Improving efficiency and feasibility of subcritical water debromination of printed circuit boards E-waste via potassium carbonate adding. (15th October 2021)

• Record Type: Journal Article
• Authors: Gandon-Ros, Gerard; Soler, Aurora; Aracil, Ignacio; Gómez-Rico, María Francisca; Conesa, Juan A.
• Is Part Of: Journal of cleaner production. Volume 319(2021)
• Publication Date: 2021-10-15
• Subjects: Hydrothermal process -- Debromination efficiency -- Printed circuit boards -- E-Waste -- Alkaline additive -- Potassium carbonate; Factory and trade waste -- Management -- Periodicals; Manufactures -- Environmental aspects -- Periodicals; Déchets industriels -- Gestion -- Périodiques; Usines -- Aspect de l'environnement -- Périodiques; 628.5
• DOI: 10.1016/j.jclepro.2021.128605
• Languages: English
• ISSNs: 0959-6526

Abstract

Abstract: Waste printed circuit boards (WCBs) were debrominated under hydrothermal treatment, using potassium carbonate as an alkaline additive to improve debromination efficiency (DE). Two different high-pressure reactors were used: a 1-L stirred reactor, where the evolution of the DE was followed over time at a low CO3 2− /Br − ratio (1:25), and an elementary 0.1-L non-stirred reactor, used to find the optimal parameters and to simplify the hydrothermal debromination (HTD) process. Considering both reactors, experiments were conducted changing the temperature (200 °C, 225 °C, 250 °C, 275 °C), and also the CO3 2− /Br − anionic ratio (1:50, 1:25, 1:10, 1:5, 1:2.5, 1:1, 2:1, 4:1) and the solid/liquid ratio (1:10, 1:5, 1:2) in the case of the 0.1-L reactor. No metallic catalyst was required. A maximum DE of about 98.9 wt % was reached in the agitated vessel at 275 °C after 4 h, with an additive/bromine ratio of 1:25. Similar DE (99.6 wt %) was also achieved in the non-stirred reactor at only 225 °C and after 2 h, using an additive/bromine ratio of 4:1 and a solid/liquid ratio of only 1:2. Concerning the solid phase behaviour during debromination, only 5 % of the net calorific value (NCV) was lost after a complete HTD treatment of WCB. Graphical abstract: Image 1 Highlights: K2 CO3 improved the efficiency of debromination of waste printed circuit boards. The effect of temperature, K2 CO3 concentration and solid/liquid ratio was studied. 99.6% of bromine was removed after 2 h in a non-stirred reactor at only 225 °C. Solid residues obtained can be used as fuel.