration, solution pH, and presence of natural organic matter) on OA degradation were systematically investigated. Radical scavenger experiments indicated that photogenerated holes, electrons, superoxide anion radicals, and hydroxyl radicals were the dominant reactive species. Moreover, AgCl-CN1.0 exhibited excellent stability and reusability for OA degradation without detectable Ag+ release in the solution over multiple reaction cycles. The efficient OA mineralization could be mainly ascribed to the moderate specific surface area, increased numbers of active sites, and effective interfacial charge transfer of AgCl-CN1.0. Overall, the AgCl-CN1.0 composite was demonstrated to be a highly efficient, stable, and recoverable photocatalyst.


Assuntos
Grafite/química , Compostos de Nitrogênio/química , Ácido Oxálico/química , Fotólise , Compostos de Prata/química , Poluentes Químicos da Água/química
12.
Environ Sci Pollut Res Int ; 26(22): 23027-23036, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31183753

RESUMO

Microplastics (MPs) in natural environments have attracted lots of attention. Although the quantity of MPs present in terrene is much higher than that in aquatic environment, few studies have investigated the chemical behavior of MPs in terrestrial environment. This study investigate the Cu2+ (as a model heavy metal) adsorption capacity of six kinds of MPs (polyamide-6 (PA), polyethylene (PE), polystyrene (PS), polyethylene terephthalate (PET), polyvinyl chloride (PVC), polymethyl methacrylate (PMMA)) in batch adsorption experiments and the effects of different soil environmental factors, including pH and the presence of cations and low-molecular-weight organic acids (LMWOAs), as well as ultraviolet (UV) aging. The Cu2+ adsorption capacities of PA and PMMA were higher than those of other MPs and their maximum equilibrium adsorption capacities (estimated by the Langmuir adsorption equation) were 323.6 µg/g ± 38.2 and 41.03 ± 1.78 µg/g, respectively. The Cu2+ adsorption on MPs was affected by pH, and the greatest amount of Cu2+ adsorbed on PA and PMMA was observed at pH = 6 and pH = 7, respectively. The presence of Ca2+ or Mg2+ inhibited Cu2+ adsorption by MPs, due to competition for the adsorption sites. Moreover, Cu2+ adsorption by MPs was affected by various types of LMWOAs. The Cu2+ adsorption on PA was significantly reduced by citric acid, followed by oxalic acid, and oxalic acid was particularly evident for Cu2+ adsorption on PMMA. UV aging (200 h) had different effect on Cu2+ adsorption on MPs and it depends on the change of carbonyl index. Results demonstrate that soil environmental factors can change the ability of different MPs to adsorb Cu2+ and affect the transport of pollutants as carriers.


Assuntos
Cobre/química , Poliestirenos/química , Poluentes do Solo/análise , Adsorção , Ácido Cítrico/química , Peso Molecular , Compostos Orgânicos , Ácido Oxálico/química , Plásticos , Polietileno/química , Solo , Poluentes do Solo/química
13.
Artigo em Inglês | MEDLINE | ID: mdl-31046556

RESUMO

Ag/ZnO nanocomposites are successfully synthesized at different Ag contents through simple, effective, high yield and low-cost mechanochemical combustion technique, with the addition of silver acetate to zinc acetate and oxalic acid mixture. The synthesized materials are characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron spectroscopy (SEM), BET surface area analysis, UV - visible diffuse reflectance spectroscopy (UV - DRS) and photoluminescence spectroscopy (PL). It is shown that the prepared nanocomposites are composed of metallic Ag0 and wurtzite ZnO. The photocatalytic performance of different composites is evaluated by the degradation of Famotidine (FMT) under UV irradiation. The results indicate it that the maximum photodegradation rate is obtained with 6 wt% metallic Ag-decorated ZnO, and it is 2.1 times better than that obtained with pure ZnO. The photocatalytic degradation of FMT with Ag/ZnO is affected by various parameters such as calcination temperature and time, doping concentrations and reusability. The Ag/ZnO demonstrates higher activity due to the reduction of electron - hole recombination and Ag0 metal catalyst. The possible photocatalytic degradation mechanism of FMT with Ag/ZnO is estimated from the scavenger test.


