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Printed circuit boards (PCBs) are the main components of e-waste. In order to reduce the negative impact of waste PCBs on human health and the environment, they must be properly disposed of. A new method is demonstrated for recycling waste PCBs. It is referred to as the high-temperature thermo-mechano-chemical gasification (TMCG) of PCBs by the detonation-born gasification agent (GA), which is a blend of H2O and CO2 heated to a temperature above 2000 °C. The GA is produced in a pulsed detonation gun (PDG) operating on a near-stoichiometric methane–oxygen mixture. The PDG operates in a pulsed mode producing pulsed supersonic jets of GA and pulsed shock waves possessing a huge destructive power. When the PDG is attached to a compact flow reactor filled with waste PCBs, the PCBs are subject to the intense thermo-mechano-chemical action of both strong shock waves and high-temperature supersonic jets of GA in powerful vortical structures established in the flow reactor. The shock waves grind waste PCBs into fine particles, which undergo repeated involvement and gasification in the high-temperature vortical structures of the GA. Demonstration experiments show full (above 98%) gasification of the 1 kg batch of organic matter in a setup operation time of less than 350 s. The gaseous products of PCB gasification are mainly composed of CO2, CO, H2, N2, and CH4, with the share of flammable gas components reaching about 45 vol%. The solid residues appear in the form of fine powder with visible metal inclusions of different sizes. All particles in the powder freed from the visible metal inclusions possess a size less than 300–400 μm, including a large fraction of sizes less than 100 μm. The powder contains Sn, Pb, Cu, Ni, Fe, In, Cd, Zn, Ca, Si, Al, Ti, Ni, and Cl. Among these substances, Sn (10–20 wt%), Pb (5–10 wt%), and Cu (up to 1.5 wt%) are detected in the maximum amounts. In the powder submitted for analysis, precious elements Ag, Au, and Pt are not detected. Some solid mass (about 20 wt% of the processed PCBs) is removed from the flow reactor with the escaping gas and is partly (about 10 wt%) trapped by the cyclones in the exhaust cleaning system. Metal inclusions of all visible sizes accumulate only in the flow reactor and are not detected in powder samples extracted from the cyclones. The gasification degree of the solid residues extracted from the cyclones ranges from 76 to 91 wt%, i.e., they are gasified only partly. This problem will be eliminated in future work. [ABSTRACT FROM AUTHOR]

The paper presents the results of experimental studies on the production of fine char powder from sunflower seed husks by a novel method of thermomechanical treatment with pulsed shock waves and supersonic jets of the mixture of ultra-superheated (above 2000 °C) steam and carbon dioxide, as well as the results of examination of the produced char powder in terms of its chemical, phase, and granulometric composition and structural, morphological, and texture characteristics. The objective of the research is to explore the possibility of using the resulting char powder as a sorption-active material for organic substances. It is shown that the obtained char particles and their agglomerates have an average size of 20–30 nm and 12–24 µm, respectively, have the shape of disks and ellipsoids, consist mainly of amorphous carbon (up to 56 wt%) and oxygen (up to 42 wt%), and have a specific surface area of 1.1–1.7 m2/g. It is concluded that such a char powder can be used as an absorbent for organic substances when dried and deagglomerated. [ABSTRACT FROM AUTHOR]