Effects of Sorbents on the Partitioning and Speciation of Cu During Municipal Solid Waste Incineration☆

Oxides of silicon, aluminium and calcium are normally dominant minerals during municipal solid waste (MSW) combustion. In flue gas, SiO2, Al2O3 and CaO all act as sorbents capturing heavy metals (and s...     

Orimulsion fly ash in clay bricks—part 3: chemical stability of ash-bearing products

The chemical stability of clay bricks containing Orimulsion ash (up to 6 wt.%) was assessed with a laboratory simulation of the brickmaking process. The development of efflorescence, the amount of water soluble salts and their elution, the fraction of S, V, Ni, Mg, Ca, Na and K immobilized in the ceramic matrix, and the amount of volatile elements potentially released during firing were determined by ICP–OES, XRPD, TGA, SEM and EMP analyses. The stabilizing mechanism acts through the capture of metals into the crystalline structure of silicates formed at high temperature. However, the firing conditions adopted in the brick industry (about 900 °C) do not permit the complete reaction of sulphates; there is considerable efflorescence and soluble salts are formed, even with 1.5% of ash added, producing a risk of sulphate attack to the mortars. On the other hand, the decompostion of sulphates during firing could bring about remarkable SO_x emissions, particularly in carbonate-free bodies. In conclusion, the disposal of Orimulsion ash in clay bricks must be practiced with caution and an amount of ash below 1 wt.% weight is strongly recommended.     

Electrochemical synthesis of glyoxylic acid from glyoxal—III. influence of the adatoms on the yields of the reaction on platinum and vitreous carbon electrodes

The addition in a cell of small amounts of adatoms like Ag, Sn, Bi, Tl or Au increases the yield of glyoxylic acid prepared by electrochemical oxidation of glyoxal on a platinum anode. The chemical yields reach values of 67 and 69% at 20 and 50°C respectively when they were of 58 and 62% in the same experimental conditions on bright platinum. The glyoxal is almost completely eliminated.     

The influence of an electric field on adsorption of organic substances at electrodes—I. Generalization of the Frumkin's theory from the modified model of two parallel condensers

The modified model of two parallel condensers [D. Schuhmann, J. electroanal. Chem.201, 247 (1986)] based on a new demonstration of the Helmholtz formula provides a consistent electrostatic interpretation of the influence of an electric field on adsorption of organic substances. Following the procedure proposed by the soviet school, deviations, with respect to congruence, due to variations in coverage of the inner properties of the surface layers, are treated for some molecular examples in the frame of the modified model.     

Thermogelling polysaccharides for aqueous gelcasting—part II: influence of gelling additives on rheological properties and gelcasting of alumina

In the present work the influence of the addition of aqueous solutions of agar, agarose and carrageenan on the rheological properties of alumina slurries is studied. Precursor binder solutions were prepared to concentrations between 1.5 and 4 wt.% in water by heating at 92 °C. Alumina suspensions were prepared at a solid loading of 50 vol.% and heated to 60 °C. At this temperature different amounts of the starting precursor solutions of each gelling binder were added so that the final concentrations of binder were 0.25, 0.5 and 0.75 wt.% referred to dry solids. For concentrations of the precursor solution ⩽2 wt.%, the viscosity of the slurry tends to decrease when the total amount of gel increases, while for concentrations of the precursor solution ⩾3 wt.% viscosity increases with the amount of gel. This defines a yield concentration of precursor solution where the suspension properties change. Gelcasting performance is a function of slurry viscosity, gelling behaviour and time, and body deformation during drying. In general, carrageenan leads to higher shape distortion in the body. Better shape retention is achieved with precursor solutions with ⩾3 wt.% additive and total content of gel of ⩾0.5 wt.%.     

