Interaction effects of air flow and depressants on selective plastics, polycarbonate (PC), polyoxymethylene (POM), and acrylonitrile butadiene styrene (ABS) separation in flotation

The separation of post-consumer plastics at high efficiency levels serves as a critical step for circular economy development and environmental protection. The research examined how different air flow rates and three depressants including tannic acid (TA) and polyvinyl alcohol (PVA) and polyethylene glycol (PEG) affect the flotation behavior of engineering plastics polycarbonate (PC) and polyoxymethylene (POM) and acrylonitrile–butadiene–styrene (ABS). The column flotation cell operated under controlled conditions to measure flotation recovery rates at different aeration levels and depressant concentrations. The results demonstrated that flotation efficiency depends heavily on the interaction between hydrodynamic conditions and chemical factors. The baseline aeration conditions enabled high floatability of PC and ABS but TA and PVA depressants reduced their recovery rates and PEG showed variable effects that depended on concentration levels. The absence of depressants allowed POM to reach 100% recovery at elevated air flow rates but TA and PVA consistently reduced its recovery. The operational synergy maps demonstrated specific conditions where air flow rates either supported or diminished the effectiveness of depressant chemicals. The findings demonstrate that engineering plastic recycling reaches its best results through combining optimized air dispersion levels with appropriate depressant amounts in the design process. The experimental results offer useful information for creating a large-scale flotation separation method for waste electrical and electronic equipment polymers.