Removal of Perfluorooctanoic Acid from Water Using a Hydrophobic Ionic Liquid Selected Using the Conductor-like Screening Model for Realistic Solvents.

The conductor-like screening model for realistic solvents was used to identify ionic liquids (ILs) to efficiently extract perfluorooctanoic acid (PFOA). The infinite dilution chemical potentials of PFOA in 14 000 ILs were calculated and used as descriptors of the chemical affinities between the ILs and PFOA. Trihexyltetradecylphosphonium pivalate ([P6,6,6,14][Piv]) was found to be a good IL for extracting PFOA because it gave a well-balanced combination of a strong chemical attraction for PFOA and useful physicochemical properties. The results of experiments indicated that [P6,6,6,14][Piv] could remove >99.9% of the PFOA in an aqueous solution. However, problematic emulsification of IL in the aqueous phase occurred at PFOA/IL molar ratios <1.9-2.1, and this limited the PFOA removal rate to 80-91%. The ability of the used IL to extract PFOA was found to be partially regenerated by washing the IL with 1% NaOH, and the IL could be reused to extract PFOA with a removal rate decreased by ∼10% in each cycle.

Mitigation of bromine-containing products during pyrolysis of polycarbonate-based tetrabromobisphenol A in the presence of copper(I) oxide.

Polycarbonate (PC) is an engineering thermoplastic that is widely used in electrical and electronic equipment. This plastic often contains tetrabromobisphenol A (TBBA), the most common brominated flame retardant. Thermal degradation of the PC-TBBA leads to generation of numerous bromo-organic products in the pyrolytic oil, hindering its appropriate utilization, as well as corrosive hydrogen bromide gas. The purpose of this study was to experimentally investigate and compare the pyrolysis products of PC-TBBA and PC-TBBA + Cu2O at various temperatures, with an emphasis on the yield and distribution of brominated compounds. In pyrolysis of PC-TBBA + Cu2O, at the maximum degradation temperature (600 °C), as much as 86% of total Br was trapped in the residue, while 3% and 11% were distributed in the condensate and gas fractions, respectively. In contrast, the distribution of Br from non-catalytic pyrolysis of PC-TBBA (600 °C) was 0.5% residue, 40% condensate, and 60% gas. The results of this study revealed that in the presence of Cu2O, organo-bromine products were most likely involved in Ullman-type coupling reactions, leading to early cross-linking of the polymer network that efficiently hinders their vaporization. HBr in the gas fraction was suppressed due to effective fixation of bromine in residue in the form of CuBr.

Study on simultaneous recycling of EAF dust and plastic waste containing TBBPA.

In the present work we investigated the fates of zinc, lead, and iron present in electric arc furnace dust during thermal treatment of the dust with tetrabromobisphenol A (TBBPA) and tetrabromobisphenol A diglycidyl ether (TBBPADGE). Mixtures of these materials were compressed into pellets and heated in a laboratory-scale furnace at 550 °C for 80 min, under oxidizing and inert conditions. The solid, condensed, and gaseous-phase products were characterized using an array of analytical methods: scanning electron microscopy, X-ray diffraction, electron probe microscopy, inductively coupled plasma, ion chromatography, and gas chromatography. The results indicated that heating the mixtures under specific conditions enabled high separation of zinc and lead from iron-rich residues, by a bromination-evaporation process. In the case of TBBPADGE, a maximum of 85% of zinc and 81% of lead were effectively separated under the above conditions. The process is based on the reaction between the highly reactive HBr gas evolved during thermal degradation of the flame-retarded materials with zinc (ZnO and ZnFe2O4) and lead in the dust, followed by complete evaporation of the formed metallic bromides from the solid residue.

Fate of lead oxide during thermal treatment with tetrabromobisphenol A.

