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Recycling process for waste TV sets mainly consists of dismantling, printed wiring board (PWB) heating, PWB recycling, and plastic crushing in formal recycling plant. Polybrominated diphenyl ethers (PBDEs) contained in waste TV sets are released to indoor air. Air samples at 4 different workshops were collected to measure the PBDEs concentrations in both gaseous and particulate phases. The mean concentrations of ∑PBDEs in indoor air were in the range of 6780–2,280,000 pg/m 3 . The highest concentration in gaseous phase (291,000 pg/m 3 ) was detected in the PWB heating workshop. The ∑ 12 PBDEs concentrations in PM 2.5 and PM 10 at the 4 workshops ranged in 6.8–6670 μg/g and 32.6–6790 μg/g, respectively. The gas-particle partitioning of PBDEs was disrupted as PBDEs were continuously released during the recycling processes. Occupational exposure assessment showed that only the exposure concentration of BDE-47 (0.118 μg/kg/day) through inhalation in the PWB heating workshop for workers without facemask exceeded the reference dose (0.1 μg/kg/day), posing a health hazard to workers. All the results demonstrated that recycling of TV sets was an important source of PBDEs emission, and PBDEs emission pollution was related to the composition of TV sets, interior dust, and recycling process. [ABSTRACT FROM AUTHOR]

Highlights: [•] TBBPA was detected in fine solid wastes and dust samples from PCB production at considerable levels. [•] The highest TBBPA emission to the environment was exhibited by the fine solid waste. [•] Elevated TBBPA concentrations were found in dust and PM10 from workshops of PCB production. [•] TBBPA contamination occurred mainly in the form of dust rather than suspended particulate matter in PCB production. [•] TBBPA via dust exposures were more critical than PM10 in most production processes. [Copyright &y& Elsevier]

Abstract: Leaching assessment on five heavy metals (copper, zinc, lead, nickel and cadmium) and two brominated flame retardants (BFRs), polybrominated diphenyl ethers (PBDEs) and tetrabromobisphenol A (TBBPA), from waste printed circuit boards (WPCBs) were conducted using various leaching methods. The mean leaching concentrations of copper were the highest in both toxicity characteristic leaching procedures (TCLP) and synthetic precipitation leaching procedures (SPLP) tests at 8.6mg/L and 1.1mg/L, while only lead (6.2mg/L) exceeded the TCLP criteria and Chinese EPA regulatory limit (both 5.0mg/L). However, PBDEs and TBBPA were not detected in TCLP and SPLP tests. Then the BFRs leaching trends and potential leachabilities were further investigated in actual landfill leachates using a modified method. Leaching characteristics that fast-leaching initially followed by slow-desorption over time were generally observed. In landfill leachate tests, the highest leaching concentrations of PBDEs and TBBPA were determined at 30.39 and 12.27μg/L. Meanwhile, the highest leaching rates were estimated to reach 0.08% and 1.00%, respectively, which were significantly influenced by the dissolved organic carbon contents of extracts, the hydrophobicities of target BFRs and the specific surface areas of WPCBs materials. These results proved that leaching from WPCBs was a significant emission source of BFRs in landfill and electronic waste recycling dumpsite. [Copyright &y& Elsevier]

Abstract: A new kind of wood plastic composite (WPC) was produced by compounding nonmetals from waste printed circuit boards (PCBs), recycled high-density polyethylene (HDPE), wood flour and other additives. The blended granules were then extruded to profile WPC products by a conical counter-rotating twin-screw extruder. The results showed that the addition of nonmetals in WPC improved the flexural strength and tensile strength and reduced screw withdrawal strength. When the added content of nonmetals was 40%, the flexural strength of WPC was 23.4MPa, tensile strength was 9.6MPa, impact strength was 3.03J/m2 and screw withdrawal strength was 1755N. Dimensional stability and fourier transform infrared spectroscopy (FTIR) of WPC panels were also investigated. Furthermore, thermogravimetric analysis showed that thermal degradation of WPC mainly included two steps. The first step was the decomposition of wood flour and nonmetals from 260 to 380°C, and the second step was the decomposition of HDPE from 440 to 500°C. The performance and thermal behavior of WPC produced by nonmetals from PCBs achieves the standard of WPC. It offers a novel method to treat nonmetals from PCBs. [Copyright &y& Elsevier]

