Chemical properties of rare earth elements in typical medical waste incinerator ashes in China

Medical waste (MW) ashes from different types of MW incinerators were examined to detect the characteristics and environmental impact of rare earth elements (REEs). The results showed that total REE contents in the ash samples ranged from 10.2 to 78.9mg/kg. REEs in bottom ash were apparently higher than those in fly ash. Average REE contents in the ashes followed the sequence of Ce>La>Nd>Y>Gd>Pr>Sm>Dy>Er>Yb>Ho>Eu>Tb>Lu>Tm. Some of the elements, such as Sm, Dy, Ho, Er, Yb in the ash samples were in normal or nearly normal distribution, but Y, La, Ce, Pr, Nd, Eu, Gd, Tb, Tm, Lu were not normally distributed, indicating some of the ash samples were enriched with these elements. Crust-normalized REE patterns indicated that two types of the MW ashes were obviously enriched with Gd and La. Sequential extraction results showed that REEs in the ash mainly presented as residual fraction, while exchangeable and carbonate fractions were relatively low. DTPA- and EDTA-extraction tests indicated that REEs in the MW ashes were generally in low bioavailability.     

Electron microscope investigations of activated chalcopyrite particles via the FLSmidth<Superscript>®</Superscript> ROL process

Because of its unique semiconductor properties, the world’s most abundant copper mineral, chalcopyrite (CuFeS₂), is refractory with respect to atmospheric leaching using traditional acidic ferric sulfate lixiviants. FLSmidth^® has developed a novel approach manipulating lattice properties of semi-conducting minerals with the benefit of increasing chemical reactivity and dissolution kinetics. In the FLSmidth^® Rapid Oxidative Leach (ROL) process, leach kinetics are still further enhanced by combining chemical and mechanical processes with the assistance of a Stirred Media Reactor. Due to the reduction in surface passivation problems associated with atmospheric leaching, this process is typically able to achieve copper recoveries exceeding 95% in 6 h. An important factor contributing to this extraordinary process performance is a mineral preconditioning step (the focus of this study), which uses between 0.1 and 5 mol percent of copper (II) to dope the lattice and thereby “activate” chalcopyrite. Since lattice restructuring can have such a dramatic influence on semiconductor reactivity, the associated physico-chemical phenomena are worth studying. In this regard, we investigate the relationship between chemical activation and deformation of the chalcopyrite crystal lattice through the use of electron microscopy. Although the activation process took only an hour and the extent of conversion was on the order of a few mol%, the lattice was found to be strained throughout the particle. This paper draws some insights into the impact of applying chemical activation as a pretreatment for mechanochemical processes.     

Leaching of Radioactive Waste Surrogates from a Glassy Matrix and Migration of the Leaching Products in Gneisses

Changes in the glassy matrix containing high-level waste surrogates after 24-h heating in an autoclave at 300°С with steam at 66% relative humidity were studied. Experiments were performed with an Na–Al–P glass sample containing Cs, Sr, Ce, Nd, and U. The effect of crystallization on the leaching of the elements from the glassy matrix and the form in which the waste surrogates are released into water were determined. The transport of the leaching products in a gneiss sample taken from the core of a borehole of the Yeniseiskii site of the Nizhnekansky massif was studied. REE and U occur in the solution after leaching mainly in the colloidal form. Colloidal particles of elements exhibit high mobility in migration in the rock.     

Mechanochemical effects on hydrogen absorption in Mg<Subscript>2</Subscript>Ni alloys under mechanical processing conditions

The present investigation focuses on the kinetics of hydrogen absorption in Mg₂Ni powders subjected to thermal or mechanochemical activation. The process was initially carried out under isobaric-isothermal conditions in a mechanochemical reactor at rest. Once the static hydrogen absorption process approached completion, the system was subjected to mechanical activation at constant hydrogen pressure. The mechanical treatment of powders induced further hydrogen absorption at rates depending on the processing intensity. The observed mechanochemical effect is related to the generation of reactive surfaces when mechanical loads apply on powders. The reactive surface area involved in the mechanochemical hydrogen absorption and the duration of the absorption process are roughly estimated.     

Ion chromatographic separation of rare-Earth elements using a nitrilotriacetate-type chelating resin as the stationary phase

The chromatographic retention behavior of rare-earth elements (REEs) on a chelating resin having a nitrilotriacetate group (NTA gel) was evaluated. The capacity factors for a series of REEs on the NTA gel were in fairly good agreement (R(2) = 0.978) with the stability constants of the corresponding NTA complexes. The NTA gel was applied to the column stationary phase for the ion chromatographic separation of REE. A favorable separation of a series of REEs was achieved within 15 min using a gradient elution of nitric acid. The separated REE ions were detected using the postcolumn derivatization method with chlorophosphonazo III as a colorization reagent. The present chromatographic system, interfaced with inductively coupled plasma mass spectrometry, was applied for the simultaneous determination of 14 REEs.     