Orimulsion fly ash in clay bricks—part 1: composition and thermal behaviour of ash

A bitumen-in-water emulsion (Orimulsion) is currently used as a fuel in several thermal power plants worldwide. Orimulsion combustion produces a fly ash rich in S, Mg, V and Ni, which is processed to recover metals. In order to assess the feasibility of a recycling in clay brick production, a characterization of the physico-chemical and thermal properties of ash was performed by ICP–OES, XRPD, SEM, BET and TGA–DTA techniques. Orimulsion ash resulted in fine-grained (aggregates of submicronic particles), highly hygroscopic, constituted mainly of magnesium sulphate, vanadyl sulphates and magnesium and nickel oxides, and thermally unstable in the usual brick firing conditions. These features can affect the brickmaking process, particularly the plasticity of the clay body and its drying and firing behaviour; furthermore, a mobilization of sulphates could occur, promoting the formation of efflorescence and/or the SO_x release during firing.     

Orimulsion fly ash in clay bricks—part 2: technological behaviour of clay/ash mixtures

In order to appraise the technological feasibility of the Orimulsion ash recycling in clay bricks, a laboratory simulation of the brickmaking process was carried out with various clay/ash mixtures up to 6% waste. Two different clays were selected and mixes were characterized by XRF, XRPD, TGA–DTA, TDA and PSD analyses. Plasticity, extrusion and drying behaviour, and mechanical strength, were determined on unfired mixtures, while shrinkage, water absorption, bulk density, modulus of rupture, pore size distribution, microstructure and phase composition were measured on fired bricks. Orimulsion ash caused some detrimental changes of technological properties of both unfired and fired products, concerning particularly plasticity, drying rate and drying sensitivity, porosity and colour. These effects were slightly different on the two raw materials, the carbonate-rich clay being less sensitive to the presence of ash with respect to the carbonate-free clay. In all events, drawbacks appeared to be tolerable, in technological terms, for low waste additions, approximately 1–2% ash.     

Preferred partitioning: the influence of coalescents on the build-up of mechanical properties in acrylic core–shell particles (I)

The partitioning of three coalescents of different polarity in different phases of multiphase acrylic particles was studied to provide a rationale for obtaining the desired performance of binders for wood coatings in terms of the ideal balance between hardness development, blocking resistance, and blushing resistance. Minimum film formation temperature- and aqueous differential scanning calorimetry-measurements on the hard phase polymer by itself showed the different extents to which both hydroplasticization and plasticization by the coalescent occur. Dynamic mechanical thermal analysis was subsequently used to visualize wet-T _g effects of three different coalescents in the hard and soft polymer phase of these multiphase acrylic particles. The results have important consequences for the formulation of such binders in applications for exterior wood coatings and coatings in general.     

The extrusion mechanics of pastes—the influence of paste formulation on extrusion parameters

Paste rheology has been studied with a ram extruder in which there is convergent flow followed by extrusion through a tube of constant diameter, the die-land. Pastes have been made from particles of known size distribution and liquids of known rheology. The flow has been described successfully by regarding the convergent flow to be governed by a yield mechanism and the plug flow in the die-land by wall resistance. This gives rise to two important extrusion parameters, namely the yield value and wall stress.The seven different α-alumina pastes which have been studied all comply with this pattern. Both the yield value and wall stress are dependent on velocity. In each instance, the velocity effect is proportional to the effective viscosity of the liquid phase. Particle size distribution and liquid phase content each have a substantial effect on the extrusion parameters.     

Hydrogenation of acetylene–ethylene mixtures on Pd catalysts: computational study on the surface mechanism and on the influence of the carbonaceous deposits

A time-dependent Monte Carlo algorithm was employed to study the effects of carbonaceous surface species on the hydrogenation mechanism of acetylene–ethylene mixtures on a Pd catalyst. Simulations of tail-end and front-end mixture hydrogenation were performed employing the same set of predetermined event probabilities. The involvement of the steric hindrance of the surface species was essential to simulate the experimental data. The catalyst activity and selectivity were promoted or inhibited by different concentrations of surface polymeric species formed along with the hydrocarbon hydrogenation. Tools to get a new interpretation of the catalytic reaction mechanism and an innovative basis to perform catalyst design were suggested by the approach illustrated.     

