Determination of mercury distribution inside spent compact fluorescent lamps by atomic absorption spectrometry

In this study, spent compact fluorescent lamps were characterized to determine the distribution of mercury. The procedure used in this research allowed mercury to be extracted in the vapor phase, from the phosphor powder, and the glass matrix. Mercury concentration in the three phases was determined by the method known as cold vapor atomic absorption spectrometry. Median values obtained in the study showed that a compact fluorescent lamp contained 24.52 ± 0.4 ppb of mercury in the vapor phase, 204.16 ± 8.9 ppb of mercury in the phosphor powder, and 18.74 ± 0.5 ppb of mercury in the glass matrix. There are differences in mercury concentration between the lamps since the year of manufacture or the hours of operation affect both mercury content and its distribution. The 85.76% of the mercury introduced into a compact fluorescent lamp becomes a component of the phosphor powder, while more than 13.66% is diffused through the glass matrix. By washing and eliminating all phosphor powder attached to the glass surface it is possible to classified the glass as a non-hazardous waste

Removal of mercury bonded in residual glass from spent fluorescent lamps

The current technologies available for recycling fluorescent lamps do not completely remove the phosphor powder attached to the surface of the glass. Consequently, the glass contains the mercury diffused through the glass matrix and the mercury deposited in the phosphor powder that has not been removed during treatment at the recycling plant. A low-cost process, with just one stage, which can be used to remove the layer of phosphor powder attached to the surface of the glass and its mercury was studied. Several stirring tests were performed with different extraction mixtures, different liquid–solid ratios, and different agitation times. The value of the initial mercury concentration of the residual glass was 2.37 ± 0.50 μg/g. The maximum extraction percentage was 68.38%, obtained by stirring for 24 h with a liquid–solid ratio of 10 and using an extraction solution with 5% of an acid mixture prepared with HCl and HNO3 at a ratio of 3:1 by volume. On an industrial scale the contact time could be reduced to 8 h without significantly lowering the percentage of mercury extracted. In fact, 64% of the mercury was extracted

A visual validation of the combined effect of pH and dilution on the porosity of carbon xerogels

The hypothesis about the formation of the porous structure of carbon xerogels when the pH and the dilution ratio of the precursor solution are simultaneously modified has been validated by means of scanning electron microscope analysis. The morphology of the carbon xerogels showed that the size and number of the clusters produced during the sol–gel reaction is not only influenced by the pH but also by the dilution ratio. As with a decrease in the pH value, an increase in the dilution ratio caused the formation of a small number of large clusters, leading to materials with large pores. However, depending on the values selected the effect of the pH and dilution ratio was enhanced or diminished by the effect of the other. Hence, an appropriate adjustment of these two variables allowed microporous, micro-mesoporous and micro-macroporous materials to be obtained with pore volumes that could not be achieved by modifying the pH or the dilution ratio separately.Financial support from the Ministerio de Economía y Competitividad of Spain MINECO (under Projects MAT2011-23733 and IPT-2012-0689-420000, (BES-2012-052676)) is greatly acknowledged. NRR is also grateful to MINECO for her predoctoral research grant.Peer reviewe

Advances in tailoring the porosity of tannin-based carbon xerogels

Usually, carbon xerogels are obtained from resorcinol–formaldehyde organic gels. However, more cost-effective and eco-friendly carbon xerogels can be synthesised by using tannins instead of resorcinol, provided that a suitable surfactant is added to prevent the collapse of the structure. The use of tannin, a natural phenolic compound derived from wood, allows obtaining carbon xerogels with controlled porosity, as the porous properties of these materials can be tailored by an appropriate choice of the synthesis conditions. In this work, tannin–formaldehyde xerogels containing different amounts of surfactant and formaldehyde were synthesised in order to evaluate their effect on the porous structure and chemical composition. It was found that porosity and density depend greatly on the amount of surfactant. The lowest density and highest porosity values −0.34 g/cm3 and 78%, respectively-were obtained by adding 10 wt.% of surfactant. It was also found that S-doped carbon xerogels can be easily synthesized due to the strong affinity between the carbon in the structure and the sulphur from the surfactant. Furthermore, statistical analysis showed that there is interdependence between the effect of formaldehyde and the surfactant, especially in the case of volume and pore size. Hence, the choice of the appropriate surfactant-formaldehyde concentration is essential for controlling the formation of the porous polymeric structure.Financial support from the Ministerio de Economía y Competitividad of Spain MINECO (under Projects MAT2011-23733, IPT-2012-0689-420000 and CTQ2013-49433-EXP) is greatly acknowledged. NRR is also grateful to MINECO for her predoctoral research grant. The French authors also gratefully acknowledge the financial support of the CPER 2007–2013 “Structuration du Pô le de Compé titivité Fibres Grand'Est” (Competitiveness Fibre Cluster), through local (Conseil Général des Vosges), regional (Région Lorraine), national (DRRT and FNADT) and European (FEDER) funds.Peer reviewe