Abstract: Fiberglass–resin powder (FR powder), a mixture of resin powder and glass fibers reclaimed from pulverized waste printed circuit boards (PCBs), is used as a partial substitute of wood flour in the production of modified phenolic molding compound (MPMC). The results show that incorporation of FR powder into MPMC as a filler enhances the thermal stability represented by heat deflection temperature (HDT). MPMC with FR powder smaller than 0.07mm shows better properties, with a flexural strength of 73MPa, a charpy notched impact strength of 3.0kJ/m2, a HDT of 167°C, and a dielectric strength of 3.7MV/m, all of which meet the standard data. Thermogravimetric analysis shows that thermal degradation of MPMC mainly includes three steps, and over 55% weight loss of MPMC occurs between temperatures of 370°C and 575°C. Phenol is the main volatile compound released from molding powder during the production of molding product. After molding powder cures to molding product, low level of residual phenol is detected. All the results indicate that the MPMC can be used as a new type of molding compound. [Copyright &y& Elsevier]

Abstract: The major economic driving force for recycling of waste printed circuit boards (PCBs) is the value of the metallic fractions (MFs) of PCBs. The non-metallic fractions (NMFs), which take up almost 70wt% of waste PCBs, were treated by combustion or land filling in the past. However, combustion of the NMFs will cause the formation of highly toxic polybrominated dibenzodioxins and dibenzofurans (PBDD/Fs) while land filling of the NMFs will lead to secondary pollution caused by heavy metals and brominated flame retardants (BFRs) leaching to the groundwater. Therefore, recycling of the NMFs from waste PCBs is drawing more and more attention from the public and the governments. Currently, how to recycle the NMFs environmental soundly has become a significant topic in recycling of waste PCBs. In order to fulfill the better resource utilization of the NMFs, the compositions and characteristics of the NMFs, methods and outcomes of recycling the NMFs from waste PCBs and analysis and treatment for the hazardous substances contained in the NMFs were reviewed in this paper. Thermosetting resin matrix composites, thermoplastic matrix composites, concrete and viscoelastic materials are main applications for physical recycling of the NMFs. Chemical recycling methods consisting of pyrolysis, gasification, supercritical fluids depolymerization and hydrogenolytic degradation can be used to convert the NMFs to chemical feedstocks and fuels. The toxicity characteristic leaching procedure (TCLP) and synthetic precipitation leaching procedure (SPLP) can be used to determine the toxicity characteristic (TC) of the NMFs and to evaluate the environmental safety of products made from the recycled NMFs. It is believed that physical recycling of the NMFs has been a promising recycling method. Much more work should be done to develop comprehensive and industrialized usage of the NMFs recycled by physical methods. Chemical recycling methods have the advantages in eliminating hazardous substances in the NMFs. The trend in chemical recycling of the NMFs is to make the best of advantages over physical recycling of the NMFs to compensate its higher cost. Removing and treating the hazardous substances in the NMFs is an ultimate method to eliminate the pollution. [Copyright &y& Elsevier]

Abstract: From the use of renewable resources and environmental protection viewpoints, recycling of waste printed circuit boards (PCBs) receives wide concerns as the amounts of scrap PCBs increases dramatically. However, treatment for waste PCBs is a challenge due to the fact that PCBs are diverse and complex in terms of materials and components makeup as well as the original equipment''s manufacturing processes. Recycle technology for waste PCBs in China is still immature. Previous studies focused on metals recovery, but resource utilization for nonmetals and further separation of the mixed metals are relatively fewer. Therefore, it is urgent to develop a proper recycle technology for waste PCBs. In this paper, current status of waste PCBs treatment in China was introduced, and several recycle technologies were analyzed. Some advices against the existing problems during recycling process were presented. Based on circular economy concept in China and complete recycling and resource utilization for all materials, a new environmental-friendly integrated recycling process with no pollution and high efficiency for waste PCBs was provided and discussed in detail. [Copyright &y& Elsevier]