Brannerite,UTi<Subscript>2</Subscript>O<Subscript>6</Subscript>: Crystal chemistry,synthesis, properties,and use for actinide waste immobilization

The host materials suggested for immobilization of actinide waste of military or civil origin often contain the secondary (U,Pu)Ti2O6 phase of brannerite structure. For example, the materials for incorporation of excess plutonium, mainly consisting of pyrochlore, contain up to 30% brannerite. This is a usual phase in titanate host materials for isolating spent nuclear fuel (SNF) and products of its reprocessing, including waste from production of ^99mТс for medical purposes and other kinds of waste with high U and Pu content. Despite simple ideal stoichiometry, brannerite can contain large amounts of rare earths. This feature is due to the presence of uranium not only in the 4+ oxidation state, but also in the 5+ and 6+ states, which favors the exchange of rare earth elements (REE), e.g., in accordance with the scheme 2U⁴⁺ ? U⁵⁺ + REE³⁺. The REE amount in brannerite reaches 0.5–0.7 atom per formula unit. Therefore, brannerite is of interest as a host material for the rare earth–actinide fraction of high-level waste (HLW). To evaluate the prospects for such use of brannerite, data on the radiation resistance of brannerite and its behavior in aqueous solutions are analyzed. In these properties, brannerite is inferior to pyrochlore and zirconolite. The rate of actinide leaching from brannerite is higher by an order of magnitude than from these phases, but lower by 3–4 orders of magnitude than from glass host materials. Natural brannerite is stable in media with weakly alkaline and reducing waters. Therefore, brannerite seems suitable for immobilization of rare earth–actinide waste. This host material can be synthesized by sintering or cold crucible induction melting followed by crystallization.     

Influence of mechanochemical pretreatment on leaching of silver in cyanide and non-cyanide medium

The leaching of silver from a mechanochemically pretreated silver-bearing complex sulphide concentrate of Peruvian origin (Casapalca) has been studied. The results with as-received concentrate have shown very low extraction of silver (up to 5.7%) in all cases of leaching. The mechanochemical pretreatment has caused 85% amorphization of tetrahedrite as silver-bearing mineral and an increase in the specific surface area of the concentrate from 0.3 m² g^?1 to a maximum value of 15.7 m² g^?1. This fact manifested itself in the subsequent process of silver extraction. By application of thiosulphate and thiourea leaching 99% recovery of Ag was reached already after 3-5 min of leaching.     

Mechanochemical synthesis of salicylic acid–formaldehyde chelating co-polymer

A mechanochemical synthesis of a co-polymer of salicylic acid and formaldehyde is reported. New IR absorbance bands found after the performance of the mechanochemical synthesis are attributed to the formation of a salicylic acid–formaldehyde co-polymer. Dislocation deformation along slide planes in the salicylic acid structure occurs in the course of the mechanochemical activation causing no essential changes in the more stable hydrogen bonds net. The weaker inter-layer bonds in the acid structures are broken during activation, but are restored soon after the completion of the process. Polycondensation reaction occurs as a result of the mechanochemical process of the salicylic acid–formaldehyde mixture. The obtained co-polymer is a chelating agent capable of binding Pb²⁺, Cu²⁺, and Fe³⁺ ions. A comparison was made of the ion exchange capacity and metal ion binding capacity of the mechanochemically produced co-polymer with the co-polymer synthesized using the conventional “wet” method.     

Radiological characterization and treatment of contaminated phosphogypsum waste

Preparation of uncontaminated phosphogypsum (PG) produced by wet-process phosphoric acid plant for its safe use in industry was investigated. PG is mainly composed of calcium sulfate and contains enhanced natural radioactivity. The activity of ²³⁸U, ²²⁶Ra, ²¹⁰Pb, ²³²Th, and ⁴⁰K in PG samples was measured by γ-ray spectrometry. The values of radiation hazard indices, calculated to evaluate the environmental impacts of PG samples, were higher than the permissible safe levels. Therefore, the PG should be treated before use in agriculture and/or building materials. This involves the leaching of PG with organic extractant such as TOPO in kerosene. Reduction in the radionuclide concentration was accompanied by a decrease in the concentration of total rare earth elements (ΣREE). Extraction treatment of PG waste under optimum conditions allows preparation of a decontaminated product that can be safely used in many branches of industry.     