In this paper, the bromination reaction between lead oxide and hydrogen bromide originating from the thermal decomposition of tetrabromobisphenol A (TBBPA), under inert and oxidizing atmospheres, was investigated, using a laboratory-scale furnace. The results obtained under inert conditions indicated that bromination of PbO proceeded simultaneously with debromination of TBBPA, with an average effectiveness of 69% (max. 80%). Volatilization of the formed PbBr2 began at 315°C, intensified at 750°C, and reached 98% at 850°C. The formed organic char served as a source of carbon for reduction of the unreacted lead oxide to metallic lead in the range 315-750°C. Additional experiments conducted at selected temperatures under slightly oxidizing (5 vol% O2) and quasi-atmospheric (20 vol% O2) conditions showed no significant effects on bromination-evaporation of lead in the studied mixture. However, in isothermal treatment under quasi-atmospheric oxygen levels, complete vaporization of the formed lead bromide was obtained at a temperature of only 650°C.

Distribution of copper, silver and gold during thermal treatment with brominated flame retardants.

The growing consumption of electric and electronic equipment results in creating an increasing amount of electronic waste. The most economically and environmentally advantageous methods for the treatment and recycling of waste electric and electronic equipment (WEEE) are the thermal techniques such as direct combustion, co-combustion with plastic wastes, pyrolysis and gasification. Nowadays, this kind of waste is mainly thermally treated in incinerators (e.g. rotary kilns) to decompose the plastics present, and to concentrate metals in bottom ash. The concentrated metals (e.g. copper, precious metals) can be supplied as a secondary raw material to metal smelters, while the pyrolysis of plastics allows the recovery of fuel gases, volatilising agents and, eventually, energy. Indeed, WEEE, such as a printed circuit boards (PCBs) usually contains brominated flame retardants (BFRs). From these materials, hydrobromic acid (HBr) is formed as a product of their thermal decomposition. In the present work, the bromination was studied of copper, silver and gold by HBr, originating from BFRs, such as Tetrabromobisphenol A (TBBPA) and Tetrabromobisphenol A-Tetrabromobisophenol A diglycidyl ether (TTDE) polymer; possible volatilization of the bromides formed was monitored using a thermo-gravimetric analyzer (TGA) and a laboratory-scale furnace for treating samples of metals and BFRs under an inert atmosphere and at a wide range of temperatures. The results obtained indicate that up to about 50% of copper and silver can evolve from sample residues in the form of volatile CuBr and AgBr above 600 and 1000°C, respectively. The reactions occur in the molten resin phase simultaneously with the decomposition of the brominated resin. Gold is resistant to HBr and remains unchanged in the residue.

Vaporization of zinc during thermal treatment of ZnO with tetrabromobisphenol A (TBBPA).

In the present work we investigate the vaporization of zinc or its compounds during thermal treatment of ZnO with tetrabromobisphenol A. Samples of 2g of ZnO:TBBPA (3.34:1) were isothermally heated in a laboratory-scale furnace at temperatures from 490 °C to 950 °C, and the solid, condensed and gaseous products formed were analyzed by X-ray diffraction analysis, electron probe microanalysis, inductively coupled plasma analysis, ion chromatography, and gas chromatography coupled with mass spectrometry. The results obtained indicate that the vaporization of ZnBr(2) formed strongly depends on heating time and temperature, yet is restrained by char, if formed with sufficient yield (above 15 wt%). Starting from 850 °C, this char commences carbothermic reduction of any remaining ZnO, which from then begins to evaporate as zinc metal vapor. Volatilization of zinc is completed at 950 °C. The presence of 5 vol.% of oxygen has no significant effect on the vaporization of formed ZnBr(2), the carbothermic reduction or the volatilization of metallic zinc. Strongly oxidizing conditions (20 vol.% of oxygen), however, boost the oxidation of char and thus the vaporization of ZnBr(2), but prevent carbothermic reduction of any un-reacted ZnO by depleting this char.

Influence of temperature and heating time on bromination of zinc oxide during thermal treatment with tetrabromobisphenol A.