• Thermal degradation behavior varied with the composition of organic substances. • HCl, benzene, and toluene were detected from pyrolysis of capacitor scarfskin. • Generous amount of particulate matter emitted from the heating of WPCB. • Phenol is one of the main VOCs from the heating of board resin. Waste printed circuit boards mounted with electronic components (WPCB-ECs) are generated from electronic waste dismantling and recycling process. Air-borne pollutants, including particulate matter (PM) and volatile organic compounds (VOCs), can be released during thermal treatment of WPCB-CEs. In this study, organic substances from WPCB-ECs were pyrolyzed by both thermo-gravimetric analysis (TGA) and in a quartz tube furnace. We discovered that board resin and solder coating were degraded in a one-stage process, whereas capacitor scarfskin and wire jacket had two degradation stages. Debromination of brominated flame retardants occurred, and HBr and phenol were the main products during TGA processing of board resin. Dehydrochlorination occurred, and HCl, benzene and toluene were detected during the pyrolysis of capacitor scarfskin. Benzene formation was found only in the first degradation stage (272–372 °C), while toluene was formed both in the two degradation stages. PM with bimodal mass size distributions at diameters of 0.45–0.5 and 4–5 μm were emitted during heating WPCB-ECs. The PM number concentrations were highest in the size ranges of 0.3–0.35 μm and 1.6–2 μm. The research produced new data on pollutant emissions during thermal treatment of WPCB-ECs, and information on strategies to prevent toxic exposures that compromise the health of recyclers. [ABSTRACT FROM AUTHOR]

• The thermal decomposition was online analyzed by TG-FTIR-MS technique. • HBr was preferentially removed from resin body at initial stage of pyrolysis. • The possible pathways from macromonomers to small molecules was discussed. • The mechanism function obtained by Škvára-Šesták method was G (α) = - l n 1 - α 2. Pyrolysis is an important pre-treatment technology for pyrometallurgy, which could reduce pollution and recover materials from waste printed circuit boards (WPCBs). However, present studies on mechanism of pyrolysis were insufficient, which results in the unclear of controlling reaction rate and inhibiting side reaction. To further develop pyrolysis technology, the in-depth research on the pyrolysis mechanism is necessary. In this study, we investigated the thermal decomposition process and pyrolysis pathways from macromonomers to products of WPCBs. The results showed that HBr was produced at the initial stage of pyrolysis. Then, the resin body depolymerized into macromonomers, followed by random rupture and free radical reactions to form pyrolysis products. Besides, possible mechanism for bisphenol A thermal decomposing was analyzed by bond energy. The results suggested that methyl groups in bisphenol A would be preferentially removed because of low bond energy. The six possible pathways may occur simultaneously when energy sufficient. Moreover, the mechanism function was determined by Škvára-Šesták method as: G (α) = - l n 1 - α 2 , which indicated pyrolysis reaction agreed with the model of random nucleation followed by random growth. This study provided the theoretical basis for pollution control, process optimization and reactor design of WPCBs pyrolysis. [ABSTRACT FROM AUTHOR]

