Evaluation of an organo-layered double hydroxide and two organic residues as amendments to immobilize metalaxyl enantiomers in soils: A comparative study

Many pollutants released into the environment as a result of human activities are chiral. Pollution control strategies generally consider chiral compounds as if they were achiral and rarely consider enantiomers separately. We compared the performance of three different materials, an organically-modified anionic clay (HT-ELA) and two organic agro-food residues (ALP and ALPc), as amendments to immobilize the chiral fungicide metalaxyl in two soils with different textures, addressing the effects of the amendments on the sorption, persistence, and leaching of each of the two enantiomers of metalaxyl (R-metalaxyl and S-metalaxyl) separately. The effects of the amendments were both soil- and amendment-dependent, as well as enantiomer-selective. The organo-clay (HT-ELA) was much more efficient in increasing the sorption capacity of the soils for the two enantiomers of metalaxyl than the agro-food residues (ALP and ALPc), even when applied at a reduced application rate. The enhanced sorption in HT-ELA-amended soils reduced the bioavailability of metalaxyl enantiomers and their leaching in the soils, mitigating the particularly high leaching potential of the more persistent S enantiomer. The immobilizing capacity of the agro-food residues was more variable, mainly because their addition did not greatly ameliorate the sorption capacity of the soils and had variable effects on the enantiomers degradation rates. HT-ELA showed potential to reduce the bioavailability and mobility of metalaxyl enantiomers in soil and to mitigate the contamination problems particularly associated with the higher leaching potential of the more persistent enantiomer. 11 páginas.-- 5 figuras.-- 2 tablas.-- referencias.-- Supplementary data related to this article can be found at http://dx.doi.org/10.1016/j.jenvman.2016.06.019This work has been financed by the Spanish Ministry of Economy and Competitiveness (MINECO Projects AGL2011-23779 and AGL2014-51897-R) and Junta de Andalucía (JA Research Group AGR-264), co-financed with FEDER-FSE funds. The authors thank B. Gamiz for her help in the design of the experiments and L. Cox for kindly supplying the organic residues. R. Lopez-Cabeza also thanks MINECO for a pre-doctoral fellowship linked to the Project AGL2011-23779 (Grant BES-2012-059945)Peer Reviewe

Synthesis and proton conduction properties of lanthanide amino-sulfophosphonates

Crystalline acid-functionalized metal phosphonates are potential candidates as proton conducting electrolytes. Their frameworks can be chemically modified to contain proton carriers such as acidic groups (P-OH; -SO3H, -COOH,…) and guest molecules (H2O, NH3,…) that generates hydrogen bond networks stable in a wide range of temperature [1,2]. In this work, focus is laid on properties derived from the combination of lanthanide ions with the amino-sulfophosphonate ligand (H2O3PCH2)2-N-(CH2)2-SO3H. Hightrough-put screening was followed to reach the optimal synthesis conditions under solvothermal conditions at 140 ºC. Isolated polycrystalline solids, Ln[(O3PCH2)2-NH-(CH2)2-SO3H].2H2O (Ln= La, Pr and Sm), crystallize in the monoclinic (La) and orthorhombic (Pr and Sm) systems with unit cell volume of ~2548 Å3. Preliminary proton conductivity measurements for Sm derivative have been carried out between 25º and 80 ºC at relative humidity (RH) values of 70 % and 95 %. The sample exhibits enhanced conductivity at high RH and T (Figure 1) and constant activation energies of 0.4 eV, typical of a Grothuss mechanism of proton.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. FQM-1656; MAT2013-41836-

Proton conductivity of lanthanide nitrilotris-methylphosphonates

Multifunctional metal phosphonates are acidic coordination polymers (CPs) with remarkable stability and proton conducting properties owing to their structure is usually composed of extended hydrogen-bond networks that favor proton transfer pathways [1]. In this communication, three different families of proton conductors based on lanthanide nitrilotris-methylphosphonates are examined. Compounds were isolated by crystallization at room temperature at pH <0.8 in the presence of. When chloride is presented in solution two families of compounds were isolated, depending on the concentration of chloride in solution: free-chloride 1D solids with formula Ln2(H3NMP)2(H2O)4]·4.5H2O [Ln= La3+] [2] or layered chloride-containing Ln(H4NMP)(H2O)2]Cl·2H2O [Ln= La3+ - Ho3+] materials [3]. In absence of chloride, a third series of compounds was obtained. This structural versatility leads to a wide range of proton conductivity varying between 3 × 10−4 S·cm−1 and 2 × 10−3 S·cm−1 as measured at 80 °C and 95% RH.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Ammonia effects on proton conductivity properties of coordination polymers