Thermal evaluation of the use of porous ceramic plates on ventilated façades—part II: Thermal behavior

The effects of porous ceramic plates on the thermal behavior of ventilated façades were evaluated, and the results are presented herein. Thermal behavior in a ventilated façade of specimens containing 40 wt% of lime mud and a firing temperature of 1100°C was evaluated and compared with a commercial porcelain ceramic tile, which was the reference material. An experimental apparatus was designed to evaluate the thermal performance of the studied ventilated façades. The results revealed that the ventilated façade composed of the studied porous ceramic tiles produced a greater reduction in temperature between the external environmental and the interior of a box representing a building (ΔT5) of 65.7°C, compared with the façade composed of the commercial porcelain ceramic tiles (ΔT5 = 56.0°C) and even the traditional façade (ΔT5 = 49.1°C). Thus, porous ceramic tiles based on byproducts are promising candidates for ventilated façade systems.     

Studies on the promotion of nickel—alumina coprecipitated catalysts: I. Titanium oxide

A series of TiO₂-promoted nickel—alumina catalysts has been prepared and characterized. The promoter was added in various proportions to a calcined coprecipitated nickel—alumina material by adsorption of the acetylacetonate complex of titanium, followed by further calcination and reduction. The structure of the resultant materials was similar to that of the unpromoted coprecipitated nickel—alumina. The chemisorption properties of the catalyst and its behaviour in the CO/H₂ reaction were characteristic of a strong metal-support interaction (SMSI) reported in the literature for Ni/TiO₂. The strong adsorption of both carbon monoxide and hydrogen were suppressed while the activity for carbon monoxide hydrogenation was increased, the activation energy being lowered. The higher activity, however, was relatively unstable under reaction conditions.     

The influence of boron compounds’ particles (TiB2, BNcub) on the thermal stability and the mechanical strength of synthesized carbonado after heating

Carbonado-type synthesized polycrystalline diamond (CSPD) is produced from graphite at high pressure and temperature in the presence of metallic melt, which favours decrease of P, T-parameters of the synthesis process. Solidified metal/alloy becomes part of CSPD, as metal phase inclusions, which are located along the diamond grain boundaries. In the present work, the thermal stability (resistance to oxidation of the CSPD) and the mechanical strength of the CSPD after heating were investigated. Experimental results show a trend to increase the thermal stability and the conservation in mechanical strength of the CSPD up to higher temperature through the addition of refractory particles (TiB₂, BN^cub) to an initial Ni+15% Mo alloy. The improvement of CSPD physico-chemical properties, dependent on the content of TiB₂ and BN^cub dispersed in an initial alloy, is explained by the transformation of TiB₂ as a result of a chemical interaction to amorphous boron oxide B₂O₃ (which stands duty as a protective layer from oxidation and graphitization of the CSPD), and by the decrease of the residual stresses level after the heating of the CSPD, since BN^cub has a thermal expansion coefficient close to that of diamond.     

β-TCP coatings on zirconia bioceramics: The importance of heating temperature on the bond strength and the substrate/coating interface

β-tricalcium phosphate (β-TCP) coatings were synthesized on tetragonal zirconia (Y-TZP) discs by heating the apatite coating between 800?°C and 1200?°C. The study results suggest that heating temperature has a strong influence on the coating bond strength and microstructure of the substrate/coating interface. The β-TCP coatings fired at 800?°C and 900?°C exhibited excellent tensile bond strength (～50?MPa) while heating at 1100?°C and 1200?°C led to decreased bond strength (～30?MPa) as the result of substantial structural and microstructural changes: diffusion of Y³⁺ from the zirconia substrate in the coating resulting in partial crystal transformation (t-m) of zirconia, formation of surface uplifts and nanoporosity in zirconia, as well as generation of large residual thermal stresses leading to microcracking of the β-TCP coatings. However, these structural changes did not have any measurable effect on the flexural strength of the bulk zirconia substrates.     

