a b s t r a c tIn this study, supercritical methanol (SCM) process was successfully used for the preparation of ultrafine copper materials from waste printed circuit boards (PCBs) after nitric acid pretreatment. Waste PCBs were pretreated twice in nitric acid. Sn and Pb were recovered by the first nitric acid pretreatment. The leach liquor with a high concentration of copper ions after the second nitric acid leaching was subjected to SCM process. The mixture of Cu and Cu 2 O with poor uniformity of particle size was formed due to the effect of ferric iron contained in the leach liquor of waste PCBs, while more uniform and spherical Cu particles with high monodispersity and smaller size could be prepared after the removal of Fe. The size of Cu particles increased obviously with the decline of SCM temperature, and particles became highly aggregated when the reaction temperature decreased to 300°C. The size of Cu particles decreased markedly with the decrease of initial concentration of copper ion in the leach liquor of waste PCBs. It is believed that the process developed in this study is simple and practical for the preparation of ultrafine copper materials from waste PCBs with the aim of recycling these waste resources as a high value-added product.

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h i g h l i g h t s• We report a novel electronic waste-based flame retardant for PVC.• The SCWO-treated PCBs significantly improves the flame retardancy of PVC.• The flame retardant mechanism of SCWO-treated PCBs was studied.• Appropriate amount flame retardant does not degrade the mechanical property of PVC. a r t i c l e i n f o b s t r a c tIn this study, a novel reutilization method for waste printed circuit boards (PCBs) as flame retardant and smoke suppressant for poly (vinyl chloride) (PVC) was successfully testified. A supercritical water oxidation (SCWO) process was applied to treat waste PCBs before they could be used as flame retardants of PVC. The results indicated that SCWO conditions had a significant effect on the flame retarding and smoke suppressing properties of waste PCBs for PVC. Cu 2 O, CuO, and SnO 2 were the main active ingredients in waste PCBs-derived flame retardants. A conversion of Cu elements (Cu 0 → Cu + → Cu 2+ ) during SCWO process with the increase of reaction temperature was found to be the key influence factor for the flame retarding properties of SCWO-treated PCBs. The experiment results also showed that there was a synergistic effect of flame retardancy between Cu + and Cu 2+ . After the optimized SCWO treatment, SCWO-treated PCBs significantly improved the flame retardancy and smoke suppression of PVC. Limiting oxygen index (LOI) and char yield (CY) increased with increasing SCWO-treated PCBs content in PVC, while smoke density rating (SDR) and maximum smoke density (MSD) decreased markedly. The mechanical properties of PVC samples were influenced in different degree by adding different content SCWO-treated PCBs.

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On 12 August 2015, Tianjin port, Tianjin City, China, a catastrophic explosion of Ruihai International Logistics Co., Ltd. (Tianjin, China) killed 173 and hurt almost 798 people, accompanying a financial loss of almost USD 2 billion. The ignition of the first fire due to the autocatalytic decomposition of nitrocellulose was verified by differential scanning calorimeter (DSC) isothermal tests. A crater with a diameter of 97 m was created by the second explosion. For the second catastrophic explosion, an amount of 577 tons of trinitrotoluene was determined by the average through scaling law, crater inverse analysis and blast effects on structures. The overpressure against distance for consequence analysis was conducted using Baker’s, Sadovski’s and Alonso’s methodologies. A distinctive scenario of “two-successive-sympathetic detonations-following-a-fire” was proposed and discussed. Isothermal time-to-maximum-rate was validated to be approximately 9 days for the nitrocellulose inside the containers with an internal temperature of 60 °C stored at Tianjin port. A fatality radius chosen at the overpressure of 0.6 bar was ascertained to be nearly 410 m from the explosion origin.

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