Towards a feasible and scalable production of bio-xerogels

© 2015 Elsevier Inc. Hypothesis: The synthesis process of carbon xerogels is limited, mainly due to two drawbacks that prevent their introduction onto the market: (i) the long time required for producing the material and (ii) the reagents used for the synthesis, which are costly and harmful to the environment. Microwave radiation is expected to produce a reduction in time of more than 90%, while the use of tannin instead of resorcinol will probably result in a cost-effective carbonaceous material. Experiments: Resorcinol-tannin-formaldehyde xerogels containing different amounts of tannin, either with or without a surfactant (sodium dodecyl sulphate), were synthesized by means of two different heating methods: conventional and microwave heating. The effects of the surfactant, the heating method and the addition of tannin upon the porous structure and the chemical composition of the final materials were evaluated. Findings: It was found that the addition of surfactant is essential for obtaining highly porous xerogels when using tannins. The heating method also plays an important role, as conventionally synthesized samples display a greater volume of large pores. However, tannins are less sensitive to microwave radiation and their use results in tannin-formaldehyde xerogels that have a porous structure and chemical composition similar to those of resorcinol-formaldehyde xerogels.Financial support from the Ministerio de Economía y Competitividad of Spain MINECO (under Projects MAT2011-23733, IPT-2012-0689-420000 and CTQ2013-49433-EXP) is greatly acknowledged. NRR is also grateful to MINECO for her predoctoral research grant. The French authors also gratefully acknowledge the financial support of the CPER 2007–2013 “Structuration du Pôle de Compétitivité Fibres Grand’Est” (Competitiveness Fibre Cluster), through local (Conseil Général des Vosges), regional (Région Lorraine), national (DRRT and FNADT) and European (FEDER) funds.Peer Reviewe

Energy consumption estimation in the scaling-up of microwave heating processes

The specific energy consumption of six different microwave-driven processes and equipments has been studied and it was found that the scale used dramatically affects it. Increasing the amount of sample employed from 5 to 100 g leads to a reduction in the specific energy consumption of 90–95%. When the amount of sample is 200 g or higher, the specific energy consumption remains practically constant. This means that to assess the real energy efficiency of a microwave-driven process a minimum mass of about 200 g needs to be used. The energy results can then be easily extrapolated to larger scales. Otherwise, a correlation should be used to avoid overestimated energy values and inaccurate energy efficiencies.The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement no. 311815 (SYNPOL project). D.B. and N.R.R. are also grateful to FICYT of the Government of Principado de Asturias (Spain) and the Ministry of Economy and Competitiveness of Spain (under Project MAT2011-23733), respectively, for their predoctoral research grants. The help of Xerolutions S.L. in providing experimental data is also acknowledged.Peer reviewe

Effect of methanol content in commercial formaldehyde solutions on the porosity of RF carbon xerogels

Methanol is used commercially as a stabilizer in solutions of formaldehyde to prevent its precipitation. However, the methanol content of commercially available formaldehyde solutions differs from one supplier to another. The pH, dilution and R/F ratio have been demonstrated to be interdependent variables that can be manipulated to tailor the porous properties of RF carbon xerogels. This work considers the methanol contained in formaldehyde solutions as a new variable to be studied in conjunction with those just mentioned. For the purpose of this study, the influence of methanol on the final porous properties of RF carbon xerogels has been evaluated. It was found that carbon xerogels synthesized using formaldehyde solutions with lower concentrations of methanol showed a higher total pore volume and pore size, and in turn, a lower density and a greater porosity. The porosity of RF carbon xerogels could therefore be radically modified depending on the commercial formaldehyde solution used for their synthesis.The financial support from the Ministerio de Economía y Competitividad of Spain MINECO (under Projects MAT2011-23733, IPT-2012-0689-420000 and CTQ2013-49433-EXP) is greatly acknowledged.Peer Reviewe

Producción y caracterización del CSR procedente del rechazo de una planta de recuperación y compostaje

La valorización energética constituye una de las alternativas para la gestión de los rechazos de las plantas de tratamiento de residuos, ya que se trata de un material que no se puede reciclar, ni compostar ni biometanizar. De esta forma, el rechazo puede transformarse en CSR (combustible sólido recuperado), apto para ser utilizado como combustible alternativo. Esta posibilidad es la que ha estudiado el grupo de investigación INGRES, de la Universidad Jaume I, en la planta de reciclaje y compostaje de RSU que la empresa Reciplasa tiene en Onda (Castellón). Y a tenor de los resultados que han obtenido, parece que la fabricación de CSR es una alternativa posible de valorización energética de aquellos residuos cuyo destino final es su depósito en vertederos