Our prior research indicates that hydrogen bromide (HBr) evolved during thermal decomposition of tetrabromobisphenol A (TBBPA) can be utilized as a reagent for selective bromination and evaporation of zinc oxide. The present work investigated dependency of the bromination reaction on time at selected temperatures using a laboratory-scale furnace. The formed solid, condensed, and gaseous products were analyzed by X-ray diffraction analysis, electron probe microanalysis, inductively coupled plasma analysis, ion chromatography, and gas chromatography coupled with mass spectrometry. Results indicate that the bromination rate is strongly dependent on heating time. This dependency is a direct consequence of progress in the decomposition of TBBPA, which provides inorganic bromine suitable for the reaction. The bromination rate increases with time until the bromine source is depleted. The process is shorter at higher applied temperatures and appears instantaneous at 310 degrees C and above. However, the maximum bromination yield is independent of the applied conditions and ranges from 64 to 70%. Additionally, the influence of oxidizing conditions on the bromination reaction and the effect of ZnO on decomposition of TBBPA were investigated in this study.

Studies on bromination and evaporation of zinc oxide during thermal treatment with TBBPA.

Thermodynamic considerations indicate that base metal oxides such as ZnO, PbO, Cu2O, etc. should easily react with HBr, the main gaseous product from the thermal decomposition of tetrabromobisphenol A (TBBPA), to form low boiling point metallic bromides suitable for volatile separation. In this work a differential scanning calorimeter and laboratory-scale furnace was used to investigate the scope and conditions for the bromination of ZnO by the thermal decomposition of TBBPA. The formed solid, condensed, and gaseous products were analyzed by X-ray diffraction analysis, electron probe microanalysis, inductively coupled plasma analysis, ion chromatography, and gas chromatography coupled with mass spectrometry. The results obtained in this study indicate that the bromination of ZnO occurred at 272 degrees C (DSC) and above 290 degrees C (furnace) with an effectiveness of 41, 64, and 81% dependent on the experimental conditions. Volatilization of the formed ZnBr2 began at 340 degrees C and had a 45% yield at 650 degrees C. This yield corresponded to 28-36% of the original zinc content in the mixture under the present experimental conditions.

Fate of PCDD/PCDF during mechanical-biological sludge treatment.

In this preliminary study the seventeen 2,3,7,8-substituted congeners of PCDD/PCDF were analyzed at the inlet and outlet water and for three sewage sludge samples taken from different treatment stages to check behaviours of PCDD/PCDF at a municipal wastewater treatment plant (MWTP) in Poland. At the inlet (untreated sewage) water dominated PCDD congeners, whereas in the outlet (treated water) dominated the PCDF congeners. The octaCDD, 1,2,3,4,6,7,8-heptaCDD/CDF and octaCDF congeners dominated in all of the sludge samples. The total toxicity load gradually increased in the series excess, digested and dewatered sludge and amounted to 12.2, 14.4 and 16.9ngI-TEQkg(-1).

Application of the conductor-like screening model for real solvents for prediction of the aqueous solubility of chlorobenzenes depending on temperature and salinity.

The conductor-like screening model for real solvents (COSMO-RS) is applied to the prediction of the aqueous solubility of chlorobenzenes (CBZs) in a liquid-liquid and liquid-solid equilibrium. The solubilities of CBZs at temperatures ranging from 5 to 60 degrees C are reported, and the enthalpies of solution are derived from van't Hoff plots. The salting effect of 12 chlorobenzenes is determined for sodium, potassium, and calcium solutions at concentrations ranging from 0.01 to 3.5 mol/L. A new experimental aqueous solubility value is given for the isotopic labeled 1,2,4-trichlorobenzene determined at 25 degrees C by the generator column procedure. The COSMO-RS method presented in this study can be useful to estimate the magnitude of the salt effect and temperature influence on the behavior of any chlorobezene under environmental conditions.