Effect of phosphorus on the attenuation of lead and chromium

This study analyses the adsorption of Pb(II) and Cr(III) in soils. These metals are commonly found together in nature in urban wastes or industrial spillages, and the theoretical approach of the work was to evaluate the response of the soil to continuous Cr and Pb spillages to soil in terms of several physicochemical parameters. The influence of an anthropogenic input of phosphorus was evaluated. Continuous flow experiments were run in duplicates in acrylic columns (25 cm × 3.2 cm). The influent Cr(III) and Pb(II) solutions of 10 mg l−1 and 25 mg l−1 at pH 5 were pumped upward through the bottom of the columns to ensure saturation flow conditions. Also, successive experiments were run with the above concentrations of Cr(III) and Pb(II) and NaH2PO4, keeping metal to phosphorus ratio of 1:0, 1:0.1 and 1:1. Modelling parameters included Freundlich and Langmuir equations, together with the Two-site adsorption model using CXTFIT code. Results obtained allowed concluding that Pb(II) adsorption presents a certain degree of irreversibility and the continued spillages over soil increment the fraction which is not easily desorbed. Cr(III) desorption was almost complete, evidencing its high mobility in nature. The presence of an anthropogenic input of phosphorus leads to a marked increase of both Pb(II) and Cr(III) adsorption in soils. Z-potential measurements allow to discard the electrostatic attraction of Cr(III) and Pb(II) with the surface charged soil as the dominant process of metal sorption. Instead, CheaqsPro simulation allows to identify PbH2PO4 +, PbHPO4 (aq) and CrHPO4 + as the dominant species which regulate Cr(III) and Pb(II) transport in soils.Fundação para a Ciência e a Tecnologi

Effects of Past Copper Contamination and Soil Structure on Copper Leaching from Soil

Copper contamination affects biological, chemical, and physical soil properties and associated ecological functions. Changes in soil pore organization as a result of Cu contamination can dramatically affect flow and contaminant transport in polluted soils. This study assessed the influence of soil structure on the movement of water and Cu in a long-term polluted soil. Undisturbed soil cores collected along a Cu gradient (from about 20 to about 3800 mg Cu kg−1 soil) were scanned using X-ray computed tomography (CT). Leaching experiments were performed to analyze tracer transport, colloid leaching, and dissolved organic carbon (DOC) and Cu losses. The 5% arrival time (t0.05) and apparent dispersivity (lapp) for tracer breakthrough were calculated by fitting the experimental data to a nonparametric, double-lognormal probability density function. Soil bulk density, which did not follow the Cu gradient, was the main driver of preferential flow, while macroporosity determined by X-ray CT (for pores >180 mm) proved the best predictor of solute transport. Higher preferential flow due to the presence of well-aligned pores and small cracks controlled water movement in compacted soil. Transport of Cu was rapid during the first flush (»1 pore volume) in association with the movement of colloid particles, followed by slower transport in association with the movement of DOC in the soil solution. The relative amount of Cu released was strongly correlated with macroporosity as determined by X-ray CT, indicating the promising potential of this visualization technique for predicting contaminant transport through soil

Novel Zn(II) Coordination Polymers Based on the Natural Molecule Bisdemethoxycurcumin

