Separation and recovery of materials from scrap printed circuit boards

Printed circuit boards from waste computers, televisions, and mobile phones were pyrolysed in a fixed bed reactor with the aim of separating and recovering the organic and metallic materials. A selection of printed circuit boards from each of the three waste classes was pyrolysed at 800°C and the pyrolysis products were analysed using GC-FID, GC-TCD, GC-MS, GC-ECD, ICP-MS, and SEM-EDX. The pyrolysis oils contained high concentrations of phenol, 4-(1-methylethyl)phenol, and p-hydroxyphenol, as well as bisphenol A, tetrabromobisphenol A, methyl phenols, and bromophenols. The pyrolysis oils also contained significant concentrations of organo – phosphate compounds and a number of tetrabromobisphenol A pyrolysis products were also identified. The pyrolysis residues were very fragile and the organic, glass fibre, and metallic fractions could easily be separated and the electrical components could easily be removed from the remains of the printed circuit boards. The ash in the residue mainly consisted of copper, calcium, iron, nickel, zinc, and aluminium, as well as lower concentrations of valuable metals such as gallium, bismuth, silver, and gold, silver was present in particularly high concentrations. Many other metals were also identified in the ash by ICP-MS and SEM EDX. The pyrolysis gases mainly consisted of CO2 and CO but all of the C1 – C4 alkanes and alkenes were present, as were some inorganic halogens

Removal of organobromine compounds from the pyrolysis oils of flame retarded plastics using zeolite catalysts

Two flame retarded plastics have been pyrolysed in the presence of two Zeolite catalysts to remove the organobromine compounds from the derived pyrolysis oil. The flame retarded plastics were, acrylonitrile – butadiene – styrene (ABS) that was flame retarded with tetrabromobisphenol A and high-impact-polystyrene (HIPS) that was flame retarded with decabromodiphenyl ether. The two catalysts investigated were Zeolite ZSM-5 and Y-Zeolite. Pyrolysis was carried out in a fixed bed reactor at a final pyrolysis temperature of 440 ºC. The pyrolysis gases were passed immediately to a fixed bed of the catalyst bed. It was found that the presence of Zeolite catalysts increased the amount of gaseous hydrocarbons produced during pyrolysis but decreased the amount of pyrolysis oil produced. In addition, significant quantities of coke were formed on the surface of the catalysts during pyrolysis. The Zeolite catalysts were found to reduce the formation of some valuable pyrolysis products such as styrene and cumene, but other products such as naphthalene were formed instead. The Zeolite catalysts, especially Y-Zeolite, were found to be very effective at removing volatile organobromine compounds. However, they were less effective at removing antimony bromide from the volatile pyrolysis products, although some antimony bromide was found on the surfaces of the spent catalysts

The kinetics of iodination and bromination of 2,6-dibromophenol and 2,6-dibromophenol-4-d

M.S.Erling Grovenstein, Jr

Comparison studies of the mechanistic formation of polyhalogentaed dibenzo-p-dioxins and furans from the thermal degradation of 2-bromophenol and 2-chlorophenol

Emissions of polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) and polybrominated dibenzo-p-dioxins and furans (PBDD/Fs) from hazardous waste incinerators, and many other sources for combustion have been considered environmentally hazardous and a major health threat. Recently, a growing number of materials containing brominated hydrocarbons, commonly used flame retardants, have been disposed in municipal and hazardous waste incinerators. This results in the increased potential for formation of PBDD/Fs and other hazardous combustion by-products. In contrast to chlorinated hydrocarbons, the reactions of brominated hydrocarbons have been studied only minimally. In fact, studies have shown that brominated phenols form higher yields of PBDD/Fs than the analogous chlorinated phenols form PCDD/Fs. For this study, the individual homogeneous, gas-phase oxidative and pyrolytic thermal degradations of 2-bromophenol and 2-chlorophenol were studied in a 1 cm i.d., fused silica flow reactor at a concentration of 88 ppm, with a reaction time of 2.0 s, and over a temperature range of 300 to 1000°C. In addition, 50:50 mixture of 2-chlorophenol and 2-bromophenol with a combined concentration of 88 ppm was studied under similar conditions. Also in order to compare previous work with 2-chlorophenol, the surface catalyzed gas-phase reactions for 2-bromophenol to form PBDD/Fs are described over a temperature range from 250 to 550°C. The results are compared and contrasted with each other in order to understand the roles oxygen, chlorine and bromine play in the formation of PCDD/Fs and PBDD/Fs. Reaction pathways to PCDD/F and PBDD/F products as well as all other products detected are proposed that are consistent with the experimental data for each condition. The presence of oxygen increases the formation of PBDFs and PCDFs. Presence of bromine increases the concentration of Cl radicals which in turn increases chlorination and formation of 4,6-dichlorodibenzofuran (4,6-DCDF). However the yields of the PCDFs and PBDFs are considerably less with the presence of both bromine and oxygen. The pool of ·OH and concentration of the chlorine atoms is reduced and thus prevents these furans from becoming major products