Crystalline metal phosphonates are referred to as a type of structurally versatile coordination polymers [1]. Many of them contain guest molecules (H2O, heterocyclics, etc.), acidic sites and, furthermore, their structure can be also amenable for post‐synthesis modifications in order to enhance desired properties [2]. In the present work, we examine the relationships between crystal structure and proton conductivity for several metal phosphonates derive from multifunctional ligands, such as 5-(dihydroxyphosphoryl)isophthalic acid (PiPhtA) [3] and 2-hydroxyphosphonoacetic acid (H3HPAA). Crystalline divalent metal derivatives show a great structural diversity, from 1D to 3D open-frameworks, possessing hydrogen-bonded water molecules and acid groups. These solids present a proton conductivity range between 7.2·10-6 and 1.3·10−3 S·cm-1. Upon exposure to ammonia vapor, from an aqueous solution, solid state transformations are observed accompanied of enhance proton conductivities. The stability of these solids under different environment conditions (temperature and relative humidities) as well as the influence of the ammonia adsorption on the proton conduction properties of the resulting solids will be discussed.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Structural study of the local order in ammonia-modulated FE(II) hydroxyphosphonoacetate proton conductors

Layered Fe(II) carboxiphosphonate, Fe-HPAA·2H2O, is a crystalline multifunctional coordination polymer exhibiting properties as photocatalyst and proton conductor. Postsynthesis modification by ammonia/water adsorption strongly enhances its proton conductivity. However, this process entails a progressive amorphization but in no case intercalation of the guest species was detected. Understanding the mechanism involved in this increased conductivity is crucial to develop novel high performance proton conductors for PEMFCs. Thus, total scattering and PDF study has been carried out to explore the mechanism of ammonia adsorption and subsequent amorphization. Different lenght scales have been investigated to characterize the average and local structure at variable ammonia loaded in order to ascertain posible structural modifications after gas/solid reactions. While significant short range order (from 1.4 to 10 Å) variations were observed even for low loadings, the average structure seems to be basically preserved except for the highest ammonia/water contents.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

New Multifunctional Lanthanide and Zr(IV) Phosphonates Derived from the 5-(dihydroxyphosphoryl) Isophthalate Ligand as Proton Conductors

Metal phosphonates are essentially acidic solids featured by groups such as P-OH, -COOH, etc. Moreover, the presence of coordination and lattice water molecules favors the formation of H-bond networks, which make these compounds appropriate as proton conductors, attractive for proton exchange membranes (PEMs) of fuel Cells.1 We report here, general characteristics of metal phosphonate derivatives composed of the polyfunctional 5-(dihydroxyphosphoryl) isophthalate ligand2 and lanthanides or zirconium ions. In the case of the lanthanide derivatives, crystalline compounds were synthesized under hydrothermal conditions. Preliminary results suggest that at least three isostructural series of compounds are formed. One of them, with La3+ derivative as prototype, is characterized by an orthorhombic unit cell (a = 12.7745(6) Å, b = 11.8921(4) Å, c = 7.2193(5) Å). Pr3+, Eu3+ and Gd3+ compounds, displays a monoclinic unit cell likewise the Yb3+ solid, the latter exhibiting different crystallographic parameters. Zr(IV) = compound, with formula Zr[(HO3P-C6H3-(COO)2H)2]·8H2O; was obtained at 80 ºC in the presence of HF as mineralizing agent. This solid crystallizes in an orthorhombic unit cell (a = 21.9306 Å, b = 16.6169 Å, c = 3.6462 Å). All these compounds contain in their frameworks water molecules that contribute to the formation of H-bond networks, making them prone as proton conductor candidates. Structural and proton conductivity are underway.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. Plan Propio de Investigación de la UMA MAT2016-77648

Synthesis and proton conduction properties of lanthanide amino-sulfophosphonates

Acidic groups-containing metal phosphonates exhibit a wide range of proton conductivity depending on the water content and functionality. Moreover, this property can be enhanced by appropriate post-synthesis chemical and/or thermal treatments [1,2]. In this work, focus is laid on properties derived from the combination of lanthanide ions with the amino-sulfophosphonate ligand (H2O3PCH2)2-N-(CH2)2-SO3H. Highthrough-put screening was used to reach the optimal synthesis conditions under hydrothermal conditions at 140 ºC. Isolated polycrystalline solids, Ln[(O3PCH2)2-NH-(CH2)2-SO3H]·2H2O (Ln= La, Pr, Sm, Eu, Gd, Tb and Er), crystallize in the monoclinic (La and Er) and orthorhombic (Pr, Sm, Eu, Gd and Tb) systems with unit cell volume of ~1200 and 2548 Å3 respectively. Their crystal structures, solved ab initio from X-ray powder diffraction data, correspond to different layered frameworks depending on the lanthanide cation size. Thus, compounds with orthorhombic symmetry show free acidic sulfonic pointing to the interlayer space, while La- and Er- derivatives display layered structures where both phosphonate and sulfonated groups are coordinated to the metal, leaving free P-OH groups. As consequence of this structural variability, different H-bond networks and proton transfer pathways are generated. Preliminary proton conductivity measurements have been carried out between 25 and 80 ºC at 70-95 % relative humidity. The sample exhibits conductivities near to 3.10-3 S.cm-1 and activation energies characteristics of a Grotthuss-type mechanism of proton transfer.Proyectos de investigación del ministerio MICINN, Españam(MAT2016-77648-R), Proyectos de la Junta de Andalucía (P12-FQM-1656), Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech