Eleonora Aneggi

BMP tests of source selected OFMSW to evaluate anaerobic codigestion with sewage sludge

The aim of this study is to characterize different types of source selected organic fraction of municipal solid waste (SS-OFMSW) in order to optimize the upgrade of a sewage sludge anaerobic digestion unit by codigestion. Various SS-OFMSW samples were collected from canteens, supermarkets, restaurants, households, fruit-vegetable markets and bakery shops. The substrates characterization was carried out getting traditional chemical-physical parameters, performing elemental analysis and measuring fundamental anaerobic digestion macromolecular compounds such as carbohydrates, proteins, lipids and volatile fatty acids. Biochemical methane potential (BMP) tests were conducted at mesophilic temperature both on single substrates and in codigestion regime with different substrates mixing ratios. The maximum methane yield was observed for restaurant (675 NmlCH4/gVS) and canteens organic wastes (571 and 645 NmlCH4/gVS). The best codigestion BMP test has highlighted an increase of 47% in methane production respect sewage sludge digestion.

Fast firing of tiles containing paper mill sludge, glass cullet and clay

The paper describes results obtained in the development of a previous research. We study here, in fast firing, the sintering behaviour and measure some properties of tiles containing a mixture of 60 wt% of paper mill sludge and 40 wt% of glass cullet. The behaviour of this material is compared to those displayed by materials obtained by the same mixture added with 10, 20 and 30 wt% of a natural red clay. In parallel, the same properties are measured also on a reference blend, which is presently used to produce commercial tiles. We show that powders containing 60 wt% of paper sludge and 40 wt% of glass cullet to which 30 wt% of clay is added give rise to materials that display a stable sintering process and have good hardness and strength and therefore could be used for the industrial production of tiles.

Salt-assisted thermal desorption of mercury from contaminated dredging sludge

In this study, we tested a new procedure for the decontamination of mercury-polluted dredging sludge (Marano-Grado Lagoon, northeastern Italy) based on cationic exchange associated with thermal desorption at a low temperature. Four mercury-polluted sludge slurries were treated using thermal desorption at 393 K for 2h. Three different salts, NaCl (sodium chloride), (CH(3))(4)NCl (tetramethylammonium chloride) and (C(4)H(9))(4)NCl (tetrabutylammonium chloride) were used as exchangers. The selected salts have a monovalent cationic part that progressively increases in molecular weight. The results show that the association of cationic exchange with thermal treatment leads to a significant improvement in the removal of mercury from the contaminated material at a low temperature compared to samples that were not treated with salt. The highest levels of decontamination were attained were obtained when the slurries, which had mercury pollution ranging from 20 to 200 ppm, were treated with a 15% solution of (C(4)H(9))(4)NCl. The efficiency of the removal at 393 K (from 24% up to 60%) depended on the nature of the sample. When the samples were treated at a similar temperature without the salt, no remediation of mercury was detected. Our results show that the thermal decontamination temperature can be significantly lowered by this remediation approach, which is the first example based on cationic exchange of the pollutant with an appropriate salt.

Ambient Pressure Photoemission Spectroscopy Reveals the Mechanism of Carbon Soot Oxidation in Ceria-Based Catalysts

Removing soot is one of the most important challenges in minimizing the impact of combustion engines on the environment. Catalysts based on CeO2 have proved suitable to oxidize soot owing to their capacity to store and release oxygen easily while maintaining structural integrity, although their mode of operation in a complex environment involving two solid phases (catalyst and soot) and a gas phase (oxygen) is not yet fully understood. Herein, we provide a study of the surface/subsurface of ceria–soot and ceria–zirconia–soot mixtures under working conditions by means of near‐ambient‐pressure photoelectron spectroscopy. Soot abatement involves two cooperative routes: one occurring at the ceria–soot interface with formation of oxygen vacancies and CeIII and the other at the surface of soot, mediated by active superoxide species, which result from the reaction between gas‐phase O2 and oxygen vacancies. The two routes occur simultaneously and mutually reinforce each other.

Development of a modified co-precipitation route for thermally resistant, high surface area ceria-zirconia based solid solutions

Abstract In this work a modified co-precipitation route for ceria-zirconia based material with a high surface area, high thermal stability and enhanced OSC properties has been developed and the importance of the addition of surfactants and H2O2 in order to promote the stability of these materials at high temperatures has been developed.