Assuntos
Acetatos/química , Famotidina/química , Compostos de Prata/química , Óxido de Zinco/química , Catálise , Nanocompostos/química , Ácido Oxálico/química , Fotólise , Temperatura , Raios Ultravioleta
14.
Environ Sci Pollut Res Int ; 26(15): 15406-15413, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-30941713

RESUMO

In soil, vanadium (V) contamination is commonly concomitant with chromium (Cr) contamination, which poses potential risks to humans, animals, and plants due to the transfer of toxic metals and the increase in their concentrations via the food chain or through direct exposure. This study applied a multi-step column leaching process using low-molecular-weight organic acids (LMWOAs) to treat V-contaminated soil from a smelter site that contains 2015.1 mg V kg-1 and 1060.3 mg Cr kg-1. After leaching three times with an equivalent solution/soil ratio of 0.3 mL/g using 1.0 M oxalic acid solution, the total removal rates reached 77.2% and 7.2% for V and Cr, respectively, while the removal rates of the extractable fractions reached 118.6% and 99.2% due to the reduction in residual fraction (F4) of toxic metals. Simultaneously, the distribution and redistribution of geochemical fractions of V and Cr were determined with a sequential extraction technique, and the greater proportion of potential mobile fractions of V (65.1%) may increase its leaching from soil relative to Cr (7.1%). In addition, a lower pH of the leaching agent increased the efficiency of the leaching process to an extent. Compared with batch extraction with a typical solution to soil ratio of 10 mL/g, multi-step column leaching used less agent and hence produced less wastewater. This strategy could reduce the mobilization and bioavailability of toxic metals, and potentially enhance in situ soil flushing for the remediation of V- and Cr- contaminated soil.


Assuntos
Cromo/isolamento & purificação , Recuperação e Remediação Ambiental/métodos , Ácido Oxálico/química , Poluentes do Solo/isolamento & purificação , Vanádio/isolamento & purificação , Disponibilidade Biológica , China , Cromo/análise , Cromo/farmacocinética , Recuperação e Remediação Ambiental/instrumentação , Concentração de Íons de Hidrogênio , Malatos/química , Metalurgia , Peso Molecular , Solo/química , Poluentes do Solo/análise , Poluentes do Solo/farmacocinética , Tartaratos/química , Vanádio/análise , Vanádio/farmacocinética , Águas Residuárias
15.
Artigo em Inglês | MEDLINE | ID: mdl-31013864

RESUMO

Chelators including DTPA (diethylene triamine pentaacetic acid) and oxalic acid were selected for inducing phytoextraction of heavy metals (HMs) from Pb-, Tl-, and Pb-Tl- contaminated soil, in which heavy metals leakage was highly remarkable. Results showed that compared with the control group without chelating agent under planting conditions, the extraction efficiency (i.e., uptake coefficient) of Pb, Tl increased by 86%, 43% from Pb-Tl- contaminated soil in the presence of oxalic acid, and there was no significant change in heavy metal leakage under rainfall conditions. It was the best phytoremediation scheme in this work. Under rainfall conditions, the HMs concentration in the leachate showed a linear decreasing trend. Acid rain promoted the leakage of heavy metals, and the average leached amount of Tl increased by 1.47 times under acid rain conditions. However, for Pb, DTPA was the main influencing factor, followed by acid rain.


