Joint removal of pollutants from sulfide ore flotation wastewater using composite oily sludge-based adsorbents

This study explores a sustainable "waste-treating-waste" strategy by synthesizing two distinct adsorbents, tank-bottom oily sludge adsorption material (TSAM) and refinery oily sludge adsorption material (RSAM). These materials are produced by pyrolysis at 800 °C and applied to the removal of complex sulfide ore flotation wastewater. Characterization results revealed that RSAM possesses a superior surface area (204 m² g^-1) and a well-developed mesoporous structure, providing abundant active sites for organic molecules. In contrast, TSAM is characterized by a higher ash content and the presence of active mineral phases, such as CaS and FeS, which play a crucial role in heavy metal pollutant immobilization. Adsorption experiments demonstrated distinct but complementary performance: RSAM exhibited exceptional removal efficiency for butyl xanthate (BX), achieving 99.60% removal within 45 minutes, a process primarily driven by physical mechanisms, including pore filling within the carbon matrix and strong hydrophobic interactions between the adsorbent surface and xanthate. Conversely, TSAM showed superior efficacy in removing heavy metal ions (Cd²⁺, Cu²⁺, Zn²⁺) with removal efficiencies exceeding 97%. The removal of heavy metals by TSAM was governed by combined chemical mechanisms, involving chemical precipitation (forming stable metal sulfides and carbonates), surface complexation with oxygen-containing functional groups, and ion exchange, further facilitated by the material's strong alkaline-buffering capacity. The treatment of actual flotation wastewater demonstrated that pollutant levels were significantly below discharge limits. This research provides a cost-effective solution for the simultaneous removal of organic and heavy metal pollutants, demonstrating the high-value valorization of petroleum hazardous waste within a circular economy framework.