Characterisation and classification of solid wastes coming from reductive acid leaching of low-grade manganiferous ore

The present work was focused on the acid leaching process for manganese extraction in reducing environment to low-grade manganiferous ore that comes from Central Italy. The aim of this study was to establish optimum leaching operating conditions to reduce treatment costs of waste or, even better, to allow a waste valorisation as raw materials for other applications. Consequently, the main focus of the work was the characterization and classification of the solid wastes coming from the process carried out at different operating conditions; at the same moment the effect of process parameters on Mn extraction was also analysed. The effect of particles size on the manganese extraction in reductive acid leaching process was investigated, by using lactose as reducing agent. Particle size did not show a large influence on the Mn extraction yields in the investigated process conditions. This aspect suggests the use of the leaching waste for civil and/or environmental application: use of leaching solid wastes like filling material is to be applied, for example, for environmental restoration. The classification of the solid wastes, according to the Italian Laws about Release Test (RT), has demonstrated that the solid waste produced by leaching can be classifiable as "hazardous special waste". An improvement of solid washing let to reduce the SO(4)(2-) and an appropriate treatment is necessary to reduce the dangerousness of these solids. Possible application of ore and waste as raw materials in the ceramic industry was demonstrated not to be feasible.     

Use of grape stalk, a waste of the viticulture industry, to obtain activated carbon

Grape stalk is an organic waste produced in great amounts in the industrialization processes of grape. This work presents the results of studies carried out to use this waste as raw material to prepare activated carbon through the physical and chemical route. The physicochemical characterization of this material suggests the presence of unusually high levels of ashes. Metal content was determined and high levels of potassium, sodium, iron, calcium and magnesium in carbonized and raw grape stalk were exhibited. This characteristic made difficult physical activation at high temperatures. A leaching step was included before the activation with steam, and adsorbents with surface areas between 700 and 900 m²/g were obtained. Physical activation was also performed at lower temperatures using carbonized grape stalk without leaching, leading to the development of some grade of porosity, with an area of 412 m²/g. These results would indicate the catalytic effect of the minerals present in this raw material. Chemical activation using phosphoric acid as activating agent seemed to be a very efficient method as final products with BET areas between 1000 and 1500 m²/g were obtained.     

The mechanochemical processing of aerospace metals

The status of mechanochemical processing of aerospace metals (aluminum and titanium) is reviewed. It is demonstrated that the activation of chemical reactions by mechanical energy can lead to many interesting applications including production of advanced materials with novel constitutional and microstructural effects leading to enhanced mechanical properties.     

Photoluminescence green in microspheres of CaWO4:Tb processed in conventional hydrothermal

Green-phosphor spherical microparticles (2–4 μm in diameter) of CaWO₄:Tb³⁺ (CWO:Tb) exhibiting excellent emission at 545 nm have been synthesized by a conventional hydrothermal process directly without further sintering treatment. X-ray diffraction (XRD), scanning electron microscope (SEM), photoluminescence excitation and emission spectra and decay curve were used to characterize the CWO:Tb phosphors. Because 12 at.% CWO:Tb phosphor shows broad and strong absorption in UV region, exhibits intensive green emission under 254 nm excitation in comparison with the commercial green fluorescent lamp phosphor (LaPO₄:Ce,Tb), it is considered to be a new promising phosphor for fluorescent lamps application.     

A novel red phosphor NaLa4(SiO4)3F: Eu

A novel red phosphor NaLa₄(SiO₄)₃F: Eu³⁺ was synthesized by the conventional solid-state reaction at 950 °C for the first time. The luminescence properties of NaLa₄(SiO₄)₃F: Eu³⁺ were investigated, and the critical concentration of the activator concentration (Eu³⁺) was found to be 0.1 mol per formula unit. The phosphor presented red luminescence under the ultraviolet excitation of 254 or 395 nm, attributed to the transitions from ⁵D₀ excited states to ⁷F_J ( J = 0-4) ground states of Eu³⁺ ions. The results indicated that this newly-developed phosphor could find applications in tricolor fluorescent lamp, phosphor-liquid crystal displays and white lighting devices utilizing GaN-based excitation in the near UV.     

