Julia Moltó

Thermal decomposition of electronic wastes: mobile phone case and other parts.

Pyrolysis and combustion runs at 850°C in a horizontal laboratory furnace were carried out on different parts of a mobile phone (printed circuit board, mobile case and a mixture of both materials). The analyses of the carbon oxides, light hydrocarbons, polycyclic aromatic hydrocarbons (PAHs), polychlorodibenzo-p-dioxin, polychlorodibenzofurans (PCDD/Fs), and dioxin-like PCBs are shown. Regarding semivolatile compounds, phenol, styrene, and its derivatives had the highest yields. In nearly all the runs the same PAHs were identified, naphthalene being the most common component obtained. Combustion of the printed circuit board produced the highest emission factor of PCDD/Fs, possibly due to the high copper content.

Pollutant emissions during pyrolysis and combustion of waste printed circuit boards, before and after metal removal

The constant increase in the production of electronic devices implies the need for an appropriate management of a growing number of waste electrical and electronic equipment. Thermal treatments represent an interesting alternative to recycle this kind of waste, but particular attention has to be paid to the potential emissions of toxic by-products. In this study, the emissions from thermal degradation of printed circuit boards (with and without metals) have been studied using a laboratory scale reactor, under oxidizing and inert atmosphere at 600 and 850 °C. Apart from carbon oxides, HBr was the main decomposition product, followed by high amounts of methane, ethylene, propylene, phenol and benzene. The maximum formation of PAHs was found in pyrolysis at 850 °C, naphthalene being the most abundant. High levels of 2-, 4-, 2,4-, 2,6- and 2,4,6-bromophenols were found, especially at 600 °C. Emissions of PCDD/Fs and dioxin-like PCBs were quite low and much lower than that of PBDD/Fs, due to the higher bromine content of the samples. Combustion at 600 °C was the run with the highest PBDD/F formation: the total content of eleven 2,3,7,8-substituted congeners (tetra- through heptaBDD/Fs) was 7240 and 3250 ng WHO2005-TEQ/kg sample, corresponding to the sample with and without metals, respectively.

Decomposition of two types of electric wires considering the effect of the metal in the production of pollutants

Combustion runs at 700 °C in a horizontal laboratory furnace were carried out on two different electric wires (PVC and halogen-free wire). Tests were performed in the presence and in the absence of the metal conductor of the wires. The analyses of the polycyclic aromatic hydrocarbons (PAHs), chlorobenzenes (CBzs), chlorophenols (CPhs), mono- to octa-chlorodibenzo-p-dioxin and dibenzofurans (PCDD/Fs), and dioxin-like PCBs are shown. Regarding semivolatile compounds, PAHs production decreases in the presence of metal, while a higher amount of chlorinated compounds are emitted. Respect to the PCDD/Fs, the PVC wire in the presence of metal presents the highest emission, with a much more emission of furans than dioxins. The maximum emission is with 2 or 3 chlorine atom PCDD/Fs. PCBs emission correlates with PCDD/F production and represents 3-4% of total toxicity, determined by using WHO2005 factors.

Formation of polychlorinated compounds in the combustion of PVC with iron nanoparticles

The influence of iron nanoparticles in the fuel-rich combustion of PVC has been studied in this work. Dynamic runs for PVC and the mixture PVC and iron nanoparticles were firstly carried out by TGA-MS in order to study the influence of iron on the compounds evolved in the thermal degradation of PVC. To complete the study both PVC and a mixture of PVC and iron nanoparticles were burnt in a laboratory reactor under two different operating conditions: at 850 degrees C and in two stages, the first one at 375 degrees C and the resulting char cooled and subsequently burnt at 850 degrees C. Carbon oxides, light hydrocarbons, PAHs, chlorophenols, chlorobenzenes and PCDD/Fs were analyzed. It was observed that the mixture of PVC with iron nanoparticles at 375 degrees C greatly enhances the formation of light hydrocarbons and polychlorinated compounds, probably indicating that the presence of iron during the thermal decomposition of PVC causes the formation of iron chloride which may have a high catalytic effect.

Thermogravimetric kinetic analysis and pollutant evolution during the pyrolysis and combustion of mobile phone case