Assuntos
Biodegradação Ambiental , Chumbo/química , Ácido Oxálico/química , Ácido Pentético/química , Poluentes do Solo/química , Tálio/química , Quelantes , Solo/química
16.
Molecules ; 24(6)2019 Mar 20.
Artigo em Inglês | MEDLINE | ID: mdl-30897825

RESUMO

The habit of eating wild plants in Europe is often associated with times of famine; an example of such is the nectar of Cytinus hypocistis (L.) L., a parasitic plant. To the authors' best knowledge, there are no studies on its nutritional and chemical composition; thus, the whole C. hypocistis (L.) L. subsp. macranthus Wettst. plant (CH) and its nectar (NCH) were nutritionally and chemically characterized. The proximate composition of CH and NCH were very similar in terms of energy, ash, and carbohydrate content. Protein and fat were approximately 2-fold higher in NCH, and crude fiber was 4.6-fold higher in CH compared to NCH. Fructose, glucose, sucrose, and trehalose were the free sugars present in both samples. Oxalic, malic, and citric acids were the identified organic acids in both samples, with citric acid as the most abundant molecule. For both samples, polyunsaturated and saturated fatty acids (PUFA and SFA, respectively) predominate over monounsaturated fatty acids (MUFA) due to the significant contribution of linoleic and palmitic acids, respectively. However, unsaturated fatty acids (UFA) prevail over SFA in CH and NCH. Therefore, CH proved to be an excellent source of nutritional compounds, which supports its use during past periods of scarcity.


Assuntos
Malvaceae/química , Carboidratos/química , Ácidos Graxos Monoinsaturados/química , Ácidos Graxos Insaturados/química , Malatos/química , Ácido Oxálico/química
17.
Environ Sci Process Impacts ; 21(4): 738-747, 2019 Apr 17.
Artigo em Inglês | MEDLINE | ID: mdl-30895974

RESUMO

Here we study the precipitation of lead (Pb)-phosphate minerals over the pH range of 4.0 to 8.0 with and without oxalate, a ubiquitous and abundant low-molecular-weight organic acid derived from plants and microorganisms in environmental matrices. In the aqueous Pb-phosphate systems, phosphate precipitated Pb efficiently, reducing the dissolved Pb concentration below 1 µM at all the tested pH values, with the minimum solubility of about 0.1 µM measured at the intermediate pH of 6.0. The measured dissolved Pb and free Pb2+ ion activity were not in agreement with predictions from generally-accepted solubility products of the Pb phosphate minerals, particularly hydroxypyromorphite [Pb5(PO4)3OH]. Discrepancies between our measured Pb phosphate solubility products and older reported values are attributed to non-ideal behavior of these minerals (incongruent dissolution) as well as uncertainties in stability constants for soluble Pb-phosphate ion pairs. The presence of equimolar levels of oxalate and phosphate resulted in up to 250-fold increase in Pb solubility at acidic pH and about a 4-fold increase at pH 7.0, due to the strong suppression of Pb phosphate precipitation by oxalate and formation of soluble Pb-oxalate complexes. At pH 4.0 and 5.0, Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) identified a Pb-oxalate mineral phase as the only precipitate despite the presence of phosphate; in the absence of oxalate, Pb hydrogen phosphate, PbHPO4, stably formed under these acidic conditions. At pH 6.0 and greater, FTIR and XRD data revealed that Pb-phosphate [Pb3(PO4)2], and hydroxypyromorphite [Pb5(PO4)3OH] to a lesser extent, were the predominant precipitates both in the absence and presence of oxalate. Therefore, oxalate did not strongly interfere with Pb-phosphate mineral formation at aqueous pH greater than 6.0 but oxalate controlled Pb solubility at acidic pH values.


Assuntos
Concentração de Íons de Hidrogênio , Chumbo/química , Minerais/química , Ácido Oxálico/química , Fosfatos/química , Compostos Orgânicos , Solubilidade , Difração de Raios X
18.
Ecotoxicol Environ Saf ; 174: 401-407, 2019 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-30851537