This article introduces a new family of coordination polymers (CPs) that contains a natural biocompatible curcumin derivative, the bisdemethoxycurcumin (BDMC), coordinated to Zn(II) centers. The reaction between BDMC and zinc acetate, performed under mild conditions in ethanol, provides a new 1D phase termed BDMCZn-1. In addition, dimensionality and porosity of this network have been expanded by studying the reaction occurring between three species, the BDMC, the Zn(II) and a ditopic co-linker: 1,2-bis(4-pyridyl)ethylene, 1,3-bis(4- pyridyl)propane or 4,4'-bipyridine. In total, seven new CPs are presented, named as BDMCZnx. The structures of five of them could be elucidated by single crystal X-ray diffraction. Moreover, we show that the combination of the latest technique with solid-state 13C nuclear magnetic resonance is a powerful tool set to analyze the coordination modes of the BDMC, providing insight into the two unresolved structures. In the achievement of the new CPs, we further discuss the coordination capacity of BDMC, the relevance of solvents and supramolecular interactions.This work has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 R&D programme (ERC-724981). We also acknowledge the Spanish Government, Ministerio de Ciencia e Innovación (projects CTQ2017-83632, CTQ2015-68370-P and PGC2018-098630-B-I00 - MAT2016-77852-C2-1-R, and Ramon y Cajal grant RYC-2017-22910) and the Generalitat de Catalunya for the grant 2017SGR1277. C.D., N.A.A., A.L.P., A.G.C., and L.R.C. acknowledge the financial support through the “Severo Ochoa” program for Centres of Excellence in R&D (SEV-2015-0496) under the FUNMAT-FIP-2016 fellowship. Special thanks to the Alba synchrotron for the possibility of carrying out the measurements of the crystals in the experiments AV-2017042211, AV-2018052864, AV-2018072912, and AV-2019023285 at beamline BL13–XALOC. This work (L.R.C.) has been done in the framework of the doctoral program “Chemistry” of the Universitat Autònoma de Barcelona.Peer reviewe

Supramolecular Isomerism in Cobalt(II) Coordination Polymers Built from 3,5-Bis(trifluoromethyl)benzoate and 4,4′-Bipyridine

The reaction of [Co2(H2O)(TFMBz)4(py)4] (1) (TFMBz: 3,5-bis(trifluoromethyl)benzoate; py: pyridine) with 4,4′-bipyridine (bpy) in different solvents yields four coordination polymers with unlikely structures but with the same stoichiometry. Three of them contain similar ladder chains consisting of binuclear nodes "Co2(TFMBz)4", in which two of the TFMBz ligands show bidentate bridge coordination, double linked to each adjacent node by bpy but packed in different fashions. The different packing affects the compound porosity; thus, [Co2(TFMBz)4(bpy)2]n(2), precipitated using low-polarity solvents such as supercritical CO2(scCO2), n-butyl acetate, or heptane and also in acetonitrile, is microporous, with a surface area of 330 m2g-1, showing the N2adsorption/desorption isotherm at 77 K with a gate-opening effect at low relative pressures (P/P0= 0.05). The isomer [Co2(TFMBz)4(bpy)2]n(3), synthesized in ethoxyethanol, presents a surface area of 230 m2g-1. A third chain packing isomer, [Co2(TFMBz)4(bpy)2]n(4), is obtained in acetone and has only non-interconnected voids. Finally, precursor 1 is combined with bpy in a highly polar solvent such as water to give [Co(TFMBz)2(bpy)]n(5). In this isomer, all the carboxylate units act as bidentate bridging ligands, generating chains that are interlinked by bpy, leading to a 2D network, which after packing yields a non-porous structure. The resolution of structures 2-5 is only possible with the recently developed 3D electron diffraction method based on the collection of diffraction patterns on sub-micron-sized single crystals. The variation of magnetic susceptibility as a function of temperature is also measured. Overall, our work provides insightful information on the complex landscape of metal-organic framework solids that are formed by crystallization using different solvent media.This work was supported by the Spanish Ministry of Science and Innovation MICINN through the Severo Ochoa Program for Centers of Excellence (CEX2019-000917-S) and the Spanish National Plan of Research with projects PID2020-115631GB-I00. F.P., A.E.L., and M.G. would like to thank Regione Toscana for funding the purchase of the ASI MEDIPIX detector through the FELIX project (POR CREO FERS 2014–2020). The measures for the elucidation of the crystal structure of compound 1 were performed at the XALOC beamline at ALBA Synchrotron with the collaboration of ALBA staff.With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000917-S).Peer reviewe