Microwave-assisted organic swelling promotes fast and efficient delamination of waste printed circuit boards

• Type: Article in International Scientific Journal
• Date: 2021

Authors

Bruno Monteiro (Author) Other; Liliana M. Martelo (Author) Other; Paulo M. S. Sousa (Author) Other; Margarida M. S. M. Bastos (Author) FEUP; Helena Soares (Author) FEUP

Journal

Title: Waste Management

Vol. 126

Pages: 231-238

ISSN: 0956-053X

Publisher: Elsevier

Indexing

ISI Web of Knowledge - 1 Citation

Scopus - 2 Citations

Other information

Authenticus ID: P-00T-PXH

DOI: 10.1016/j.wasman.2021.03.012

Abstract (EN): A large amount of waste printed circuit boards (WPCBs) that contain valuable metals, namely gold and copper, are produced annually. WPCBs are constituted by a multi-layer structure reinforced by a brominated epoxy resin (BER), which is very difficult to separate into the metallic and non-metallic components. The main aim of this work was to evaluate the ability of microwave for assisting in the delamination of WPCBs by organic swelling of the BER. Additionally, its performance was compared with other strategies (thermostatic and ultrasonic baths) previously described in the literature. Firstly, a library of solvents [dimethyl formamide (DMF), dimethyl acetamide (DMAc), dimethyl sulfoxide (DMSO), N-methylpyrrolidone (NMP), cyclohexanone (CH), gamma-butyrolactone (GBL), tetrahydrofurfuryl alcohol (TFA) and dimethyl malonate (DM)] was selected based on the calculation of Hansen solubility parameters plus others exclusion parameters and their performance to detach all components of WPCBs (25 mm(2)) was tested by microwave (200 degrees C for 10 min), thermostatic (153 degrees C for 10 min) and ultrasonic (60 degrees C for 25 h) baths. Microwave showed to be the most efficient approach and the delamination order for WPCBs was: NMP > DMSO > DMF > DMAc. Subsequent optimization of key parameters (dimensions of WPCBs and reaction time) were obtained: dimensions of 225 mm(2) using NMP (solid/liquid ratio of 300 g/L) at 200 degrees C with 2 cycles of 10 min. In conclusion, microwave-assisted swelling revealed to be more efficient and faster process to delaminate WPCBs into metallic and non-metallic components, which are important advantages when envisaging a future industrial waste management implementation.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 8