Waste-polystyrene foams-derived magnetic carbon material for adsorption and redox supercapacitor applications

The current impact of plastic waste on the environment and nature pushes for coming up with methods for their efficient reuse and recycle. Expanded polystyrene waste, massively produced worldwide, is presented in this work as a novel precursor of magnetic activated carbons (MAC) for the first time. A simple methodology based on the impregnation of EPS samples with Fe3+ in solution, followed by pyrolysis under Ar pressure and chemical activation is proposed. The as-prepared carbonaceous magnetic materials present nanometric phases of Fe0, Fe3C, and Fe3O4, and showed high specific surface area (672 m2 g−1) and total pore volume (0.35 cm3 g−1), one of the highest found in the carbonaceous magnetic materials literature. Their excellent textural, chemical and electrical properties, combined with the possibility of magnetically collection and regeneration after operation guaranteed an excellent performance of MAC in two different applications: as adsorbents of organic contaminants and as electrodes of redox supercapacitors.The authors would like to thank the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) and Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG) for the financial support. P.F.R. Ortega acknowledges the FAPEMIG (DOF nº. 2720262/2018). The authors are also grateful to Rede Mineira de Química. R.L. Lavall is recipient of fellowship from CNPq (grant number 313304/2017-3). N. C. F. Machado, K. H. A. Mendes, and L. A. M. de Jesus would like to thank CEFET-MG and FAPEMIG for scholarships receivedPeer reviewe

Valorization of compost obtained from the mechanical and biological treatment of municipal solid waste: catalysts for wet peroxide oxidation of landfill leachates

Since humanity started living in communities and towns, the generation of solid waste has largely increased and, in 2017, each European citizen generated 480 kg of municipal solid waste (MSW). The main concern with MSW is its management and final destination since in many cases MSW is just thrown in landfills. In mechanical and biological plants, MSW is first sorted into discarded, recyclable, and organic waste streams. This organic fraction goes to the biological treatment stage, generating biogas, and as by-products, leachate, and compost are obtained, the compost being mainly used as an agriculture fertilizer. However, the amount of compost produced is higher than its demand, resulting in an excess that is currently accumulated in landfills. This work deals with the valorization of compost to produce hydrochairs, and pyrochars, through hydrothermal carbonization (HTC) and pyrolysis, respectively, with suitable properties as catalysts for the catalytic wet peroxide oxidation of the landfill leachate. Up to seven catalysts were synthesized under several conditions, 2 from HTC and 5 from pyrolysis. The catalysts were characterized to determine the ash content and elemental analysis. All materials were assessed in the degradation of H 2 O 2 , leading to its complete degradation after 2 h of reaction time. Some selected catalysts were further tested in the CWPO of the landfill leachate (TOC = 27 g L -1 , COD = 60 g L -1 , 38.8 mS/cm, and 5 g L -1 of chloride ions) under the following operating conditions: C Catalyst = 1.8 g L -1 ; T = 80 ºC; C H2O2 = 85.7 g L -1 and pH from 3.0 to 7.3.This work was financially supported by project “VALORCOMP - Valorización de compost y otros desechos procedentes de la fracción orgánica de los residuos municipales”, with reference 0119_VALORCOMP_2_P, through FEDER under Program INTERREG; Base Funding - UIDB/50020/2020 of the Associate Laboratory LSRE-LCM - funded by national funds through FCT/MCTES (PIDDAC); CIMO (UIDB/00690/2020) through FEDER under Program PT2020, and national funding by FCT, Foundation for Science and Technology, through the individual research grant SFRH/BD/143224/2019 of Fernanda Fontana Roman.info:eu-repo/semantics/publishedVersio

Catalytic wet peroxide oxidation of leachate waters using low-cost carbon-based materials as catalysts