The increase in electronic waste, including cellular telephones, worldwide is a worrying reality. For this reason, urgent action on the management of these wastes is necessary within a framework that respects the environment and human health. Mobile phone components can be physically segregated through grinding at the dismantling sites, in order to reuse or reprocess (via chemical or physical recycling) the recovered plastics and valuable metals. A kinetic study of the thermal decomposition of a mobile phone case has been carried out under different conditions by thermogravimetry. Several experiments were performed in a nitrogen atmosphere (pyrolysis runs) and also in an oxidative atmosphere with two different oxygen concentrations (10% and 20% oxygen in nitrogen). Dynamic runs and dynamic+isothermal runs have been carried out to obtain much decomposition data under different operating conditions. Moreover some TG-MS runs were performed in order to better understand the thermal decomposition of a mobile phone case and identify some compounds emitted during the controlled heating of this material. A scheme of two independent reactions for pseudocomponents has been proposed for the pyrolysis process. For the combustion runs, the scheme proposed includes two pyrolytic reactions competing with other two reactions with formation of an intermediate residue, and finally the reaction of oxidation/burning of the intermediate residue. Furthermore, pyrolysis and combustion runs at 500 °C in a horizontal laboratory furnace were carried out. More than 50 compounds, including carbon oxides, light hydrocarbons, and polycyclic aromatic hydrocarbons (PAHs) have been identified and quantified. The main semivolatile compounds detected were phenol and styrene. Furthermore, polychlorodibenzo-p-dioxin and polychlorodibenzofurans (PCDD/Fs) and dioxin-like PCBs produced were analyzed. In the combustion run, PCDDs were obtained in higher amounts than PCDFs and HxCDD was the most emitted homologue.

De novo synthesis of brominated dioxins and furans

On the basis of laboratory experiments with model mixtures (active carbon+CuBr2 at different loads), this work studies the formation of polybrominated dibenzo-p-dioxins and dibenzofurans (PBDD/Fs) by de novo synthesis. For the different samples, the temperature of the maximum carbon oxidation rate was determined by thermogravimetric analysis, and a kinetic model was proposed for the degradation of the materials in an oxidizing atmosphere (synthetic air). The effect of the addition of different amounts of CuBr2 was studied, finding that its presence accelerates the degradation of the carbonaceous structure in the presence of oxygen. The thermal degradation of the samples in air is satisfactorily described by a first-order single-reaction model. In addition, combustion runs of one of the mixtures (consisting of activated carbon+50 wt % CuBr2, pyrolyzed at 700 °C) were performed in a quartz horizontal laboratory furnace. The analysis of the emissions and the solid residue proved the formation of brominated dioxins and furans at 300, 400, and 500 °C, with a maximum yield at 300 °C (91.7 ng/g of total PBDD/Fs) and a higher bromination degree with increasing temperature.

Low temperature thermal degradation of PCDD/Fs in soil using nanosized particles of zerovalent iron and CaO.

This study investigated the degradation of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in contaminated soil using low temperature treatment (200-280°C) both alone and in combination with nanosized zerovalent iron (nZVI) particles or CaO. Control soil samples and soil fortified with nZVI particles or CaO were treated at 200 and 250°C in sealed glass ampoules. Treatment of the ampouled samples at 250°C was more effective than treatment at 200°C and the reduction in PCDD/F concentration was greatest when soil was treated at 250°C with nZVI addition (indeed, treatment at 200°C in the absence of nZVI resulted in increases in total PCDD and PCDD/F concentrations). In larger-scale experiments based on the obtained results, using a rotary furnace, the greatest reduction in total PCDD/F concentration was achieved by treating soil at 280°C, and adding nZVI to the soil resulted in almost no detectable PCDD/F in the gas phase.

Analysis of dioxin-like compounds formed in the combustion of tomato plant

In an initial effort to minimize some of the uncertainty regarding the open burning of biomass, emission factors of carbon oxides, light hydrocarbons, PAHs, PCDD/Fs and dioxin-like PCBs were determined in the combustion of tomato plant in a residential stove and in two runs at 500 degrees C and 850 degrees C in a laboratory scale reactor. In all the runs nearly the same PAHs were identified, being naphthalene the main obtained. Combustion of tomato plant at 500 degrees C in the laboratory scale reactor produced the highest emission factors for all compounds analyzed. Tomato plant was analyzed for PCDD/F and dioxin-like PCB content in order to establish the level of pollutants in the sample itself. Ash obtained in the combustion carried out in the residential stove was analyzed for the dioxin-like compound content and compared with a sample of ash collected from the open burning of tomato plant.

Relationship between serum dioxin-like polychlorinated biphenyls and post-testicular maturation in human sperm

The relationship between dioxin-like polychlorinated biphenyl (DL-PCB) levels in serum and semen parameters were investigated. Our case-control included two groups of patients. Total concentrations of PCBs were significantly higher in the low semen quality (n=24) than in the normal semen quality (n=26) group. A significant negative correlation was found between PCB 126 and viability in men with low semen quality, while PCBs 77 and 81 were positively correlated with morphology, and PCB 118, mono-ortho and total DL-PCBs were positively correlated with volume. In the normal semen quality group, PCB 189 and 118 were negatively correlated with sperm motility and volume, respectively. In addition, positive significant correlations were found between PCB 77, 23 and total non-ortho PCBs with regard to morphology. Our findings suggest that sperm motility, viability, volume and morphology are parameters sensitive to alteration by exposure to DL-PCBs, although PCB effects on spermatogenesis were not of clinical significance.