Occurrences and inventories of heavy metals and brominated flame retardants in wastes from printed circuit board production

Effects of polymer matrix and temperature on pyrolysis of tetrabromobisphenol A: Product profiles and transformation pathways

Plastics are crucial constituents in electronic waste (e-waste) and part of the issue in e-waste recycling and environmental protection. However, previous studies have mostly focused on plastic recovery or thermal behavior of flame retardants, but not both simultaneously. The present study simulated the process of e-waste thermal treatment to explore tetrabromobisphenol A (TBBPA) pyrolysis at various temperatures using polystyrene (PS), polyvinyl chloride (PVC), and e-waste plastics as polymer matrices. Pyrolysis of TBBPA produced bromophenol, bromoacetophenone, bromobenzaldehyde, and bromobisphenol A. Co-pyrolysis with the polymer matrices increased emission factors by 1 - 2 orders of magnitude. The pyrolytic products of TBBPA, TBBPA+PS, and TBBPA+PVC were mainly low-brominated bisphenol A, while that of TBBPA in e-waste plastics was consistently bromophenol. Increasing temperature drove up the proportions of gaseous and particulate products, but lowered the relative abundances of inner wall adsorbed and residual products in pyrolysis of pure TBBPA. In co-pyrolysis of TBBPA with polymer matrix, the proportions of products in different phases were no longer governed solely by temperature, but also by polymer matrix. Co-pyrolysis of TBBPA with PS generated various bromophenols, while that with PVC produced chlorophenols and chlorobrominated bisphenol A. Transformation pathways, deduced by ab initio calculations, include hydrogenation-debromination, isopropylphenyl bond cleavage, oxidation, and chlorination.

Review of the environmental occurrence, analytical techniques, degradation and toxicity of TBBPA and its derivatives

BFRs (brominated flame retardants) are a class of compounds that are added to or applied to polymeric materials to avoid or reduce the spread of fire. Tetrabromobisphenol A (TBBPA) is one of the known BFR used many in industries today. Due to its wide application as an additive flame retardant in commodities, TBBPA has become a common indoor contaminant. Recent researches have raised concerns about the possible hazardous effect of exposure to TBBPA and its derivatives in humans and wildlife. This review gives a thorough assessment of the literature on TBBPA and its derivatives, as well as environmental levels and human exposure. Several analytical techniques/methods have been developed for sensitive and accurate analysis of TBBPA and its derivatives in different compartments. These chemicals have been detected in practically every environmental compartment globally, making them a ubiquitous pollutant. TBBPA may be subject to adsorption, biological degradation or photolysis, photolysis after being released into the environment. Treatment of TBBPA-containing waste, as well as manufacturing and usage regulations, can limit the release of these chemicals to the environment and the health hazards associated with its exposure. Several methods have been successfully employed for the treatment of TBBPA including but not limited to adsorption, ozonation, oxidation and anaerobic degradation. Previous studies have shown that TBBPA and its derivative cause a lot of toxic effects. Diet and dust ingestion and have been identified as the main routes of TBBPA exposure in the general population, according to human exposure studies. Toddlers are more vulnerable than adults to be exposed to indoor dust through inadvertent ingestion. Furthermore, TBBP-A exposure can occur during pregnancy and through breast milk. This review will go a long way in closing up the knowledge gap on the silent and over ignored deadly effects of TBBPA and its derivatives and their attendant consequences.

Cutting down on the ozone and SOA formation as well as health risks of VOCs emitted from e-waste dismantlement by integration technique