Thermal behaviour of ESP ash from municipal solid waste incinerators

Stricter environmental regulations demand safer treatment and disposal of incinerator fly ashes. So far no sound technology or a process is available for a sustainable and ecological treatment of the waste incineration ashes, and only partial treatment is practised for temporary and short-term solutions. New processes and technology need to be developed for comprehensive utilization and detoxification of the municipal solid waste (MSW) incinerator residues. To explore the efficiency of thermal stabilisation and controlled vitrification, the thermal behaviour of electrostatic precipitator (ESP) ash was investigated under controlled conditions. The reaction stages are identified with the initial moisture removal, volatilisation, melting and slag formation. At the temperature higher than 1100 °C, the ESP ashes have a quicker weight loss, and the total weight loss reaches up to 52%, higher than the boiler ash. At 1400 °C a salt layer and a homogeneous glassy slag were formed. The effect of thermal treatment on the leaching characteristics of various elements in the ESP ash was evaluated with the availability-leaching test. The leaching values of the vitrified slag are significantly lowered than that of the original ash.     

Mechanochemical modification and synthesis of drugs

Various aspects of the application of mechanochemistry and mechanical activation in the study of pharmaceutical materials are presented including the use of mechanical activation for modification of the physical and chemical properties of drugs and solid state synthesis of the drugs by mechanochemical methods. It is necessary to take the mechanochemical factors into account during grinding and tabletting the drugs.     

Controllable white light emission from Dy<Superscript>3+</Superscript>–Eu<Superscript>3+</Superscript> co-doped KCaBO<Subscript>3</Subscript> phosphor

Potassium calcium borate, KCaBO₃:Eu³⁺ phosphors with various Dy³⁺ concentrations (0–3 wt%) were synthesized by solid state reaction and studied for the first time. Under various UV–violet excitations, the obtained single monoclinic phased Dy³⁺–Eu³⁺ co-doped KCaBO₃ polycrystalline phosphors emit a combination of yellow–blue and red–orange wavelength giving intense white light, which can easily be controlled by varying the concentration of Dy³⁺. The increase in white light emission with the increase of Dy³⁺ concentration indicates the efficient energy inter-ion transfer from Dy³⁺ to Eu³⁺ ions. Furthermore, the observed emission lifetimes and the intense white light emission are suggestive exploration for the present phosphor for potential optoelectronic applications such as white light-emitting phosphor for blue LEDs chips.     

A Contribution to the Mechanism of Formation of Humic Acids in Coal

This paper presents a study of the influence of mechanochemical activation of coal on the process of formation and degradation of humic acids. The increasing period of mechanical activation of coal causes an increase in hydrophility, electrophoretic mobility, and of electrokinetic potential of surface layers as a result of acidic carboxyl and phenolic OH groups. The effective activation requires a short period of grinding. The increased time of activation causes the secondary processes of grain agglomeration and degradation of humic acids.     

Manganese waste mud immobilization in cement – natural zeolite – lime blend: Process optimization using artificial neural networks and multi‐criteria functions

In this study, stabilization/solidification process of manganese contaminated mud using portland cement was optimized. For that purpose, immobilization process was modeled applying artificial neural networks with radial basis activation function. The optimal model presented satisfactory prediction characteristics (R² value for manganese leaching was 0.9615 while and for concrete flexural strength 0.8748). Therefore, it was used in combination with seven in‐house developed multi‐criteria optimization functions, separately, in order to optimize concrete formulation. The used approach proved itself as efficient and cost effective alternative in ecological material formulation process. The best properties (i. e. high flexural strength and lowest manganese leaching) manifested stabilization/solidification matrix consisted of 350 g of portland cement, 20 g of lime, 70 g of natural zeolite, 10 g of manganese waste mud and 180 g of water.     

Use of colloidal silica to obtain a new inert from municipal solid waste incinerator (MSWI) fly ash: first results about reuse

The MSWI (Municipal Solid Waste Incinerator) fly ash may represent a potential health and environmental hazard for its high heavy metal content. Fly ash is commonly disposed in specific landfills to prevent the leaching of pollutants into underground aquifers. Several technologies (for example, thermal treatment, physical/chemical separation, and stabilization/solidification techniques) have been developed for treatment of fly ash to obtain second-hand inert materials. Moreover, reuse of these materials is strictly dependent on their physical and mechanical features. Possible applications of these materials are clinkering, road pave, and construction works where, specific performances are required. Recently, at the University of Brescia (Italy) a new process has been developed to inertize fly ash, by means of colloidal silica. The new inertization process involves low temperature reactions and produces a final material named COSMOS (Colloidal Silica Medium to Obtain Safe inert) that can be employed as a filler substituting natural materials such as carbon black, sand, etc. The project is supported by LIFE program of the European Community (LIFE + 2008 project ENV/IT/000434). In this study we present results about the reuse of COSMOS in different high quality controlled plaster materials. An appropriate waste management, based on the principles of sustainable development, is based on the principle that waste cannot be considered as something to eliminate but rather a potential resource.