Flotation enhancement mechanism of near electroneutral complex pollutants: The influence on the surface properties and structure of Cu-Sodium diethyldithiocarbamate

Traditional flotation separation relies heavily on the electrostatic attraction mechanism for surfactant adsorption. The low surface potential of heavy metal-organic aggregates poses a challenge to flotation. This near-neutrality causes the traditional electrostatically driven adsorption mode to fail, creating a critical bottleneck for efficient pollutant removal. In this study, the near electroneutral aggregates of DDTC-Cu were selected as the research object, and the regulatory effect of surfactants on them was innovatively revealed. Zeta potential measurements and DFT simulations revealed that surfactants cause charge redistribution. This enables directional adsorption through local electrostatic and van der Waals interactions and alters the flocculation morphology and structure. The addition of DTAB did not significantly change the particle contact angle but enhanced aggregate floatability. It significantly increased the zeta potential from near zero to a moderately positive level, reduced the aggregate size from large to medium, and increased the fractal dimension from relatively loose to more compact and smooth, resulting in a denser and smoother structure. AFM confirmed that the interaction energy increased by 4.4 times. Therefore, the improvement in flotation recovery of near electroneutral particles by surfactants is not mainly driven by enhanced hydrophobicity. Instead, it results from the synergistic regulation of surface potential and the optimization of aggregate structure. This study provides key mechanistic insights for improving the flotation process of complex pollutants with near electroneutral characteristics.