Electrosorption from multicomponent liquid systems with particular regard to ternary solutions—I. The influence of ionic co-adsorption and the effects of reorientation of adsorbate

A theory is presented to describe the electrosorption from a three component system Mathematical formalism can be easily extended to describe electrosorption from a multicomponent system. The theory allows us also to describe the problem of reorientation of adsorbate inside of the double layer. The influence of reorientation equilibrium constant onto electrosorption isotherm has been demonstrated. Besides, sampled investigations of the effects of molecular size and particle-particle interactions have been performed. The possibilities of a phase separation and a phase transition inside of the double layer have been tentatively indicated. The role of the electrochemical free energy of mixing of surface solution has been briefly discussed.     

Adsorption of thiourea at the polycrystalline silver electrode from aqueous KF solutions—I

Differential capacity of polycrystalline silver electrode in aqueous KF solutions containing thiourea (TU) of concentrations from 0.001 to 0.25 mol dm⁻³ has been measured by the previously described potentiostatic method [M. Brzowstowska-Smolska et al., J. electroanal. Chem.89, 389 (1978)]. The TU adsorption is discussed on the basis of differential capacity results and the potential shift caused by TU concentration changes. Furthermore, the surface pressure has been obtained by integration of the ΔE_σM vs σ_M curves for a number of TU concentrations.     

Heating rate effects on the crystallization behavior of isotactic polypropylene from mesophase – A de-polarized light transmission study

It was ever reported in a communication of this journal that the large crystal grains having “bamboo leaf-like (BL)” morphology were produced by a rapid heating of isotactic polypropylene (iPP) from the mesophase. In order to optimize the condition to generate the BL crystals, heating rate effects on the crystallization behavior from the mesophase of iPP have been studied by utilizing a de-polarized light transmission (DPLT) method. The DPLT sensitively detected not only the cold crystallization from the mesophase around 100–120 °C but also the crystal grain growth in a narrow temperature region just below the melting temperature. With increasing the heating rate, both the temperature regions of the cold crystallization and the crystal grain growth shifted toward the higher temperatures. When the heating rate is slow (<20 °C/min), the crystal grain growth was not conspicuous. With increasing the heating rate, the rate of the crystal grain growth increased and showed a maximum when the heating rate is approximately 60–80 °C/min. However, excessively fast heating (>100 °C/min) also suppressed the crystal grain growth.     

The influence of preparation method on the physicochemical properties of titania–silica aerogels: Part two

Titania–silica aerogels with different titania content were prepared. Four preparation methods differing mainly in approach to precursors hydrolysis were applied, while only three of them allowed total hydrolysis of silica precursor before titania precursor was added. The preparation of mixed products of titania and silica hydrolysis precursors containing gels was followed by high temperature supercritical drying (HTSCD) and thermal treatment at 500 °C. Obtained mixed oxides in form of aerogels were characterized by BET surface areas up to 1000 m²/g, mesopore volumes up to 1.6 cm³/g and bulk densities as low as 0.04 g/cm³. Even 18 h lasting aging did not allow to produce narrow diameter range mesoporous materials, their broad pore diameter distributions resulted in average pore sizes varying from 10 to nearly 30 nm. XRD measurements proved the presence of anatase crystalline form of titania, while silica was present in amorphous form. SEM studies indicated presence of isolated titania particles on titania–silica surface while joint hydrolysis method was applied. Titania–silica aerogels obtained by the simultaneous hydrolysis of precursors and the impregnation method showed high photocatalytic activity in degradation of salicylic acid in water. Activities of these mesoporous photocatalysts were higher than commercial P25 Degussa TiO₂. Comparison of activity of pure TiO₂ (P25 Degussa) and aerogels indicates higher utilization of titania present in mesoporous mixed oxides.     

Gravity flow of granular materials round obstacles—I: Investigation of the effects of inserts on flow patterns inside a silo

Triangular and square inserts were placed at different heights within a tall observation bunker of rectangular cross-section. The flow patterns produced by the materials were photographed through the float glass front wall of the bunker. The photographs taken at different exposure times were used to determine particle streamlines, vertical velocity contours and the boundaries of the so-called stagnant zones formed inside the bunkers.Velocity contours within the converging flow zones were compared with the predictions based on the kinematic flow model proposed earlier by the authors. The results presented seem to indicate a dependence of the observed flow fields on the magnitude of particle velocities within the bunker.