Elimination of volatile organic compounds (VOCs) in the e-waste dismantling industry by an integration technique of spray tower-electrostatic precipitation-photocatalysis was conducted to investigate its application possibility for reducing formation of O₃ and secondary organic aerosols (SOAs) as well as exposure risk. Results revealed the average 5.4 × 10² μg m^-3 of VOCs with the top two groups being aromatic hydrocarbons (AHs, 55.93%) and halogenated hydrocarbons (HHs, 33.33%), contributing to 1.3 × 10³ and 3.0 × 10⁴ μg m^-3 of the O₃ and SOA (OFP and SOAFP) formation potential, respectively. Furthermore, 86.47% of OFP and 99.87% of SOAFP were ascribed to AHs, in which toluene ranked first (35.30% and 48.07%). The highest removal efficiency (76.92%) for VOCs by the integrated technique resulted in excellent prevention efficiencies of OFP (71.54%) and SOAFP (80.62%). Occupational cancer risk assessment found that HHs (62.63%) and AHs (36.93%) were the top two contributors. After the treatment by the integrated technique, 55.44% of the total risk index was reduced with the accumulation of few low-concentrated and more toxic AHs (e.g. 6.6 μg m^-3 benzene on average). All results suggest that controlling AH and HH emissions from the e-waste dismantling source could efficiently prevent atmospheric secondary pollution and human exposure risk to industrial emission.

Life cycle assessment of a printed circuit board manufacturing plant in Turkey

The objective of this study is to investigate the environmental impacts of a printed circuit board (PCB) manufacturing plant through streamlined life cycle assessment approach. As a result, the most effective recommendations on minimizing the environmental impacts for the mentioned sector are revealed and first steps towards establishing a country specific database are taken. The whole PCB production consists of two consecutive stages: namely board fabrication followed by the manufacturing of PCB. Manufacturing of PCB contributes the highest shares to freshwater aquatic ecotoxicity potential (FAETP) and ozone layer depletion potential (ODP). Eighty-nine percent of FAETP is found to be generated from the manufacturing of PCB. Almost all of this contribution can be attributed to the disposal of copper containing wastewater treatment sludge from etching operations to incineration. On the other hand, PCB manufacturing has 73% share in total ODP. Within the manufacturing of PCB, as etching operations are found to be of importance for all the impact categories except eutrophication potential (EP), it is recommended to focus further studies on in-plant control of etching.

Kinetic simulation and prediction of pyrolysis process for non-metallic fraction of waste printed circuit boards by discrete distributed activation energy model compared with isoconversional method

Kinetic studies on the pyrolysis process for non-metallic fraction (NMF) of waste printed circuit boards (WPCBs) were conducted using both the isoconversional SKAS method and the discrete distributed activation energy model (discrete DAEM). The pyrolysis process of the NMF sample could be classified into three stages, and a large mass loss was observed from 98 to 570 °C, attributed to thermal degradation of epoxy resins in the NMF sample. The kinetic parameters, including activation energies (E _i), pre-exponential factors (A _i), and contributed fractions (f _i,0), were determined. It indicated that the discrete DAEM could predict the pyrolysis process of the NMF more accurately and completely when compared with the isoconversional SKAS method. In the discrete DAEM, E _i and A _i values were evaluated at 99 equally spaced intervals of conversion. The E _i and A _i (in the form of lnA _i) transformed with reaction progress, ranging from 80.9 to 240.5 kJ/mol and 19.07 to 39.55 s^-1, respectively, with the conversion increased from 0.01 to 0.99. The pyrolysis of the NMF of WPCBs could be accurately characterized as 17 dominating reactions from f _i,0 results. Graphical abstract ᅟ.

A review of the environmental distribution, fate, and control of tetrabromobisphenol A released from sources

Tetrabromobisphenol A (TBBPA), a high use brominated flame retardant (BFR), raising concerns of widespread pollution and harm to human and ecological health. BFR manufacturing, TBBPA-based product manufacturing, e-waste recycling, and wastewater treatment plants have been identified as the main emission point sources. This paper discusses the occurrence, distribution, and fate of TBBPA from source to the environment. After release to the environment, TBBPA may undergo adsorption, photolysis, and biological degradation. Exposure of humans and biota is also discussed along with the role of treatment and regulations in reducing release of TBBPA to the environment and exposure risks. In general this review found stronger enforcement of existing legislation, and investment in treatment of e-waste plastics and wastewater from emission point sources could be effective methods in reducing release and exposure of TBBPA in the environment.