The Directive 2008/98/EC established a hierarchy for management of Municipal Solid Waste (MSW), according to which landfilling should be avoided. In this direction, Mechanical and Biological Treatment (MBT) plants play an important role, since it allows the conversion of the organic fraction of MSW into biogas and compost, with applications as fuel and fertilizer, respectively. However, MBTs generate a wastewater, referred as leachate, with high load of organic matter, that is not properly treated by conventional systems. In addition, the production of compost in MBTs tends to be higher than its demand, resulting in accumulation on landfilling sites. This works aims to address the Catalytic Wet Peroxide Oxidation (CWPO) of a real leachate effluent obtained from a MBT, whose properties are summarized in Table 1. The compost obtained from the MBT was considered to produce the catalyst for the CWPO process. The lowcost catalytic materials were prepared by hydrothermal carbonization at previously optimized operating conditions (230 ºC, 4 h and 130 gcompost/L). Figure 1 shows the profile of H2O2 decomposition, COD and TOC upon time of reaction at 50 °C (solid line) and at 80 °C (dashed lines). At 80 °C, a removal of 40% and 55% for COD and BOD5, respectively, was achieved, increasing BOD5/COD ratio from 0.33 to 0.45, along with a reduction on turbidity (to 12 NTU) and color of the effluent, as observed in Figure 1.This work was financially supported by project “VALORCOMP - Valorización de compost y otros desechos procedentes de la fracción orgánica de los residuos municipales”, with reference 0119_VALORCOMP_2_P, through FEDER under Program INTERREG; the Associate Laboratory LSRE-LCM (UIDB/50020/2020) funded by national funds through FCT/MCTES (PIDDAC); CIMO (UIDB/00690/2020) through FEDER under Program PT2020, and national funding by FCT, Foundation for Science and Technology, through the individual research grant SFRH/BD/143224/2019 of Fernanda Fontana Roman.info:eu-repo/semantics/publishedVersio

Solvent effects on the dimensionality of oxamato-bridged manganese(II) compounds

<p>Two new oxamate-containing manganese(II) complexes, [{Mn(H₂edpba)(H₂O)₂}₂]_n (<b>1</b>) and [Mn(H₂edpba)(dmso)₂]∙dmso∙CH₃COCH₃∙H₂O (<b>2</b>) (H₄edpba = <i>N,N′</i>-ethylenediphenylenebis(oxamic acid) and dmso = dimethylsulfoxide), have been synthesized and the structures of <b>1</b> and <b>2</b> were characterized by single crystal X-ray diffraction. The structure of <b>1</b> consists of neutral honeycomb networks in which each manganese(II) is six-coordinate by one H₂edpba²⁻ ligand and two carboxylate–oxygens from two other H₂edpba²⁻ ligands building the equatorial plane. Each manganese is connected to its nearest neighbor through two carboxylate(monoprotonated oxamate) bridges in an <i>anti</i>-<i>syn</i> conformation. A dmso solution of single crystals of <b>1</b> was placed under acetone atmosphere affording <b>2</b>, whereas putting <b>2</b> in equimolar water:ethanol mixture results in <b>1</b>. The molecular structure of <b>2</b> is made up of mononuclear manganese(II) units which are interlinked by weak C–H⋯π and edge-to-face π-stacking interactions leading to supramolecular chains along the crystallographic <i>b</i> axis. Magnetic measurements reveal the occurrence of an antiferromagnetic coupling between two manganese(II) ions through <i>anti-syn</i> carboxylate bridges for <b>1</b> [<i>J</i> = −1.18 cm⁻¹, the Hamiltonian being defined as <b><i>H</i> </b>= −<i>J</i> <b><i>S</i></b>₁^.<b><i>S</i></b>₂] and very weak intrachain ferromagnetic interactions in <b>2</b> [<i>J</i> = + 0.046 cm⁻¹, <b><i>H</i></b> = −<i>J</i> ∑_i<b><i>S</i></b>_i^.<b><i>S</i></b>_i + 1].</p