Effects of pre-treatment on product characteristics and bromine behavior during pyrolysis of waste printed circuit boards for resource recovery

IF 6.2 2区化学 Q1 CHEMISTRY, ANALYTICAL

Journal of Analytical and Applied Pyrolysis Pub Date : 2025-09-08 DOI:10.1016/j.jaap.2025.107375

Bibari Boro, Pankaj Tiwari

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Abstract

Pyrolysis presents a viable route for resource recovery from waste printed circuit boards (WPCBs); however, the presence of brominated flame retardants (BFRs) pose challenges due to their toxicity and potential to contaminate recovered products. This study investigates the influence of pre-treatment methods-acid leaching and Soxhlet extraction on the pyrolysis behavior of WPCBs. Four feedstocks were evaluated: raw WPCB (RW), nonmetallic fraction post-acid leaching (NM), and their Soxhlet-treated counterparts (RW-sox, NM-sox). Pyrolysis was conducted at 500 °C, with a 30 °C/min heating rate and a 156 min hold time. FTIR and ¹H NMR analyses confirmed the aromatic nature of pyrolytic oil, while GC-SimDist indicated a predominance of light hydrocarbons (C₇-C₁₁) across all feedstocks. GC-MS analysis revealed that metallic constituents in RW and RW-sox suppressed phenol formation and elevated p-cumenol concentration. However, Soxhlet extraction had minimal effect on oil composition. Gas chromatography (GC-TCD/FID) showed major gaseous products to be H₂, CO, CO₂, and minor light hydrocarbons (C₁-C₅), with higher H₂ and CO yields associated with metal-containing feedstocks. Bomb calorimeter-ion chromatography analysis indicated that acid leaching promoted bromine volatilization, increasing Br transfer to the liquid and gas phases while reducing its retention in char. These findings highlight the potential of pre-treatment strategies to optimize pyrolysis for higher resource recovery while mitigating environmental impact from brominated compounds.

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预处理对废印刷电路板热解过程中产物特性及溴行为的影响

热解为废弃印刷电路板（wpcb）的资源回收提供了一条可行的途径；然而，溴化阻燃剂（BFRs）的存在由于其毒性和污染回收产品的潜力带来了挑战。研究了酸浸和索氏萃取两种预处理方法对多氯联苯热解行为的影响。对四种原料进行了评价：粗WPCB （RW）、酸浸后的非金属组分（NM）和索氏处理的对应物（RW-sox, NM-sox）。热解温度为500℃，升温速率为30 ℃/min，保温时间为156 min。FTIR和1H NMR分析证实了热解油的芳香性质，而GC-SimDist显示所有原料中轻烃（C7-C11）占主导地位。GC-MS分析表明，RW和RW-sox中的金属成分抑制了苯酚的形成，提高了对异丙酚的浓度。然而，索氏提取对油的成分影响很小。气相色谱分析（GC-TCD/FID）显示，主要的气态产物是H₂、CO、CO₂和少量的轻烃（C1-C5），含金属原料的H₂和CO的产率较高。弹量热-离子色谱分析表明，酸浸促进了溴的挥发，增加了溴向液相和气相的转移，同时减少了溴在炭中的保留。这些发现强调了预处理策略的潜力，以优化热解，提高资源回收率，同时减轻溴化化合物对环境的影响。

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来源期刊

Journal of Analytical and Applied Pyrolysis 化学-分析化学

CiteScore

9.10

自引率

11.70%

发文量

340

审稿时长

44 days

期刊介绍： The Journal of Analytical and Applied Pyrolysis (JAAP) is devoted to the publication of papers dealing with innovative applications of pyrolysis processes, the characterization of products related to pyrolysis reactions, and investigations of reaction mechanism. To be considered by JAAP, a manuscript should present significant progress in these topics. The novelty must be satisfactorily argued in the cover letter. A manuscript with a cover letter to the editor not addressing the novelty is likely to be rejected without review.