RESUMO

The contamination of soil by copper (Cu) and lead (Pb) is a serious concern because of its high health risk via the food chain. Oxalic acid-activated phosphate rock (APR) and bone meal (BM) were applied to Cu and Pb co-contaminated soil to investigate their efficacy in the immobilization of Cu and Pb. APR and BM were applied into the contaminated soil (158.8 mg/kg total Pb and 573.2 mg/kg Cu) at four levels of dosages (0.1%, 0.5%, 2%, and 4%) and incubated for one year. The results demonstrated that the acid exchangeable Pb fraction in the soil treated with APR and BM decreased compared to the control, while there was no noticeable change in the acid-exchangeable Cu fraction in the soil treated with either APR or BM. Meanwhile, the application of BM and APR increased the fraction of residual Cu and Pb in the polluted soils. Moreover, the addition of either APR or BM at the dose of 4% decreased the concentrations of CaCl2-extractable Cu and Pb in the amended soil, and the percentages of that reduction in the APR amended soils were 56% and 91% and in BM amended soils were 67% and 64%, respectively. The immobilization of Cu and Pb by APR and BM might be induced by the increased soil pH and soluble P contents in the amended soils. In general, BM is more effective than APR on the immobilization of Cu in polluted soil, while APR had greater efficiency than BM on the immobilization of Pb when the levels of amendments were above 2%.


Assuntos
Metais Pesados/análise , Minerais/química , Mineração , Ácido Oxálico/química , Fosfatos/química , Poluentes do Solo/análise , Solo/química , Produtos Biológicos/química , China , Cobre/análise , Chumbo/análise , Modelos Teóricos
19.
Chemosphere ; 222: 38-45, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-30690399

RESUMO

Photocatalytic ozonation is an attractive advanced oxidation process for wastewater treatment, but highly active catalysts with strong response to visible light are urgently needed to push forward its practical application. In this study, a hierarchical biomimetic monoclinic bismuth vanadate (BiVO4) with leaves morphology was synthesized by a hydrothermal method, and employed as catalyst for oxalic acid and penicillin degradation in photocatalytic ozonation. The results show that the organics degradation was more efficient using leaves shaped BiVO4 as catalyst than the bulk shaped one in photocatalytic ozonation and the synergy index is ranged from 2.8 to 3.3, indicating a superior positive synergistic effect between photocatalysis and ozonation. The higher activity of the leaves shaped BiVO4 was probably attributed to the distinctive biomimetic morphology and preferable band structure with more negative CB potential. Mechanism studies suggested that the main reactive species were h+ and OH for the degradation of persistent oxalic acid in photocatalytic ozonation. In addition, the effect of ozone concentration and inorganic ions and reusability of the material were also intensively investigated.


Assuntos
Biomimética/métodos , Bismuto/química , Luz , Ozônio , Vanadatos/química , Águas Residuárias , Catálise , Ácido Oxálico/química , Oxirredução , Penicilinas/química , Fotólise , Vanadatos/síntese química , Poluentes Químicos da Água
20.
Anal Chim Acta ; 1052: 57-64, 2019 Apr 04.
Artigo em Inglês | MEDLINE | ID: mdl-30685042

RESUMO

The geochemical fate of indium in natural waters is still poorly understood, while recent studies have pointed out a growing input of this trivalent element in the environment as a result of its utilisation in the manufacturing of high-technology products. Reliable and easy-handling analytical tools for indium speciation analysis are, then, required. In this work, we report the possibility of measuring the total and free indium concentrations in solution using two complementary electroanalytical techniques, SCP (Stripping chronopotentiometry) and AGNES (Absence of Gradients and Nernstian Equilibrium Stripping) implemented with the TMF/RDE (Thin Mercury Film/Rotating Disk Electrode). Nanomolar limits of detection, i.e. 0.5 nM for SCP and 0.1 nM for AGNES, were obtained for both techniques in the experimental conditions used in this work and can be further improved enduring longer experiment times. We also verified that AGNES was able (i) to provide robust speciation data with the known In-oxalate systems and (ii) to elaborate indium binding isotherms in presence of humic acids extending over 4 decades of free indium concentrations. The development of electroanalytical techniques for indium speciation opens up new routes for using indium as a potential tracer for biogeochemical processes of trivalent elements in aquifers, e.g. metal binding to colloidal phases, adsorption onto (bio)surfaces, etc.


Assuntos
Eletroquímica/métodos , Índio/química , Adsorção , Eletroquímica/instrumentação , Eletrodos , Substâncias Húmicas/análise , Ácido Oxálico/química
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