Predator deterrence and 2,4-dibromophenol conservation by the enteropneusts Saccoglossus bromophenolosus and Protoglossus graveolens

Saccoglossus bromophenolosus King et al., 1994 and Protoglossus graveolens Giray and King, 1996 contain high concentrations of 2,4-dibromophenol (DBP), the function of which is uncertain. Mature enteropneusts that were collected from the field and maintained in vitro without bromide retained DBP, which is inconsistent with active DBP secretion into the burrow environment. DBP was also conserved during field manipulations that decreased food availability in situ. Further, DBP did not deter predation in feeding experiments with the anomuran crab Pagurus longicarpus and the polychaetes Glycera dibranchiata, Nereis virens and Nepthys incisa. The hermit crabs fed on S. bromophenolosus readily, and in preference to shrimp, in the field and in laboratory aquaria. Elevated DBP levels were measured in crabs that had recently consumed S. bromophenolosus, and ingested DBP was degraded to 4-bromophenol. Elevated levels of DBP in polychaetes were associated with the disappearance of enteropneusts during in vitro feeding experiments. Control incubations with DBP-containing agar plugs indicated that the polychaetes did not accumulate DBP passively. These results suggest that DBP is not an effective anti-predatory agent against hermit crabs or some predatory polychaetes. A definitive role for DBP in enteropneusts remains to be shown

Effect of naturally occurring bromophenols on sulfate reduction and ammonia oxidation in intertidal sediments

We examined the effect on ammonium oxidation and sulfate reduction of several brominated compounds [4-bromophenol, 2,4-dibromophenol (2,4-DBP), 2,6-dibromophenol and 2,4,6-tribromophenol] that occur naturally in enteropneusts. We compared rates of these processes with and without bromoorganics using bulk intertidal sediments and burrow wall sediments from 3 enteropneust species (2 containing 2,4-DBP and 1 containing 2,3,4-tribromopyrrole), a mollusc (Mya arenaria) and a polychaete (Nereis virens). Sulfate reduction in bulk sediment was unaffected by bromophenols at concentrations sediment, but was inhibited temporarily at 1 μmol cm-3. Sulfate reduction in burrow wall sediments differed from bulk sediments, but was not correlated with concentrations of naturally occurring bromophenols. Ammonium oxidation was inhibited in surface sediments by bromophenol concentrations as low as 1 nmol cm-3 sediment. Ammonium oxidation was enhanced in burrow wall sediments of N. virens, M. arenaria and the enteropneust Saccoglossus bromophenolosus relative to surface sediments, but was markedly lower and negatively correlated with ambient 2,4-DBP in burrow wall sediments of a second enteropneust, Protoglossus graveolens

Synthesis of Enantioenriched Indolines by a Conjugate Addition/Asymmetric Protonation/Aza-Prins Cascade Reaction

A conjugate addition/asymmetric protonation/aza-Prins cascade reaction has been developed for the enantioselective synthesis of fused polycyclic indolines. A catalyst system generated from ZrCl_4 and 3,3′-dibromo-BINOL enables the synthesis of a range of polycyclic indolines in good yields and with high enantioselectivity. A key finding is the use of TMSCl and 2,6-dibromophenol as a stoichiometric source of HCl to facilitate catalyst turnover. This transformation is the first in which a ZrCl_4⋅BINOL complex serves as a chiral Lewis-acid-assisted Brønsted acid

Enantioselective Total Synthesis of (-)-Lansai B and (+)-Nocardioazines A and B

The concise total syntheses of the bis(pyrroloindolines) (−)-lansai B and (+)- nocardioazines A and B are reported. The key pyrroloindoline building blocks are rapidly prepared by enantioselective formal [3+2] cycloaddition reactions. The macrocycle of (+)-nocardioazine A is constructed by an unusual intramolecular diketopiperazine formation