• Cu facilitate the beginning of WPCBs pyrolysis by catalysis. • Cu changes the mechanism function and increases Ea of WPCBs pyrolysis. • Cu can promote the conversion of organic bromides to Br 2 and HBr. • The catalytic mechanism of Cu on pyrolysis of WPCBs was discussed. Pyrolysis is a promising technology for recycling organic materials from waste printed circuit boards (WPCBs). Nevertheless, the generated organic bromides are toxic and urgently needed to be removed. The coexisting copper (Cu) of WPCBs has potential performance on debromination. However, the catalytic effect and mechanism of Cu on pyrolysis process and products were still unclear. To clarify the in-situ catalysis of Cu, the analysis on kinetics and pyrolysis products was performed. The results showed that Cu can change the mechanism function of pyrolysis, which reduced the apparent activation energy (Ea). The mechanism function of Cu-coated WPCBs was obtained by Šesták-Berggren model and expressed as: d α d t = 1.65 × 1 0 7 × 1 - α - 1.30 α 6.09 - l n 1 - α - 6.03 e x p ⁡ - 202.45 K J / m o l R T . Product analysis suggested that Cu promoted the conversion of organic bromides to Br 2 and HBr. During the process of pyrolysis, bromide atoms interacted with Cu to form coordination compound, which can weaken the strength of C-Br bond and generate bromide free radical (Br*). Besides, Cu can promote the conversion of aromatic-Br to Br 2 as the catalyst for Ullmann cross-coupling reaction. Therefore, the presence of Cu was beneficial to pyrolysis. This work provided the theoretical basis for the improvement and application of pyrolysis technology. [ABSTRACT FROM AUTHOR]

• HBr and organic bromide were simultaneously removed by Ca(OH) 2. • The Ca(OH) 2 can be activated by captured HBr and its thermal decomposition. • The coordination of bromide and calcium can stretch and weaken the C-Br bond. Completely and deeply removed bromide from waste printed circuit boards (WPCBs) is necessary due to their toxicity and carcinogenicity. To achieve this purpose, calcium hydroxide (Ca(OH) 2) as a debromination agent was added during pyrolysis process of WPCBs. The results showed that hydrogen bromide (HBr), 4-bromophenol, 2-bromophenol and 2,4-dibromophenol were the main bromide species in pyrolysis products. The Ca(OH) 2 plays a significant role for removing HBr and organic bromide, but not affects products yield. Optimal removal efficiency for 4-bromophenol, 2-bromophenol and 2,4-dibromophenol reached 87.5 %, 74.6 % and 54.5 %, respectively. And debromination efficiency was related to the steric hindrance caused by bromide atoms. The Ca(OH) 2 can be activated by captured HBr and its thermal decomposition. And the newly-generated calcium bromide and calcium oxide significantly facilitate debromination due to their high surface energy and reactivity. The debromination mechanism was clarified by experiments coupled with computational chemistry: the coordination of bromide and calcium to form [Ph-Br···Ca2+ or [Ph-Br···Ca atom. Then, electrons were delivered form bromide atom to Ca2+ or Ca atom , which resulted in the stretch and weaken the C-Br bond. Hence, the C-Br bond was more easily to break. This work can provide support for designing novel and efficient debromination agents applied for high-temperature system. [ABSTRACT FROM AUTHOR]

• Mechanochemical reactions occurred in the process of crushing WPCBs. • The increase of revolution speed and time improved degradation efficiency. • Bromine distributed evenly on the surface of submicron particles after milling. • Debromination pathway of PBDEs in WPCBs under ball milling was proposed. Degradation of brominated flame retardants (BFRs) in waste printed circuit boards (WPCBs) occurred due to mechanical force during the crushing process. In this study, a planetary ball-milling simulation experiment was designed to explore the mechanochemical debromination process of BFRs in WPCBs. The results showed that CaO had a better debromination performance than MgO and the mixture of Fe + SiO 2 , and high revolution speed and low mass ratio of WPCBs to CaO promoted the degradation of BFRs. After milling for 1 h, the particle size distribution was stable while the debromination efficiency increased with the increase of milling time. Ball milling promoted the migration of bromine from the inside to the new surface of WPCBs powder, and submicron particles adhered to the micron size aggregates. The polybrominated diphenyl ethers (PBDEs) detection showed that the concentrations of most PBDE congeners decreased with the increase of milling time, and a possible degradation pathway was proposed according to the experimental results. All the results provided new data for the mechanism of degradation of BFRs in WPCBs during the mechanical crushing process. [ABSTRACT FROM AUTHOR]