Ceria-zirconia particles wrapped in a 2D carbon envelope: improved low-temperature oxygen transfer and oxidation activity

Engineering the interface between different components of heterogeneous catalysts at nanometer level can radically alter their performances. This is particularly true for ceria-based catalysts where the interactions are critical for obtaining materials with enhanced properties. Here we show that mechanical contact achieved by high-energy milling of CeO2–ZrO2 powders and carbon soot results in the formation of a core of oxide particles wrapped in a thin carbon envelope. This 2D nanoscale carbon arrangement greatly increases the number and quality of contact points between the oxide and carbon. Consequently, the temperatures of activation and transfer of the oxygen in ceria are shifted to exceptionally low temperatures and the soot combustion rate is boosted. The study confirms the importance of the redox behavior of ceria-zirconia particles in the mechanism of soot oxidation and shows that the organization of contact points at the nanoscale can significantly modify the reactivity resulting in unexpected properties and functionalities.

Potential of Ceria-Based Catalysts for the Oxidation of Landfill Leachate by Heterogeneous Fenton Process

In this study, ceria and ceria-zirconia solid solutions were tested as catalyst for the treatment of landfill leachate with a Fenton-like process. The catalysts considered in this work were pure ceria and ceria-zirconia solid solutions as well as iron-doped samples. All the catalysts were extensively characterized and applied in batch Fenton-like reactions by a close batch system, the COD (chemical oxygen demand) and TOC (total organic carbon) parameters were carried out before and after the treatments in order to assay oxidative abatement. Results show a measurable improvement of the TOC and COD abatement using ceria-based catalysts in Fenton-like process and the best result was achieved for iron-doped ceria-zirconia solid solution. Our outcomes point out that heterogeneous Fenton technique could be effectively used for the treatment of landfill leachate and it is worth to be the object of further investigations.

Efficient fluoride adsorption by mesoporous hierarchical alumina microspheres

Mesoporous Hierarchical Alumina Microspheres (HAM) with high efficiency for fluoride removal have been synthesized and characterized. Two types of HAM, differing mostly in crystallinity, surface area and pore size have been obtained. Fluoride adsorption studies have been carried out by means of potentiometry and Isothermal Titration Calorimetry (ITC). The latter method has been applied for the first time to obtain direct determination of the adsorption enthalpy (ΔHads) of F− ion on HAM. The kinetics of the reaction revealed a two-step process for fluoride adsorption on the adsorbent material. The ΔHads values obtained are clearly negative for the different samples investigated. Experimental adsorption data are well fitted by a Langmuir isotherm. The adsorption constant obtained for type A is 1 order of magnitude higher than for type B, showing that the synthetic protocol has a remarkable effect on this parameter. The highest defluoridation capacity reaches 26 mmol g−1 after 1 hour of equilibration for the amorphous HAM, which is higher than for other adsorbents reported in the literature.

Simultaneous Removal of Soot and NOx Over Silver and Ruthenium-Based Catalysts

Silver- and ruthenium-based materials are herein investigated for the simultaneous removal of particulate matter (soot) and NOx and their behaviour is compared with that of a model Pt–Ba/Al2O3 catalyst. The catalytic activity for diesel soot combustion, in loose contact conditions, is studied by means of TPO (temperature programmed oxidation) while NOx removal is investigated through NOx Storage-Reduction cycles (SRC), performed both in the presence and in the absence of soot. Both the Ag- and Ru-based formulations result active in the soot oxidation, more than the traditional Pt-containing DPNR catalyst. Also, the Ru-based sample shows remarkable performances in the DeNOx-DeSoot activity, although its activity in the reduction step of the stored NOx still needs further improvements.

Sintering Behaviour of Waste Olivine and Olivine/Alumina Blends

The sintering behaviour of several green compacts made with olivine or olivine/alumina powder blends has been examined. To this goal, powders were attrition milled, uniaxially pressed into specimens and air sintered at temperatures ranging from 1100 to 1300 °C. The resulting samples were characterized by water absorption, shrinkage, phase composition and density. Compositions containing 5%, 10% and 20% Al2O3 have a sintering behaviour similar to that of olivine alone, reaching low residual porosity when fired at 1300 °C. Conversely, the composition containing 40% Al2O3 displays an almost flat shrinkage profile and maintains high residual porosity in the examined temperature range.